Phasal Considerations of a Female Cyclist: Exploring the Hormone-related Implications for Training and Competitive Performance

Serene L Lee

Historical data suggests that oral contraceptive (OC) use is prevalent among the female athletic population to alter bleeding patterns and/or alleviate menstrual cycle (MC) symptoms for training and competition. The steroidal hormones in OC suppress the endogenous circa-mensal ovarian hormonal milieu while also exerting additional biological actions on a female’s body; yet little is known about the impact of OC use on sports and exercise performance. This considerable lack of knowledge has prompted calls for future studies to prioritise OC users. However, recent anecdotal evidence suggests a shift away from OC use amongst female athletes due to an evolving perception towards a regular MC being an indicator of good health and training status. Given the above, there is a need to investigate the current climate of OC use, MC symptoms and their associated perceived and actual impact on training and competitions to continually optimise performance in female athletes. Seminal work on MC/OC hormones also revealed molecular mechanisms that indicate their influence on the availability of carbohydrate (CHO), which is the predominant energy source to sustain and/or repeat bouts of moderate-high-intensity exercise. While such mechanistic studies are informative, it is still relatively unclear how cyclical hormonal fluctuations impact exercise performance due to the lack of high-quality research. Therefore, this thesis sought to address this gap in literature with an overall aim of understanding how MC/OC phases impact upon cycling training and performance. This was achieved through the completion of three studies that were designed to 1) determine the current climate of menstrual manipulation (particularly OC use) in female cyclists in Australia (Chapter Three), 2) investigate the impact of OC use on in-exercise CHO supplementation and endurance performance (Chapter Four) and 3) examine how MC/OC phases influence substrate utilisation and fatigue resistance, which are key determinants of competitive success (Chapter Five). Chapter Three explored the extent of menstrual manipulation, period-related symptoms, and training disruptions in 205 Australian female cyclists (28 elite, 98 sub-elite and 79 recreationally active). The survey data indicated that while menstrual manipulation is still a common practice (44%), Australian female cyclists are becoming less likely to utilise OC to manipulate their MC. The respondents who reported reduced ‘workout tolerance’ had a higher likelihood of practising menstrual manipulation. Study findings also confirmed the presence of period-related symptoms and perceived training impairments. Period pain, increased irritability, lower energy levels and more sugar cravings were the most commonly reported symptoms; and high-intensity interval exercise was the most compromised training session. Importantly, it was evident that the affective needs surrounding period-related concerns are unique in its frequency and severity. The large variation in symptoms experienced between individuals precludes group-level understanding of period-related performance impacts. Instead, the female cyclist should be empowered to monitor her own unique symptoms and communicate her concerns to her support network. Additionally, the need to increase dialogue and education of female cyclists and their coaches surrounding the biology and performance impacts of MC and OC use was also identified. Chapter Four investigated the impact of OC phase on performance, and the physiological and subjective responses to prolonged, high-intensity exercise with and without in-exercise carbohydrate (CHO) supplementation, in a group of well-trained female cyclists (n = 10). This study also aimed to address the shortfall in research on OC users and to determine if current in-exercise CHO recommendations of 60 g.h-1 (derived from male populations) can be extrapolated to women. Study findings showed that the lack of CHO supplementation resulted in a decrease in time trial performance (~5%; p=0.002) and emotional well-being in the active pill phase when compared with the sugar pill phase. However, the reduction in performance was overcome by CHO supplementation. These findings indicate that OC-using athletes should be mindful of the implications of OC use on endurance performance, considering the documented difficulties of consuming sufficient food in-exercise. Furthermore, as the active pill constitutes three out of a four-week OC cycle, the impact of OC use on performance should be of concern. Chapter Five examined the effect of ovarian hormones and their OC synthetic equivalents on substrate utilisation and fatigue resistance during a race-specific cycling protocol. Participants included both eumenorrheic females (n = 11) and OC users (n = 8). A standardised, CHO-loading diet of 8 g.kg-1 body mass was provided 24-h pre-trial to maximise endogenous CHO stores as per current nutritional guidelines. No food was provided during the trial to simulate reduced energy availability as per typical race scenarios. Study findings demonstrated increased fatigue (~ 3.5% reduction in average power; p=0.032) during the high-hormone luteal phase in eumenorrheic females, possibly due to the combination of higher CHO utilisation (~4%; p=0.020) during the moderate-intensity component of the trial (observed in the study) and the theoretical reduction in ability to access stored glycogen. Hormone-induced ventilatory inefficiencies (~7% increase in minute ventilation; p<0.001) may also have increased metabolic demand, which further reduced CHO availability for energy production in the trial-concluding fatigue resistance test. In OC users, despite some phasal changes in cardiorespiratory and metabolic data in moderate-intensity cycling (~6% higher blood glucose and ~2% higher minute ventilation in active pill phase; p=0.024 and 0.020 respectively), none of the performance parameters in the FRT was different. These findings suggest that ovarian hormones may have greater influences on physiological parameters within eumenorrheic females, than OC synthetic equivalents within OC users. There may be an increased need to maintain CHO availability during the high-hormone luteal phase to sustain CHO-sourced energy production during high-intensity exercise. Additionally, the low-hormone follicular phase not only revealed better in-trial exercise performance, but also augmented post-trial affective responses. These outcomes may confer benefits in multi-day training blocks and stage races. The collective findings of this PhD indicate that some phasal differences exist between and within eumenorrheic and OC-using well-trained female cyclists; and its effect on performance becomes particularly notable when faced with metabolic stress. Irrespective of MC or OC, the maintenance of CHO availability, especially through in-exercise CHO supplementation, can help mitigate hormone-induced variations in substrate utilisation and should be prioritised to minimise declines in performance. We also present evidence of hormone-related changes in the emotional well-being in all three studies, which have the capacity to negatively influence future performances. Additionally, collective findings demonstrate that perceptions (in Chapter Three) were not always congruent with measurements (from Chapters Four and Five); however, we need to be cautious with this interpretation considering that the cohort of survey respondents and experimental trial participants were not the same. Regardless, the combined interpretation of experiences of period-related symptoms, and the impact of OC use on perceived and observed performance outcomes from Chapters Three, Four and Five indicated that that the relationship between MC, OC use and exercise performance is complex and must be carefully nuanced. When considered in concert, improving athlete-coach communication may help optimise performance – female cyclists and their coaches can collaborate to better design training plans and nutritional strategies with intentional modifications to account for their MC and OC phases. Thesis findings also advocate for future dialogue and education surrounding cyclical hormonal fluctuations to not only include scientific findings of biology, physical adaptation, and their possible impact on performance, but also the anecdotal and lived experiences of female athletes. This will potentiate the development of mitigation strategies for female athletes to overcome some of the hormone-related signs and symptoms, which are perceived to be debilitating, but have no significant impact on objective exercise performance.

Phasal Considerations of a Female Cyclist: Exploring the Hormone-related Implications for Training and Competitive Performance

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