Motor cortical excitability is differentially modulated by HIIT and strength exercise

Area of Science:

• Neuroscience
• Exercise Physiology
• Motor Control

Background:

• High-intensity interval training (HIIT) and strength exercise (SE) are known to induce plasticity in exercised muscles.
• The systemic neuromodulatory effects of HIIT are well-documented, but comparable remote responses to SE are less understood.

Purpose of the Study:

• To investigate changes in corticospinal, intracortical, and spinal excitability in a non-exercised muscle (flexor carpi radialis) after single-session HIIT and plantar flexion SE.
• To compare the motor performance outcomes between HIIT and SE in remote muscle groups.

Main Methods:

• A randomized crossover design was employed with 18 participants undergoing HIIT cycling, plantar flexion SE, and a control condition.
• Transcranial magnetic stimulation and peripheral nerve stimulation assessed corticospinal and spinal excitability.
• Motor performance was evaluated using reaction time tasks and maximum voluntary force measurements.

Main Results:

• HIIT significantly increased motor-evoked potential amplitude and reduced short-interval intracortical inhibition in the non-exercised muscle.
• Both HIIT and SE improved reaction time compared to baseline and control conditions.
• HIIT demonstrated greater reductions in silent period duration compared to SE.

Conclusions:

• HIIT induces more widespread corticospinal excitability enhancements in remote, non-exercised muscles compared to unilateral, small-muscle SE.
• Single-session SE may not be sufficient to elicit significant remote corticospinal excitability changes.
• Findings have implications for designing neurorehabilitation strategies targeting remote muscle groups.