A Saadé

F Gabrielli

S Paganelli

P Pudlo

M Lempereur

O Rémy-Néris

The influence of an arm sling on sit-to-stand of hemiplegic subjects

Keywords: sit-to-stand, handgrip, hemiplegia, asymmetry, inverse dynamic

Introduction

Arm sling is often recommended to hemiplegic patients to protect their paretic limb, but is not always mandatory, for example when the patient has some remaining control over the paretic limb. In this case, the paretic limb remains available for balance.

It might be relevant to investigate whether the arm sling is a real benefit for the patient. For example, this is not the case for gait, as the suppression of arm swing, by the mean of crossing the arms on the chest, has been proven to be unhelpful [START_REF] Ortega | Effects of aging and arm swing on the metabolic cost of stability in human walking[END_REF][START_REF] Umberger | Effects of suppressing arm swing on kinematics, kinetics, and energetics of human walking[END_REF]. But, what about other daily activities? Among them, the sit-to-stand (STS) task is one of the most frequent tasks related to walking abilities. The STS can be realized with a handgrip to ease the task and allow more patients to successfully stand.

The purpose of this study was to investigate the impact of an arm sling on the STS task, when realized with a handgrip. The study is placed within Bobath concept, also known as neurodevelopmental treatment [START_REF] Seneviratne | Neurodevelopmental treatment and stroke rehabilitation: a critique and extension for neuroscience nursing practice[END_REF]. Following that concept, any assistive technique or device will be considered positively if the patient's behaviour gets closer to standard subject. Knee joints seem a wise spot to investigate the influence of arm sling on STS, as already done for gait [START_REF] Umberger | Effects of suppressing arm swing on kinematics, kinetics, and energetics of human walking[END_REF]. As hemiplegia is an asymmetric motor deficiency by nature, the impact of arm sling will be evaluated on the asymmetry of the STS task, based on knee joint moments and compared to a reference population.

Methods

The tested population was composed of eighteen healthy subjects (15 male and 3 female) and nine right hemiplegic subjects (5 male and 4 female) with remaining control over their paretic upper limb. Healthy subjects' age, body mass and height were 24 (±5) years, 72 (±11) kg and 173 (±5) cm, respectively (mean ± std). Hemiplegic subjects' age, body mass, height and functional independence measure (score for a non disabled: 127) were, respectively, 72 (±10) years, 82 (±14) kg, 169 (±7) cm and 111 (±5). A specifically designed device was built for experimentation, based on a handgrip and a chair, both adjustable in height and distance. The chair height was set, respectively, to 120% of subject's shank length and the chair-handgrip distance in a way that the subjects sat comfortably straight with the left hand on the handgrip. All subjects performed STS task with and without arm sling. The arm sling was used to immobilize the right upper limb. For both STS conditions (arm free and arm immobilized by an arm sling), subjects rose from their initial sitting position to an upright position using the handgrip, at a free speed.

The motion of the subjects was recorded using a VICON system. Two force plates, one for each foot, were used to measure the external contact loads between the subject and the floor. Reflective markers were placed on anatomical landmarks, following the ISB recommendations. External loads and inertial parameters (de Leva 1996) were used for computation of joint moments using inverse dynamics [START_REF] Doriot | Analyse tridimensionnelle du membre inférieur durant la phase d'appui de la marche [A three-dimensional study of the lower limb during the stance phase of gait[END_REF] on the left and right lower limb open chains (foot, shank and thigh), and moments were normalized by body mass.

Asymmetry of task was given by the absolute difference between the sagittal maximal knee joint moments of both lower limbs. A statistical non-parametric test -Wilcoxon -was used to determine the significance of the studied variable between the two performances of one group (hemiplegic or healthy). Another statistical test -Mann-Whitney -was used to determine the significance of the studied variable between the hemiplegic and the healthy group.

1/2 joint. Thirdly, knee joint was preferred because it showed the largest difference during previous studies on the influence of arm swing in gait [START_REF] Umberger | Effects of suppressing arm swing on kinematics, kinetics, and energetics of human walking[END_REF]. Some other joint moments or kinematic variable might have complementary information for describing the biomechanical effects of arm sling.

Conclusions

Influence of arm sling on STS task for hemiplegic subjects was investigated on the basis on Bobath concept. By immobilizing the upper limb with an arm sling, the STS task realized by hemiplegic subjects did not get closer to the behaviour of standard subjects, and went against Bobath concept, indicating an unhelpful technique. Moreover, if the symmetry of the movement seems a characteristic of the normal STS, the asymmetry observed in hemiplegic subjects might be a compromise between their remaining abilities and the biomechanical requirements of the task. Future works will investigate the relationship between asymmetry and other biomechanical parameters in STS. It might also be interesting to highlight the influence of an arm sling on daily activities.

Results and discussion

Figure 1 shows that the use of an arm sling for hemiplegic subjects increased the asymmetry between the two knees by an average of 37% (p = 0.004), whereas the use of the same accessory for healthy subjects, did not significantly increase the asymmetry (p = 0.76). Also, between the two groups (healthy and hemiplegic), no significant difference was found when an arm sling was not used, whereas a significant difference was found when an arm sling was used (p < 005).

Our results show that the asymmetry was influenced by the presence of an arm sling only for hemiplegic subjects. This is coherent with previous observations from the literature: from STS studies, it has been shown that subjects swung more their arms at lower seat heights [START_REF] Mazzã | Association between subject functional status, seat height, and movement strategy in sit-to-stand performance[END_REF], and that STS become a more demanding task also at lower seat heights [START_REF] Roy | The effect of foot position and chair height on the asymmetry of vertical forces during sit-to-stand and stand-to-sit tasks in individuals with hemiparesis[END_REF]). Therefore, it seems to be a link between STS task difficulty, such as done by hemiplegic subjects, and arm swing. In this study, the arm swing being blocked by the arm sling, hemiplegic subjects were hindered, as shown by a STS task more asymmetric. Now, this study has some limitations. Firstly, results are limited by the low number of subjects who participated in the study (18 healthy and 9 hemiplegic subjects) and the lack of anthropometric match between the two groups, preventing inter group comparison. Secondly, the chosen asymmetry indicator is built from maximal joint moments and hides any chronological interpretation. This was preferred to an averaged torque, for example because not only it hides chronological aspect but also it levels any peak torque that brings an indicator of internal stress in the

Figure 1 .

 1 Figure 1. absolute difference between knee joint moments, normalized to body mass (n m/kg), during sts without and with arm sling. White: right hemiplegic subjects; grey: healthy subjects. *p < 0.05; **p < 0.01.

Acknowledgements

This work was supported by the French National Research Agency [ANR-12-TECS-0001].


Laguerre Audrey

Helen Fisher

Etain Bruno

M Ary É Alexandre

Caroline Soussy

Sz Ke Ö Andreï

Leboyer Marion

Franck Sch

Self-reported childhood trauma correlates with schizotypal measures in schizophrenia but not bipolar pedigrees Sch rhoff ü

Background

Strong evidence supports the association between childhood trauma and psychotic disorders. In two different high-risk populations, we looked for a correlation between the magnitude of schizotypal dimensions and the importance of self-reported childhood trauma.

Methods

A sample of 138 unaffected first-degree relatives was recruited (67 relatives of schizophrenic probands and 71 relatives of bipolar probands). The relationship between schizotypal dimensions and childhood trauma scores was analyzed by partial correlations.

Results

A positive correlation was found between childhood trauma scores and total schizotypal scores in first-degree relatives of schizophrenic subjects but not in first-degree relatives of bipolar probands. This correlation was primarily due to a strong association with the positive dimension of schizotypy.

Conclusions

The significant correlation between childhood trauma and schizotypal dimensions in subjects at high genetic risk for schizophrenia suggests that susceptibility genes for schizophrenia may interact with childhood trauma to induce the emergence of schizotypal dimensions, mainly positive psychotic features. ' " Moffitt et al., 2005 of sensitivity to environmental factors, or as the environmental control of gene expression ( ). Several recent studies Kendler & Eaves, 1986

Introduction

Among the several explanations invoked to explain failures to find susceptibility genes, gene-environment interaction (GxE) suggests that " ignoring nurture may have handicapped the field s ability to understand nature (

). GxE can be defined as the genetic control demonstrated that the GxE approach can be of practical benefit as a tool in the search for genes connected with mental disorders (Kahn et al., ; , ;

). 2003 [START_REF] Caspi | Influence of life stress on depression: moderation by a polymorphism in the 5-HTT gene[END_REF]2005[START_REF] Kendler | The interaction of stressful life events and a serotonin transporter polymorphism in the prediction of episodes of major depression[END_REF] Childhood trauma has been repeatedly associated with psychotic features not only in schizophrenia (for review, see

) but Read et al., 2005 also in bipolar disorders ( ; ) and schizotypy ( ; ). Therefore, [START_REF] Hammersley | Childhood trauma and hallucinations in bipolar affective disorder: preliminary investigation[END_REF][START_REF] Neria | Assaultive trauma and illness course in psychotic bipolar disorder: findings from the Suffolk country mental health project[END_REF][START_REF] Yen | Traumatic exposure and posttraumatic stress disorder in borderline, schizotypal, avoidant, and obsessive-compulsive personality disorders: findings from the collaborative longitudinal personality disorders study[END_REF][START_REF] Berenbaum | Psychological trauma and schizotypal symptoms[END_REF] childhood trauma may be a good candidate environmental risk factor for psychotic disorders. Schizotypy is a multidimensional construct that represents a mild imitation of the symptoms of schizophrenia ( ). Although schizotypy is the core feature of [START_REF] Vollema | Neurocognitive correlates of schizotypy in first degree relatives of schizophrenia patients[END_REF] schizotypal personality disorder, it is thought to be a continuous or dimensional, rather a categorical construct (

). Schizotypal [START_REF] Irwin | The relationship between dissociative tendencies and schizotypy: an artefact of childhood trauma?[END_REF] dimensions have been described as a potential intermediate phenotype for both schizophrenia and bipolar disorders and could be the consequence of a gene-environment interaction. This association is difficult to examine prior to the identification of disease genes. The study of a population at high genetic risk which carries several unknown genes related to the disorder, may improve the possibility of identifying " " environmental risk factors. This approach may be more appropriate than studying the interaction between an environmental factor and a specific candidate gene. Studying the impact of childhood trauma on schizotypal dimensions among unaffected relatives has several advantages. Firstly, dimensional models of psychosis (positive, negative and disorganized symptoms) are becoming established as conceptually and clinically useful ( ). Secondly, first-degree relatives are free from the multiple artifacts that potentially confound research [START_REF] Van Os | A comparison of the utility of dimensional and categorical representations of psychosis. UK 700 group[END_REF] in schizophrenia, including the effects of long-term and usually ongoing medication treatment, multiple hospitalizations or institutionalization, and prolonged functional impairment secondary to chronic disease and social deterioration.

We investigated whether childhood trauma is correlated with the phenotypic expression of schizotypyal dimensions (positive, negative and disorganized) in two different populations of unaffected first-degree relatives. We hypothesized that the correlation between childhood trauma and schizotypal dimensions could be different among these two high-risk populations.

Materials and methods

Subjects

Consecutively admitted probands meeting DSM-IV criteria for bipolar disorder or schizophrenia were recruited from a university-affiliated hospital (Psychiatry department, Paris XII University). Their unaffected first-degree relatives were contacted and asked to participate in the study. Relatives were interviewed with the French version of the Diagnostic interview of Genetic Studies (DIGS) ( ; [START_REF] Nurnberger | Diagnostic interview for genetic studies. Rationale, unique features, and training. NIMH Genetics Initiative[END_REF] ) to confirm the absence of diagnosis of schizophrenia or bipolar disorders. We used the validated French translation ( Preisig et al., 1999 Dumas ) of the self-rating Schizotypal Personality Questionnnaire (SPQ) ( ), to measure schizotypal dimensions in the two et [START_REF] Dumas | Validation of the French version of the Raine Schizotypal Personality Questionnaire categorical and dimensional approach to schizotypal personality traits in a normal student population[END_REF]al., Raine, 1991 different groups of first-degree relatives. This questionnaire contains 74 items with yes/no answers and identifies the three classical dimensions of psychosis (positive, negative and disorganized). The SPQ can be used in the general population to identify individual differences in schizotypal dimensions.

Subjects also completed the French translation ( ) of the Childhood Trauma Questionnaire (CTQ) [START_REF] Paquette | Validation of the French version of the CTQ and prevalence of the history of maltreatment[END_REF] Bernstein & Fink,

), a 28-item self-report questionnaire, which gives scores for physical, emotional and sexual abuse, physical and emotional neglect, and a 1998 total weighted score.

The Research Ethics Board reviewed and approved the study. After completely describing the study, written informed consent was obtained from all participants.

Data analysis

Differences between groups were tested using a two-tailed t-test for continuous variables and a chi-squared test for discrete variables.

The relationships between schizotypal dimensions and CTQ scores were analyzed by partial correlation to control for the potential confounding influences of sex and age. Sex was used as covariable because of its influence on both CTQ and SPQ scores ( ; [START_REF] Paquette | Validation of the French version of the CTQ and prevalence of the history of maltreatment[END_REF] ). Age at interview was also used as a covariable because some studies have observed a negative correlation between age of [START_REF] Dumas | Validation of the French version of the Raine Schizotypal Personality Questionnaire categorical and dimensional approach to schizotypal personality traits in a normal student population[END_REF] the subjects and scores for the SPQ scale and sub-scales ( ; ). To limit the risk of type I error due to [START_REF] Venables | The structure of schizotypy, its relation to subdiagnoses of schizophrenia and to sex and age[END_REF][START_REF] Mata | Schizotypal Personality Questionnaire-Brief: factor structure and influence of sex and age in a nonclinical population[END_REF] multiple statistical tests, we examined only the total score of the CTQ, and we used Bonferroni procedure to establish the significance threshold (p < 0.05 divided by 12 statistical analyses; we retained p < 0.004). We also analyzed the variables dichotomously and calculated odds ratios and 95 confidence intervals (CI) for schizotypy given childhood trauma in the two populations of relatives. To do that, we determined the % presence or absence of childhood trauma according to the cut-off of the French validation of the CTQ. The cut-off for the schizotypal dimensions was determined as the mean score of the SPQ full-score for the whole sample.

Results

The study group was composed of 67 first-degree relatives of schizophrenic probands (31men and 36 women, mean age (SD) 54.2 (15.4) = years) and 71 first-degree relatives of bipolar probands (37 men and 34 women, mean age (SD) 53.1 (15) years). The sex ratio ( 2 0.47, p = χ = = 0.49) and the age at interview (t 0.43, p 0.67) did not differ between groups. The samples of first-degree relatives are composed of different

= =
types of relatives. In the two samples of relatives, the majority of the relatives are parents of the proband with an over-representation of parents in the sample of first-degree relatives of schizophrenic subjects (80.5 vs 59.2 ). The highest completed school grade (education level) was % % recorded, according to usual conventions ( ) as a trichotomous variable (1 elementary school; 3 at least high school [START_REF] Pichot | L estimatin du niveau intellectuel pr morbide la WAIS-R. Comparaison entre la m thode de Barona et l Index de psychosis proneness[END_REF] completed; 2 intermediate between 1 and 3). However, we finally decided to pool the first two levels together because level 1 was infrequent = in all groups. The two samples did not differ in terms of educational level (p 0.40). In the sample of schizophrenic relatives: the mean SPQ = scores (full-scale and for the positive, negative and disorganized dimensions) were 10.2 7.9; 3.9 3.8; 4.7 4.4 and 1.6 1.7 respectively;

+ + + +
the mean CTQ score was 38.6 8.5. In the sample of bipolar relatives: the mean SPQ scores (full-scale and for the positive, negative and + disorganized dimensions) were 9.6 7.5; 3.3 3.4; 4.3 4.7 and 1.9 2 respectively; the mean CTQ score was 39.3 9.8. The SPQ full-score

+ + + + +
and the CTQ score did not differ between the two groups (SPQ full-score: p 0.73 and CTQ full-score: p 0.95). The mean CTQ and SPQ

= =
scores were similar between males and females (p 0.58 and p 0.77, respectively). In the whole sample of relatives, we found a significant

= =
positive correlation between the CTQ score and the SPQ full-score (r 0.27; p 0.001). This correlation was fully explained by a correlation in

= =
the sample of first-degree relatives of schizophrenic subjects (r 0.43; p < 0.0001), whereas no significant correlation was found in the = first-degree relatives of bipolar probands (r 0.13; p NS). This positive correlation was found with the positive and negative dimensions of

= =
schizotypy (positive schizotypy: r 0.41 and negative schizotypy: r 0.36) but not with the disorganized dimension ( ). We have also

= =
Table 1 investigated partial correlation coefficients between each schizotypal dimension and childhood trauma adjusted for the two other schizotypal dimensions. Only the correlation between positive dimension and childhood trauma remains significant.

Based on a dichotomous approach, the calculation of the odds ratios leads to similar results. The odds of having high schizotypal traits in presence of childhood trauma were higher in the population of schizophrenic relatives (OR 3.6, 95 CI 1.09 11.8 ) than in the population

= % [ - ]
of the bipolar relatives (OR 1.64, 95 CI 0.57 4.72 ), which were not significant.

= % [ - ]

Discussion

We found a significant positive correlation between history of childhood trauma and schizotypal dimensions in unaffected first-degree relatives of schizophrenic subjects but not in relatives of bipolar probands. This correlation was mainly due to a strong association with the positive dimension of psychosis. To our knowledge, this is the first study exploring the influence of an environmental risk factor in two populations with different genetic backgrounds. Even though schizotypy was shown to be elevated in relatives of bipolar subjects (Kety et al.,

;

) suggesting some shared genetic vulnerability factors, the only difference between our two populations is that one 1994 Sch rhoff et al., 2005 ü is at genetic risk for schizophrenia and the other for bipolar disorders. We observed that the impact of childhood trauma on the expression of schizotypal dimensions was strongest among subjects who were at high genetic risk for schizophrenia suggesting that susceptibility genes specific to schizophrenia may interact with childhood trauma to induce the emergence of schizotypal dimensions, mainly positive psychotic features. This is in accordance with several previous reports from the literature (for review, see

) showing a high influence of Read et al., 2005 childhood trauma on positive dimension in schizophrenia and schizotypy. In line with our results, using a follow-up design, Spauwen et al.

found an association between self-reported trauma and psychosis proneness. The strength of the association increased with a narrower (2006) psychosis definition. These authors have speculated that extended exposure to trauma may increase the risk for positive symptoms through direct effects on dopamine function. Along similar lines, have suggested that early, prolonged, and severe traumas increase Read et al. (2005) the risk for later positive symptoms through lasting on the hypothalamic-pituitary-adrenal axis. Even if associations between negative dimension and childhood trauma have been previously reported ( ), this association is more difficult to Resnick et al., 2003[START_REF] Lysaker | Childhood sexual trauma and psychosocial functioning in adults with schizophrenia[END_REF] interpret. A plausible explanation is that traumatic avoidance, emotional numbing and reduced responsiveness may resemble negative dimension and may be interpreted as a reaction to the trauma. Conversely, in rodents and nonhuman primates, trauma (for example, forced swim test) has been used as a model of the negative symptoms of schizophrenia such as flattening of affect and avolition (

). [START_REF] Corbett | Animal models of negative symptoms: M100907 antagonizes PCP-induced immobility in a forced swim test in mice[END_REF] Concerning the disorganized dimension, as in previous studies, we did not show any correlation with childhood trauma ( ; Read & Argyle, 1999

). However, this could be also explained by the small variation of this dimension. Our study could be considered as an [START_REF] Hammersley | Childhood trauma and hallucinations in bipolar affective disorder: preliminary investigation[END_REF] example of how an environmental factor interacting with specific susceptibility genes can influence susceptibility to a disorder or to a particular dimension of a disorder. Our results can suggest that the same dimensions have different genetic background in bipolar disorders and schizophrenia. However, there is also a more plausible explanation. The same genes cause susceptibility for a common phenotype in bipolar disorders and schizophrenia, in particular the positive dimension ( ; ). In order to become manifest, this Berretini, 2003Sch rhoff et al., 2003 ü susceptibility needs to interact with some environmental factors. However, other factors, disorder-specific, can exert a protective or permissive role on the action of these environmental factors. For example, traits that have been associated with genetic susceptibility to bipolar disorders (i.e cyclothymic, hyperthymic or depressive temperaments) might have a protective effect on the emergence of positive schizotypal traits in the presence of childhood trauma.

The possibility that susceptibility genes for schizophrenia may increase exposure to childhood trauma can be excluded as rates of childhood trauma were similar among the two groups of relatives. However, because of the design of our study, two alternative hypotheses could be proposed. Indeed, our results could also be explained by shared family environmental factors amongst the schizophrenia relatives rather than genetic factors this could only be ruled out by employing an adoption study design. In other words, the childhood trauma could be a proxy for other environmental risks such as social disadvantage or family discord/chaos specific to schizophrenic families. Moreover, due to the retrospective assessment of the childhood trauma, we cannot exclude that subjects reported high level of childhood trauma because they have a high level of schizotypal features. Nevertheless, the fact that no association is found in the relatives of bipolar probands suggests that a bias cannot entirely explain the association found in relatives of schizophrenic subjects between trauma and schizotypal dimensions. It is also interesting to note that despite the fact that relatives tend to be defensive in their response, the use of the SPQ discriminates the two samples of relatives. Overall, our results support the assumption that the clinical expression of the vulnerability induced by environmental risk factors depends on gene-environment interactions. Speculation about the implications of this finding should be guarded until these results are replicated as we cannot formally exclude the possibility that childhood trauma interacted with other specific environmental risk factors.

In conclusion, our findings suggest that susceptibility genes specific to schizophrenia may influence response to pathogenic environments.

It is clear that if a gene s connection to disorder is conditional to the environment, this will have the natural consequence of diminishing ' researchers capacity to detect the association between the gene and disorder. Research to uncover specific environmental risk factors for ' diseases may be more effective if we recruit samples on the basis of their high genetic loading and if we investigate which genes discriminate between exposed individuals who did, versus did not, become ill.

  Fenton BT , Matthey ML , Berney A , Ferrero F 1999; Diagnostic interview for genetic studies (DIGS): inter-rater and test-retest reliability of the French version. European Archives of Psychiatry and Clinical Neuroscience. 249: 174-179 Raine A 1991; The SPQ: a scale for the assessment of schizotypal personality based on DSM-III-R criteria. Schizophrenia Bulletin. 17: 555-564 Read J , Argyle N 1999; Hallucinations, delusions and thought disorders among adult psychiatric inpatients with a history of child abuse. Psychiatry Services. 50: 1467-1472 Read J , Van Os J , Morrison AP , Ross CA 2005; Childhood trauma, psychosis and schizophrenia: a literature review with theoretical and clinical implications. Acta Psychiatrica Scandinavica. 112: 330-350 Resnick S , Bond G , Mueser K 2003; Trauma and PTSD in people with schizophrenia. Journal of Abnormal Psychology. 112: 415-423 Sch rhoff ü F , Sz ke ö A , M ary é A , Bellivier F , Rouillon F , Pauls D , Leboyer M 2003; Familial aggregation of delusional proneness in schizophrenia and bipolar pedigrees. M 2005; Schizotypal dimensions: continuity between schizophrenia and bipolar disorders. Schizophrenia Research. 80: 235-242

Table 1

 1 Correlation matrix for childhood trauma and schizotypal dimensions

	SPQ full-score	Positive	Negative	Disorganized

* p<0.004

Ackowledgements:

This work was supported by grants from the Agence Nationale de la Recherche (Manage-BP), the Fondation pour la Recherche sur le Cerveau,

The RTRS (R seau Th matique Translationel de Recherche et de Soins) and the Institut de la Sant et de la Recherche M dicale (INSERM). The authors would like to thank Marie-Jos De Sousa and Emmanuelle Abadie for their technical assistance. We also thank an anonymous reviewer for é helpful comments.

Footnotes:

Declaration of interest None