Bilateral synergies in foot force production tasks

Area of Science:

• Neuroscience
• Biomechanics
• Motor Control

Background:

• Bilateral force production tasks involve coordinating both limbs.
• Understanding task symmetry's role in motor control is crucial for rehabilitation and performance enhancement.

Purpose of the Study:

• To investigate the impact of task symmetry on bilateral force production synergies in the legs.
• To test the hypothesis that bilateral deficit influences synergy indices during accurate force production.

Main Methods:

• Subjects performed symmetrical (same direction) and asymmetrical (opposite direction) plantar flexion and dorsiflexion tasks with both feet.
• The uncontrolled manifold (UCM) hypothesis framework was used to quantify force variability (V UCM and V ORT).
• Synergy indices and anticipatory synergy adjustment (ASA) were calculated to assess motor coordination.

Main Results:

• Synergy indices were higher during asymmetrical tasks compared to symmetrical ones.
• This difference was attributed to higher V UCM or lower V ORT, depending on the symmetrical task.
• Anticipatory synergy adjustment (ASA) was shorter and smaller in magnitude for asymmetrical tasks.

Conclusions:

• Bilateral deficit has minimal impact on two-leg force production synergies.
• The findings support existing models of neural control for redundant motor systems.
• This study provides the first evidence of bilateral synergies in leg force production.