Reduction in the effectiveness of a muscle or muscle group reflected by a decline in peak tension. Local muscular fatigue may be due to one or more reasons, such as failure of a motor nerve to transmit nerve impulses to the muscle; fatigue at the neuromuscular junction through depletion of neurotransmitters; inability of the contractile mechanism (the actin and myosin myofilaments) to generate force; accumulation of protons from lactic acid in the muscle; depletion of ATP and phosphocreatine; or failure of the central nervous system to initiate and relay nerve impulses to the muscle. The most probable sites of local muscular fatigue are the neuromuscular junctions, the contractile mechanism of the muscle itself, and the central nervous system. Fatigue at the neuromuscular junction, which might be more common in fast twitch fibres, is probably due to depletion of acetylcholine. Fatigue within the contractile mechanism may be caused by accumulation of protons, depletion of ATP and phosphocreatine; depletion of muscle glycogen; dehydration; or lack of oxygen and inadequate blood flow.
Subjects: Sports and Exercise Medicine.