Physical profiling of the female footballer : Special reference to the menstrual cycle

Abstract

There has been an exponential rise in the development and professionalism of female football, which has led to an increase in scientific research. However, there still remains a large disparity to male football and alarmingly, much of the current research has been replicated from male football ignoring the inherent physical and physiological differences between genders. One such physiological phenomena is the menstrual cycle. The menstrual cycle is a common and regular occurrence for females, whereby, monthly fluctuating hormones work in synergy and cause alterations in physiology and potentially physical performance. Though these physiological and physical changes have been well documented, there remains a paucity of research investigating the effects of the menstrual cycle on physical performance in team sports and particularly football. Accordingly, the aims of this thesis were three-fold 1) to investigate football-specific physical and physiological characteristics of the female footballer, 2) to determine the potential effects of the menstrual cycle on isolated measures of football-specific performance, and 3) to observe whether the menstrual cycle modulates changes in physical performance during competitive match-play. To facilitate aim one, 36 sub-elite female footballers provided blood samples and completed a battery of isolated physical tests of football-specific performance (countermovement jump, 3x30m sprint, 4x5m change of direction and the Yo-Yo intermittent endurance test level 2) at three timepoints throughout the season. To fulfil aim two, nine sub-elite females completed the same series of physical tests as aim one (except the Yo-Yo intermittent endurance test level 1 was used) during two specifically chosen phases of the menstrual cycle (follicular phase, days 5-7; luteal phase, days 21-22). Finally, to accomplish aim three, 15 elite female footballers were observed during a 4-month period throughout a total of 76 match observations, during the main phases of the menstrual cycle (36 in follicular phase and 40 in luteal phase). There was an observed change in physical performance across the season. Peak performance was observed following the preseason period, however, reductions in physical performance were observed as the season continued. Inversely, blood-borne parameters (e.g. creatine kinase) were elevated when performance was at its highest level, whilst decreasing as the season continued. The results of study two suggested there was an observed reduction in maximal endurance performance during the luteal phase, with a 14% reduction in meters covered during the Yo-Yo intermittent endurance test level 1 compared to the follicular phase. However, no changes were observed in sprinting, agility, or countermovement jump performance. The findings of study three indicated that during competitive match-play there was an observed difference in high intensity distance covered across the menstrual cycle; with 12% greater distance covered during the luteal phase. However, this difference was smaller than the matchto- match variation (coefficient of variation = 39.5%). There were no observed differences between phases across all other competitive physical performance metrics. On the individual level, differences between phases were only systematically observable in one player. The findings of this thesis provide further insight into the physical profile of the female footballer and is the first to consider female specific physiology as a factor that could potentially alter physical performance. The current studies indicate that isolated sport-specific physical performance fluctuates throughout the season, nevertheless, when assessing or monitoring endurance performance, it would appear advantageous to keep the phase of the menstrual cycle (when possible) consistent or at least documented. However, these observed effects were not so prominent during competition. Therefore, the menstrual cycle, does not seem do play a major contributing factor to variations in physical performance during matches and interventions are not particularly necessary. The current studies provide implications for the design and micro management of training, monitoring and the assessment of the female footballer, whilst affirming that the menstrual cycle should not be perceived as a mitigating factor for changes in physical performance. Finally, this thesis has also provided further evidence of the complexity when assessing the menstrual cycle alongside aspects of physical activity and overall performance.