Polymorphonuclear leucocyte phagocytic function, γδ T-lymphocytes and testosterone as separate stress-responsive markers of prolonged, high-intensity training programs

Excessive exercise with limited recovery may lead to detrimental states of overreaching or the overtraining syndrome. Chronic maladaptation in endocrine and immune mechanisms occur with the incidence of these states. Exercise-induced cortisol and testosterone responses have been proposed as biomarkers of overreaching, with blunted responses following intensified-training periods. Yet, limited information on the effects of overreaching in immunity is available. Healthy individuals completed a 30-min running protocol (the RPETP) before and after a 12-day intensified-training period. Blood and saliva were collected before, after and 30min after RPETP at pre-training and post-training. Plasma and salivary cortisol and testosterone, leucocyte proliferation and polymorphonuclear leucocyte phagocytic activity were examined. Plasma and salivary cortisol were acutely unaffected pre-training (−14% and 0%, p > 0.05) and post-training (−14% and +46%, p > 0.05). Comparing pre-training with post-training, blunted responses were observed in plasma testosterone (43%–19%, p < 0.05) and salivary testosterone (55%–24%, p > 0.05). No acute or resting changes in total leucocyte counts or most leucocyte subsets occurred pre-training or post-training. Yet, a 194% acute elevation in γδ T-lymphocyte number occurred pre-training (p < 0.05), and average resting concentrations were 174% higher post-training. Baseline phagocytic activity was 47% lower post-training (p < 0.05). Intensified training was detrimental, significantly reducing phagocytic activity. Testosterone blunted post-training, indicating an excessive training-related hypothalamic-pituitary gonadal dysfunction. The γδ T-lymphocytes sensitivity to exercise was noted, rendering it as a potential stress-responsive cellular marker. The usefulness of the RPETP to track the onset of overreaching is proposed.