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. During a 16 y period, anthropometric profiles (n = 616) were measured from 126 cyclists categorised as World class, Elite and Sub-Elite. The date of each profile measurement was categorised to a season phase: Off-Season (October 1 – December 31); Early-Season (January 1 – April 30) and Late-Season (May 1 – September 30). Compared to Sub-Elite and Elite road cyclists, World class road cyclists were on average (Mean [95 % CI]) 1.18 kg [0.46, 1.90] and 0.60 kg [0.05, 1.15] lighter and had skinfolds that were 7.4 mm [3.8, 11.0] and 4.6 mm [1.8, 7.4] lower respectively. There were main effects for season phase with higher values measured for body weight (0.41 kg [0.04, 0.77]) and skinfolds (4.0 mm [2.1, 6.0]) in the Off-Season compared to the Early-Season. Compared to Track Endurance cyclists at the World Class level, female Road cyclists had lower body weight (6.04 kg [2.73, 9.35]) and skinfolds (11.5 mm [1.1, 21.9]). Study 2 concluded that higher performing female road cyclists are lighter and leaner than their less successful peers as well as track endurance cyclists.
While a low body weight is a common goal of road cyclists, little is known about the relationship between functional lean mass and power output. In study three (Chapter 5), amateur female road cyclists (n = 33) performed a power profile (6, 15, 30, 60, 240, s maximal effort) on a wind-braked ergometer. Maximal mean power (MMP) for each bout was compared to lower body lean mass (LBLM) measured using dual energy X-ray absorptiometry (DXA). The MMP for efforts of all durations were significantly correlated with LBLM. Relative to the durations of the effort, the slope of the relationship reduced in a curvilinear fashion indicating that the contribution of LBLM to power output for efforts greater than 240 s is stable at ~10 W/kg LBLM. For shorter durations, the slope was greater: MMP 1 s, 64.6 W/kg LBLM (R2 = 0.64); MMP 5 s, 59.5 W/kg LBLM (R2 = 0.65); MMP 15 s, 40.5 W/kg LBLM (R2 = 0.50). The study showed that LBLM explains a moderate-to-high proportion of maximal cycling power output for efforts lasting less than 2 min in duration.
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 (GEtest = 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 (GEIND). There was no effect of VAR on GEtests. The difference between GE (mean ± SD) measured during CON (18.4±1.6%) and VAR cycling (18.6 ± 1.1%) was trivial. SRM based estimates of EE using each athlete’s mean GE were all <2% of CAL. The findings of this study support the use of calibrated power meters for estimating cycling EE during variable intensity cycling <75% MAP.
Study five (Chapter 7) presents a case study of a female cyclist returning to elite competition following a period of post-viral chronic fatigue associated with poor weight management. Body composition was measured using DXA and anthropometry. Dietary manipulation involved a modest reduction in energy availability (EA) to 30 - 40 kcal / kg / fat free mass / d and an increased intake of high quality protein, particularly following training (~20 g). Through the re-training period, total body weight decreased (-2.82 kg), lean mass increased (+0.88 kg) and fat mass decreased (-3.47 kg). Favourable body composition changes and training adaptations were achieved through a subtle energy restriction associated with increased protein intake and sufficient EI during training.
Being weight conscious and having a desire to optimise power output relative to weight, exposes female cyclists to an increased risk of poor bone health. The final two studies (Chapters 8 & 9) investigate the effects of a pre-exercise calcium supplementation via a meal on cycling performance, gut comfort and biomarkers of bone turnover to consider the effects of this strategy in maintaining bone health. Well-trained female cyclists (n = 32) completed two 90 min cycling trials (80 min at 60% MAP followed by a 10 min time trial) separated by 1 day. Exercise trials were preceded by 2 h with either a calcium-rich (1352 ± 53 mg calcium) dairy based meal (CAL) or a control meal (CON; 46 ± 7 mg calcium). Blood was sampled pre-trial; pre-exercise; and immediately, 40 min, 100 min and 190 min post-exercise. Blood was analysed for ionized calcium (iCa) and biomarkers of bone resorption: Cross Linked C-Telopeptide of Type I Collagen (CTX-I) and Parathyroid Hormone (PTH) using the enzyme-linked immunosorbent assay (ELISA) technique. Parathyroid Hormone and CTX-I concentrations increased from pre-exercise to post-exercise in both conditions but were attenuated in CAL. Parathyroid Hormone was 1.55 [1.20, 2.01] times lower in CAL immediately post-exercise and 1.45 [1.12, 1.88] times lower at 40 min post-exercise. Cross Linked C-Telopeptide of Type I Collagen was 1.40 [1.15, 1.70] times lower in CAL immediately post-exercise, 1.30 [1.07 – 1.57] times lower at 40 min post-exercise and 1.22 [1.00, 1.48] times lower at 190 min post-exercise. There was no effect of meal type on measures of time trial performance or gut comfort. The investigation found that a calcium-rich pre-exercise breakfast meal containing ~1350 mg of calcium consumed ~90 min before a prolonged and high intensity bout of stationary cycling attenuates the exercise induced rise in markers of bone resorption.
In conclusion, this thesis represents a unique collection of studies that investigate a broad range of themes around body composition in female cyclists. The findings provide insight into body composition performance relationships, how body composition might be manipulated and a potential strategy to better maintain bone health. The data support and extend research which has been performed with male cyclists and provides practical tools and strategies which can be realistically implemented by female endurance athletes and sport scientists in the daily training environment.