The main aim of the taper is to reduce the negative physiological and psychological impact of daily training. In other words, a taper should eliminate accumulated or residual fatigue, which translates into additional fitness gains. To test this assumption, Mujika and colleagues (1996a) analyzed the responses to three taper segments in a group of national- and international-level swimmers by means of a mathematical model, which computed fatigue and fitness indicators from the combined effects of a negative and a positive function representing, respectively, the negative and positive influence of training on performance (figure 1.1). As can be observed in figure 1.1, NI (negative influence) represents the initial decay in performance taking place after a training bout and PI (positive influence) a subsequent phase of supercompensation.
The mathematical model indicated that performance gains during the tapering segments were mainly related to marked reductions in the negative influence of training, coupled with slight increases in the positive influence of training (figure 1.2). The investigators suggested that athletes should have achieved most or all of the expected physiological adaptations by the time they start tapering, eliciting improved performance levels as soon as accumulated fatigue fades away and performance-enhancing adaptations become apparent.
The conclusions of Mujika and colleagues (1996a), drawn from real training and competition data from elite athletes but attained by mathematical procedures, were supported by several biological and psychological findings extracted from the scientific literature on tapering. For instance, in a subsequent study on competitive swimmers, Mujika and colleagues (1996d) reported a significant correlation between the percentage change in the testosterone-cortisol ratio and the percentage performance improvement during a 4-week taper. Plasma concentrations of androgens and cortisol have been used in the past as indexes of anabolic and catabolic tissue activities, respectively (Adlercreutz et al. 1986). Given that the balance between anabolic and catabolic hormones may have important implications for recovery processes after intense training bouts, the testosterone-cortisol ratio has been proposed and used as a marker of training stress (Adlercreutz et al. 1986, Kuoppasalmi and Adlercreutz 1985). Accordingly, the observed increase in the testosterone-cortisol ratio during the taper would indicate enhanced recovery and elimination of accumulated fatigue. This would be the case regardless of whether the increase in the testosterone-cortisol ratio was the result of a decreased cortisol concentration (Bonifazi et al. 2000, Mujika et al. 1996c) or an increased testosterone concentration subsequent to an enhanced pituitary response to the preceding time of intensive training (Busso et al. 1992, Mujika et al. 1996d, Mujika et al. 2002a).