| Abstract: | Physiological events during the normal menstrual cycle are determined by feedback loops within the hypothalamic-pituitary-ovarian axis. Hormonal changes within the menstrual cycle have potential impact on human performance. Relevant stages to consider are pre-menses and menses, the follicular and luteal phases separated by an abrupt elevation in lutenizing hormone and characterised by a sharp rise in body temperature coinciding with ovulation. Strenuous athletic training may affect the normal menstrual cycle. Such disruptions include delayed menarche in ballet dancers and gymnasts, shortened luteal phase and secondary amenorrhea associated with high training loads and competitive stress. Amenorrhea is also noted in flight attendants, linked with an inhibiting effect of disrupted circadian rhythm on lutenizing hormone. The so-called 'athlete triad' considers secondary amenorrhea, abnormal eating behaviour and osteoporosis (attributed to chronic hypoestrogenia). The normal cycle may also be disrupted when circadian rhythms are disturbed, for example in rapid time-zone transitions. Fluctuations in the steroid hormones have been associated with changes in muscle strength. There is evidence also of elevations in heart rate: changes may be partly specific to time of day. Effects on muscle strength may be determined at selected stages of the menstrual cycle, using whole-body performance, local muscle groups or isolated individual muscles. Whilst oestrogen has been implicated in the ergogenic effect of steroid hormones, there is accumulating evidence that a role for progesterone cannot be discounted. The isolation of the ovarian hormones separately is feasible with studies of IVF patients or groups on hormone replacement therapy. |
