Stenholm, Johanna. Immune system adaptations during competition period in female cross-country skiers. Master’s Thesis in Exercise Physiology, Department of Biology of Physical Activity. University of Jyväskylä. 95pp.
Purpose. This study was undertaken to characterize the extent of immune and endocrine changes in competition period and related to two competition weekends in well trained athletes in different parts of the competition period. An additional purpose was to evaluate if the changes in immunological variables would have an effect on the incidence of upper-respiratory-tract infections. The effect of the nutrition, nutrient and training status was also studied.
Methods. Ten (10) national level female skiers were investigated as they followed their normal race preparation routines. Blood samples were taken for basal and recovery measurements in the mornings approximately an hour after the athletes had woken up. Saliva samples were taken in the basal measurement morning, in
the first normal distance competition morning, immediately after finishing the race and in the recovery measurement morning. The ski race distances were between 4-12 kilometres and the race finishing time were between 12 and 45 minutes. The first competition was in early December and the second took place in Finnish championships in late January. The second competition of the present athletes took place in extremely cold weather (approximately -20 Celsius degrees). If the athletes were not able to participate to the scheduled competition, they were measured during the next possible weekend. The athletes filled their daily training diaries, food diaries both 3 days before the competition and during the competition weekend, and they reported upper-respiratory tract (URTI)-symptoms using WURSS-21 questionnaire.
Results. URTI-symptoms were the most common reason for the athletes to miss training. There was a significant difference (p<0.05) in URTI-symptoms between the control group and the athlete group in the main competition period measurements. Blood leukocytes of the athletes were at a clinically normal level but were slightly higher in athletes in the competition period than in the controls but lower in the transition phase. The athletes had significantly (p<0.05) lower salivary IgA levels in the competition period than in the transition phase. In the basal measurements there were significant correlations between average serum IgA (R=0.820; p<0.05) and serum IgG (R=-0.857, p<0.05) levels to the number of days that athletes were unable to participate in their training sessions. Iron intake correlated negatively with testosterone/cortisol ratio (R= -0.750; p<0.05) and with the total amount of blood leukocytes (R= -0.778; p<0.01) in the main competition period. The amount of low and moderate training had a significant negative correlation with salivary IgA levels (R= -0.750; p<0.05) and with testosterone/cortisol -ratio(R= -0.714; p<0.05).
Discussion and conclusion. The significant increase in the upper-respiratory tract infection was seen to be related to competitions when compared to the transition phase. Previously, it has been shown that the international level cross-country skiers adapt well to an acute exhaustive exercise test of short duration in a laboratory settings, even during the periods of heavy training and multiple competitions. But the effect on the athlete’s health still remains unclear. In conclusion, substantial chances were observed in several immune-endocrine, substrate and metabolic measurements related to competition period and competition weekend. The immunoglobulin levels of A and G and testosterone/cortisol-ratio might be good indicators of the immunological state of the athletes. When designing training, competition and nutrition of the athletes, the sufficient recovery time has to be taken into account to avoid catabolic state and immune suppression. It is also recommended to take care of the adequate intake of nutrients but avoid excess doses, especially iron, as they might have suppressant effect on immunity of the athletes.
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