Reproducibility of acute steroid hormone responses in men to short-duration running

PURPOSE: Progressively overloading the body to improve physical performance may lead to detrimental states of overreaching/overtraining syndrome (OTS). Blunted cycling-induced cortisol and testosterone concentrations have been suggested to indicate overreaching following intensified-training periods. However, a running-based protocol is yet to be developed or demonstrated reproducible. This study develops two 30-min running protocols: (i) 50/70 (based on individualised physical capacity) and (ii) RPETP (self-paced) and measures the reproducibility of plasma cortisol and testosterone responses. METHODS: Thirteen recreationally active, healthy males completed each protocol (50/70 and RPETP) on three occasions. Venous blood was drawn Pre-, Post- and 30 min Post-Exercise. RESULTS: Cortisol was unaffected (both p > 0.05; 50/70: η2 = 0.090; RPETP: η2 = 0.252) whilst testosterone was elevated (both p < 0.05; 50/70: 35%, η2 = 0.714; RPETP: 42%, η2 = 0.892,) with low intra-individual coefficients of variation (CVi) as mean ± standard deviation (50/70: 7 ± 5%; RPETP: 12 ± 9%). Heart rate (50/70: ES = 0.39; RPETP: ES = -0.03), speed (RPETP: ES = -0.09) and rating of perceived exertion (50/70: ES = -0.06) were unchanged across trials (all CVi < 5%, p < 0.05). RPETP showed greater physiological strain (p < 0.01). CONCLUSIONS: Both tests elicited reproducible physiological and testosterone responses, but RPETP induced greater testosterone changes (likely due to increased physiological strain) and could therefore be considered a more sensitive tool to potentially detect OTS. Advantageously for the practitioner, RPETP does not require a priori exercise-intensity determination, unlike the 50/70, enhancing its integration into practice.