Central fatigue during isometric exercise in amyotrophic lateral sclerosis

Area of Science:

• Neurology
• Muscle Physiology
• Motor Neuron Diseases

Background:

• Amyotrophic lateral sclerosis (ALS) involves both upper and lower motor neuron dysfunction, impacting muscle function.
• The specific mechanisms underlying muscle fatigue in ALS remain unclear.

Purpose of the Study:

• To investigate the central and peripheral factors contributing to muscle fatigue in ALS patients.
• To compare muscle fatigue mechanisms between ALS patients and healthy controls.

Main Methods:

• Intermittent submaximal isometric ankle dorsiflexion exercise was performed by 7 ALS patients and 6 healthy controls.
• Measurements included voluntary and stimulated force, muscle activation indices, and intramuscular energy metabolism.
• Central and peripheral fatigue indices were assessed before and during exercise.

Main Results:

• The ALS group exhibited increased "added force" post-exercise, indicating significant central fatigue.
• ALS patients showed less phosphocreatine depletion and less fatigue in stimulated tetanic force compared to controls.
• Central fatigue in ALS led to decreased muscle activation, lower metabolic demand, and reduced muscle fatigue.

Conclusions:

• Central factors play a major role in muscle fatigue experienced by individuals with ALS.
• Impaired central motor drive contributes significantly to the pathophysiology of muscle fatigue in ALS.
• Understanding these central mechanisms is crucial for managing muscle dysfunction in ALS.