Franco M. Impellizzeri, Aldo Sassi
Overtraining (OT) is defined as an imbalance between training stimulus and recovery so that performance is impaired despite continued training. Professional road-cycling is characterized by heavy training load and many days of competitions (from 100 to 120). Therefore, due to high psychological and physiological stress professional cyclists can be considered at high risk of overtraining (OT). Several studies have investigated the physiological and psychological alterations during OT. The aim of this study was to evaluate ACTH and Cortisol responses to exhaustive exercise in OT professional cyclists.
Eleven professional cyclists out of fifty-two were suspected of overtraining (OT) during two seasons due to persistent performance impairment (i.e. incapacity to end competitions) even after a period of rest or tapering. To confirm the OT state athletes had to show 1) an increased of Total Mood Disturbance Indices (TMD) determined from the Profile of Mood States, 2) a decreased time to exhaustion (TE) during a cycling test at an absolute costant workload of 5.4 W·Kg-1 compared to previous test, and 3) the absence of viral infections. Before and 5 min after the cycling test (conducted at 10.00 AM) blood samples were collected and ACTH and Cortisol concentrations were determined. All the athletes were retested when considered out of the OT conditions, corresponding to return to competitions with good performances.
To analyse TMD and TE corresponding to the period before, during and after OT, a one-way ANOVA for repeated measure were used.
The ACTH and Cortisol values during and after OT were analysed using paired t test. Significance was set at P<0.05. Seven cyclists (age 24.3 ± 4.0 yrs, height 177.3 ± 3.2 cm, body mass 68.1 ± 5.1 kg, VO2max 4.832 ± 0.326 l·min-1, % body fat 4.4 ± 1.6, maximum power 432.0 ± 33.1 W) out of eleven were considered OT (four showed viral infections). TE during OT was significantly lower (P<0.01) than before and after OT, whereas TMD was significantly (P<0.01) higher. ACTH and Cortisol concentrations were not different at rest. ACTH response after exhaustive exercise was blunted (P<0.05) whereas the lower Cortisol response was not significant.
The results of this study showed that OT professional cyclists had a diminished ACTH response after an exhaustive exercise as already showed by Urhausen et al. (1998) in OT endurance athletes, and by Odagiri et al. (1996) in “exhausted” triathletes after an ultraendurance event. We fail to detect a difference in the Cortisol response similarly to Odagiri (1996) but differently to Urhausen et al. (1998) who found a tendency to a lower Cortisol response . Failure to show a diminished Cortisol response in this study may be due to a too short sampling period (5 min after exercise).
Odagiri et al. (1996) Int J Sports Med 17: 325-331Urhausen et al. (1998). Med Sci Sports Exerc 30: 407-414