Fatigue-Related Injuries in Athletes

During a maximum contraction of many mixed muscles, it is common to see a 50% reduction of force over a period of a few seconds. This is known as fatigue (Rothwell, 1994). The term fatigue though can refer to both physical and mental exhaustion due to prolonged stimulation or exertion. As such, it is a phenomenon that is of interest to many scientific disciplines, including the science of coaching, as is used in a variety of contexts. Of particular interest is localized progressive muscle fatigue which has been defined as an inability to maintain required force level after prolonged use of muscle (Gandevia et al. 1998). While reduction in force production is obviously detrimental in many circumstances, progressive muscle fatigue has also been shown to impair postural stability (Johnston et al., 1998), muscle coordination (Carpenter et al., 1998) and control of limb velocity and acceleration (Jaric et al., 1997).

Fatigue has traditionally been attributed to the occurrence of a “metabolic endpoint”, where muscle glycogen concentrations are depleted, plasma glucose concentrations are reduced and plasma free fatty acid levels are elevated (cf: Meeusen et al., 2006). However, one of the major complications that arise in studying muscle fatigue is that both peripheral and central mechanisms contribute to the manifestations of muscle fatigue (Enoka & Stuart, 1992). These mechanisms are highly interactive in nature, and should both be acknowledged as a complex phenomenon. Unfortunately, both their independent and collective contributions to progressive muscle fatigue are still poorly understood.