Force-velocity properties' contribution to bilateral deficit during ballistic push-off

Area of Science:

• Biomechanics
• Human Physiology
• Sports Science

Background:

• Bilateral force deficit (BLD) describes the phenomenon where the sum of forces produced by limbs acting unilaterally exceeds the force produced when acting bilaterally.
• Understanding the underlying mechanisms of BLD is crucial for optimizing athletic performance and rehabilitation strategies.

Purpose of the Study:

• To quantify the contribution of force-velocity (F-v) properties to BLD during ballistic lower limb push-off.
• To investigate the relationship between individual F-v mechanical properties and BLD.

Main Methods:

• Assessed individual F-v relations from mechanical measurements during maximal ballistic lower limb push-offs in 14 participants.
• Employed a theoretical macroscopic approach to analyze the contribution of F-v properties to BLD, considering movement dynamics and neuromuscular capabilities.

Main Results:

• A BLD of 36.7% ± 5.7% was observed during ballistic lower limb push-off.
• F-v mechanical properties accounted for a 19.9% ± 3.6% decrease in force, representing a 43.5% ± 9.1% non-neural contribution to BLD.
• This non-neural contribution was negatively correlated with maximum unloaded lower limb extension velocity (r = -0.977, P < 0.001).

Conclusions:

• BLD during ballistic lower limb push-off arises from both neural alterations and F-v mechanical properties.
• The contribution of F-v properties to BLD is linked to changes in movement velocity between bilateral and unilateral actions.
• Individual F-v profiles dictate the extent of force loss; those optimized for velocity show less force reduction in bilateral actions.