Motor adaptation capacity as a function of age in carrying out a repetitive assembly task at imposed work paces

The working population is getting older. Workers must adapt to changing conditions to respond to the efforts required by the tasks they have to perform. In this laboratory-based study, we investigated the capacities of motor adaptation as a function of age and work pace. Two phases were identified in the task performed: a collection phase, involving dominant use of the lower limbs; and an assembly phase, involving bi-manual motor skills. Results showed that senior workers were mainly limited during the collection phase, whereas they had less difficulty completing the assembly phase. However, senior workers did increase the vertical force applied while assembling parts, whatever the work pace. In younger and middle-aged subjects, vertical force was increased only for the faster pace. Older workers could adapt to perform repetitive tasks under different time constraints, but adaptation required greater effort than for younger workers. These results point towards a higher risk of developing musculoskeletal disorders among seniors.

Martine Annie Gilles, Jean-Charles Guélin, Kévin Desbrosses, Pascal Wild

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Intrinsic movement variability at work. How long is the path from motor control to design engineering?

For several years, increasing numbers of studies have highlighted the existence of movement variability. Before that, it was neglected in movement analysis and it is still almost completely ignored in workstation design. This article reviews motor control theoriesand factors influencing movement execution,and indicateshowintrinsic movement variability is part of task completion. These background clarifications shouldhelp ergonomists and workstation designers to gain a better understanding of these concepts,which can then beusedto improve design tools. We also question whichtechniques – kinematics, kinetics or muscular activity – and descriptors are most appropriate for describing intrinsic movement variability and for integrationinto design tools. By this way, simulations generated by designers for workstation design should be closer to the real movements performed by workers. This review emphasises the complexity of identifying, describing and processing intrinsic movement variability in occupational activities.

Clarisse Gaudez, Martine Gilles, Jonathan Savin

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Learning to tune the antero‑posterior propulsive forces during walking: a necessary skill for mastering upright locomotion in toddlers

This study examines the process of learning to walk from a functional perspective. To move forward, one must generate and control propulsive forces. To achieve this, it is necessary to create and tune a distance between the centre of mass (CoM) and the centre of pressure (CoP) along the antero-posterior axis. We hypothesize that learning to walk consists of learning how to calibrate these self-generated propulsive forces to control such distance.
We investigated this question with six infants (three girls and three boys) who we followed up weekly for the first 8 weeks after the onset of walking and then biweekly until they reached 14–16 weeks of walking experience. The infants’ walking patterns (kinematics and propelling forces) were captured via synched motion analysis and force plate.
The results show that the distance between the CoM and the CoP along the antero-posterior axis increased rapidly during the first months of learning to walk and that this increase was correlated with an increase in velocity. The initial small values of (CoM–CoP) observed at walking onset, coupled with small velocity are interpreted as the solution infants adopted to satisfy a compromise between the need to generate propulsive forces to move forward while simultaneously controlling the disequilibrium resulting
from creating a with distance between the CoM and CoP.

Blandine Bril, Lucile Dupuy, Gilles Dietrich, Daniela Corbetta

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Interpersonal Distance Modeling During Fighting Activities

The aim of this article is to elaborate a general framework for modeling dual
opposition activities, or more generally, dual interaction. The main hypothesis is that opposition behavior can be measured directly from a global variable and that the relative distance between the two subjects can be this parameter. Moreover, this parameter should be considered as multidimensional parameter depending not only on the dynamics of the subjects but also on the “internal” parameters of the subjects, such as sociological and/or emotional states. Standard and simple mechanical formalization will be used to model this multifactorial distance. To
illustrate such a general modeling methodology, this model was compared with actual data from an opposition activity like Japanese fencing (kendo). This model captures not only coupled coordination, but more generally interaction in two-subject activities.

Gilles Dietrich, Jonathan Bredin, and Yves Kerlirzin

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Functional mastery of percussive technology in nut-cracking and stone-flaking actions

Various authors have suggested behavioural similarities between tool use in early hominins and chimpanzee nut cracking, where nut cracking might be interpreted as a precursor of more complex stone flaking. In this paper, we bring together and review two separate strands of research on chimpanzee
and human tool use and cognitive abilities. Firstly, and in the greatest detail, we review our recent experimental work on behavioural organization and skill acquisition in nut-cracking and stoneknapping tasks, highlighting similarities and differences between the two tasks that may be informative
for the interpretation of stone tools in the early archaeological record. Secondly, and more briefly, we outline a model of the comparative neuropsychology of primate tool use and discuss recent descriptive
anatomical and statistical analyses of anthropoid primate brain evolution, focusing on corticocerebellar systems. By juxtaposing these two strands of research, we are able to identify unsolved problems that can usefully be addressed by future research in each of these two research areas.

Blandine Bril,, Jeroen Smaers, James Steele, Robert Rein, Tetsushi Nonaka, Gilles Dietrich, Elena Biryukova, Satoshi Hirata and Valentine Roux

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Ethnographier le tour de main

Cet article aborde le défi ethnographique particulier que pose le tour de main. Si l’on s’interroge sur la dimension corporelle de la connaissance, ce que la main ou le corps sait, il apparaît inévitable avant toute chose de parvenir à une description systématique et comparable de « comment la main et le corps agissent », aspect sur lequel nous insistons plus particulièrement dans cet article. Les questions qui serviront de fil rouge à notre réflexion sont alors les suivantes : quelle démarche méthodologique choisir pour enregistrer, décrire, analyser et comparer les tours de main, de façon à exposer tangiblement le contenu sous-tendu par cette expression métaphorique ? Pour y répondre, une première étape consiste à mettre en évidence les principales difficultés méthodologiques spécifiques à l’ethnographie des pratiques corporelles. Afin de dépasser ces difficultés, des moyens complémentaires aux outils classiques d’observation et de compilation ethnographiques seront ensuite proposés. Trois propositions méthodologiques seront avancées, illustrées chacune par un cas d’étude développé par notre équipe. Les terrains sont contrastés (France, Corée, Inde, Éthiopie), les domaines techniques différents (poterie, taille de la pierre, danse), mais ces trois exemples ont en commun une démarche pluridisciplinaire (expérimentation de terrain) qui implique notamment l’intégration d’outils issus de disciplines spécialisées dans le domaine des activités motrices (notation du mouvement dansé, sciences du mouvement). Chacune des recherches présentées à travers sa problématique particulière permettra de spécifier concrètement un aspect de la démarche générale.

Nicole Rodda, Blandine Bril, Anne-Lise Goujon, Kyung-eun Shim

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Du mouvement sans sens ou du sens sans Mouvement

Par leur richesse méthodologique et la diversité des activités qu’ils
abordent, les travaux de E.J. Marey auraient pu être le point de départ de recherches conjuguant les exigences de contrôle expérimental reconnues aux sciences de la vie et la pertinence à l’égard des situations de terrain qu’offrent les sciences humaines.
Cependant l’étude du mouvement demeure clivée entre des travaux privilégiant l’étude du sens, de la finalité ou de la fonction sociale des mouvements ou des recherches en sciences du mouvement recourant souvent à des mouvements sans sens, dénués de fonctionnalité. Quatre exemples volontairement éclectiques (marche, taille de la pierre, jeu du piano et du violon) nous permettront de montrer le rôle primordial
du contexte de l’action et de la finalité dans l’organisation des comportements à travers deux types d’interactions : celles du corps et de l’environnement et celles du sujet manipulant un outil. Ces recherches tracent la voie d’une approche pluridisciplinaire du mouvement qui permettrait de sortir des apories auxquelles conduit l’étude de sens sans mouvement et de mouvements sans sens.

Blandine Bril ,Rémi Goasdoué

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