Purpose: The objective of this study is to quantify the contribution of the force–velocity (F-v) properties to bilateral force deficit (BLD) in ballistic lower limb push-off and to relate it to individual F-v mechanical properties of the lower limbs.
Methods: The F-v relation was individually assessed from mechanical measurements for 14 subjects during maximal ballistic lower limb push-offs; its contribution to BLD was then investigated using a theoretical macroscopic approach, considering both the mechanical constraints of movement dynamics and the maximal external capabilities of the lower limb neuromuscular system.
Results: During ballistic lower limb push-off, the maximum force each lower limb can produce was lower during bilateral than unilateral actions, thus leading to a BLD of 36.7% ± 5.7%. The decrease in force due to the F-v mechanical properties amounted to 19.9% ± 3.6% of the force developed during BL push-offs, which represents a nonneural contribution to BLD of 43.5% ± 9.1%. This contribution to BLD that cannot be attributed to changes in neural features was negatively correlated to the maximum unloaded extension velocity of the lower limb (r = −0.977, P < 0.001).
Conclusion: During ballistic lower limb push-off, BLD is due to both neural alterations and F-v mechanical properties, the latter being associated with the change in movement velocity between bilateral and unilateral actions. The level of the contribution of the F-v properties depends on the individual F-v mechanical profile of the entire lower limb neuromuscular system: the more the F-v profile is oriented toward velocity capabilities, the lower the loss of force from unilateral to bilateral push-offs due to changes in movement velocity.
1Laboratory of Exercise Physiology (EA4338), University of Savoie, Le Bourget-du-Lac, FRANCE; 2Department of Biomedical Sciences and Technologies, University of Udine, Udine, ITALY; and 3Laboratory of Exercise Physiology (EA4338), University of Lyon, Saint Etienne, FRANCE
Address for correspondence: Pierre Samozino, PhD, Laboratoire de Physiologie de l’Exercice, Université de Savoie, UFR CISM-Technolac, Le Bourget-du-Lac F-73376, France; E-mail: firstname.lastname@example.org.
Submitted for publication June 2012.
Accepted for publication June 2013.
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