Strength Training Preferentially Enhances Corticospinal Output Compared with High-Intensity Interval Training

Area of Science:

• Neuroscience
• Exercise Physiology
• Motor Control

Background:

• Corticospinal responses vary with training type, muscle group, and contraction.
• The differential effects of high-intensity interval training (HIIT) and strength exercise (SE) on corticospinal excitability and inhibition are not fully understood.
• Previous research often focused on upper limbs, not lower limbs involved in HIIT.

Purpose of the Study:

• To investigate the distinct effects of HIIT and SE on corticospinal, intracortical, and spinal responses in lower-limb muscles.
• To compare the impact of a single bout of high-intensity SE versus a 20-minute HIIT cycling session on neural excitability.

Main Methods:

• Eighteen healthy, untrained subjects participated in three conditions: HIIT, SE, and a control session.
• Transcranial magnetic stimulation (TMS) and peripheral nerve stimulation were used to assess corticospinal, intracortical, and spinal excitability.
• Measurements were taken at baseline and 5 minutes post-exercise.

Main Results:

• Both HIIT and SE increased motor-evoked potential (MEP) amplitude compared to control, with SE showing a significantly greater increase.
• Only SE significantly increased MEP amplitude at higher stimulation intensities (150% AMT).
• SE reduced silent period duration and short-interval intracortical inhibition, while HIIT only reduced silent period duration at higher intensities. Spinal excitability remained unchanged.

Conclusions:

• Strength exercise (SE) preferentially enhances acute corticospinal excitability in lower-limb muscles compared to high-intensity interval training (HIIT).
• These findings suggest SE may be more effective for improving neural output in the short term.
• The results have implications for designing neurorehabilitation programs for conditions characterized by reduced corticospinal excitability.