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The aim of this work was to study the effect of hypoxic stress on the physical growth of prepubertal Bolivian boys (10-11.5 years of age) of the same socioeconomic and nutritional conditions. The subjects consisted of 143 boys living in La Paz (altitude 3600 m, n = 67) and Santa Cruz de la Sierra (altitude 420 m, n = 76). Among the boys studied at high altitude, 23 were from a high socioeconomic background (HA1) and 44 from a low socioeconomic background (HA2). The group studied at low altitude consisted of 47 boys from a high socioeconomic background (LA1) and 29 from a low socioeconomic background (LA2). A scientific evaluation of the nutritional status of the boys was realized from specific anthropometric characteristics (height, body weight, upper arm muscle circumference, body fat mass and body mass index) and haematological (haematocrit, haemoglobin, serum iron, serum ferritin, red cell protoporphyrin, transferrin saturation) and biochemical (total serum protein, albumin and prealbumin) parameters. At high as at low altitudes, the biometric characteristics of boys from a low socioeconomic background were significantly lower than those of boys from a high socioeconomic background. The physical growth of HA2 and LA2 boys was delayed by approximately 2 years. All the boys had biochemical and haematological parameters within the normal range. Boys from a low socioeconomic background were considered as marginally undernourished and those from a high socioeconomic background as well-nourished. Within the same socioeconomic class there was no nutritional difference between highland and lowland boys. Similarly, and this is the most important feature of this study, there was no difference for the overall biometric characteristics between highland and lowland boys of the same socioeconomic and nutritional status. Therefore, it appears that when socioeconomic and nutritional conditions are taken into account, there is no effect of hypoxic stress on the physical growth of prepubertal Andean highland boys.

SummaryMaximal aerobic power (V˙o2max) was assessed in seven male and one female middle- and long-distance recreational runners residing in La Paz, Bolivia (3600m). All runners were born and raised at high altitudes (>2500). Mean V˙o2max in the male runners was 60·8 ml/kg/min while V˙o2max in the female runner was 55·5 ml/kg/min. These values are higher than in any previously reported sample of either trained or untrained highaltitude natives. In addition, mean V˙o2max in the La Paz male runners and V˙o2max in the La Paz female runner were very similar to those found in comparable low-altitude samples of recreational athletes, suggesting that the cardiorespiratory systems of both normally active and highly active native Andean highlanders are capable of successfully responding to the stress of hypobaric hypoxia. This ability may have both developmental and genetic components.

SummaryThe physical growth of 351 upper-socioeconomic-status children (9–20 years) of European ancestry residing in La Paz, Bolivia (altitude 3600 m) is described and compared with that of lowland children of similar background. The purpose is to evaluate the independent effect of continual exposure to atmospheric hypoxia during the period of growth and development on linear growth. The data presented here indicate that the effect of hypoxia on achieved stature ranges from minimal in males and none in females to a maximum of 3 cm in both sexes. The magnitude of this effect is relatively small compared to the potential effect of other factors which affect the growth of highland children.

The patterns of development of FVC, FEV and %FEV are examined in 217 male and 195 female youths of Aymara ancestry residing in La Paz, Bolivia (altitude 3600 m). The data provide some evidence of an acceleration in the development of lung function relative to stature in Aymara children, beginning during early adolescence, and also indicate that there is a strong relationship between lung function and chest dimensions in Aymara children. Similar patterns have been observed among Quechua youth. However, despite the general similarity between Quechua and Aymara youths in the development of lung function, there are potentially important differences between them. In particular, the magnitude of the acceleration of lung volumes relative to stature among Aymara children appears to be considerably less than is exhibited by highland Quechua children. In addition, shorter Quechua boys have FVC values similar to those of shorter Aymara boys, despite having significantly larger chests, while taller Quechua boys have considerably larger FVC values than taller Aymara boys, without a corresponding increase in chest size relative to stature. Thus, although lung volumes and chest dimensions are closely related in both groups, the development of lung function to chest size of Quechua boys appears to be somewhat different from that of Aymara boys and, in particular, to be amplified during adolescence in response to factors other than simply an increase in chest size.