Chest Morphology of Young Bolivian High-Altitude Residents of European Ancestry

The chest width and chest depth of 171 male and 180 female youths (9-19 yr) of European ancestry who were born and raised at high altitudes are compared with those of a sample of highland Aymara children. There is much less sexual dimorphism in chest size and shape among the Aymara than among the European children. This finding is probably at least partially due to altitude independent genetic differences but may also involve adaptation to altitude. After controlling for the greater stature of the Europeans, both the male and the female Aymara had significantly larger and deeper chests than their European counterparts. However, the slopes of the regression relationships between each chest dimension and stature did not differ significantly between ethnic groups, suggesting that the relative effect of hypoxia on chest growth is similar in both groups after an age of 9 years. Finally, comparison of the European highlanders with Aymara, Quechua and Tibetan highlanders indicates that a wide range of variation in chest dimensions relative to stature, and presumably in the underlying pulmonary system, is compatible with normal life at high altitude. This suggests that not all groups adapt to hypoxia with the same accelerated development of cardiorespiratory-system organs as is found in Quechua highlanders

Effect of Altitude on the Stature, Chest Depth and Forced Vital Capacity of Low-to-High Altitude Migrant Children of European Ancestry

The effect of varying levels of exposure to chronic hypoxia on the stature, chest depth and forced vital capacity (FVC) of low-to-high altitude migrant children of European ancestry was examined. The results of these analyses confirm that growth and development at high altitude results in a moderate delay in the linear growth of well-nourished children and a significant increase in chest depth and FVC. The magnitude of the increase in FVC is closely associated with the extent of the expansion of the thorax.Birth and lifelong residence at altitude were estimated to have a maximum average negative effect on stature of 4.3 cm and maximum average positive effects on chest depth and FVC of 1.8 cm and 384 ml, respectively. Finally, the magnitude of the effect of hypoxia on the chest depths and FVC’s of migrants appears to be similar at all stages of development, which is not consistent with the hypothesis that highlanders exhibit an accelerated de­velopment of chest depth and FVC relative to stature during childhood and especially adolescence

Aerobic Capacity of Modernizing Samoan Men

Maximal exercise tests were given to 34 American Samoan men between the ages of 18 and 30 years. The sample included men who performed traditional bush-fallow agriculture and men who were employed in a wage economy as office employees and manual laborers. Aerobic capacity, or V02max(ml/kg/min), of the total sample was very low, 38.9 ml/kg/min, suggesting that these men had a low level of physical fitness. Also, aerobic capacity was negatively related to body fatness as measured by the sum of the skinfolds and positively related to activity level as measured by occupational energetic requirements. Since modernization in American Samoa is associated with increases in body fatness and decreases in occupational activity level, these findings suggest that changes associated with modernization have had a significant negative impact on the aerobic capacity of modernizing Samoan adult males

Physical Growth and Maximal Work Capacity in Preadolescent Boys at High-altitude

Maximal exercise tests were given to 67 boys of European ancestry and between the ages of 8.8 and 13.1 years in La Paz, Bolivia (mean altitude of 3600m). Thirty-four of the boys were born at high altitude while the remaining 33 were born at low altitude. The boys born at high altitude were significantly fatter than the low-altitude born boys after controlling for age and had larger chest circumferences after controlling for stature. Otherwise the samples were morphologically similar. Also, the statures and weights of the boys in both groups were similar to those of normal U.S. boys, suggesting that their growth may not have been affected by hypoxia to any great extent. Although most measures of maximal work performance, including maximal aerobic power (V02max), did not differ significantly between the samples, maximal work output was significantly greater in the high- altitude born boys than in the low-altitude born boys. Length of residence at high altitude and maximal work output were positively related in the low-altitude born boys but no other relationships were found between maximal work performance and length of exposure to hypobaric hypoxia. The considerable individual variability in the responses of these boys to maximal exercise may have masked these relationships, however, and longitudinal studies may be needed to reveal developmental adaptations to hypoxia

Submaximal Work Performance of Native and Migrant Preadolescent Boys at High Altitude

Fifty-five preadolescent boys of European ancestry were given submaximal exercise tests in La Paz, Bolivia (mean altitude of 3600 m). Twenty-nine of the boys were born at high-altitude (HAB) and 26 were born at low-altitude (LAB). V02 and relative work intensity (V02W02max) were significantly lower in HAB boys than in LAB boys, suggesting that the HAB boys were better adapted to hypobaric hypoxia than the LAB boys. After controlling for relative work intensity, there were no significant differences between the groups in their physiological responses to sub­maximal exercise, suggesting that the greater V02 of the LAB boys was not due to a less efficient oxygen transport system. Also, interindividual variability was considerably greater in LAB than HAB boys for many measures, including V02. This may reflect considerable individual differences in the development of adaptive responses to hypobaric hypoxia among LAB boys