Hormonal, Metabolic and Cardiorespiratory Responses of Young and Adult Athletes to a Single Session of High Intensity Cycle Exercise

Abstract

This study aimed to determine the effects of a single High Intensity Interval Training (HIIT) session on salivary cortisol (SC) levels, physiological responses and performance in trained boys and men. Twenty-three boys (11.5±0.8 years) and 25 men (29.7±4.6 years) performed HIIT (four consecutive Wingate Anaerobic Tests). SC in boys and men increased after HIIT from 5.55±3.3 nmol/l to 15.13±9.7 nmol/l (+173%) and from 7.07±4.7 nmol/l to 19.19±12.7 nmol/l (+171%), respectively (p<0.01). Pre-test SC as well as post-test changes were comparable in both groups (both p<0.01). Peak blood lactate concentration was significantly lower in boys (12.6±3.5 mmol/l) than in men (16.3±3.1 mmol/l; p<0.01). Throughout the HIIT, mean heart rates in boys were higher (p<0.001) but relative peak oxygen uptake (ml∙min-1∙kg-1; p<0.05) and performance were lower (p<0.001) in boys than in men. HIIT in young athletes is associated with a higher activation of the hormonal stress axis than other types of exercise regimes as described in the literature. This study is the first to show a pronounced SC increase to HIIT in trained boys accompanied by elevated levels of blood lactate concentrations and heart rate suggesting a high cardio-respiratory, metabolic and hormonal response to HIIT in 11-year-old boys.