Anna Macaranas
email: amacaran@sfu.ca

Gina Venolia
email: ginav@microsoft.com

Kori Inkpen

John Tang
email: johntang@microsoft.com

Sharing Experiences over Video: watching video programs together at a distance

Keywords: Shared experiences, proxy, telepresence, teleconferencing, video conferencing, video-mediated communication, home

While video communication is becoming quite popular among remote friends and family, recent usage practices have been extending beyond just talking heads to remotely sharing an experience by doing an activity together. However, current video chat tools are aimed at sharing talking heads and need to be reconsidered to support remotely sharing activities. We explore a specific remote shared activitywatching video programsthrough a threephase study. We surveyed people's interest in watching video together, studied how people currently watch together in their homes, and compared different conditions for watching together in the lab. Our work explored people's current and desired practices, interactions, and technical implementations. We present our findings in themes that provide insights for designing systems that better support using video-mediated communication to share watching videos together over distance. We found that remotely watching video programs together while connected by video-mediated communication is engaging, fun, and fosters social bonds between the participants, and that these results are stronger with increased fidelity of the communication media.

Introduction

Recent trends in technology have made video-mediated communication (VMC) widely available for family and friends to maintain long distance relationships. In an exploratory study on how people use VMC to stay connected, Brubaker et al. [START_REF] Brubaker | Focusing on Shared Experiences: Moving beyond the camera in video communication[END_REF] found that distributed family and friends used video in tandem with activities such as cooking, watching TV, and even giving birth. In a similar study, O'Hara et al. [START_REF] O'hara | Everyday practices with mobile video telephony[END_REF] found that mobile VMC was being used for casual conversation, show-and-tell, and everyday routines (i.e., entertaining one's child during bath time). We are intrigued in how people are appropriating current VMC technologies to go beyond "talking heads" conversations (which can be awkward to sustain for prolonged periods of time), to shared experiences that range from everyday routine events to major life events [START_REF] Brubaker | Focusing on Shared Experiences: Moving beyond the camera in video communication[END_REF][START_REF] Inkpen | Experiences2Go: Sharing Kid's Activities Outside the Home with Remote Family Members[END_REF][START_REF] Kirk | Home Video Communication: Mediating 'Closeness[END_REF][START_REF] O'hara | Everyday practices with mobile video telephony[END_REF]. Prior work included stories of awkwardly chasing a toddler with a laptop to share with grandparents or snaking a webcam into an engine compartment to diagnose a problem with a father. This need for appropriation identifies ways that current technologies do not directly support the use of video to enable sharing an activity (other than talking) together over distance. We wanted to explore how to design systems that mitigate the issues inherent in VMC (i.e. background noise, privacy, framingsee [START_REF] Inkpen | Experiences2Go: Sharing Kid's Activities Outside the Home with Remote Family Members[END_REF][START_REF] O'hara | Everyday practices with mobile video telephony[END_REF]) and foster doing an activity together with someone in a different location, i.e. to remotely share an experience. We focus on watching video together across distance as a specific kind of remote shared experience. Watching movies, TV shows, or other online video content is a popular social activity. Yet, with the dispersion of friends and family across different geographic locations, users might be remote from the people with whom they would like to watch together. We wanted to explore how adding watching videos together to VMC can use video to naturally sustain sharing activities together. This approach contrasts with adding communication to enable social TV watching over distance, which has been extensively explored in prior work [START_REF] Cesar | Social Television and User Interaction[END_REF][START_REF] Coppens | Towards a social TV experience[END_REF]24,[START_REF] Shirazi | Real-time nonverbal opinion sharing through mobile phones during sports events[END_REF]. We use watching video together not only as a remote shared experience to design for, but as a specific activity to learn more about remote shared experiences in general. One particular question we wanted to investigate was whether the combination of audiovisual entertainment with audiovisual communication would result in a divided-attention task in which neither activity was pleasant or effective.

In this paper, we describe a three-phase study that explores how people use VMC (e.g., Skype, Google+ Hangouts, FaceTime) in tandem with remotely watching videos together to create a shared experience. We present the concepts behind shared experiences and the relevant literature that has explored this area within Human Computer Interaction. We describe our three-phase methodology that integrates a survey, exploratory field study, and comparative lab experiment. We analyze the results of our study to provide guidelines on how to design systems to better support video communication during remote shared activities.

2

Related Work

Beyond Talking Heads to Shared Spaces

Recent work shows that VMC has multiple benefits when the field of view shifts from "talking heads" and towards visually sharing an environment [START_REF] Junozovic | IllumiShare: Sharing any surface[END_REF][START_REF] Kraut | The Use of Visual Information in Shared Visual Spaces: Informing the development of virtual co-presence[END_REF][START_REF] Whittaker | Things to talk about when talking about things[END_REF]. Research has shown that shared visual environments can improve communication [START_REF] Kraut | The Use of Visual Information in Shared Visual Spaces: Informing the development of virtual co-presence[END_REF][START_REF] Whittaker | Things to talk about when talking about things[END_REF], task performance [START_REF] Kraut | The Use of Visual Information in Shared Visual Spaces: Informing the development of virtual co-presence[END_REF] and help establish common ground [START_REF] Clark | Grounding in communication[END_REF]. Common ground is the mutual awareness between a group of people in understanding the state of the task, as well as another member's state, intention, and comprehension in relation to the task [START_REF] Clark | Grounding in communication[END_REF]. By achieving common ground, group members can be more focused on completing the task as opposed to coordinating each other's roles in regards to it.

2.2

Shared Experiences

While much work has explored sharing visual environments for collaborative work, a recent wave of work has explored ways in which shared spaces and VMC can create shared experiences in home and consumer settings. Previous work has shown a desire for geographically separated family and friends to stay in touch and be part of the day-to-day activities [START_REF] Brubaker | Focusing on Shared Experiences: Moving beyond the camera in video communication[END_REF][START_REF] Inkpen | Experiences2Go: Sharing Kid's Activities Outside the Home with Remote Family Members[END_REF][START_REF] Kirk | Home Video Communication: Mediating 'Closeness[END_REF][START_REF] O'hara | Everyday practices with mobile video telephony[END_REF]. Unlike the work focused on understanding how VMC improves collaborative tasks, this wave of work is focused on how it can help maintain and improve the social relationships between people. We expand this work by focusing on watching videos together as a shared activity domain.

Leisure Activities and Social TV

In our research, we focus on how pairs of remote individuals share leisure activities.

Previous work has shown that regular participation in leisure activities has positive effects on physical and mental health [START_REF] Fitzpatrick | The Quality of Dyadic Relationships, Leisure Activites and Health Among Older Women[END_REF] and dyadic relationships [START_REF] Berg | Dyadic Exploration of the Relationship of Leisure Satisfaction, Leisure Time, and Gender to Relationship Satisfaction[END_REF]. In this study, we focus on people who are remotely watching video programs together --watching video programs (e.g., broadcast TV, recorded movies) together but from different locations. We chose this activity because it is a good example of a leisure activity that can easily be done remotely. When synchronized, the video program can act as a shared space and create a common ground for conversation.

In recent years, many researchers have built systems that embed a communication channel into the TV console (i.e. SocialTV or iTV) [START_REF] Cesar | Social Television and User Interaction[END_REF][START_REF] Coppens | Towards a social TV experience[END_REF]24,[START_REF] Shirazi | Real-time nonverbal opinion sharing through mobile phones during sports events[END_REF]. While much of the research has focused on building systems that share audio or text messaging while remotely watching TV together, some research has focused on the social interaction in these settings [START_REF] Dezfuli | A Study on Interpersonal Relationships for Social Interactive Television[END_REF][START_REF] Ducheneaut | Social TV: Designing for distributed, sociable television viewing[END_REF][START_REF] Harboe | The Uses of Social Television[END_REF][START_REF] Liu | Zync: the design of synchronized video sharing[END_REF]. Dezfuli et al. found that people most often gathered together locally to watch video programs with family but had a high preference for watching with close friends [START_REF] Dezfuli | A Study on Interpersonal Relationships for Social Interactive Television[END_REF]. Ducheneaut et al. found that the social discussion among the people was largely shaped and carefully crafted to fit in with the flow of the TV program, both when watching collocated and when watching remotely with an audio connection [START_REF] Ducheneaut | Social TV: Designing for distributed, sociable television viewing[END_REF]. Harboe et al. ran field studies to see if people enjoy using audio-based SocialTV, how they behaved and what problems they faced doing this activity [START_REF] Harboe | The Uses of Social Television[END_REF]. They found that people valued the experience, even if reluctant to try it at first. Metcalf Our research focuses on enhancing the experience of video communication by augmenting it with the leisure activity of watching videos together. This approach complements most of the work on SocialTV that enhances the leisure activity of TV watching by augmenting it with communication. We build on Flora and Segrin's exploration on the effect of different leisure activities on relationships [START_REF] Flora | Joint Leisure Time in Friend and Romantic Relationships: The Role of Activity Type, Social Skills and Positivity[END_REF], by focusing specifically on watching video programs together and better understanding how to support it. While Aaltomen et al. [START_REF] Aaltonen | Measuring Mediated Communication Experience[END_REF] used groups of strangers to study how VMC configuration affected the experience of a remote shared activity, we use groups of people with an established relationship and who enjoy spending time together.

Methodology

In this section we describe the three studies comprising this paper. We combine our findings of the three phases and present the results at the end based on key themes we identified that were consistent throughout the phases.

Initial Survey

To contextualize our studies, we wanted to understand the relevance of watching video together in people's everyday lives. In particular, we had two questions in mind:

 Are people watching video programs together remotely or interested in doing so?  If people are participating in this activity, how are they doing it?

We began exploring the answers to these questions with a survey. We ran this survey across two groups: full time employees and interns in our global software engineering company. A random selection of 1000 full time employees was invited to do this study via e-mail. All interns working during the summer received an invitation through a distribution e-mail list. 106 participants (59 full time, 47 intern) completed the survey. The majority of participants were male (78% in the full time group, 64% in the intern group). The majority of full time employees were in their 30's (49%) and 40's (32%). Almost all intern students were in their 20's (94%).

The survey consisted of 37 questions separated into five sections: basic demographics, current practices, desired practices, desired interaction, and miscellaneous. In basic demographics we collected age, gender, video program watching habits and video chat habits. Most importantly, we asked if they had ever communicated with someone at a different location while watching the same video program. This determined which sections they needed to complete. The number of responses to any question varied due to this branching and because all questions were optional.

Participants who had tried to watch video programs remotely completed the current practices section. It explored what they watched, with whom, what devices they used to watch video programs, and what devices and applications they used to communicate. Participants who had attempted or wanted to watch video programs remotely completed the desired practices and desired interaction sections. The desired practices section was almost identical to current practices, allowing us to compare what partici-pants wanted versus what they did. In desired interaction, participants ranked which forms of interaction (e.g., touch, sight, talking) were most desirable as well as the best configuration to see and hear someone from a different location. All participants completed the miscellaneous section. Here, participants were able to share their thoughts and experiences regarding watching video programs remotely. The survey took approximately ten to fifteen minutes to complete.

Field Study

While the survey was effective in gauging how many people were interested in or regularly doing this activity and how they thought they did it, we were also interested in seeing how people actually did this and what elements resulted in high and low levels of social presence. We ran a field study to explore these questions.

For the field study, we selected 56 participants (29 male, 27 female) from an inhouse database of usability subjects. 59% of participants were in their 20's, 25% were in their 30's, 9% were in their 40's, none were in their 50's, and 7% were 60 and above. Participants signed up for this study in pairs. Each participant knew their partner previously and was in a different location from them during the study. 13 of the pairs were same-gender pairs (7 male, 6 female), while the remaining 15 pairs were mixed-gender. 36% of pairs were in romantic relationships, 32% were close friends, 29% were immediate family and 7% were acquaintances. 96% of participants reported using video chat applications (e.g., Skype, FaceTime, Google+ Hangouts) at least once or twice a year -27% using them on a weekly basis.

Participants scheduled a time with their remote companion to watch a video program (e.g., broadcast TV, DVD, internet streaming) together. 15 minutes prior to watching the program, participants logged into Skype and initiated a group video chat with their remote companion. For an additional gratuity credit, participants had the option of adding our auto-answer Skype account to the group video call so we could record it. Once the group video chat was established, participants started the video program at the same time. While the program was running, participants were encouraged to act as they normally would while watching video programs together. After the video program was complete, participants disconnected the video call and completed an online survey. Participants were rewarded for their participation with credit that could be traded for company merchandise. Figure 1 shows a typical set up pairs used to complete this study. We studied the quality of their shared experience, the role of the communication device and the issues and events that affected the quality of their experience. To measure the quality of their shared experience, we looked at social presence, enjoyment and closeness. We used Biocca et al.'s definition of social presence, described as "a sense of co-presence with a mediated person and an awareness for their psychological, emotional and intentional state" [START_REF] Biocca | Toward a more robust theory and measure of social presence: review and suggested criteria[END_REF]. We selected nine questions from the Networked Minds Social Presence Scale [START_REF] Biocca | Networked Minds Social Presence Inventory (Scales only, ver. 1.2)[END_REF] most relevant to the nature of our study. Each question was asked on a 7-point Likert scale 1 . We also asked participants to rate how close they felt with their remote companion after completing the activity on a 7point Likert scale. This construct was added since Kirk et al.'s work described closeness as the main reason behind people's usage of domestic video chat [START_REF] Kirk | Home Video Communication: Mediating 'Closeness[END_REF]. Finally, we asked them to rate how much they enjoyed the activity on a 7-point Likert scale.

We explored the role of the communication device in various ways. First, we investigated if the communication device was different or the same as the device streaming video programs. Second, we looked at the placement of the device. Last, we measured how the setup affected the video program watching experience in terms of connectedness and interference. We measured connectedness by asking participants to rate how much video chat made them feel connected to their remote companion during the activity. We measured interference by asking participants to rate how much video chat interfered with their experience of watching TV. These measures were in the post-task survey but also examined in the video data as well.

To understand the issues that affected each pair's shared experience, we analyzed it from a technical and context-specific perspective. Technically, we collected audio and video quality ratings of the video chat on 7-point scale plus a rationale behind each rating via open-ended responses within the post-task survey. We also looked at the video data for any technical issues that arose. Contextually, we qualitatively analyzed the video data based on the relationship between a pair of participants, where their attention was focused, and the type of interaction that occurred between each pair.

Lab Study

The do-it-yourself nature of the field study and its between-subjects design introduced significant variability that made it difficult to compare the different device configurations. We ran a within-subjects lab study that focused on comparing the differences between watching video programs in the same room, watching video programs and using video chat on the same device, and watching video programs and using video chat on different devices. Eight pairs of participants were recruited from the in-house usability database. They were screened for watching video programs and using video chat on a fairly regular basis, and enjoying video programs with others. All were from the Puget Sound area (6 male, 10 female) ranging from 20 to 60 years of age (median 31).

After being briefed on the study and giving their consent, participants chose a 60 minute television program that they would be interested in watching during the study. We had five prerecorded shows, which included drama, comedy, and a sporting event. Pairs tried three conditions of watching togethertwo being remotely connected using video chat. After each condition, they individually completed a short survey; because all questions were optional the number of responses to any given question varied. At the end of the study, they participated in a post-task interview. The study took approximately two hours to complete and participants were rewarded for their participation with credit that could be exchanged for company merchandise.

There were three experimental conditions. Our baseline condition, Local, had participants watching a third of the program side by side (Figure 2A). In the Picture-in-Picture (PIP) condition they watched a third of the program in separate rooms. The remote person's video was overlaid in the corner of the TV screen and their audio came from a speaker placed near the TV (Figure 2B). Our final condition, Proxy, was like PIP but the remote person's video and audio came from a separate device placed near them (Figure 2C). Condition ordering was counterbalanced. In the remote conditions we used high-quality speakers, high-definition webcams, and lavalier microphones to mitigate audio crosstalk. We reused our shared experience measures from the field study (social presence, enjoyment and closeness) and integrated them into our post-condition surveys. We did this to compare the experiences in the field and lab studies for any overlapping trends. In addition to the quality of shared experience, we expanded on the concept of enjoyment and revisited connectedness by asking participants to state which condition they enjoyed most/least as well as which condition they felt most connected with their companion. We asked participants to describe the differences between watching video programs remotely and locally. We specifically asked them to reflect on how the second screen's location in the Proxy condition affected their experience. We also asked if they knew anyone with whom they would like to do this activity with in the future.

Results and Discussion

Together, our three studies demonstrate that remotely watching TV together is a desirable, fun activity that augments social communication and reinforces social connection. We found that having the communication channels on a separate device was associated with better outcomes than picture-in-picture on the TV. We found that communication media richness corresponded to better outcomes. Finally we found that there are many technical challenges that can substantially degrade the experience. We present the results of the three studies together to focus on the insights supported by these converging lines of evidence.

Emerging Practice

Watching video programs, such as television, movies and online content, is often a social activity: 30% of respondents to our initial survey reported watching video programming with one or more other people every day; 75% reported doing it daily or weekly (n=105). At the same time, a substantial amount of watching is done solo: 40% reported watching video programs alone every day; 72% reported doing it daily or weekly (n=95, Figure 3). Some of our respondents (24%) had already communicated with someone in a different location while watching the same video program at least once, using a variety of communication channels, while others (26%) expressed interest in trying it (n=105). Significantly more young people (<30 years old) reported having watched video programs together remotely than older people (39%, n=49 vs. 11%, n=56, Mann-Whitney U=987, p=.001, Figure 4). Prior research also found that some participants find watching video programs as time alone to unwind from work [START_REF] Harboe | The Uses of Social Television[END_REF]. Other participants found certain genres like news and films to require more conscious attention on the video program and allowed less attention for socializing [START_REF] Dezfuli | A Study on Interpersonal Relationships for Social Interactive Television[END_REF].

Following our studies, most participants responded positively when asked if they would be interested in watching video programs with a remote partner again (field study: 88%, n=56; lab study: 88%, n=16). This interest is substantially higher than the combination of the 24% who had tried it and 26% interested in trying it in our initial survey. This difference suggests that getting people over the hump of first trying it may increase the potential audience for this kind of remote shared activity. Harboe et al.'s found similar results with sharing audio chat while watching TV, although our results demonstrate video chat as a desirable form of SocialTV [START_REF] Harboe | The Uses of Social Television[END_REF].

Insight: Some people, particularly young adults, are creating their own remote video watching experiences. There is an opportunity for bringing this capability to a larger audience, especially once they have had the opportunity to try it.

Enjoyment

Most participants (80%) in our field study responded positively when asked if they enjoyed the experience (n=55, M=5.4, SD=1.5). Several field study participants also commented on their enjoyment using Skype while watching together:

"It is fun because you can comment and talk about things that are happening. [My study partner] and I watched a lot of tv together in college and it really reminded me of that experience." [Field P15a]

Likewise, most participants in our lab study had enjoyable experiences in the remote conditions with 81% responding positively (i.e. somewhat agree, agree, or strongly agree) in enjoyment (n=31, M=5.6, SD=1.3). A significant main effect of condition (Local, PIP and Proxy) was found on enjoyment (Friedman, Χ 2 =17.92, p<.001). Posthoc pairwise comparisons revealed no significant difference between the Local and Proxy condition (Z=-1.996, p=.046) but the PIP condition was rated significantly lower than both the Local and the Proxy conditions (Z=-3.204, p=.001 and Z=-2.705, p=.007 respectively). During the post-study interview, some participants described watching video programs remotely as a fun way to spend time together:

"Sometimes you can't be together but want to have Survivor parties or something. It's a great way to hang out if you actually couldn't." [Lab P7a]

A few participants reported that using Skype while watching the same video program was initially awkward:

"It was a new experience and slightly awkward at first but then realizing

we were laughing at the same things was fun" [Field P17b]

Several participants reported, unsurprisingly, that it was not as pleasant as watching together in person.

"I still was able to easily communicate with my companion, as well as see their instant reactions to exactly what I was watching. However, because I was not physically in the room with them, it didn't seem to be as enjoyable." [Field P13b]

Previous research provides possible reasons for this preference. Gaze and gestures are difficult to interpret during video chat, making an assessment of body language difficult [START_REF] Hirsh | People Do and Don't Use Videoconferencing Systems[END_REF]. Participants in video chat have a harder time reading their companion's mood and attention which can hinder effective interaction and negatively affect the shared experience [START_REF] Flora | Joint Leisure Time in Friend and Romantic Relationships: The Role of Activity Type, Social Skills and Positivity[END_REF]. Similarly, video chat lacks a shared physical space. Some people simply feel that digital representations of their companion are insufficient in comparison to having them physically there [START_REF] Heath | Disembodied conduct: Communication through video in a multimedia environment[END_REF]. While we did not expect it to be as good as watching together in the same room, our goal was to explore enabling a shared watching video experience when they could not be together physically. Some participants felt that the communication enhanced their enjoyment of the content.

"It was far more enjoyable than watching it alone; it's nice to discuss the show or make comments!" [Field P27a]

Others felt that the communication lessened their enjoyment of the content.

"I'm more distracted from the video program and can't fully enjoy it." [Field P17a]

The field study questionnaire results also showed mixed results regarding whether communication interfered with the content: 31% agreed, 40% neutral, and 29% disagreed (n=55, M=4.0, SD=1.6).

Insight: Most people enjoy the experience of remotely watching video, but challenges remain to make it more natural and to reduce the conflict between the video program and the communication.

Social Presence and Connectedness

We used nine questions from Biocca & Harms' Social Presence Inventory [START_REF] Biocca | Networked Minds Social Presence Inventory (Scales only, ver. 1.2)[END_REF], along with our additional question of closeness, to gauge participants' level of social presence in the field study (Figure 5).

SP1. I often felt as if my remote companion(s) and I were in the same room together. SP2. My remote companion(s) were often aware of me. SP3. My remote companion(s) paid close attention to me. SP4. I was easily distracted from my remote companion(s) when other things were going on. (Note: Response scale was inverted for analysis and presentation.) SP5. I was sometimes influenced by my remote companion(s)' moods. SP6. My remote companion(s) were able to communicate their intentions to me. SP7. My thoughts were clear to my remote companion(s). SP8. My actions were often dependent on my remote companion(s)' actions. SP9. The behavior of my remote companion(s) was often in direct response to my behavior. --Watching video media together remotely made me feel closer to my remote companion(s). In order to compute a composite social presence score, we utilized a principal components factor analysis to extract relevant factors from these ten questions. Two different factors (factor load greater than .5) were revealed. The first factor included six of the questions from the Social Presence Inventory (SP1, SP2, SP3, SP4, SP6, and SP7) along with the closeness question. The second factor included the remaining three questions from the Social Presence Inventory (SP5, SP8, and SP9). The first factor was significantly (p<.01) correlated with users' feelings of connectedness (r=.75), their enjoyment (r=.60), and their willingness to do the activity again (r=.52). As a result, we used the mean of these seven measures to compute the composite "Social Presence" (SP) score (the resulting score was in the range of 1-7, with 1 being low and 7 being high). The second factor was not significantly correlated with any of the other measures (r<.1) so these questions were not used in subsequent analyses.

In the field study, 86% of participants' SP scores were positive (>4) (M=5.09, SD=.97). Examining all of the demographic data for the participants (gender, age, level of experience with Skype, relationship with their partner), as well as their equipment configuration (device used for program and communication, and placement of the device) revealed no significant impact on the resulting SP scores (using Kruskal-Wallis test with alpha=.01). This may be a result of high individual differences across these variables, as well as the fact that most participants enjoyed their experience, regardless of the setup.

We used the same measure of SP in the lab study (Figure 6). For the two remote conditions, participants' enjoyment ratings were significantly correlated with their SP scores (PIP: r=.74, p<.001; and Proxy: r=.54, p=.027). This correlation supports previous work that found individual satisfaction (or enjoyment) from a leisure activity was the most influential factor on relationship satisfaction [START_REF] Berg | Dyadic Exploration of the Relationship of Leisure Satisfaction, Leisure Time, and Gender to Relationship Satisfaction[END_REF]. A significant main effect of condition (Local, PIP and Proxy) was found on SP scores (Friedman, Χ 2 =30.63, p<.001). Posthoc pairwise comparisons revealed that Local had significantly higher SP scores, than Proxy (Z=-3.367, p=.001) or PIP (Z=-3.724, p=.001), and Proxy had significantly higher SP scores than PIP (Z=-2.976, p=.003). These results support prior literature comparing VMC to face-to-face communication [START_REF] Heath | Disembodied conduct: Communication through video in a multimedia environment[END_REF][START_REF] Hirsh | People Do and Don't Use Videoconferencing Systems[END_REF]. They are also consistent with Media Richness Theory [START_REF] Daft | Organizational information requirements, media richness and structural design[END_REF], suggesting that the communication media fidelity plays a strong role in the social connection of the experience. Most participants expressed that using VMC while watching video programs made them feel connected with their remote partner. In the field study, 75% of the participants responded positively that the experience made them feel connected (n=56, M=5.3, SD=1.3). Qualitative data from the field study provides some reasons why: Other comments suggested that the reason for feeling connected could be the common ground provided by the shared activity.

"
"You get to enjoy something together, rather than just talk." [Field P2b] "just skyping makes me feel as i need to be talking about something when i dont really have something to say but when watching media we can comment on whats going on" [Field P12b] "Well, when you are doing the same thing while Skyping, you have that little bit more in common with them. It definitely makes it more satisfying."

[Field P24a]
These results matched our hypothesis that the video program could serve as a shared space and coincides with Clarke and Brennan's concept of grounding [START_REF] Clark | Grounding in communication[END_REF]. The shared reference enabled participants to spend more time enjoying the activity and discussing the show or personal topics rather than spending the time trying to establish a shared perspective.

On the other hand, there is some design tension around competing video channels as some participants reported that watching the video programs distracted them from their normal Skype conversation behavior and decreased their sense of connectedness.

"When I usually Skype, I'm not doing anything else but Skyping, so it was a little strange because I felt like I was ignoring her... I think it takes away from the chat because you are watching the video therefore neither one gets your full attention" [Field P11a]

"when I Skype with my husband it is usually to show him the baby or dog or important mail. Not eat up our time with a tv show" [Field P25b] O'Hara et al.'s work on mobile video chat [START_REF] O'hara | Everyday practices with mobile video telephony[END_REF] observed similar findings. Their participants described VMC as mentally demanding and, unlike mobile audio chat, made multitasking more difficult because the other party could see that you were not fully attending to them.

Insight: For most people, remotely watching video resulted in a strong sense of connection or social presence. It strengthens ties when framed as an additional activity that increases the time spent together rather, than taking time away from talking together; controlling this framing is a significant design tension.

Placement of the Skype Window

In the initial survey, 48% of respondents ranked the picture-in-picture configuration most highly, where the video of their remote partner is shown embedded on the display showing the video program. 24% respondents wanted it on a separate device close to them, 16% wanted it on a separate device near the television, and 12% wanted it on a device they were holding (n=25).

In the field study, where users were able to choose whichever configuration they preferred or had access to, 61% used a picture-in-picture configuration and 39% used a Proxy configuration (n=54). Mann-Whitney U tests did not detect any significant differences between PIP and Proxy configurations in terms of enjoyment (Z=-.853, p=.394), SP (Z=-.116, p=.908) or their desire to do the activity again (Z=-.055, p=.956). The lab study however showed a clear benefit of Proxy over PIP (Wilcoxon Signed Ranks Test) for both participants' level of enjoyment (Z=-2.705, p=.007), and SP scores (Z=-2.976, p=.003).

In the lab study post-test interview, eight participants reported liking the proxy in the position we had set, five wanted it at the same distance but more in line of sight of the television, and three wanted it farther from them and closer to the TV. Note that the Proxy could be positioned to more easily see both the video content and the remote person than the head turning needed if sitting side-by-side in the same room.

It should be noted that the PIP conditions of the initial survey and lab study are not identical to that of the field study. In the former, PIP referred to both content and communication being placed on a television screen viewed from a distance. In the latter, all PIP configurations devised by our participants were on a laptop or desktop viewed close up.

Media Richness Theory [START_REF] Coppens | Towards a social TV experience[END_REF] suggests that the Proxy condition would be preferred over PIP. The Proxy condition presented the remote companion on a larger screen, allowing for a higher quality representation of the individual. Likewise, the separation of TV and Proxy speakers allowed the participant to directly perceive the sound sources as spatially distinct. The visual and audio representations came closer to emulating the remote individual's physical representation and as a result made participants feel closer to having the actual person in the room [START_REF] Aaltonen | Measuring Mediated Communication Experience[END_REF][START_REF] Daft | Organizational information requirements, media richness and structural design[END_REF].

Likewise, Grounding Theory [START_REF] Clark | Grounding in communication[END_REF] can further explain the Proxy's success over PIP. In the Proxy condition, a participant receives a visual cue when the other person shifts their visual attention between the content and the remote view. Because of this, less effort was needed to reorient between focused conversation and attending to the video program. For example, as seen in the video data, a participant could tell if their remote companion's attention was primarily focused on them based on how often they would turn their gaze toward the video chat screen. The participant in return could reciprocate and look back at the remote companion or keep looking at the TV, indicating that they are engrossed in the show and do not wish to chat right now.

Insight:

When the video program is on a television, having the remote person on a proxy device on the coffee table is much preferred over picture-in-picture. Future work should compare these conditions to picture-in-picture on a laptop or tablet, as our results were inconclusive.

Communication Channels

Remote social TV can employ a variety of communication modalities. Prior work has focused on textual [START_REF] Cesar | Social Television and User Interaction[END_REF][START_REF] Coppens | Towards a social TV experience[END_REF][START_REF] Dezfuli | A Study on Interpersonal Relationships for Social Interactive Television[END_REF]24,[START_REF] Shirazi | Real-time nonverbal opinion sharing through mobile phones during sports events[END_REF] or audio [START_REF] Ducheneaut | Social TV: Designing for distributed, sociable television viewing[END_REF][START_REF] Harboe | The Uses of Social Television[END_REF] modalities. The use of VMC in this application is largely an unexplored design space. Respondents to our initial survey ranked which modalities they felt were most important to help them feel connected. Talking verbally (i.e. audio) was rated highest, followed by text, then visual, then touch (Figure 7). As noted above (Figure 6), in the lab study the Proxy condition had more positive outcomes than PIP. The most notable difference between these conditions is the greater visual angle subtended by the remote video. This result suggests that the video of the remote partner adds a key element to the experience.

While Figure 7 shows that touch was the lowest-ranked medium, 10% of respondents ranked it #1 and 10% ranked it #2 (n=36). In the field study questionnaire we asked, "If there was a magical device that could increase your feeling of being connected with your companion(s), what key function or property does it need to have?" Several respondents described wanting some form of touch: "For me it's spatial. I want to feel warmth from loved ones in close proximity... so something that could make me feel like she was sitting right next to me." [Field P16b] Many researchers have investigated haptic interpersonal communication (e.g. [START_REF] Brave | Tangible interfaces for remote collaboration and communication[END_REF]) and watching video together remotely may be a scenario that is ripe for exploring it.

Insight: While audio is fundamental for communication, video appears to play a key role in creating social presence. Tactile communication deserves more study.

Technical Problems

There were many technical hurdles that our field study participants needed to surmount, including synchronizing the content, handling the multiple audio streams, and general computer/networking glitches. Pairs spent a median of 3.6 minutes on setup (n=24). Twelve pairs continued to have technical problems throughout the session. We discarded the data of one pair because they were unable to solve the technical ). This supports previous work that lists technical components as one of three factors (along with social and psychological) that affect the experience of communication [START_REF] Aaltonen | Measuring Mediated Communication Experience[END_REF].

While Liu et al. have developed a system for synchronizing video in a popular IM system [START_REF] Liu | Zync: the design of synchronized video sharing[END_REF], there is currently no widely-available standalone mechanism for perfectly synchronizing video playback between a pair of computers in different locations. For prerecorded programming, most participants used a technique where one counted down and then both pressed Play. Even broadcast programming is not perfectly synchronized since different broadcasting pipelines (e.g., satellite, cable, antenna) introduce different delays. While sync issues can be less noticeable in text chat, the slightest sync issue is much more obvious in video chat. Eight pairs in the field study had sync issues. Four pairs mitigated the sync issues by muting the content audio at one side and listened to it via Skype audio. When the content was out of sync even slightly, it impeded the interaction between the participants.

"My companion became annoyed that I was trying to make it so we were watching the shows at the exact same time. But if we weren't it was strange because we would laugh in different places." [Field P18b]

These findings replicate similar findings from studies that suggest minor sync differences within video chat have significant negative effects on communication [START_REF] Krauss | Effects of transmission delay on the efficiency of verbal communication[END_REF][START_REF] Kraut | The Use of Visual Information in Shared Visual Spaces: Informing the development of virtual co-presence[END_REF].

Audio was problematic because the microphone, which was intended to pick up the viewers' speech, also picks up the video program's soundtrack. While the automatic echo cancellation capabilities of the computer can keep the speech signal clean, it typically could not suppress the echo of the video program audio. When this occurred, a participant would hear the program audio both directly and via the communication channel, adversely affecting the engagement: "Imagine sitting in a room watching TV, and having another TV in the same room, same show, but the timing is off a little bit and the volume is turned up." [Field P19b]

Even without audio crosstalk, the two audio streams competed. Speech could drown out the program content, or vice versa.

"it was hard to hear the other person when they laughed or what not." [Field P25b]

Insight: Technical complexity, content synchronization, and audio crosstalk are barriers to remote video watching. Technical problems can decrease the effectiveness of the overall experience.

Conclusion and Future Work

We found that remotely watching video programs together while connected by VMC is engaging, fun, and fosters social bonds between the participants. Our study documents the important factors that enable this particular "shared experience" [START_REF] Brubaker | Focusing on Shared Experiences: Moving beyond the camera in video communication[END_REF] to lift VMC "beyond talking heads."

We found little to suggest that the combination of audiovisual entertainment and audiovisual communication caused divided attention. Audio levels did compete, but having two separate video streams did not. Duchenaut et al. [START_REF] Ducheneaut | Social TV: Designing for distributed, sociable television viewing[END_REF] noted that the pauses and redundant content in TV shows create opportunities for communication and may mitigate this competition. The Proxy configuration's advantage over PIP may have been in part because it helps people better manage their attention. We believe that there is further opportunity for better understanding and designing for attention in shared-experience systems.

We believe that a key affordance of VMC is how it enabled more immediate and natural sharing of reactions, which is an important part of enjoying watching videos together. Video, compared to text or only audio, is well-suited for richly sharing laughter and other emotional reactions to the video program. The users' comments suggested that this sense of sharing these reactions through video contributed to the positive scores in social presence, connectedness, and enjoyment.

We believe that practical systems for remotely watching video together would have positive social impact by allowing close ties to strengthen their bonds by sharing experiences despite physical distance in a way that is different from, and complementary to, simply conversing together. Our next step is to develop softwareand possibly hardwareto support watching together remotely. There are many interesting design and technical problemsinitiating the experience, choosing the program to watch, closely synchronizing playback, and solving audio crosstalk.

Finally, watching TV is but one of many possible remote shared experiences. This study strongly supports rich media beyond audio communication in remote shared experiences. This is a rich design space that deserves more exploration.

Fig. 1 .

 1 Fig. 1. A field study pair; both watched a program on TV and used video chat on their laptops.

Fig. 2 .

 2 Fig. 2. Lab study conditions: (A) Localwatching in the same room; (B) Picture-in-Picture (PIP)watching with remote person appearing in inset on TV, which is highlighted here with an orange rectangle; (C) Proxywatching with remote person on separate device.

Fig. 3 .

 3 Fig. 3. Responses to the initial survey question, "When watching video media, I watch it..."

Fig. 4 .

 4 Fig. 4. Responses to the initial survey question, "Have you ever communicated with someone at a different location while watching the same video program?" by age bracket.

Fig. 5 .

 5 Fig. 5. Responses to the field study post-test survey questions relating to social presence.

Fig. 6 .

 6 Fig. 6. Social Presence scores from the lab study post-condition survey. (Note: SP scores have been rounded to nearest integer.)

Fig. 7 .

 7 Fig. 7. Responses to the initial survey question, "What interaction is needed to feel most connected with the person you are watching TV remotely with?"

  et al. found that people felt constrained by pre-set text messages and wanted richer forms of communication while watching video programs [24]. We expand on Dezfuli et al. and Duchenaut et al.'s work on watching video programs locally by testing their findings on relationship strength and conversational patterns on people watching video programs remotely. We use the insights found from Metcalf et al. and expand on Harboe et al.'s work by running a field study that uses video chat as the means of communication. While Harboe et al. speculate that having video chat compete with the TV program for visual attention will be problematic in SocialTV, no research has been done to validate this speculation. Unlike Harboe et al., we predict that people will enjoy video chat while watching video programs.

  While many of our respondents wanted to watch together remotely, 50% of our initial survey respondents reported being disinterested in communicating with someone at a different location while watching the same video program (n=105). When exploring reasons behind this disinterest, two consistent themes emerged. Some people are simply not interested in watching video programs:"TV isn't a primary focus of my activities." [Survey P7] 2Others reported that they do not like communicating verbally while watching:"In general I don't find watching TV together as a greatest social activity. People either watch and don't speak with each other, or speak with each other but then don't watch. With that I don't get the point of doing it together online…" [Survey P39]

				% of Respondents
			0%	25%	50%	75%	100%
	By myself (n=95)
	With one other (n=101)
	In a small group (n=97)
	In a big group (n=90)
	Every day	Every week	Every month	Once or twice a year	Never
		0%	25%	50%	75%	100%
	20's or younger (n=49)
		30's (n=30)
	40's or older (n=26)
	Yes	No but I would like to	No and I am not interested in doing so

All 7-point scales are reported with 1 = most negative, 4 = neutral, and 7 = most positive.

Participants are identified by study phase (Survey, Field or Lab), participant number, and a designator (a or b) if they were part of a pair.

(most positive) 6 5 4 (neutral) 3 2 1 (most negative)

(most positive) 6 5 4 (neutral) 3 2 1 (most negative)


Mobolaji Ayoade
email: mobolaji.ayoade@gcu.ac.uk

Stephen Uzor
email: stephen.uzor@gcu.ac.uk

Lynne Baillie
email: l.baillie@gcu.ac.uk

The Development and Evaluation of an Interactive System for Age Related Musculoskeletal Rehabilitation in the Home

Keywords: Home rehabilitation, inertial motion sensors, older adults, visualizations and musculoskeletal conditions

This paper describes a series of user studies carried out to investigate the usability, significance, and acceptance of two visualization tools designed to improve the quality of, and adherence to home-based exercise programmes for musculoskeletal rehabilitation. The core functionality of these visualization tools enabled the users to observe the optimal way to perform their exercises via a mannequin, and receive feedback on their own movements through the use of body worn sensors. Before full deployment in the home, two user studies were carried out in the laboratory, and then two in the home with seniors who had recently undergone musculoskeletal rehabilitation using a standard care paper based booklet in the home. Our key findings suggest that by using the visualization tools the participants were able to overcome the major limitations of standard care; and that these tools were considered by the users to be useful in encouraging participation in home exercise.

Introduction

Musculoskeletal conditions are the most common cause of physical disability and severe long-term pain in older adults [START_REF] Woolf | Burden of major musculoskeletal conditions[END_REF]. In particular, the degeneration of muscles and joints due to age can increase a person's risk of falling; and possibly lead to osteoarthritis (excessive joint pain) in the knees or hipswith a replacement of these joints being the recommended solution. The two conditions we focus on in this paper are rehabilitation after knee surgery or after a fall. These conditions normally affect older adults or seniors. For example, in Scotland, the average age for adults undergoing knee replacement surgery is 68 years [START_REF]Scottish Arthroplasty Project Biennial Report[END_REF] and over 30% of adults over the age of 65 suffer a fall at least once a year. These impairments in muscle strength and balance can have serious repercussions with regards to the independence and confidence of older adults [START_REF] Skelton | What are the main risk factors for falls among older people and what are the most effective interventions to prevent these falls? Copenhagen, WHO Regional Office for Europe[END_REF].

Exercise programmes are often usedboth as preventive, and rehabilitative means to help elderly patients return to functioning physical levels [START_REF] Thomas | Does the 'Otago exercise programme' reduce mortality and falls in older adults?: a systematic review and meta-analysis[END_REF]. In hospitals and community-based rehabilitation centers, strategies involving the use of exercise for rehabilitation have been very successful [START_REF] Applegate | A Randomized, Controlled Trial of a Geriatric Assessment Unit in a Community Rehabilitation Hospital[END_REF][START_REF]Physiotherapy rehabilitation after total knee or hip replacement: an evidence-based analysis[END_REF]. However, in the home setting, recovery of balance and strength can be challenging, as individuals often do not adhere to rehabilitation programmes thereby making this type of intervention less effective [START_REF] Nyman | Older people's participation in and engagement with falls prevention interventions in community settings: An augment to the Cochrane systematic review[END_REF][START_REF] Pisters | Exercise adherence improving long-term patient outcome in patients with osteoarthritis of the hip and/or knee[END_REF]. In addition, the individuals sometimes do not correctly interpret the instructions and health care professionals are not aware of this lack of understanding until the patient returns to the hospital or rehabilitation clinic for a follow-up appointment.

The consequence of this lack of adherence and poor quality performance has serious implications for the health and independence of the individual. In some cases, seniors who have had a recent injurious fall may feel isolated and fearful of future falls, thereby limiting their movement and thereby actually increasing their fall risk [START_REF] Scott | Osteoporosis and hip fractures[END_REF][START_REF] Fessel | Correlates of fear of falling and activity limitation among persons with rheumatoid arthritis[END_REF]. In another example, people who have undergone knee replacement surgery may not recover full range of movement in the new joint(s) thereby limiting their knee function and having a negative impact on their quality of lives -if they do not exercise the joint(s) regularly as recommended by health experts [START_REF] Button | Clinical effectiveness of knee rehabilitation techniques and implications for a self-care treatment model[END_REF]. In order to address these issues, it is important to identify what the short comings of standard home rehabilitation are, and investigate ways in which greater participation in home exercise can be encouraged.

One of the ways through which rehabilitation can be enhanced, we believe, is through the use of visual feedback or visualization. By visual feedback, we mean the capture of the user's movement, then presenting it in a form that is easily understandable and that indicates how well the user's movement matches the ideal movement. In previous research studies, visual feedback has been used to provide biomechanical feedback on user's performance during gait retraining [START_REF] Wheeler | Real-Time Knee Adduction Moment Feedback for Gait Retraining Through Visual and Tactile Displays[END_REF], and the use of visual feedback to retrain balance in the elderly after a stroke [START_REF] Walker | Use of visual feedback in retraining balance following acute stroke[END_REF]. However to facilitate this kind of feedback, specialized equipment and staff are often required to capture the patients' movements. Numerous studies investigating visual rehabilitation have therefore been limited to laboratory or clinical settings due to these factors [START_REF] Zhou | Human motion tracking for rehabilitation-A survey[END_REF]. To investigate the potential of visual feedback to aid rehabilitation in the home setting, there is a need to design a system capable of providing the user with meaningful feedback, while being easy to use and manage by seniors.

This paper describes a series of usability studies carried out to evaluate two distinct visualization tools to improve musculoskeletal rehabilitation for seniors using relatively cheap wireless motion capture devices. Both of these tools were designed to provide de-personalized visualizations of user movements through the use of a digital mannequin. Through the use of these systems, it is possible for the users to see the ideal range and pace of motion necessary for effective recovery, and see a visualization of their own movements during home exercise. We investigate through this research, the usability and acceptance of the visualization tools in two musculoskeletal conditions with different requirementsfalls and knee replacement rehabilitation.

Related Work

Uzor et al. [START_REF] Uzor | Identifying barriers to effective user interaction with rehabilitation tools in the home[END_REF] identified one of the barriers to the effective use of current home rehabilitation tools was the inability to maintain motivation throughout the rehabilitation programme, which usually extends over long periods, due to the passive nature of current tools such as exercise booklets and DVDs. In addition, the absence of a physiotherapist and recording of exercises performed has been reported as other factors affecting adherence to home exercise programmes [START_REF] Suttanon | Factors influencing commencement and adherence to a home-based balance exercise program for reducing risk of falls: perceptions of people with Alzheimer's disease and their caregivers[END_REF]. As a result, there has been a growing interest in the research community to seek technological solutions to these limitations [START_REF] Zhou | Human motion tracking for rehabilitation-A survey[END_REF], [START_REF] Lim | A low cost wearable wireless sensing system for upper limb home rehabilitation[END_REF], [START_REF] Doyle | BASE -An interactive technology solution to deliver balance and strength exercises to older adults[END_REF]. According to Zhou [START_REF] Zhou | Human motion tracking for rehabilitation-A survey[END_REF], however, technologies for rehabilitation have not been accepted and adopted in the home in the past, especially by seniors for the following reasons: the systems have required professional help to set them up, occupy large or fixed spaces, are quite expensive and have poor human computer interaction.

Recently, there has been a growing interest among researchers and health professionals in using commercial systems such as the Nintendo Wii as rehabilitation tools for various conditions including musculoskeletal conditions [START_REF] Harms | Advancing technology in rehabilitation[END_REF]. Video games also have the potential of improving motivation and adherence to rehabilitation programs by facilitating the enjoyability of physical activities but they do not necessarily promote correct performance of rehabilitation exercises as the game controllers capture users' gestures or gross movement patterns [START_REF] Uzor | Identifying barriers to effective user interaction with rehabilitation tools in the home[END_REF], [START_REF] Harms | Advancing technology in rehabilitation[END_REF], [START_REF] Tanaka | A Comparison of Exergaming Interfaces for Use in Rehabilitation Programs and Research[END_REF]. Consequently, researchers and game enthusiasts are currently making attempts to develop games specifically designed for rehabilitation e.g. SilverPromenade [START_REF] Gerling | Designing and evaluating digital games for frail elderly persons[END_REF] and Animal feeder [START_REF] Borghese | An integrated low-cost system for at-home rehabilitation[END_REF]. And although there is evidence of increasing acceptance of commercial video game technologies by seniors for rehabilitation [START_REF] Theng | An exploratory study on senior citizens' perceptions of the Nintendo Wii: the case of Singapore[END_REF], [START_REF] Fung | Use of Nintendo Wii Fit TM in the rehabilitation of outpatients following total knee replacement: a preliminary randomised controlled trial[END_REF], as yet the usability of such systems in an autonomous home environment is yet to be reported -all the studies have focused on rehabilitation centers or outpatient hospital departments and require help to setup. Ziefle & Röcker [START_REF] Ziefle | User Diversity as a Challenge for the Integration of Medical Technology into Future Smart Home Environments[END_REF] believed that by understanding the capabilities, limitations, needs and preferences of seniors; researchers and designers could produce acceptable technologies for home rehabilitation.

Theng et al. [START_REF] Theng | An exploratory study on senior citizens' perceptions of the Nintendo Wii: the case of Singapore[END_REF] identified ease of use as one of the factors to be considered when designing technology for seniors. Although, depth cameras such as the Microsoft Kinect have the potential to be easy to use by older adults [START_REF] Borghese | An integrated low-cost system for at-home rehabilitation[END_REF], camera based systems face the problem of occlusion and need they require at least a small amount of free and clear space. For example, the use of the SilverFit rehabilitation system in centres has been reported [START_REF] Silverfit | [END_REF]. However, the system required the presence of a physiotherapist and large dedicated free space 5x5m; and as a result would not be suitable for use in most homes. Also, given a patients injuries from their fall or knee surgery, it would not be sensible for them to start moving equipment or furniture to create free space. Another issue with regard to knee and falls patients is the need to use supports which may be between the user and the cameras while performing the exercises. For example, a knee patient must sit or lie on a bed or chair in a comfortable position while performing the exercises [START_REF]JointPathways™ Patient Guides for Knees[END_REF][START_REF]Preventing Falls: Strength and balance exercises for healthy ageing[END_REF], therefore occlusion would occur and the system would not show the users movement correctly.

More recently, researchers have started to explore the fusion of cameras systems and inertial motion sensors e.g. monitoring of the upper arm during eating activity after stroke [START_REF] Hondori | Monitoring Intake Gestures using Sensor Fusion (Microsoft Kinect and Inertial Sensors) for Smart Home Tele-Rehab Setting[END_REF] in order to overcome the limitations of camera based systems in handling occlusion [START_REF] Bo | Joint angle estimation in rehabilitation with inertial sensors and its integration with Kinect[END_REF]. Doyle et al. demonstrated the acceptance and usability of a home-based visualization system that uses 2 step counters and a web camera to track 3 reflective markers for a home physiotherapy program for falls prevention for seniors [START_REF] Doyle | BASE -An interactive technology solution to deliver balance and strength exercises to older adults[END_REF]. However, these setups would be unsuitable for providing precise movement information, which is important in maximizing physiotherapy benefits of the knee rehabilitation exercise program, although they were able to monitor the correct completion of exercises and track the number of repetitions. As with other camera based systems, the markers can easily be occluded and the cameras require sufficient free space around the user thus limiting the type of physiotherapy exercises that can be monitored. In this paper we present our visualization system that is capable of capturing finer motor movements without space constraints for two rehabilitation scenarios i.e. falls prevention and knee replacement rehabilitation.

Technology

We organized a series of user design workshops actively involving older adults in the initial design of the visualization tools [START_REF] Uzor | Identifying barriers to effective user interaction with rehabilitation tools in the home[END_REF], [START_REF] Uzor | Senior designers: empowering seniors to design enjoyable falls rehabilitation tools[END_REF]. We also consulted falls experts and physiotherapists in order to obtain their opinions on the factors to consider in the delivery of useful feedback and advice to fallers and knee replacement patients undergoing home rehabilitation. It was important for us to identify the way in which the visualizations could improve the rehabilitation process, as well as the challenges that elderly users may have when using them and the novel technology. In this section, we describe the visualization tools and technologies that were evaluated.

Inertial Sensors

Fig. 1. The inertial motion sensor

We developed inertial sensors that could be easily worn by the users. An orientation sensor fusion algorithm was implemented using the embedded C language, to trans-late the readings of the individual inertial sensor components (accelerometer, a rate gyroscope and a magnetometer) and output the orientation of the sensor in world space. While the accelerometer and gyroscope were needed to calculate the 3dimensional orientation of the sensor, the magnetometer was included to reduce the effects of 'sensor drift' (i.e. the gradual wandering of gyroscope values over time) on the accuracy of the readings. The sensor data is sent wirelessly to a data receiver attached to a computer that uses the data to feedback user movements through the visualization software. Other significant features of the sensors included: a large switch to make it easy for elderly users to switch the sensor on, and a bright LED light to let them know when it was switched on.

Visualization Tools (VT)

For this research, two variations of the visualization tool were developed for each of the musculoskeletal conditions being investigated because the main requirements for both were different. At a base level, however, the visualization tools for both falls and knee replacement were somewhat similar e.g. they were both designed to provide visual feedback to users during home exercise based on the individual requirements of the various conditions. These requirements are highlighted in Table 1. The software was written in C++, QT (to allow for flexible scripting) and Ogre (a 3D animation engine) and at the base level displays movement information using a stick figure, as well as other text based information [START_REF] Uzor | Senior designers: empowering seniors to design enjoyable falls rehabilitation tools[END_REF][START_REF] Loudon | Developing visualisation software for rehabilitation: Investigating the requirements of patients, therapists and the rehabilitation process[END_REF]. Our initial discussions with falls experts revealed that fallers vary widely in their ability to do the exercises prescribed. Therefore, they advised that the users should be able to do the exercises based on their individual abilities, as they would still be able to improve their muscle strength and balance. For this reason, the falls VT did not include visual targets for range of motion. Instead, the users were encouraged to compare their movements as shown by the user mannequin to the guide mannequin in order to ensure that they did the movements correctly (Fig 2). We required a minimum of 6 sensors to animate the human model accurately for falls, as each major body segment tracked required a sensor. Whenever possible we try to minimize the number of sensors a user must wear, however six was the minimum number of sensors needed in order to capture and then visualize the user's movement in a usable way for the end user for falls. These sensors were strapped to the legs, chest, and pelvis in order to provide the feedback necessary to show the correct movements for all of the exercises. Navigation around the software was done through the use of keyboard presses only (key '1' was used to exit to the main menu; key '2' to go back to a previous exercise or skip instructions; and key '3' to go to the next exercise). Keyboard sticker labels were placed on these keys in order to make it easier to find these keys.

Table 1. Visualization Tool (VT) Requirements

Requirement

Falls Rehabilitation Visualization Tool

Knee Replacement Visualization Tool

The aims of knee replacement rehabilitation are to recover as full a range of motion as possible for the replaced joint and recover muscle strength. Following discussions with orthopaedic surgeons and physiotherapists, we therefore included targets for the users to achieve in the knee replacement VT. However, an overlaid ghost movement was not used because it could give rise to a situation whereby a user in the early stages of recovery could over extend or flex while trying to keep up with the range of movement and pace which can lead to injury. Another unique feature of the knee rehabilitation VT is that it gives real-time feedback to only the operated leg although the whole body is shownto provide guidance on correct posture. This focus on the operated leg allows us to reduce the number of sensors needed to twoone above and one below the knee. This allows for an easier setup in the home. A graphic with a gradient of colors (red to green) was included to show the users the range of motion achieved during each repetition: a deep green represented the recommended range of movement; a light green represented an 'almost there' range; a yellow indicated a minimum range and a red indicated a poor range. For instance, Fig. 3 shows a typical visual feedback. The colored repetition icons were also included to show how well each repetition was done. To keep a user motivated, messages such as "Well done, you've done 10, try to keep going to 15" is shown under the repetition counter. Unlike the falls VT, we opted for a simpler way to show the guide mannequin by making it show only when the user needs it. This way we reduced the cluster on the screen. The users interacted with the knee replacement VT using a remote control similar to a TV remote to facilitate ease of use. The visualization buttons and options were mapped to single numeric keys on the remote control to ensure that the VT can easily be manipulated from a comfortable position. The color-coded bar chart shown in Fig. 4. shows the quality of the repetitions recorded. This way, the user and the Allied Health Profession (AHP) could tell how much progress they had made with each exercise in terms of the ability to move the affected joint and the average number of repetitions completed per week. Both the target user and the AHP participants in our design workshops suggested that progress should be shown on a weekly basis rather than a daily basis because not every exercise session will show progress. AHPs will have remote access to VT midway into the rehabilitation period (clinical follow up) and if there is consistent deterioration in performance or number of repetitions, then urgent medical attention will be provided.

Methodology

Four usability studies were carried out with fallers and former knee replacement patients in the laboratory and in the homein order to answer the following research questions:

 How easy is it for the users to use the motion sensors (strapping on and operating)?  Does the use of visualizations enable the user to perform the rehabilitation exercises more correctly in comparison to the standard care exercise booklets?  Are these visualization tools acceptable and usable by seniors?

The laboratory studies were undertaken first because we could control the environment e.g. setup, layout, interruptions and other health and safety variables. Once we had undertaken the laboratory studies and had eliminated any design issues that caused the users concerns we proceeded to the home studies.

Participants

University ethics was obtained for the studies. We recruited seniors aged 60 years and above for all four of the usability studies. Some of the participants were recruited by telephone, or had attended the previous design workshops we had undertaken one year before. Written consent was obtained from each of our participants. For the knee replacement studies, all of the users had their knee replaced in the past 18 months. For the falls studies, the participants had all had at least one fall in the12 months prior to the usability studies. Their educational backgrounds were varied and so was their experience with computerse.g. out of the 11 participants, 3 had never used a computer. Table 2 shows the distribution of participants.

Procedure

In the laboratory studies, the furniture was arranged in the laboratory to simulate a home environment with all the items necessary to carry out home exercisesa table to place a television and a laptop computer on; and a chair to do the exercises with (Fig 5). The participants were encouraged to think aloud while doing the tasks given. The second sets of studies were then carried out in users' homes in order to evaluate these visualization tools in their intended environment (Fig 6).

Fig. 6. Home A participant using the Knee VT

In both the falls and knee replacement studies, we used a within-subjects design because we believed that using the same participant to test the usability of both the exercise booklet and visualization would produce a more accurate comparison as each of the participants would have experienced the two types of rehabilitation aid first hand. Another merit of the within subject test design is that we can maximize the potential of our outcomes given the small number of participants.

The main procedure for the studies was divided into phases, each containing tasks, which were intended to investigate various aspects of the use of both standard care as well as the visualization tools. These phases are shown in tables 3 and 4 below:

Table 3. Main phases in the Falls studies

Phases

Procedure Phase 1

Participants were asked to perform 3 exercises using the booklets (the exercises were the same for all of the participants) Phase 2

Participants were asked to put on the sensors using instructions from the visualization tool only Phase 3

Participants were asked to perform 3 exercises using the visualization tool (the same exercises done in phase 1) Participants were asked to perform 3 exercises using either the booklet or visualization (the exercises were different for all of the participants) Phase 2a

A short training session was provided to the participants on how to use the visualization tool Phase 2b

Participants were asked to put on the sensors using instructions from the training, user manual or the visualization tool Phase 3

The participants were asked to perform 3 exercises using the visualization or the booklet (same exercises done in Phase 1 but with a different tool).

Given the factors above, a qualitative and quantitative approach was used to develop the procedure involving the different tasks and short breaks were given at the end of each phaseeach phase lasted between 10 and 20 minutes. At the end of each phase, participants were asked to complete short questionnaires, and semi-structured interviews on the tasks undertaken.

In phase 1, the participants were asked to do a few exercises with the booklet, while being observed. Two exercise booklets commonly used for home rehabilitation were used: a) The 'Age UK' exercise booklet for the falls studies [START_REF]Preventing Falls: Strength and balance exercises for healthy ageing[END_REF] and b) The Joint Pathways knee rehabilitation exercise booklet for the knee replacement studies [START_REF]JointPathways™ Patient Guides for Knees[END_REF]. In phase 2, the participants were asked to follow instructions on the screen while they strapped the sensors onto the various limb segments. We wanted to investigate how easy the task was for them, as well as how well the instructions described the management of these sensors. We also noted how long it took them to put on the sen-sors. In phase 3, the participants were asked to do some exercises with the visualization tool, and provide feedback on their experiences with these tools.

The sensor calibration procedure used in the falls studies required the users to stand upright for 5 seconds before each exercise. An extra 'training' phase was included in the knee replacement studies because there was a more complex sensor calibration procedure usedthan the one used in the falls studies -this was because for knee replacement we need a reference angle to provide accurate feedback on the knee's range of movement. The calibration procedure included putting a foam wedge with a known angle under the knee.

In the falls studies, the participants did the exercises with the booklet first before using the visualization tool. There were two main reasons for thisfirst, the participants had all used a booklet in the past for falls rehabilitation. Secondly, it was expected that because the visualization tool contained animated movements that demonstrated recommended paceunlike the bookletusing it before the booklet could affect the way the participants carried out an exercise using the booklet. As regards the participants in the knee replacement studies not all of them had used the knee replacement booklet in the past. Therefore, to minimize the potential transfer of learning by using either the exercise booklet or visualization first, the order of the use of the two tools was randomized among the participants with 3 of the participants using the booklet first while the other 3 used the visualization tool first.

Key Observations and Findings

In both the falls and knee studies, a facilitator closely observed the participant as the participant carried out the tasks in the various phases. In addition we took notes and timed the users during the tasks. In this section, we report on our quantitative and qualitative findings for both the home and laboratory tests because the results were broadly similar.

Performance of Rehabilitation Tools

Falls Rehabilitation.

Fig. 7. Average Repetition-pace for the Knee Bends exercise

We observed that with the standard exercise booklet the participants performed the repetitions in each exercise at a quick, but roughly uniform pace. With the visualization tool (VT), the repetitions were initially quicker (during the first few repetitions), and then slower and more regular afterwards. Figure 7 shows the difference in average time per repetition for the 'knee bends' exercise. The results were similar for the other exercises, with the participants performing the repetitions more slowly and in a more controlled manner while using the visualization tool. When asked to comment on using the visualization tool for their exercises, the participants' opinions were similar across both the laboratory and home studies. The main responses were that:

1. They tried to follow the movements as shown by the guide mannequin; the result of this was that they started to slow their movements down after a few repetitions. 2. They concentrated on the guide mannequin and not on the user mannequin i.e. the mannequin that showed their own movement, for most of the time. However when we further explored this observation with them, they said they would start to concentrate more on their own movement feedback as their confidence and understanding of the system grows. 3. They liked the ability to see the user mannequin that showed their own movement. 4. They all felt that they would use both the booklet and visualization tool if given the chance, but would use the visualization tool more, as they found the feedback helpful and important to improving their confidence in the exercise program.

Knee Replacement (KR) Rehabilitation.

The findings were similar for the knee studies in terms of quality of movement, with the visualization tool encouraging slower, more controlled movements. Fig. 8 shows the Straight Leg Raise exercise and the results shown here shows a typical result for all of the other exercises tested. One issue that we observed was with the booklet instruction for the Straight Leg Raise, the instruction asks the patient to raise your leg 6 inches. All of the participants had different concepts of how high 6 inches was. We noted that participants P01, P05 and P06 had not used the exercise booklet before and participant P06 couldn't complete the exercise with the visualization tool because there was a software bug in the calibration algorithm. As the participants used the booklet, the exercises were performed faster than the recommended pace except for P03 who did the exercise very slowly because he was very talkative and was distracted by waiting for responses from the facilitator. Furthermore, none of the participants managed to keep the hold time for the exercises and lost count of the number of repetitions completed.

On the other hand, we observed that while using the visualization tool, the participants concentrated on their own movement and tried to achieve the green targets. One of the participants in the knee replacement studies forgot his reading glasses at home however, he was still able to use the tool as large font sizes had been used. Another participant brought the laptop computer closer so it could be seen. However, she commented that the elements on the screen could be seen clearly.

When asked to comment on using the visualization tool for their exercises, the participants' opinions were similar across both the laboratory and home studies. The main responses were that:

1. They liked the color-coded fan concept and thought that it helped them to achieve the correct performance of the exercise. One participant commented: "It is very useful to have fullness of each exercise calibrated by color code". 2. Of particular note is P01 who got the instruction for the straight leg raise exercise wrong and was doing something different. He couldn't get into the green zone. He commented as follows "I'm getting this wrong isn't it? I will show the guide. Oh! I was wrong". He was able to correct this without any cue from the facilitator when he viewed the guide mannequin.

When asked, "

To what degree did the visual feedback help you to perform the rehabilitation exercises?" 5 out of the 6 participants found it very helpful and one participant found it moderately helpful. A typical comment received was "This is a big help because you don't count seconds when doing the static quad on your own. Sometimes you wait too long or too short". 4. All of the participants successfully accessed the progress charts. See Fig. 4. When the participants were asked, "To what degree do you think the progress charts will help you during your home rehabilitation?" Using a Likert scale of 1 -5 with 1 being 'Not helpful' and 5 being 'very helpful'. 2 out of 3 participants said 'very helpful' and 1 participant said 'helpful'. One participant commented, "It is very important to stimulate motivation to continue at an appropriate level". All of the participants found the charts very easy to interpret.

Evaluation of the Sensors

We took into account that the number of sensors required for the falls and knee replacement visualization tools are 6 and 2 respectively. We asked the participants to put on the sensors using the instructions provided on the screen. They were also asked to repeat this task after five minutes (in order to see how well they could remember to put on the sensors on the second attempt). Most of the participants were able to put the sensors on correctly on the first and second attempt. Some of the participants in both falls and knee replacement studies put the first sensor on the wrong way (upside down). However, they corrected this when they proceeded to the exercise session and saw a reminder to make sure that the switch was facing upwards, and that they could see the red LED light. When asked to rate how easy or difficult this task was, 5 of the participants said it was very easy and 4 were confident that they could set up the visualization tools on their own in the home. It should be noted (see Figure 2) that the sensors had been labeled and had to be worn on the front of specific limb segments with the switch facing up. When asked about "how comfortable it is to wear the sensors", all the participants said the sensors were very comfortable to wear for long periods. All the participants also said they were able to follow the on screen instructions to successfully complete their exercises.

The sensors performed well in both the home and laboratory environment but for one participant in the Knee VT group. The reason was that the calibration algorithm relied on facing the north direction and the participant's living room was facing the East, we have since eliminated the requirement for a participant to face in a particular direction.

Interaction with the Visualization Tools (Keyboard and Remote Control)

We investigated 2 setups; the falls visualization used the computer keyboard to navigate through the different visualization options while the knee replacement visualization tool provided two options the keyboard or a remote control. We introduced the remote control as a controller of the tool because of the limited movement of the users in the early stages after knee replacement surgery. All the participants found navigating the visualization tools using the keyboard easy as the navigation keys were clearly labeled and visible. In the knee replacement studies, the participants preferred the use of the remote control to the keyboard because they didn't have to stand up from the exercise position to operate the tool. All of the participants were able to navigate through the menu items with ease. 6 Discussion

Home exercise (booklet vs. visualization tool)

One of the objectives of the user studies described in this paper was to investigate whether two novel visualization tools could improve the quality of home rehabilitation for falls and knee replacementcompared with the use of standard care. Based on our findings, we identified some issues with the use of booklets (standard care), which makes them less than an ideal solution for effective therapy during rehabilitation.

First, the participants often completed the exercise repetitions too quickly with the booklet. This means that they do not get the therapeutic benefit of a controlled movement. By using the visualization tools, they were able to avoid this problem, as the participants followed the movements as demonstrated by the animated mannequins; and were able to achieve the recommended quality of movement.

Secondly, the participants missed some repetitions with the booklet because they had to rely on their memory to keep track of the repetitions. Both the quality and the quantity of physiotherapy exercises received influence the recovery of function, range of movement and muscle strength. This did not happen when they used the booklet but did happen when they used the visualizations, as they were guided through each repetition and there was a repetition counter.

Thirdly, the visualizations showed the participants their movements during each exercise (something that the booklet cannot do) and this gave them more confidence in the exercise programme.

Fourthly, showing two contrasting animations side by side resulted in the users focusing on one and missing out some frames in the other. This in the rehabilitation context is not a bad thing as long as the most important window is emphasized and held in focus. For the Falls VT, it was the correct movement pattern that was important which the users rightly tried to imitate while for the Knee VT the more important image was bigger than the guide mannequin and had changing color graphics that users held in focus. The ability to turn off the guide mannequin was also a useful future that helped users concentrate on a particular window.

Fifthly, the ability to see progress over time was considered a major motivating factor in continuing with the home exercise programme. In the past, the people had used subjective means to measure their progresse.g. amount of pain in the joint, the ability to stand up quicker, completion of exercise diaries, etc. However, these are subjective and cannot easily be tracked over time. Having objective information about progress over time could provide insights into the effectiveness of standard physiotherapy exercises. In addition, anxiety regarding recovery could be reduced if a user could objectively see that they are capable of greater movement.

Usability of Visualization Tool

Our findings suggest that seniors are capable and able to use technology for their home rehabilitation. In this section we highlight some of the design issues found during our studies and how these could contribute to our understanding of the issues surrounding acceptance of technology for rehabilitation in the home. Convenience and ease of setup: most seniors are used to operating technologies like the television. Using this metaphor in the development of home rehabilitation technology enabled seniors to feel more confident in their abilities to use a new technology. An acceptable technology should take only a couple of minutes to start and the menu easily accessible via limited numeric and arrow keys. The majority of the participants were able to set up the exercise sessions and correctly calibrate the sensors using the instructions in the visualization tools.

Initial Training and clear onscreen Instructions: An initial training session in the home environment that includes a practical walkthrough of how to use a new visualization technology increases the likelihood of its acceptance. Furthermore, because some seniors are not familiar with some technical jargon such as USB these terms should be avoided. If these terms are to be used in such a tool, it should be explained in a straightforward way so that the users understand it better. Memory is known to decline with increasing age. Therefore, it is important to provide instructions that are able to give the users the right information as soon as possible.

Accessibility: It was important for us to ensure that the visualizations were clear and visible, taking into account eyesight problemswhich are common in the elderly population. As highlighted in the findings, the use of larger font sizes, blank spacing, red, yellow and green colors in close proximity was well received -seniors appreciate bright and vibrant colors most especially when it provides information about correct performance of an objective.

Conclusion and Future work

The main function of musculoskeletal rehabilitation exercises is to recover impaired motor function in muscles and joints in the lower body. In the home setting, the lack of adherence to rehabilitation could have serious implications for the health and independence of seniors. Furthermore, if the recommended quality of motion (range and pace of movement) is not observed for these exercises, the seniors will probably not obtain the full recovery benefits offered by the rehabilitation programme(s). In this work, we evaluated two novel visualization tools with fallers and knee replacement patients; and compared the use of these tools to standard rehabilitation care (booklets) in the laboratory and in the home. One of the main objectives of this research was to investigate how useful the visualization tools were (versus standard care) in encouraging the recommended quality of motion for the exercisesthereby promoting the maximum therapeutic value of these exercises.

Based on our findings we argue that by using booklets to exercise, seniors may not observe the recommended quality of movement. The main findings supporting this are a) the inability to observe the correct pace of movement from static diagrams and b) the seniors could not tell whether they were doing the exercises the correct way. By using the visualization tools, the seniors were able to overcome these limitations, thereby getting the most out of the exercises from a therapeutic standpoint. The seniors felt that the ability to observe the correct movementsas well as receive feedback on their movements and progressduring rehabilitation was essential to increasing their confidence and motivation to exercise. Furthermore, based on the feedback from our participants, these visualization tools were easy to use and acceptable for home rehabilitation use. Another objective of this study was to investigate the usability of the body-worn sensors necessary to interact with the visualization tools. Our findings suggest that the seniors found the sensors easy to use and that they were confident in their ability to use and manage (e.g. placement on the body, charging, etc.) them without the assistance of a professional.

The study results are limited by the number of participants and the amount of time that the participants had to interact with the visualization tools. The effectiveness of these visualization tools in improving adherence to home rehabilitation programmes over an extended period of time still needs to be assessed. This is the basis for our future work, as we are now deploying these tools in home based pilot randomized controlled studies for 6 -12 weeks.

Solution provided by the VT 1 .

 1 Show the user how and where on the body the sensors should be placed Diagrams and text instructions showing the users the correct procedure 2. Show the user how the exercise should be done (emphasize quality of motion) a. An animated 'guide mannequin' highlighting the correct pace and range of motion for each exercise b. Text-based instructions describing important advice about each exercise 3. Show the user how many repetitions have been achieved during exercise A text-based repetition counter showing the number of repetitions done, and how many more to do 4. Feedback to the user on their own performance during exercise a. A user mannequin showing the users' movements as captured by the inertial sensors b. A colored graphic showing the quality of each range of movement while the user moves the affected leg (knee VT only) c. A colored icon for each repetition showing how well each repetition was done (knee VT only) 5. Show a chart of weekly progress Charts showing the average number of completed exercises and the quality of the range of motion associated with the exercises (knee VT only)

Fig. 2 .

 2 Fig. 2. Falls Visualization Tool: Knee Bend Exercise. Guide mannequin on the left and real time visual feedback on the right

Fig. 3 .

 3 Fig. 3. Knee Replacement Visualization Tool: Knee Flexion Exercise. Guide mannequin in inset and real time visual feedback in the background

Fig. 4 .

 4 Fig. 4. Knee Visualization Tool: Weekly Progress Charts for Inner Range Quad Exercise

Fig. 5 .

 5 Fig. 5. Laboratory Setup: A participant using the Fallers VT for an exercise requiring the use of a support

Fig. 8 .

 8 Fig. 8. Average pace for the Straight leg raise exercise

Table 2 .

 2 Distribution of Participants

	Group	Laboratory	Home
	Fallers	3 participant (1 female, 2 males,	2 participant (1 female, 1 male,
		mean age 68)	mean age 79)
	Knee Replacements	3 participants (3 males, mean	3 participants (1 female, 2 males,
		age 71)	mean age 63)

Table 4 .

 4 Main phases in the Knee Replacement studies

	Phases	Procedure
	Phase 1

Acknowledgements. Funding for this study comes from the Medical Research Council, UK, LLHW (Phase 2), Grant ID: 91021.