Cortisol (C) and testosterone (T) are commonly suggested as markers of overreaching and the unexplained underperformance syndrome (UPS) as taken together they highlight the body s state of stress by indicating the body s catabolic/anabolic balance. Research in this area has focused on the resting concentrations of these hormones and provided inconsistent findings with increases, decreases and no changes reported when individuals are compared in an overreached state with a normally trained state. Little attention has been given to the exercise-induced responses of these hormones and whether this could be a reliable marker of overreaching/UPS. Overreaching will only occur with an intensification of training so the aims of the studies in this thesis were to determine the effects of intensified training on the exercise-induced responses of salivary and plasma C and T concentrations.
Study 1 (Chapter 4) determined the salivary and plasma C, T and plasma adrenocorticotrophic hormone (ACTH) concentration responses in physically fit, healthy males to a double-bout cycle to fatigue protocol devised by Meeusen et al. (2004). They reported blunted exercise-induced hormonal responses to this protocol when well-trained cyclists were overreached compared with a normally trained state. Study 1 concluded that the exercise-induced responses of the salivary and plasma C and plasma ACTH concentrations were unaffected by a 4-day intensified training period. Blunted exercise-induced salivary and plasma T concentrations were found post-training but were due to blunted resting, basal T concentrations post-training compared with pre-training. The double-bout cycle to fatigue protocol did not elicit large C or T responses and so was not ideally suited to highlight alterations in the exercise-induced hormone responses. A high-intensity, short-duration exercise protocol (called the 55/80 bout) was established in Chapter 5 which induced robust elevations of salivary and plasma C and salivary T concentrations when in a normal trained state. Such a protocol could highlight any adaptations in the exercise-induced responses of C and T concentrations. It was also concluded that salivary and plasma C concentrations positively correlated if the peak post-exercise values were compared but not so with the salivary and plasma T concentrations. Chapter 6 and Chapter 7 concluded that blunted responses of the salivary C (Chapter 6) and T (Chapter 6 and Chapter 7) concentrations to a 55/80 bout occurred after an intensified endurance training period (~10 days). These results indicate that the 55/80 bout could be a useful detection tool of exercise-induced alterations in salivary C and T concentrations caused by an elevation of training loads in both recreationally active and elite athlete populations. The reproducibility of the salivary hormonal responses to the 55/80 bout needed to be established before it could be concluded that this was indeed a useful tool. Chapter 8 concluded that the responses of both salivary C and T concentrations to the 55/80 bout were reasonably reproducible with intra-individual variations of 12% (salivary C) and 7% (salivary T) reported. Chapter 8 also concluded that a familiarisation 55/80 bout was needed to reduce the variation in the responses of both salivary C and T concentrations. The final experimental chapter examined the response of salivary C and T over a competitive season in elite male triathletes and concluded that the 55/80 bout was unable to highlight any adaptations in the salivary C and T exercise-induced responses. This was suggested to be due to the low numbers of participants in this study and the ability of the triathletes to cope well with the elevations in training loads over the season.
In conclusion, the studies in this thesis suggest that the exercise-induced responses of salivary C and T do alter due to an intensification of training loads. This alteration presents as a blunting of the exercise-induced responses of these salivary hormones. The 55/80 cycle bout can highlight this blunted response in both recreationally active and elite athlete male populations and therefore may be a useful tool to examine exercise-induced adaptations in salivary C and T concentrations caused by periods of intensified training.
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.