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.
• While HIIT's systemic neuromodulatory effects are established, SE's remote responses are less understood.
• Investigating remote corticospinal and motor performance changes is crucial for optimizing exercise protocols.

Purpose of the Study:

• To compare the effects of single-session HIIT and plantar flexion SE on corticospinal, intracortical, and spinal excitability.
• To assess changes in motor performance in a non-exercised muscle (flexor carpi radialis) following these exercise types.
• To determine if SE can induce comparable remote neuroplasticity to HIIT.

Main Methods:

• Randomised crossover design with 18 participants.
• Interventions included 20-minute HIIT cycling, high-intensity resistive plantar flexion SE, and a control condition.
• Transcranial magnetic stimulation, peripheral nerve stimulation, reaction time tasks, and maximum voluntary force measurements were used.

Main Results:

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

Conclusions:

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