Investigation of the relationships that exist between athletic training, hormones and sleep in young healthy male athletes : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Physiology at Massey University
Background. Many people engage in exercise for recreation, to promote personal health and as a profession. Accordingly there is wide ranging interest in the factors that affect a person's performance during exercise and in how that performance can both he assessed and enhanced. The physiological basis of exercise performance and its enhancement have been investigated for many years. Such investigations in people are impeded by the understandable reluctance of participants to provide significant numbers of blood samples by venepuncture. The recent development of an ultrasound method for non-invasive sampling of extracellular fluid, called transdermal electrosonophoresis (ESP), offers tremendous opportunities for benign monitoring of physiological responses involving changes in blood/extracellular fluid composition associated with exercise and indeed in clinical settings. Sleep quality/quantity is considered to have significant impact on training effectiveness and performance, with poor sleep correlated with poor athletic outcome. The link here is considered to involve growth hormone, as poor sleep quality/quantity diminishes growth hormone concentrations and reduced growth hormone concentrations impede training induced muscle development. Training effectiveness and recovery have been monitored in past research through measurement of blood hormone profiles, in particular the testosterone: cortisol ratio. The overall objective of this study was to validate the use of ESP as a non-invasive blood sampling technique through the study of the relationships that exist between exercise, fatigability, fitness, and hormone levels in blood, saliva and extracellular fluid and the investigation of the impact of spontaneous sleep disturbances on these relationships in young healthy male athletes. Methods. Plasma, ESP and saliva samples were taken regularly from 14 male rugby players during a four-week study. The plasma and ESP samples were analysed for testosterone, cortisol and growth hormone concentration. The saliva samples were analysed only for testosterone and cortisol levels. Fitness was assessed each week using a maximal treadmill test and fatigability was also investigated. Sleep quantity/quality was investigated using personal sleep logs which the participants filled out daily. In addition the participants' alcohol consumption was reported in the sleep log. Results. Correlations between hormone concentrations measured in plasma and FSP were higher than the correlations for plasma and saliva. The results here were highly significant. An equation was derived to estimate plasma concentrations of testosterone, cortisol and growth hormone using the concentrations of the hormones measured in ESP samples. Few statistically significant relationships between hormone profiles, sleep quality/quantity and athletic training were revealed in the analysis of the results of this study. A negative correlation was found between the mean plasma cortisol concentration measured in the morning and the estimated VO2
, and also between the cortisol concentration measured in the ESP sample and estimated VO2max
, but this did not quite reach significance. A negative correlation between estimated VO2max
and the mean total time asleep for the previous three or four nights was revealed. Conclusions. ESP sample analysis provides a more accurate estimation of testosterone, cortisol and growth hormone concentrations in plasma than saliva sample analysis does.