INTRODUCTION: Because endurance functions are enhanced in a short period by high-altitude training, cross-country skiers frequently perform the training. However, some skiers worsen their conditions during the high-altitude training camp and others cannot obtain the training effects after the camp. Individual differences in the training effects are caused by various factors. The purpose of this study was to examine whether enhancement of psychological stress due to a long-term high-altitude training camp would become an inhibitory factor for occurrence of the training effects. METHOD: Fifteen cross-country skiers participated in the high-altitude training camp for three weeks. Psychological stress responses during the training camp were analyzed with the two-dimensional mood scale (TMS) and two constituents of saliva (cortisol and chromogranin A). TMS was determined to estimate subjective mood states (i.e., hedonic tone and negative arousal level). The skiers performed TMS immediately after getting up every day. Their saliva samples were collected immediately after getting up (every week) and before the afternoon training (every two days). The extent of physiological burden due to daily training was evaluated by the training impulse (TRIMP). The high-altitude training effects were measured by maximal oxygen uptake (VO2max) at a low altitude before and after the camp. The VO2max levels of 10 skiers (Up group) were increased after the camp, but those of five skiers (Dn group} were decreased. The mean levels of each analysis item for both groups in the early period and later period of the camp were compared. RESULTS: In the later period of the camp, the hedonic tone of the Dn group became lower than that of the Up group, and the negative arousal level showed a tendency towards becoming higher. In addition, the cortisol level of saliva in the Dn group taken after getting up was significantly higher in the later period than the early period (Fig.1). Chromogranin A level in the Dn group taken in the afternoon was also significantly higher in the later period. On the other hand, the Up group showed a tendency towards elevated TRIMP in the later period. DISCUSSION: Skiers with a decrease in VO2max after the high-altitude training camp had an increase in stress responses centering on increased reactivity of the hypothalamic-pituitary-adrenal (HPA) axis in the later period of the camp. The subjective mood states of these skiers in the later period showed a tendency towards worsening. However, the degree of physiological burden due to the training was rather low. Therefore, these 1 stress responses may be associated with a psychological camp life, etc. CONCLUSION: in the long-term, psychological stress during training in high altitude training camps may become a factor inhibiting the training effects on endurance function enhancement, etc. However, let it be noted that the number of subjects was small in this study; consequently, we need to add data confirming this speculation.
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