Modulating Effects of the Menstrual Cycle on Cardiorespiratory Responses to Exercise under Acute Hypobaric Hypoxia.

Abstract

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...

Ventilatory, metabolic, and thermal responses to hypercapnia in female rats: effects of estrous cycle, ovariectomy, and hormonal replacement

“…This has also been observed in women during the menstrual cycle (42,45). Regarding Tb, our results show an increase on the day of estrus, similar to that previously .…”

Fertility in a high-altitude environment is compromised by luteal dysfunction: the relative roles of hypoxia and oxidative stress

“…Indigenous non-pregnant women residing at a high altitude had greater progesterone levels during the luteal phase of the menstrual cycle in comparison with women living at sea level [31]. Additionally, women exposed to acute hypobaric hypoxia showed higher plasma progesterone concentrations during the luteal phase than controls under normoxia [32]. …”

Intermittent short-term graded running performance in middle-distance runners in hypobaric hypoxia

“…It is known that in both hypobaric and normobaric hypoxic environments, maximal oxygen uptake (VO 2max ) and anaerobic threshold (AT) decrease with reduction in inspired PO 2 , and that there is a consequent decrease in aerobic performance (Gavin et al1998;Koistinen et al 1995;Martin and O'Kroy 1993;Squires and Buskirk 1982;Takase et al 2002). On the other hand, McLellan et al (1990) reported that neither mean nor peak power output in a 30 s to 45 s Wingate test showed any change in hypoxia (10.8% O 2 ).…”