Steroid hormones are important regulators of physiological processes (20). They are classified according to their physiological functionality, such as androgens, glucocorticoids, estrogens and progestins (20). Testosterone is an androgenic steroid hormone secreted in humans (23). It stimulates the development of male secondary sex characteristics (e.g. deepening of the voice, hair growth and genital growth during puberty) (20), and the production of skeletal muscle (14) and red blood cells (1). Cortisol is a glucocorticoid primarily involved in gluconeogenesis, reducing glucose utilization and raising blood glucose concentrations (16). It is also actively involved in the formation of adrenaline (29), protein degradation (23) and immune function (13). Estradiol is a naturally secreted estrogen primarily responsible for the stimulation of the primary and secondary female sex characteristics (e.g. breast development, hair growth and menstrual cycle regulation) (20). It is also involved in the maintenance of bone health (10) and can increase mitochondrial efficiency and reduce oxidative stress in cerebral blood vessels (27). Progestins are essential for reproduction (20), and progesterone, the primary progestin, is a precursor for the production of other steroid hormones, including testosterone, cortisol and estradiol (20). Progesterone also stimulates neuroprotection, axonal regeneration, and myelin formation and repair (25) and has known antiestrogenic actions (15). Whilst the steroid hormones are primarily responsible for different physiological processes they also interact permissively (24), synergistically (22) and antagonistically (17). Steroid hormones are not secreted continuously, but in pulses subject to biological rhythms (19), such as diurnal (twice daily) and circadian (approximately every 24h) rhythms (18). In addition to biological rhythms, steroid hormone levels can be acutely influenced by stress (9), sleep (19), diet (4), medications (8), and exercise (11). Given the importance of steroid hormones to physiological processes (20), variations in steroid hormone levels have the potential to affect the components of physical performance, such as agility, speed, power and endurance. In males, an increase in the testosterone/cortisol ratio is positively associated with greater performance in power and strength (7) tests. Higher ttestosterone levels have been associated with improved speed, power and strength and higher cortisol levels have been associated with reduced speed and power though current evidence is inconsistent (6, 7). This research was univariate in nature evaluating the pairwise relationships of hormone effects on motor fitness and not evaluating the multiple and interacting effects. The next logical development is to evaluate these influences via multiple linear regression analysis. The aim of this study is to evaluate the capacity of testosterone, cortisol, progesterone and estradiol levels to predict countermovement jump (CMJ), agility, 5m, 10m and 20m sprint and multi stage fitness test (MSFT) performance in young male Australian Football (AF) athletes. The aim is to improve understanding of the influence that steroid hormones have on physical performance in male AF athletes, both at the level of individual hormones and in combination with each other. Due to the complex relationship between steroid hormones, it is hypothesised that a combination of testosterone, cortisol, estradiol and progesterone will be a stronger predictor of physical performance than any of the hormones predicting physical performance in isolation.
|Number of pages||4|
|Journal||Journal of Australian Strength and Conditioning|
|Publication status||Published - 2015|