Changes in corticospinal excitability during bilateral and unilateral lower-limb force control tasks

Area of Science:

• Neuroscience
• Motor Control
• Human Physiology

Background:

• Ankle dorsiflexion is crucial for daily activities.
• The corticospinal pathway's role in ankle dorsiflexion tasks requires further investigation.

Purpose of the Study:

• To compare corticospinal excitability during unilateral versus bilateral ankle dorsiflexion.
• To compare corticospinal excitability during ballistic versus tonic ankle dorsiflexion force control.

Main Methods:

• Fifteen healthy adults performed unilateral and bilateral isometric ankle dorsiflexion tasks.
• Transcranial magnetic stimulation (TMS) measured motor-evoked potentials (MEPs) from the tibialis anterior muscle.
• MEP amplitudes were analyzed during pre-contraction, ascending, and plateau phases.

Main Results:

• MEP amplitudes were significantly higher during unilateral contractions than bilateral contractions in the pre-contraction phase.
• No significant differences in MEP amplitudes were observed between ballistic and tonic contractions.
• Corticospinal involvement appears similar for ballistic and tonic tasks, potentially due to preparation for precise force control.

Conclusions:

• Both ballistic and tonic ankle dorsiflexion tasks involve similar levels of corticospinal pathway engagement.
• Unilateral contractions may provide greater central nervous system facilitation for movement preparation compared to bilateral contractions.