Nicolas Vignais

Virtual thrower versus real goalkeeper: The influence of different visual conditions on performance

In order to use virtual reality as a sport analysis tool, we need to be sure that an immersed athlete reacts realistically in a virtual environment. This has been validated for a real handball goalkeeper facing a virtual thrower. However, we currently ignore which visual variables induce a realistic motor behavior of the immersed handball goalkeeper. In this study, we used virtual reality to dissociate the visual information related to the movements of the player from the visual information related to the trajectory of the ball. Thus, the aim is to evaluate the relative influence of these different visual information sources on the goalkeepers motor behavior. We tested 10 handball goalkeepers who had to predict the final position of the virtual ball in the goal when facing the following: only the throwing action of the attacking player (TA condition), only the resulting ball trajectory (BA condition), and both the throwing action of the attacking player and the resulting ball trajectory (TB condition). Here we show that performance was better in the BA and TB conditions, but contrary to expectations, performance was substantially worse in the TA condition. A significant effect of ball landing zone does, however, suggest that the relative importance between visual information from the player and the ball depends on the targeted zone in the goal. In some cases, body-based cues embedded in the throwing actions may have a minor influence on the ball trajectory and vice versa. Kinematics analysis was then combined with these results to determine why such differences occur depending on the ball landing zone and consequently how it can clarify the role of different sources of visual information on the motor behavior of an athlete immersed in a virtual environment.

Biofeedback interventions for people with cerebral palsy: a systematic review protocol

BackgroundCerebral palsy is a life-long disability that affects motor control and activities of daily living. Depending on the type of cerebral palsy, some individuals may have trouble performing tasks with one or both of their arms and/or legs. Different strategies exist to help develop motor capacity. Biofeedback therapy is a commonly applied rehabilitation strategy. In biofeedback therapy, information about the motor behavior while completing a task is given back to the individual to help improve their performance. This can provide valuable information that would otherwise be unknown to the individual. Biofeedback may also have a unique method of operation in clinical populations, such as people with cerebral palsy. Therefore, it is important to identify the most effective mechanisms for specific populations. This review aims to evaluate the effects of biofeedback interventions that have been used towards improving motor performance and motor learning in people with cerebral palsy.MethodsUsing a customized strategy, MEDLINE, CINAHL, Embase, PsycINFO, Cochrane Central Register of Controlled Trials, SCOPUS, SPORTDiscus, and PEDro databases will be searched. Two independent reviewers will screen titles and abstracts, review full texts for inclusion criteria, and extract data from relevant articles using a standardized template. Quality of evidence and risk of bias will be assessed through the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) methodology.DiscussionSeveral studies have investigated biofeedback-based interventions for people with cerebral palsy. However, there is a great variety and limited consensus regarding how to implement biofeedback mechanisms. This systematic review will consolidate the current evidence to direct future study and develop effective biofeedback rehabilitation strategies.Systematic review registrationPROSPERO ID: CRD42016047612

Ergonomic Testing for the Design of an Innovative Mail Delivery Vehicle: A Physical Mock-up Case Study

The aim of this study was to provide ergonomic recommendations concerning passenger compartment dimensions of an innovative vehicle dedicated to mail delivery. To this aim, an ergonomic analysis of egress/ingress postures has been performed on a physical mock-up, which is considered as a reliable tool when investigating driving space. Six workers with different anthropometries participated to the experiment. The influence of three seat heights, two headlining heights and three headlining widths were tested while participants performed a simulated mail delivery task. Based on goniometers and video observations, a Rapid Entire Body Assessment (REBA) was conducted. Perceived discomfort was estimated with a Category Partitioning Scale (CP-50). Results showed that REBA scores were mainly at medium risk (5.18 ± 1.75). Discomfort scores were significantly influenced by seat height (χ2 (2) = 7.79, p = 0.02), especially for short participants when seat height was equal to 760 mm (Z = -2.21, p = 0.03). REBA scores and discomfort scores were significantly higher for the lowest headlining height and the highest headlining width. Outcomes of this study permitted to establish that: the seat height has to be adjustable (between 580 mm and 760 mm), the headlining height has to be fixed to 1360 mm, and the headlining width has to be comprised between 300 and 525 mm. The results from this research suggest that physical mock-up can provide a useful tool for defining suitable dimensions for the design of a future vehicle, taking into account anthropometric characteristics of the target population.

Biofeedback interventions for individuals with cerebral palsy: a systematic review

Abstract Purpose: The purpose of this study is to evaluate the quality of evidence of biofeedback interventions aimed at improving motor activities in people with Cerebral Palsy (CP). Second, to describe the relationship between intervention outcomes and biofeedback characteristics. Methods: Eight databases were searched for rehabilitation interventions that provided external feedback and addressed motor activities. Two reviewers independently assessed and extracted data. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) framework was used to evaluate quality of evidence for outcome measures related to two International Classification of Functioning, Disability and Health (ICF) chapters. Results: Fifty-seven studies were included. There were 53 measures related Activities and Participation and 39 measures related to Body Functions. Strength of evidence was “Positive, Very-Low” due to the high proportion of non-controlled studies and heterogeneity of measures. Overall, 79% of studies and 63% of measures showed improvement post-intervention. Counter to motor learning theory recommendations, most studies provided feedback consistently and concurrently throughout the intervention regardless of the individual’s desire or progress. Conclusion: Heterogeneous interventions and poor study design limit the strength of biofeedback evidence. A thoughtful biofeedback paradigm and standardized outcome toolbox can strengthen the confidence in the effect of biofeedback interventions for improving motor rehabilitation for people with CP. Implications for Rehabilitation Biofeedback can improve motor outcomes for people with Cerebral Palsy. If given too frequently, biofeedback may prevent the client from learning autonomously. Use consistent and concurrent feedback to improve simple/specific motor activities. Use terminal feedback and client-directed feedback to improve more complex/general motor activities.

Analysis of human-exoskeleton interactions: an elbow flexion/extension case study

Human movement may be affected by different motor deficits such as musculoskeletal disorders (MSDs) in an occupational context or hemiplegia/hemiparesis following a stroke. On the one hand, MSDs are mainly situated in the upper limbs and they represent the first occupational disease in Europe at the present time (INRS 2015). They are partly due to awkward postures and muscle efforts in response to high force requirements during a professional task. To decrease MSDs, upper-limb exoskeletons may be employed (Sylla et al. 2014). On the other hand, 130,000 strokes occur each year in France (INSERM 2013). They are responsible for most of the acquired motor disabilities in adults, with hemiplegia and hemiparesis as main consequences. Upper-limb motor control recovery may be improved via assistive technologies like upper limb exoskeleton (Lo & Xie 2012). Despite their theoretical advantages, e.g. gestures repeatability or intensive use for long periods (Lo and Xie 2012), the efficiency of exoskeletons for human motion assistance has not yet been significantly proven (Veerbeek et al. 2017). This weakness may be related to the lack of understanding about how humans interact with an exoskeleton: does the motion differ from the nominal one when the exoskeleton is supposedly ‘transparent’? How do people adapt movement kinematics and muscle activities? Some researchers addressed similar questions in the past, but the motor task concerned complex three dimensional movements with few repetitions and participants, which made difficult to draw definite conclusions (Jarrassé et al. 2008; Jarrassé et al. 2010; Pirondini et al. 2016). In contrast, the present study focused on simple elbow flexions/ extensions performed without and with an exoskeleton (programmed in transparent mode), for different ranges of motion and for several repetitions. 2. Methods

The influence of muscle action on joint loading during dynamic finger pressing tasks in an open-source modelling environment

Assessing finger joint loading is essential to the prevention of work-related musculoskeletal disorders of the hand and fingers. This study aimed to evaluate the effect of muscle action on joint loading during dynamic finger pressing tasks using an open-source musculoskeletal modelling platform. Eight participants performed submaximal dynamic index finger pressing tasks while maintaining a nominal vertical target force of 10 N. Kinematic and force data were used to develop and assess an inverse dynamics link segment model and a musculoskeletal model. Although musculoskeletal model results for metacarpophalangeal joint compression evaluated statically (34.92 ± 1.53 N) and dynamically (34.80 ± 4.40 N) did not differ, changes in anterior-posterior shear and compression throughout the motions identify where the current open-source model is able to provide valuable insight into the assessment of risk of developing MSD during sub-maximally loaded dynamic pressing tasks.