Effects of task complexity on coordination of inter-limb and within-limb forces in static bimanual manipulation.
Coordination of the hand grip (G; acting normally to the grasping surface) and load forces (L; acting in parallel) in bimanual static tasks was studied. L symmetry (either the magnitude or direction) and frequency were manipulated in healthy participants (N = 14). More complex tasks (i.e., the higher frequency and/or asymmetric ones) revealed expected deterioration in both the task performance (accuracy of the prescribed L force profiles) and force coordination (G/L ratio and G-L correlation) suggesting importance of L frequency and symmetry in prehension activities. However, the same tasks revealed a more prominent deterioration of interlimb than the within-limb force coordination. This could be interpreted by two partly different and noncompeting neural control mechanisms where the coordination of interlimb forces may be based on ad-hoc and task-specific muscle coordination (often referred to as muscle synergies) while the within-limb coordination of G and L could be based on more stable and partly reflex mechanisms.
Kinesiology and Applied Physiology Department, University of Delaware, Newark, DE, USA.
Vennila
V
Krishnan
Slobodan
S
Jaric
D000328:Adult; D000704:Analysis of Variance; D005260:Female; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D009048:Motor Skills / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D016474:Weight-Bearing / Q000502:physiology