title: Force-velocity properties' contribution to bilateral deficit during ballistic push-off.
abstract: OBJECTIVE
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: 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.
authors.forename: Pierre
authors.initials: P
authors.lastname: Samozino
authors.forename: Enrico
authors.initials: E
authors.lastname: Rejc
authors.forename: Pietro Enrico
authors.initials: PE
authors.lastname: di Prampero
authors.forename: Alain
authors.initials: A
authors.lastname: Belli
authors.forename: Jean-Benoît
authors.initials: JB
authors.lastname: Morin
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D006801:Humans; D035002:Lower Extremity / Q000502:physiology*; D008954:Models, Biological; D009068:Movement / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D055815:Young Adult