Anecdotal evidence, recently supported by scientific evidence, suggests that altitude training may offer advantages over sea-level (SL) training [1][2][3][4][5]. As a consequence, many elite athletes, female as well as male, now train at high altitude in an effort to enhance their SL performance. It is known that the menstrual cycle modulates thermoregulatory and cardiorespiratory responses, both at rest and during exercise, but it is not yet clear how this modulation is altered by moving to a higher altitude (Յ3,000 m), either acutely or chronically.In the luteal phase of the menstrual cycle, increased body-core temperature and high levels of progesterone are found. Progesterone has been shown to stimulate minute ventilation (VE) [6,7] and to be associated with a decrease in alveolar carbon dioxide tension in the luteal phase [8][9][10]. Moreover, hypoxic ventilatory response (HVR) at rest is increased in the luteal phase, although amenorrheic women show no such significant modulation in HVR [10,11]. Further, eumenorrheic women show a greater hypercapnic ventilatory response (HCVR) at rest in the luteal phase than in the follicular phase [10,[12][13][14]. Thus, the increased ventilatory response in the luteal phase is thought to be due to progesterone lowering the threshold of the medullary respiratory center and increasing its excitability [15].Given the stimulatory effects of progesterone on resting VE [7,16], VE during exercise would also be expected to be higher in the luteal phase than in the follicular phase. While a number of studies have indeed demonstrated an increase in VE during maximal or submaximal exercise in the luteal phase [10,13,14,17,18], other studies have found no differences [19][20][21][22][23]. As a result of the increased body-core temperature in the luteal phase, oxygen uptake (VO 2 ) dur- Japanese Journal of Physiology, 52, 553-560, 2002 Key words: cycle exercise, altitude training, ventilatory response, luteal phase. Abstract:The purpose of this study was to examine the hypothesis that the menstrual cycleinduced modulation of the cardiorespiratory response to exercise might be altered by acute exposure to altitude. During both the luteal and follicular phases, 9 moderately trained female subjects with normal menstrual cycles performed incremental exercise to maximal effort on a cycle ergometer at sea level (SL) and under hypobaric hypoxia (HH) at the equivalent of 3,000 m altitude. Both at rest and during exercise, minute ventilation (VE) and oxygen uptake (VO 2 ) did not differ between the luteal and follicular phases (either at SL or HH). However, the ratio of VE to VO 2 (VE/VO 2 ), both at rest and during peak exercise, was greater in the luteal phase than in the follicular phase under HH conditions. Furthermore, the partial pressure of end-tidal carbon dioxide (PET CO 2 ) during exercise was lower in the luteal phase than in the follicular phase in HH. These results suggest that the menstrual cycle-induced modulation of the ventilatory response to exercise may be altered under...

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The N‐hydroxylactams (II), (V), (VIII), and (XI) are prepared from 2‐nitrophenylpyruvic acid (I), the azlactones (III), or the aminohydroxamic acid (VI) and (X) as shown in the reaction scheme.