Mechanisms of Fatigue

Fatigue is a complex and multifaceted phenomenon. There is rarely ever one source of fatigue, as humans are also complex, multifaceted, and have many other factors and responsibilities in our lives, outside of training and athletics. Fatigue can be acute, accumulated, chronic, and/or exacerbated by additional external influences, such as nutrition, sleep, illness, and social commitments or conflicts. Additionally, the presence of fatigue may be through peripheral mechanisms, at which local muscles encounter mechanical failure due to metabolic acidosis, altered electrolyte concentrations that impair muscle contraction, and microtrauma/tissue damage; or central mechanisms, by which a decrement in motor neuron excitation and the inability to recruit high threshold motor units is presented.