Post-exercise depression following submaximal and maximal isometric voluntary contraction

Area of Science:

• Neuroscience
• Motor Control
• Exercise Physiology

Background:

• Corticomotor excitability changes post-exercise.
• The impact of force magnitude on corticomotor reorganization is not well understood.

Purpose of the Study:

• To investigate if corticomotor reorganization differs between low-force and high-force muscle fatigue.
• To examine changes in corticomotor map area, excitability, and location using transcranial magnetic stimulation (TMS).

Main Methods:

• 15 healthy adults performed low-force (30% MVC) and high-force (95% MVC) isometric contractions of the first dorsal interosseous (FDI) muscle to exhaustion.
• A control session involved 30 minutes of rest.
• TMS was used to assess FDI representation in the primary motor cortex (M1).

Main Results:

• Low-force fatigue, but not high-force fatigue, significantly reduced corticomotor map area and excitability.
• A posterior shift in the location of corticomotor excitability was observed following low-force fatigue.
• Reduced excitability was noted in regions adjacent to M1 after low-force fatigue.

Conclusions:

• Post-exercise depression occurs after low-force fatigue but not high-force fatigue.
• Low-force fatigue induces a posterior shift in corticomotor output, potentially due to increased somatosensory feedback.
• Exercise intensity influences the nature and extent of motor cortex adaptation and recovery.