Intramuscular mechanisms of overtraining

Area of Science:

• Exercise physiology
• Sports science
• Skeletal muscle biology

Background:

• Strenuous exercise stimulates beneficial skeletal muscle adaptations like increased endurance and strength.
• Adequate post-exercise recovery is crucial for metabolic and structural adaptations to occur.
• An imbalance between intense training and insufficient recovery can lead to overreaching and overtraining syndrome (OTS).

Purpose of the Study:

• To review the underlying mechanisms contributing to exercise-induced OTS in skeletal muscle.
• To discuss conditions leading to OTS and their impact on skeletal muscle function.
• To assess proposed mechanisms for skeletal muscle weakness in OTS.

Main Methods:

• Review of existing literature on overtraining syndrome and skeletal muscle physiology.
• Assessment of hypotheses including glycogen depletion, muscle damage, inflammation, and oxidative stress.
• Analysis of the role of reactive oxygen and nitrogen species (ROS) and inflammatory pathways.

Main Results:

• Current evidence points to reactive oxygen and nitrogen species (ROS) and inflammatory pathways as primary contributors to OTS in skeletal muscle.
• Glycogen depletion and muscle damage hypotheses are considered but less conclusive than oxidative stress and inflammation.
• The review identifies key factors contributing to impaired skeletal muscle function in OTS.

Conclusions:

• Oxidative stress and inflammation are implicated as the most likely mechanisms driving skeletal muscle dysfunction in OTS.
• Understanding these mechanisms is vital for developing effective interventions to mitigate OTS.
• Further research into mitigating OTS in skeletal muscle is warranted.