Skeletal muscle fatigue

Skeletal muscle fatigue is a complex problem which deserves attention from physiotherapists and other clinical practitioners. This article will discuss the findings of recent literature to explore some of the main mechanisms thought to underlie fatigue in skeletal muscles. These mechanisms may be peripheral in origin, occurring within the muscle fibres themselves, or central, affecting the neural control of muscle contraction. Peripheral mechanisms of fatigue include metabolic factors such as the availability and utilization of metabolic substrates (e.g. glycogen, phosphocreatine and adenosine triphosphate) during muscle activity as well as the influence of muscle pH on both metabolism and muscle contractile properties. Impairment in neuromuscular transmission and excitation–contraction coupling may also cause muscle fatigue. Central fatigue mechanisms include both psychological and physiological factors which may influence motor cortex activity and hence muscle force output. Pathological factors which may cause abnormal muscle fatigue are also discussed.