ABSTRACT
Human skeletal muscle fatigue can be defined as a transient, exerciseinduced reduction in the maximal force capacity of the muscle (Vollestad et al., 1984; Barry and Enoka, 2007) (see Chapter 1). This is especially apparent during multiple-sprint exercise with limited recovery between sprints, where there is a decrease in performance following the first sprint
(Spencer et al., 2005) (Figure 8.1). Despite numerous studies however, there is still no clear explanation for the mechanisms underlying this transient decrease in performance. A better understanding of the underlying mechanisms of fatigue would provide greater insight into how to delay the onset of fatigue and thus improve multiple-sprint performance. Various ergogenic aids have been used to minimise fatigue during multiple-sprint activities and provide a valuable means to experimentally assess possible determinants of fatigue during multiple-sprint tasks. Such information may assist in the design of training programmes which could enhance sports performance (especially in team sports), some occupational tasks, and also exercise capability in clinical situations. One factor complicating a description of the effects of ergogenic aids on fatigue during multiple-sprint activities is the recent evidence that the mechanisms underlying force decline are likely to be highly task-specific (Enoka and Stuart, 1992; Gandevia, 2001) (see Chapter 1). This means that muscle fatigue can be induced by a combination of processes, contributing in different ways to the decline in force, according to the details of the task (e.g. intensity, duration, mode of contraction, muscle, etc). Therefore, where possible, this chapter will focus on research that has investigated fatigue and/or the use of ergogenic aids specifically during multiple-sprint activities. Another important factor to consider is that human skeletal muscle fatigue has been reported to be influenced by the biological sex of the individual (see Chapter 6). It needs to be acknowledged however, that the vast majority of the research summarised in this chapter is based on the
responses of young adult males. While it has been suggested that there is likely to be little difference in the fatigue response of males and females during multiple-sprint exercise (Billaut and Bishop, 2009), caution should be exercised when extrapolating the conclusions made in this chapter to females.
