Browsing by Autor "Brutsaert, Tom D"

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Absence of work efficiency differences during cycle ergometry exercise in Bolivian Aymara
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 2004) Brutsaert, Tom D
ABSTRACT. This study tested the hypothesis that Andean natives are adapted to high altitude (HA) via high work ef ficiency during exercise in hypoxia. A total of 186 young males and females were tested in Bo livia, comprising eight different subject groups. Groups were identified based on gender, an cestry (Aymara vs. European), altitude of birth (highlands vs. lowlands), and the altitude where tested (420, 3600, 3850 m). This design allows partitioning of ancestral (i.e., genetic) and devel opmental effects. To minimize measurement error, subjects were given two submaximal exer cise tests on a cycle ergometer (on separate days). Each test consisted of four 5-min work bouts (levels), each separated by a 5-min rest period. For all groups, the oxygen consumption (VO2)–work rate relationship was not different from the sea-level reference. Gross and net effi ciencies (GE and NE) were not different between groups at any work level, with the exception of European men born in the lowlands and acclimatized and tested at 3600 m. These men showed slightly lower VO2 at high work output, but this may be due to a nonsteady-state VO2 kinetic, rather than to an altered steady-state VO2–work rate relationship per se. There were no signifi cant group differences in delta efficiency (DE). In sum, these results provide no support for the hypothesis of energetic advantage during submaximal work in Andean HA natives. A review and analysis of the literature suggest that the same is true for HA natives in the Himalayas.
Effect of developmental and ancestral high-altitude exposure on chest morphology and pulmonary function in andean and european/north american natives
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 1999) Brutsaert, Tom D
Abstract. Chest depth, chest width, forced vital capacity (FVC), and forced expiratory volume (FEV1) were measured in 170 adult males differing by ancestral (genetic) and developmental exposure to high altitude (HA). A complete migrant study design was used to study HA natives (Aymara/Quechua ancestry, n = 88) and low altitude (LA) natives (European/North American ancestry, n = 82) at both altitude (La Paz, Bolivia, 3,600 m) and near sea level (Santa Cruz, Bolivia, 420 m). HAN and LAN migrant groups were classified as: Nth generation migrants, born and raised in a non-native environment; child migrants who migrated during the period of growth and maturation (0–18 yrs); and adult migrants who migrated after 18 years of age. Chest depth, FVC, and FEV1 measures were larger with increasing developmental exposure in both HAN migrants at LA and LAN migrants at HA. Developmental responses were similar between HAN and LAN groups. FVC and FEV1 measures were larger in HANs vs LANs born and raised at HA to suggest a genetic effect, but were similar in HANs and LANs born and raised at LA. The similarity of HAN and LAN groups at LA suggests that the genetic potential for larger lung volumes at HA depends upon developmental exposure to HA. Additional data for females (HANs at HA, n = 20, and LAN adult migrants to HA, n = 17) show similar differences as those shown between male HAN and LAN groups. Am. J. Hum. Biol. 11:383–395, 1999. © 1999 Wiley-Liss, Inc.
Effect of developmental and ancestral high-altitude exposure on VO2peak of andean and european/north american natives
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 1999) Brutsaert, Tom D
ABSTRACT. Peak oxygen consumption (V02peak) was measured in 150 adult males (18-35 years old) in Bolivia, using a complete migrant study design to partition developmental from ancestral (genetic) effects of high altitude (HA) exposure, High-altitude natives (HANs, Aymara/Quechua ancestry, n = 75) and low-altitude natives (LANs, European/North American ancestry, n = 75) were studied at high altitude (3,600-3,850 m) and near sea level (420 m). HAN and LAN migrant groups to a nonnative environment were classified as: multigeneration migrants, born and raised in a nonnative environment; child migrants who migrated to the nonnative environment during the period of growth and development (0-18 years old); and adult migrants who migrated after 18 years of age. Variability in VO2peak due to high-altitude adaptation was modeled by covariance analysis, adjusting for fat-free mass and physical activity (training) differences between groups. A trend for increased VO2peak with increasing developmental high-altitude exposure in migrant groups did not reach statistical significance, but low statistical power may have limited the ability to detect this effect. HANs and LANs born, raised, and tested at high altitude had similar V02peak values, indicating no genetic effect, or an effect much smaller than that reported previously in the literature. There was no functional correlation between forced vital capacity and VO2peak, within or across groups. These results do not support the hypothesis that Andean HANs have been selected to express a greater physical work capacity in hypoxia.
Effect of menstrual cycle phase on exercise performance of high-altitude native women at 3600 m
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 2002) Brutsaert, Tom D
Summary. 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 (VO2max) 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 pgml–1 and 22.9 pgml–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 VO2max. 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 .VO2 max (lmin–1) was unchanged (P=0.063). Post-hoc analyses revealed no significant relationship between changes in P levels and changes in VO2max from F to L (P=0.072). In sum, the menstrual cycle phase has relatively modest effects on ventilation, but no effect on VO2 max of HA native women.
Higher arterial oxygen saturation during submaximal exercise in bolivian aymara compared to european sojourners and europeans born and raised at high altitude
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 2000) Brutsaert, Tom D
Abstract. Arterial oxygen saturation (SaO(2)) was measured at 3,600-3,850 m by pulse oximetry at rest and during submaximal exercise in three study groups: 1) highland Aymara natives of the Bolivian altiplano (n = 25); 2) lowland European/North American sojourners to the highlands with at least 2 months of acclimatization time to 3,600 m (n = 27); and 3) subjects of European ancestry born and raised at 3,600 m (n = 22). Aymara subjects maintained approximately 1 percentage point higher SaO(2) during submaximal work up to 70% of their maximal work capacity, and showed a smaller rate of decline in SaO(2) with increasing work compared to both European study groups. The higher-exercise SaO(2) of Aymara compared to Europeans born and raised at 3,600 m suggests genetic adaptation. The two European study groups, who differed by exposure to high altitude during their growth and development period, did not show any significant difference in either resting or exercise SaO(2). This suggests that the developmental mode of adaptation is less important than the genetic mode of adaptation in determining exercise SaO(2). A weak correlation was detected (across study groups only) between the residual forced vital capacity (FVC) and the residual SaO(2) measured at the highest level of submaximal work output (P = 0.024, R = 0.26). While firm conclusions based on this correlation are problematic, it is suggested that a part of the higher SaO(2) observed in Aymara natives is due to a larger lung volume and pulmonary diffusion capacity for oxygen. Results from this study are compared to similar studies conducted with Tibetan natives, and are interpreted in light of recent quantitative genetic analyses conducted in both the Andes and Himalayas.
Permormance of altitude acclimatized and non-acclimatized professional football (soccer) players at 3,600 M
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 2000) Brutsaert, Tom D
European football (soccer) matches frequently are played at the international level in mountainous regions of South America. In this study, the exercise response during cycle ergometry and the rate of football match energy expenditure (RFE) were measured in two groups of professional football players at high altitude (3,600 m) and near sea level (420 m). Subjects either resided at high altitude and were therefore altitude acclimatized (n= 9) (HA), or resided near sea level and were non-acclimatized to high altitude (n=11) (LA). Both study groups showed a large decrement in the RFE (0.187 kcal/kg/min, or a 16% decrease) and peak oxygen consumption (VO2peak) at altitude (10.78 mL/kg/min for HA and 6.27 mL/kg/min for LA). This VO2peak decrement with altitude was larger in LA versus HA players (20% vs. 13%). The LA players also showed higher ventilatory equivalents for oxygen, lower arterial oxygen saturations, and higher arterial lactate concentrations during submaximal exercise. Because aerobic capacity is an important determinant of football match performance, these results may have some relevance to the debate over an advantage to altitude acclimatized teams for football matches played at moderate to high altitude.
Rendimiento de futbolistas profesionales aclimatados y no aclimatados a la altura, a 3600 metros
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 2003) Brutsaert, Tom D
Resumen. Los partidos del Fútbol Europeo son frecuentemente jugados a nivel internacional en regiones montañosas de Sudamérica. En este estudio, fueron medidas las respuestas del ejercicio durante una ergometría en ciclo ergómetro y la tasa de gasto energético (RFE) en un partido de fútbol. Las evaluaciones fueron realizadas en dos grupos de futbolistas profesionales a gran altura (3600 m) y cerca del nivel del mar (420 m). Los sujetos residían en la altura y de este modo estaban aclimatados (n = 9) (HA), o residían cerca del nivel del mar y no estaban aclimatados (n = 11) (LA). Los dos grupos estudiados mostraron una gran disminución del RFE (0,187 kcal/kg/min, o una disminución de un 16%) y del pico de consumo de oxígeno (pico de VO2) en la altura (10,78 ml/kg/min para HA y 6,27 ml/kg/min para LA). Esta disminución en pico de VO2 con la altura fue mayor en el grupo de jugadores LA vs. el grupo HA (20% vs. 13%). Los jugadores LA mostraron también los mayores equivalentes ventilatorios para el oxígeno, menores saturaciones arteriales de oxígeno, y mayores concentraciones arteriales de lactato durante el ejercicio submáximo. Debido a que la capacidad aeróbica es una determinante importante del rendimiento en un partido de fútbol, estos resultados pueden tener alguna relevancia para debatir sobre una ventaja de los equipos aclimatados a la altura en los partidos de fútbol jugados en alturas moderadas a altas.