Kinematic features of whole-body reaching movements underwater: Neutral buoyancy effects.
Astronauts' training is conventionally performed in a pool to reproduce weightlessness by exploiting buoyancy which is supposed to reduce the impact of gravity on the body. However, this training method has not been scientifically validated yet, and requires first to study the effects of underwater exposure on motor behavior. We examined the influence of neutral buoyancy on kinematic features of whole-body reaching underwater and compared them with those produced on land. Eight professional divers were asked to perform arm reaching movements toward visual targets while standing. Targets were presented either close or far from the subjects (requiring in the latter case an additional whole-body displacement). Reaching movements were performed on land or underwater in two different contexts of buoyancy. The divers either wore a diving suit only with neutral buoyancy applied to their center of mass or were additionally equipped with a submersible simulated space suit with neutral buoyancy applied to their body limbs. Results showed that underwater exposure impacted basic movement features, especially movement speed which was reduced. However, movement kinematics also differed according to the way buoyancy was exerted on the whole-body. When neutral buoyancy was applied to the center of mass only, some focal and postural components of whole-body reaching remained close to land observations, notably when considering the relative deceleration duration of arm elevation and concomitant forward trunk bending when reaching the far target. On the contrary, when neutral buoyancy was exerted on body segments, movement kinematics were close to those reported in weightlessness, as reflected by the arm deceleration phase and the whole-body forward displacement when reaching the far target. These results suggest that astronauts could benefit from the application of neutral buoyancy across the whole-body segments to optimize underwater training and acquire specific motor skills which will be used in space.
Aix-Marseille Université, CNRS, ISM UMR 7287, 13288 Marseille Cedex 09, France.
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Macaluso
Aix-Marseille Université, CNRS, ISM UMR 7287, 13288 Marseille Cedex 09, France.
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Bourdin
Aix-Marseille Université, CNRS, ISM UMR 7287, 13288 Marseille Cedex 09, France.
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Buloup
Aix-Marseille Université, CNRS, ISM UMR 7287, 13288 Marseille Cedex 09, France; Université de Toulon, 83957 La Garde, France; Department of Physical Therapy and Human Movement Sciences, Northwestern University Medical School, Chicago, IL 60611, United States.
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Mille
Aix-Marseille Université, CNRS, ISM UMR 7287, 13288 Marseille Cedex 09, France.
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Sainton
Aix-Marseille Université, CNRS, ISM UMR 7287, 13288 Marseille Cedex 09, France.
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Sarlegna
COMEX S.A., 36 Bvd des Océans, 13009 Marseille, France.
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Taillebot
Aix-Marseille Université, CNRS, ISM UMR 7287, 13288 Marseille Cedex 09, France.
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Vercher
COMEX S.A., 36 Bvd des Océans, 13009 Marseille, France.
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Weiss
Aix-Marseille Université, CNRS, ISM UMR 7287, 13288 Marseille Cedex 09, France. Electronic address: lionel.bringoux@univ-amu.fr.
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Bringoux
D000328:Adult; D001132:Arm / Q000502:physiology; D001696:Biomechanical Phenomena / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009048:Motor Skills / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D014893:Weightlessness; D055815:Young Adult
arm kinematics; neutral buoyancy; postural strategy; underwater; whole-body reaching