Bilateral Force Deficit in Proximal Effectors Versus Distal Effectors in Lower Extremities

Area of Science:

• Biomechanics
• Neuroscience
• Human Physiology

Background:

• Bilateral force deficit (BFD) is the reduction in force during simultaneous bilateral contractions compared to the sum of unilateral forces.
• Neural inhibition is the primary proposed mechanism for BFD.
• Potential differences in neural organization between proximal and distal effectors may influence BFD magnitude.

Purpose of the Study:

• To investigate if bilateral force deficit differs between proximal (knee extension) and distal (ankle dorsiflexion) effectors in the lower extremities.
• To compare the relative and absolute bilateral force deficit for proximal versus distal muscle groups.

Main Methods:

• Fifteen young adults participated in the study.
• Maximal voluntary isometric contractions were performed for ankle dorsiflexion and knee extension, both unilaterally and bilaterally.
• Absolute and relative bilateral force deficits were calculated for each movement.

Main Results:

• A significant absolute bilateral force deficit was observed for both proximal and distal effectors.
• The relative bilateral force deficit was significantly larger for proximal knee extension (19.98%) compared to distal ankle dorsiflexion (10.27%).
• These findings indicate a greater bilateral force deficit in proximal compared to distal muscle groups.

Conclusions:

• Proximal effectors exhibit a more pronounced bilateral force deficit than distal effectors, potentially due to greater bilateral neural communication and higher perceived exertion.
• Neuroanatomical and neurophysiological differences between proximal and distal muscles likely underlie the observed disparities in bilateral force deficit.
• Understanding these differences is crucial for optimizing training and rehabilitation strategies.