Physiques that perform: The interaction between body composition management, performance and calcium homeostasis in female cyclists

Abstract

Body composition of female cyclists is believed to have an impact on performance. The central aim of this thesis was to address social, technical and health related issues around body composition management in this population. The first study (Chapter 3) examined the satisfaction of elite female cyclists with their body weight in the context of race performance, the magnitude of body weight manipulation and the association of these variables with menstrual function. Female competitors in the Australian National Road Cycling Championships (n = 32) and the Oceania Championships (n = 5) completed a questionnaire designed to identify attitudes towards body weight as it relates to performance, the magnitude of body weight change and the techniques used to manipulate body weight. All but one cyclist reported that female cyclists are a weight conscious population and 54% reported having a desire to change body weight at least once weekly. Of the cyclists surveyed, 62% reported that their current body weight was not ideal for performance. The perceived ideal body weight was (mean ± SD) 1.6 ± 1.6 kg (2.5 ± 2.5%) less than their current weight and 73% reported their career lowest body weight was either 'beneficial' or 'extremely beneficial' for performance. A majority (65%) of the cyclists reported successfully reducing body weight in the previous 12 mo with a mean loss of 2.4 ± 1.0 kg (4.1 ± 1.9%). The most common weight loss technique was reduced energy intake (76%). Five cyclists (14%) had been previously diagnosed as having an eating disorder by a physician. Of the 18 athletes not using a hormonal contraceptive, 11 reported menstrual dysfunction (oligomenorrhea or amenorrhea). The first study showed that elite female cyclists are a weight conscious population who may not be satisfied with their body weight leading into a major competition and in some cases, are frequently weight conscious.The purpose of the second study (Chapter 4) was to describe normative values and seasonal changes for body composition in female road and track endurance cyclists. In order to better understand changes in energy balance (EB) when body composition is being manipulated, measures of energy intake (EI) as well as energy expenditure (EE) require accurate measurement. Study four (Chapter 6) validated the use of commercially available power meters (Schoberer Resistance Measurement, Jülich, Germany; SRM) for estimating EE during variable intensity cycling. Female road cyclists (n = 9) completed a gross efficiency test (GE test = 4 min at ~45%, ~55%, ~65% and ~75% maximal aerobic power; MAP) before and after 10.5 min of either constant (CON) or variable (VAR) intensity cycling averaging ~55% MAP. Gross efficiency (GE) measured pre-, post-and during CON and VAR cycling was compared. Total EE for 10.5 min of VAR cycling was estimated using indirect calorimetry (CAL) and compared to estimates based on mechanical power (SRM) using each athlete's mean GE (GE IND ). There was no effect of VAR on GE tests . The difference between GE (mean ± ...