Browsing by Autor "Robert T. Chatterton"

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Effect of menstrual cycle phase on exercise performance of high-altitude native women at 3600 m
(The Company of Biologists, 2002) Tom D. Brutsaert; Hilde Spielvogel; Esperanza Cáceres; Mauricio Araoz; Robert T. Chatterton; Virginia J. Vitzthum
At sea level normally menstruating women show increased ventilation (VE) and hemodynamic changes due to increased progesterone (P) and estrogen (E2) levels during the mid-luteal (L) compared to the mid-follicular (F) phase of the ovarian cycle. Such changes may affect maximal exercise performance. This repeated-measures, randomized study, conducted at 3600 m, tests the hypothesis that a P-mediated increase in VE increases maximal oxygen consumption (V(O(2)max)) during the L phase relative to the F phase in Bolivian women, either born and raised at high altitude (HA), or resident at HA since early childhood. Subjects (N=30) enrolled in the study were aged 27.7 +/- 0.7 years (mean +/- S.E.M.) and non-pregnant, non-lactating, relatively sedentary residents of La Paz, Bolivia, who were not using hormonal contraceptives. Mean salivary P levels at the time of the exercise tests were 63.3 pg ml(-1) and 22.9 pg ml(-1) for the L and F phases, respectively. Subset analyses of submaximal (N=23) and maximal (N=13) exercise responses were conducted only with women showing increased P levels from F to L and, in the latter case, with those also achieving true (V(O(2)max)). Submaximal exercise VE and ventilatory equivalents were higher in the L phase (P<0.001). P levels were significantly correlated to the submaximal exercise VE (r=0.487, P=0.006). Maximal work output (W) was higher (approximately 5 %) during the L phase (P=0.044), but (V(O(2)max)) (l min(-1)) was unchanged (P=0.063). Post-hoc analyses revealed no significant relationship between changes in P levels and changes in (V(O(2)max))) from F to L (P=0.072). In sum, the menstrual cycle phase has relatively modest effects on ventilation, but no effect on (V(O(2)max)) of HA native women.
Salivary progesterone levels and rate of ovulation are significantly lower in poorer than in better-off urban-dwelling Bolivian women
(Oxford University Press, 2002) Virginia J. Vitzthum; Gillian R. Bentley; Hilde Spielvogel; Esperanza Cáceres; Jonathan Thornburg; Lisa Jones; Sarah Shore; Kelly R. Hodges; Robert T. Chatterton
Progesterone levels appear to be influenced by chronic and acute ecological conditions, evidenced by the association with body-size and the probability of ovulation respectively. These findings have implications for understanding cancer aetiology, developing population-appropriate hormonal contraceptives, and modelling the evolution and functioning of the reproductive system.