Effects of menstrual phase and amenorrhea on exercise performance in runners. There are few well controlled studies in terms of subject selection, menstrual classification, and exercise protocol that have examined both maximal and submaximal exercise responses during different phases of the menstrual cycle in eumenorrheic runners and compared these runners to amenorrheic runners. Thus, the purpose of this study was to measure selected physiological and metabolic responses to maximal and submaximal exercise during two phases of the menstrual cycle in eumenorrheic runners and amenorrheic runners. Eight eumenorrheic runners (29.0 +/- 4.2 yr) and eight amenorrheic runners (24.5 +/- 5.7 yr) matched for physical, gynecological, and training characteristics were studied. The eumenorrheic runners performed one maximal and one submaximal (40 min at 80% VO2max) treadmill run during both the early follicular (days 2-4) and midluteal (6-8 d from LH surge) phases. The amenorrheic runners performed one maximal and one submaximal (40 min at 80% VO2max) treadmill run. Cycle phases were documented by urinary luteinizing hormone and progesterone assays and by plasma estradiol and progesterone assays. No differences were observed in oxygen uptake, minute ventilation, heart rate, respiratory exchange ratio, rating of perceived exertion, time to fatigue (maximal), and plasma lactate (following the maximal and submaximal exercise tests) between the follicular and luteal phases in the eumenorrheic runners and the amenorrheic runners. We conclude that neither menstrual phase (follicular vs luteal) nor menstrual status (eumenorrheic vs amenorrheic) alters or limits exercise performance in female athletes. 