EFFECT OF THE DIFFERENT PHASES OF THE MENSTRUAL-CYCLE AND ORAL-CONTRACEPTIVES ON ATHLETIC PERFORMANCE

The female athlete, during her reproductive years, has a complex and e ver-changing milieu of female steroid hormones, whether it is the endo genous variations in estradiol and progesterone of a regular menstrual cycle, or the exogenous synthetic hormones of the oral contraceptives . Both estrogens and progestins have individual, interactive and somet imes opposing physiological actions with potential implications for th e exercising female. In retrospective surveys on the menstrual cycle a nd performance, from 37 to 63% of athletes did not report any cycle 'p hase' detriment, while 13 to 29% reported an improvement during menstr uation. The best performances were generally in the immediate postmens trual days, with the worse performances during the premenstrual interv al and the first few days of menstrual flow. However, this type of stu dy has an inherent built-in bias, and is further limited by the lack o f substantiation of cycle phase. Many of the women studied associated premenstrual symptoms, such as fluid retention, weight gain, mood chan ges, and dysmenorrhoea with performance decrement. Such factors have a lso been causally linked with an increase in traumatic musculoskeletal injuries during the premenstrual and menstrual period. Neuromuscular coordination, manual dexterity, judgement and reaction time for comple x tests have been shown to be adversely affected in women with premens trual syndrome or symptoms, but confounding variables may include nutr ition status and blood sugar levels. In addition, not all women suffer to the same level with premenstrual symptoms. Fluctuations in many ph ysiological functions occur throughout the normal menstrual cycle. Res ults of early studies are difficult to interpret owing to the small nu mbers of women studied, wide range of fitness levels, and variability in the definitions of cycle phase. Nevertheless, investigators did not document any significant changes in measures of athletic performance as a function of timing of testing during the menstrual cycle. Swimmer s have shown a premenstrual worsening of performance times, with impro vement during the menstrual phase and on the eighth day of the cycle. An increase in perceived exertion was noted premenstrually and during the early menstrual stage with very intense exercise. In cross-country skiers, the best times were recorded in the postovulatory and postmen strual phases, prompting the recommendation that training loads be sel ected according to cycle phase to achieve maximum benefit. Investigati ons using estradiol and progesterone levels as a confirmatory index of ovulation have not generally found significant differences across the cycle in either maximal or submaximal exercise responses, although a slight decrease in aerobic capacity during the luteal phase has been r eported. In contrast, an enhancement of endurance performance during t he luteal phase, without any concomitant changes in cardiovascular var iables has also been reported. There is evidence to suggest a decremen t in isometric strength and endurance, potentially related to an incre ase in deep muscle temperature during the luteal phase, however, littl e accurate information exists on the influence of menstrual cycle phas e on strength. nstrual symptoms. Some cross-sectional studies have fou nd an increase in oxygen consumption for a standardised workload in wo men taking oral contraceptives. A slight decrease in maximal aerobic c apacity with a decrease in muscle mitochondrial citrate has been demon strated, suggesting a potential cellular mechanism. Recent investigati ons have shown a slight decrease in maximum oxygen uptake (VO2max), wi thout alterations in any of the cardiovascular variables.