Motor-evoked potentials in response to fatiguing grip exercise in multiple sclerosis patients

Area of Science:

• Neuroscience
• Exercise Physiology
• Clinical Neurology

Background:

• Fatiguing exercise impacts central and peripheral motor pathways.
• Multiple Sclerosis (MS) is characterized by neurological deficits, including motor weakness.

Purpose of the Study:

• To investigate the central and peripheral effects of fatiguing exercise in healthy controls and individuals with MS, categorized by motor function.
• To compare the force production, cortical excitability, and metabolic recovery between groups.

Main Methods:

• Utilized transcranial magnetic stimulation (TMS) to measure motor-evoked potentials (MEPs) in hand muscles before and after a 3-minute maximal grip exercise.
• Assessed exercise-induced phosphocreatine (PCr) depletion and recovery using (31)P magnetic resonance spectroscopy ((31)PMRS).
• Measured central motor conduction time (CMCT) and MEP facilitation via contralateral muscle activation.

Main Results:

• MS subjects exhibited lower peak force and faster force decline than controls.
• Contralateral hand grip increased MEP amplitudes post-exercise in controls and MS subjects with normal motor function, but not in those with weakness.
• Fatiguing exercise prolonged CMCT in MS subjects, and post-exercise depression of MEPs persisted beyond PCr recovery, indicating central fatigue.

Conclusions:

• Fatiguing exercise reveals central fatigue mechanisms are more pronounced in MS patients, particularly those with motor weakness.
• MS subjects demonstrate an impaired ability to enhance cortical excitability following fatigue compared to controls.
• Findings suggest potential impairments in central motor conduction pathways, possibly involving the corpus callosum, in individuals with MS.