Achieving optimum athletic performance requires a balance of stress induced by training and competition with appropriate recovery. It is thought that the physiological stress associated with repeated high intensity intermittent sprint exercise over a number of weeks would be relatively low in well-trained individuals, perhaps due to familiarisation with the exercise mode and protection from muscle damage due to the repeated-bout effect. The aims of the present study were twofold: (1) to ascertain the level of exercise-induced fatigue and recovery profile after an intermittent shuttle run test designed to replicate the demands of a football match; and (2) to compare the fatigue and recovery response when the same exercise bout is repeated 2 weeks later. Eight males (23±3 years) well-trained individuals (VO2max 54.6±5.2 ml/kg/min), who regularly participated in repeat sprint field sports (rugby, hockey and football), completed two 90-min intermittent shuttle run tests separated by 2 weeks. Maximal isometric voluntary contraction (MIVC) of the knee extensors, countermovement jump (CMJ), delayed-onset muscle soreness (DOMS), creatine kinase (CK) and interleukin 6 (IL-6) were measured before exercise and at a series of time points up to 72 h after both tests. MIVC, CMJ, DOMS, CK and IL-6 all showed significant time effects (p<0.05) over the two exercise bouts indicating exercise-induced fatigue after both tests. CK peaked at 24 h in bout 1 (1375±1247 U/l) and bout 2 (1225±595 U/l). Only CMJ showed a significant bout effect (p<0.05), indicating muscle damage was reduced after the second bout. Declines in CMJ (−4.0±4.8% at 24 h) and MIVC (−8.6±6.3% at 24 h) indicated considerable reductions in muscle function after the second bout. This study indicates that well-trained individuals experience substantial levels of exercise-induced fatigue after a repeated bout of exercise. Consequently, it is likely that well-trained individuals do not benefit from the repeated bout effect phenomenon in the same way that untrained individuals do. Therefore interventions that attenuate these repeated increases in fatigue indices are justified in well-trained individuals.
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