Muscle mass and peripheral fatigue: a potential role for afferent feedback?

Area of Science:

• Exercise Physiology
• Neuromuscular Function
• Skeletal Muscle Physiology

Background:

• Voluntary exercise cessation is linked to sensory feedback limits from muscle afferents.
• Peripheral quadriceps fatigue is associated with exercise termination during cycling.
• Group III and IV muscle afferents influence exercise tolerance.

Purpose of the Study:

• To investigate the impact of reduced muscle mass on peripheral quadriceps fatigue.
• To constrain muscle afferent feedback to the central nervous system (CNS).
• To examine the relationship between muscle mass engagement and exercise tolerance.

Main Methods:

• Eight males performed exhaustive large (cycling) and small (knee extensor) muscle mass dynamic exercises.
• Maximal voluntary contractions (MVC) and femoral nerve stimulation (Q(tw,pot)) quantified peripheral quadriceps fatigue.
• Exercise intensity was set at 85% of modality-specific maximal workload.

Main Results:

• Quadriceps fatigue was significant in both cycling and knee extensor exercises.
• Greater peripheral quadriceps fatigue occurred with knee extensor exercise compared to cycling.
• Exercise duration was longer for knee extensor exercise, indicating a similar rate of peripheral fatigue development.

Conclusions:

• The CNS tolerates greater peripheral fatigue and metabolic disturbance when muscle afferent feedback is limited to a small muscle mass.
• Small muscle mass exercise may lead to enhanced exercise-induced muscular adaptations.
• Constraining afferent feedback influences exercise tolerance and fatigue perception.