HARTMANN, U., and J. MESTER. Training and overtraining markers in selected sport events. Med. Sci. Sports Exerc., Vol. 32, No. 1, pp. 209-215, 2000.
Purpose: Varieties of symptoms are supposed to detect overtraining (OT). Besides the problems of diagnosis and analysis in elite athletes, a daily monitoring of training status takes place with measurement of the parameters serum urea (SU) and serum creatine kinase (CK); therefore, their meaningfulness will be examined, with special respect inter- and intra-individually.
Methods: Data were obtained from determinations during training from athletes in rowing and athletes of international level.
Results: For 6981 SU determinations (male, N = 717; female, N = 285), a slightly asymmetric normal distribution was found (male, 80%, 5-7 mmol·L-1; female, 75%, 4-6 mmol·L-1). Values for women were approximately 1.5 mmol·L-1 lower. Individual variability was enormous; there seems little point in setting fixed value as 8.3 mmol·L-1 for men and 7.0 mmol·L-1 for women as a critical limit for OT. CK has also been measured and evaluated in sports as an essential parameter for determination of muscular stress. Frequency distributions of CK in 2790 samples (male, N = 497; female, N = 350) presented an asymmetric normal distribution with distinct trend toward higher values being evident for the range between 100 and 250 U·L-1. Conspicuously elevated values occurred in the ranges 250-350 U·L-1 and 1000-2000 U·L-1. Men's maximal values were 3000 U·L-1 and 1150 U·L-1 for women. Individual variability was enormous. Athletes with chronically low CK exhibited mainly low variability; those with chronically higher values exhibited considerable variability.
Conclusions: Establishment of both parameters should be useful to determine individual baselines from a large number of samples. Determinations should be made at least every 3 d in standardized conditions. If a large increase is observed in combination with reduced exercise tolerance after a phase of exertion (2-4 d), then the possibility of a catabolic/metabolic activity or insufficient exercise tolerance becomes much more likely.
According to the Oxford Dictionary of Sport Science and Medicine (29), overtraining is a complex syndrome, and it is described as a combination of signs and symptoms of overtraining which typically causes the sufferer to feel mentally fatigued in absence of physical fatigue and causes deterioration of performance. The sufferer's basal metabolic rate is elevated, there is usually a loss of body weight associated with a negative nitrogen balance, and the rate of return of exercise pulse-rate to resting pulse-rate is delayed. The overtraining syndrome involves changes in the neuron and endocrine systems, particularly the hypothalamus.
Following Lehmann et al. (33), overtraining (OT) is understood as a long-term form of overloading, whereas overreaching is short-term overtraining. Foster et al. (13) suggest two stages of the adaptation process related to the average load of training (volume × intensity). In the beginning, the performance increases with a load up to a plateau, and beyond this, there is a slight decrease of performance named overreaching followed by a dramatic loss due to the stages of OT.
However, this division is only a rough guideline because the transitions between the points listed above are fluent. However, the causes, symptoms, and treatments of OT are not sport-specific, and the results of a study of OT are transferable to many other sports.