Effects of endurance training interventions on resting metabolic rate, body composition and performance in highly trained athletes

Abstract

Resting metabolic rate (RMR) can be used to assess energy availability (EA),which, if suboptimal, can lead to impaired physiological function, increased risk of illness and injury and maladaptation to training. Low EA has been investigated predominantly in females with menstrual disturbances, bone fragility and disordered eating; however there is a lack of literature regarding athletes who may suffer energy restriction simply due to a mismatch between energy intake and their training load. In a high performance setting, athletes commonly undertake periods of heavy training, either by increasing volume and intensity at sea level, or adding environmental stimuli such as hypoxia, in order to improve performance. It is unknown, however, how such training interventions can affect the body at a metabolic level. This thesis aimed to provide an examination of how intensified training periods undertaken at sea level and upon altitude exposure could affect RMR, body composition and performance in highly trained endurance athletes. The key findings of this research were: 1) RMR measurement can be implemented into the daily training environment using the ParvoMedics TrueOne 2400 metabolic cart, once corrected for minute ventilation (Study 1); 2) RMR, body mass and performance can decrease following four weeks of intensified training (Study 2),or after 12 days of altitude exposure at 1800 m in elite rowers (Study 4), likely due to insufficient energy intake to support heavy training demands; 3) Favourable adaptations to training and RMR can occur following three weeks of altitude exposure at 2200 m in middle-distance runners, likely related to a greater appetite and energy intake, and a more moderate energy expenditure (Study 3); and 4) RMR is one of a series of markers of training distress that can be employed to determine athletic responses to training (Study 5). The findings of this thesis can be used to safeguard athletes undertaking intensified training from decreased RMR and EA, subsequently improving training consistency and performance. Although RMR does not appear to respond immediately to changes in training load, it is nonetheless a key marker within a continuum of training-related disturbance involving metabolic, hormonal and neural mechanisms; the combination of which are proposed to aid practitioners in the assessment of an athletes’ state of wellbeing. The data further reinforces the need for proactive measures to be employed prior to heavy blocks of training, for example supplementing energy intake before appetite declines, to alleviate fatigue and attenuate any potential decreases in RMR related to insufficient energy intake. Training at altitude must also be moderated based on the modality of training and its metabolic demands in order to achieve training and performance goals. Principally, the findings of this thesis suggest that RMR may provide a useful monitoring tool alongside other validated markers of overreaching to assess training-related distress. Regular RMR measurement has the potential to safeguard athletes from the adverse effects of reduced EA, allowing more optimal conditions for positive training adaptations and ultimately, athletic performance.

Date of Award	2017
Original language	English
Supervisor	Kevin Thompson (Supervisor), Luara Garvican-Lewis (Supervisor) & Anthony Rice (Supervisor)