The fundamental aim of an endurance athlete is to improve their ability to physically perform at a high intensity for a prolonged period of time. Furthermore, this high performance area of sport can be metabolically demanding, requiring high rates of oxidative (aerobic) and non-oxidative (anaerobic) metabolism with precise regulation and control. To meet these requirements, monitoring of training is an essential component of a successful training plan, as manipulation of training volume, frequency, intensity and recovery is vital for optimal results. Due to the long-distance nature of endurance events, high-volume and low-intensity training has traditionally been the main focus for endurance athletes. However, this high-volume load can often lead to overtraining and/or a performance plateau. More recently, a shift in training volume and intensity involving low volume but high intensity sessions (termed high-intensity interval training; HIT), has become more commonly used by endurance athletes. While endurance athletes have long appreciated the role of HIT as part of a comprehensive training program, the recent surge in HIT popularity is mainly due to the efficiency of the training and the recent evidence that it causes gene expression and phenotypic performance changes that resemble those of endurance training. Studies have suggested that in young healthy persons of average fitness, intense interval training is therefore a time-efficient strategy with results comparable to traditional endurance training.However, despite recent research advancements, the fundamental question remains regarding the minimum volume of exercise necessary to improve performance. The aim of the proposed study was to investigate two different regimes of high intensity exercise (low-volume/high-frequency and high-volume/low-frequency) in 26 well-trained endurance cyclists, measure their effect on both physiological changes and gene expression changes, and determine whether the changes caused by HIT are due to total work or areregime-dependent. The training intervention consisted of nine bouts of 30-second sprints per week for two weeks at different volumes per group: one low-volume/high-frequency group with 3 repetitions 3 times per week (9 subjects), one high-volume/low-frequency group with 9 repetitions once per week (9 subjects), and one control group without training intervention (8 subjects). The physiological measures of interest related to the metabolic changes from the endurance capacity test, VO2max test, and Wingate test, which were measured on all subjects at time-points before (baseline) and after the intervention period.To achieve a full understanding of the biochemical adaptation, regulation and markers associated with HIT, an examination of the gene expression changes in vivo was performed by taking blood samples from participants before training (baseline), immediately after the final training session (acute response), and 72 hours after the final training session (delayed response), extracting RNA from white blood cells, and undertaking a genome-wide microarray analysis to identify genes differentially expressed after high-intensity exercise.The aim was also to investigate the changes in expression levels in response to varying levels of exercise (frequency of weekly sessions and number of bouts per session), and which of these training regimes would achieve a higher performance outcome.Some significant differences were found in the physiological traits measured between training intervention groups and the control group, as well as between the groups themselves. While there were no significant changes in ventilation threshold (VT1) between the two training groups themselves, a significant difference was found between both of the training groups and the control group post-training. Furthermore, a significant increase from baseline (p = 0.006) was found in the post-training intervention endurance capacity test (ECT) for the high-volume/low-frequency group, while no significant change was seen inthe low-volume/high-frequency group or the control group. These findings suggest that the high-volume/low-frequency regime may be more effective at improving endurance performance in relation to the endurance capacity test.In relation to gene expression changes, data was only available for 6 subjects in the low volume/high-frequency group and 4 subjects in the high-volume/low-frequency group.Microarrays were performed for these subjects at three time-points (baseline, acute post training and delayed post-training); however, after normalisation, quality control and statistical analysis of participant data, no significant changes in gene expression were found between either of the two post-training time-points compared to baseline, or between different training regime groups.Overall, however, this study allowed researchers to obtain an increased understanding of the physiological and gene expression adaptations that can result from high intensity training and determined that training regime influences performance outcome. By implementing the minimum training regime necessary to obtain performance improvements it may be possible to optimise athlete response to training whilst avoid overtraining and illness. Additionally, no alteration in gene expression was detected after the training intervention, possibly due to that the effect size investigated being smaller than anticipated. Further research in this area may provide sport coaches, exercise physiologists,sport scientists, and athletes another tool to optimise training prescription for athletes as well as evaluating and monitoring an individual’s biological response to exercise.
|Date of Award||18 Jun 2016|
|Supervisor||Bon Gray (Supervisor) & Lotti Tajouri (Supervisor)|