|dc.description.abstract||There is a growing number of female athletes playing in ‘professional’ contact team sport competitions in Australia. One such sport is rugby league with a year-on-year increase in participation of girls and women. Undoubtedly, women have unique physical and physiological characteristics that are likely to alter competition loads and subsequent recovery when compared to men. Nonetheless, there is limited research that has characterized the external load (e.g., movement patterns) of female rugby league players during competition. Therefore, the aim of the first study of this thesis was to describe the movement patterns of women playing rugby league during competition for immediate application in training prescription programs. In addition to external load monitoring, longitudinal biological monitoring is an important consideration in contact team sports, whereby biochemical disturbances such as oxidative stress can inform how athletes are responding to training and competition. Blood biomarkers are typically assessed via a sample of saliva, urine or blood, which are analyzed in a laboratory by highly skilled technicians using expensive procedures that can take several hours or days. Therefore, while the locomotive movement patterns of players during rugby league can be measured ‘in the field’ with validity and reliability and in real-time, it can be difficult to measure biochemical responses to exercise in an applied sport science setting. Portable point-of-care devices have become available to make this process easier to conduct ‘in the field’, with such tests offering rapid results. While two point-of-care blood oxidative stress biomarkers (i.e., Free Oxygen Radical Test and Free Oxygen Radical Defense) have been used in an applied setting, their between-day reliability remains to be determined. Therefore, the aim of the second study of this thesis was to determine the between-day reliability of these two point-of-care tests to measure oxidative stress at rest and after exercise. Although ‘in the field’ studies are important for understanding biological changes in response to sport-specific training and/or competition, a reductionist approach must be taken in women since the female sex hormones are likely to influence blood biomarkers in addition to alterations in training and competition loads. As such, the influence that exogenous and endogenous female sex hormones have on physiology should be determined before blood biomarker monitoring is applied ‘in the field’ to monitor the responses to training in an elite team sport environment. Furthermore, women are heavily underrepresented in sports science research so, at present, greater control over contextual factors in laboratory-based studies will help to contribute to a more robust understanding of female physiology. Therefore, the aim of study three and four in this thesis were to conduct well-controlled laboratory studies to interrogate the effects of the exogenous and endogenous female sex hormones on blood oxidative stress biomarkers at rest and during exercise.
The first study in this thesis examined the movement patterns of women playing rugby league during international match-play to enable specificity in training prescription for women. Global Positioning Systems and associated technology recorded the movements of players from the Australian Rugby League Women’s team (n = 31) during seven international rugby league matches. Total distance traveled was greater in the first compared to the second half (3332.9 m compared to 3249.0 m; p = 0.044), along with distances traveled at speeds >15 km·h-1 (p < 0.05), whereas players traveled further at speeds < 6 km·h-1 in the second half (p = 0.005). Backs traveled further at speeds < 6 km·h-1 (p = 0.002) and > 15 km·h-1 (p = 0.007) compared to forwards. Mean speed significantly reduced across the first and second halves (p < 0.05), while mean speed above 12 km·h-1 reduced by ~40% in the first half of the match (i.e., first ~5 min compared to the last ~5 min). These results provide practitioners and coaches with sport-specific activity profiles of female rugby league players that can be used to individualize training prescription.
Since oxidative stress monitoring has been used to assess training stress, a device that can provide rapid results and be used reliably in the field is desirable. The purpose of Study 2 was to establish between-day reliability measures of two point-of-care tests; 1) free oxygen radical test (FORT) and, 2) free oxygen radical defense (FORD) for determining oxidative stress so reliable longitudinal monitoring can be employed in future applied research. Active participants completed two trials performed on separate days comprising blood sampling at rest (n = 22) and after treadmill-running (n = 14). Between-day coefficient of variation for FORT (4.6%) and FORD (4.8%) were acceptable at rest. There was no difference in the between-day magnitude of change in FORT or FORD from pre- to post-exercise (p > 0.05). Therefore, these point-of-care tests could be reliably implemented across multi-week team sport competitions to make informed decisions about optimal recovery and reduce the risk of illness or injury. However, it was noted in this study that FORT was significantly higher in women using OC, and this required further examination to ensure the interpretation of oxidative stress monitoring in women using OC was accurate.
Within-group changes in oxidative stress across a menstrual cycle (follicular and luteal phase) and across a 4-mo OC cycle (active and inactive OC) were examined to inform practitioners and researchers of the variation in selected blood biomarkers for data interpretation and deciding on appropriate hormone profiles for experimental research designs where biomarkers of oxidative stress are a primary outcome, respectively. Blood samples were acquired from women using OC (WomenOC) and women natural-cycling (WomenNC) at three time-points of the menstrual cycle and OC packet for determination of estradiol, progesterone, oxidative stress, C-reactive protein (CRP) and other cardiometabolic biomarkers. Malondialdehydes (MDA), lipid hydroperoxides and CRP concentrations were significantly higher in WomenOC during the last week of the active OC compared to the inactive OC (+23% +96% and +104%, respectively, p < 0.05). However, there were no significant changes in these biomarkers across the menstrual cycle in WomenNC (p > 0.05). WomenOC presented with elevated lipid hydroperoxides (+28, +48% and +50%) and CRP (+71%, +117% and +130%) concentrations compared to WomenNC (p < 0.05, partial η2 > 0.25). This study demonstrated temporal changes in oxidative stress across one month of habitual OC use. As such, the day of OC use should be taken into account when interpreting changes in oxidative stress and CRP in conjunction with competition loads acquired via training or competition. From these findings, it was apparent that a laboratory-based study was required to investigate how OC may influence the redox environment during exercise, and whether specific antioxidant support i.e., N-acetylcysteine (NAC) may help to blunt excessive RONS generation in women using OC during exercise.
The purpose of Study 4 was to characterise blood indices of oxidative stress and physiology during a controlled exercise task in WomenOC compared to WomenNC, as well as assess whether NAC supplementation acts as an ergogenic aid for performance in active women using OC. Twenty recreationally-active or trained women (n = 11, WomenNC; n = 9, WomenOC) completed five trials/visits, including two cross-over experimental trials that controlled for OC (late active-OC) and menstrual cycle (mid-luteal) phase. Cardiopulmonary parameters and blood biochemistry were assessed during and after a 40-min of fixed-intensity cycling at 105% of gas exchange threshold and a 1-km cycling time-trial after acute (1-h) ingestion of a beverage containing NAC or placebo. WomenOC had higher ventilation (β [95% confidence interval] = 0.07 L·min-1 [0.01, 0.14]) and blood biomarkers of lipid peroxidation (MDA; β = 12.00 mmol·L-1 [6.82, 17.17]) and inflammation (CRP; 1.53 mg·L-1 [0.76, 2.30] compared to WomenNC (i.e., effect of Group) during fixed-intensity cycling. The exercise-induced increase in lipid peroxidation observed in the placebo trial was blunted from NAC ingestion in WomenNC but not in WomenOC. NAC did not affect 1-km cycling time-trial performance.
This study provided evidence of alterations in exercise physiology in women using OC compared to women naturally-cycling. Excessive oxidant damage to lipids from both OC metabolism and exercise metabolism may have implications for exercise adaptations associated with redox signalling or recovery from exercise.
This thesis provided new insights into the locomotive movement patterns of female rugby league players during international competition, and female-specific physiology at rest and during exercise that may have practical implications when conducting future applied sports science research in women playing rugby league (or other team sports). The implications of high oxidative stress at rest and during exercise in women using OC are unknown. However, the characterization of the temporal changes in blood oxidative stress biomarkers across the weeks of OC use, and responses to exercise provide impetus for future mechanistic studies examining redox signalling processes related to training adaptations, recovery or health in female athletes.||