Serum insulin-like growth factor I and physical performance in prepubertal Bolivian girls of a high and low socio-economic status.

The aim of the study was to determine if a decrease in serum insulin-like growth factor I (Igf-I) levels under marginal malnutrition is responsible for the lower physical performance of girls of a low socio-economic status (LSES). Girls were selected after physical examination (Tanner's stage 1) and anthropometric measurements (height, body mass or mb, body mass index or BMI = mb height2). Lean body mass mb,1 was measured after skinfold thickness determination; serum IGE-I, by radioimmunoassay; maximal O2 consumption, (VO2max), directly during incremental exercise up to exhaustion; and maximal aerobic power (Wmax), using the force-velocity test. LSES girls (n = 31) had been malnourished in the past and, currently, were suffering from marginal malnutrition: they were smaller (135.2 +/- 5.5 vs 146.1 +/- 4.3 cm), lighter (31.7 +/- 3.9 vs 37.6 +/- 5.0 kg), exhibited a lower mb,1 (24.2 +/- 2.5 vs 27.5 +/- 3.0 kg) but same BMI compared with HSES (high socio-economic status) girls (n = 32). Igf-I levels (27.7 +/- 7.9 vs 34.1 +/- 6.5 nmol.1(-1), VO2max (45.26 +/- 4.72 vs 50.74 +/- 6.02 ml. min-1.kg-1 LBM) and Wmax (6.00 +/- 1.15 vs 8.70 +/- 1.53 W.kg-1 mb,1 were lower in LSES girls. Moreover, the differences in every parameter were not the consequence of the younger age (10.8 +/- 0.9 vs 11.2 +/- 0.6 years) of the LSES girls. Our results provide evidence that the lower Wmax of undernourished prepubertal girls was partly the consequence of alterations in muscle function at the qualitative level, as a result of a decrease in Igf-I levels. Conversely, under normal nutritional conditions, anthropometric characteristics only are explicatory factors for physical performances.

Effect of altitude and socioeconomic status on VO2max and anaerobic power in prepubertal Bolivian girls.

The aim of this work was to evaluate the effects of high altitude and low socioeconomic status (SES) on aerobic and anaerobic power in 11-yr-old Bolivian girls. At both high (3,600 m) and low (420 m) altitudes, low-SES groups of girls were compared to similarly aged, high-SES girls. At low altitude, low-SES girls were also compared with younger high-SES girls with the same anthropometric characteristics. Anthropometric data were similar between high-SES and low-SES girls at both altitudes, but low-SES girls showed a 9-mo growth delay. Maximal O2 uptake was significantly lower for low-SES girls at both altitudes. Values did not differ when expressed relative to body weight at high altitude for high-SES vs. low-SES girls (37.6 +/- 1.2 vs. 39.3 +/- 1.0 ml.min-1.kg body wt-1), but a difference persisted at low altitude between high- and low-SES girls (37.5 +/- 1.0 vs. 34.7 +/- 0.7 ml.min-1.kg body wt-1). Anaerobic power (Pmax, force-velocity test; Pwing, Wingate test) was reduced for low-SES girls at both altitudes, whatever the mode of expression. For a given SES, the relative anaerobic performances were lower at low altitude. At low altitude, low-SES girls developed lower anaerobic power than did younger high-SES girls with similar anthropometric characteristics. In conclusion, at both altitudes, the reduction of anaerobic performances observed in girls of low SES could not be totally explained by anthropometric factors. Structural and/or functional muscle alterations are suggested. Moreover, at low altitude, tropical and other factors may have contributed to differences in performance between low- and high-SES girls.

Effect of anthropometric characteristics and socio-economic status on physical performances of pre-pubertal children living in Bolivia at low altitude.

We have previously observed that 11-year-old children of low socio-economic status (LSES) showed a delayed physical growth of approximately 2 years and developed lower normalized short-term power output than children of high socio-economic status (HSES) of the same age. In contrast, maximal oxygen uptake (VO2max) per unit of fat free mass was no different in either group. The aim of this study was to evaluate the effect of anthropometric characteristics between HSES and LSES prepubertal children in aerobic and anaerobic performance. To compare children of the same body dimensions, 11-year-old boys (n = 30) and girls (n = 31) of LSES and 9-year-old boys (n = 21) and girls (n = 27) of HSES were studied. Anthropometric measurements, VO2max (direct test), maximal anaerobic power (Pmax, force-velocity test) and mean anaerobic power (P, Wingate test) were determined. In these children having the same body dimensions: mean VO2max were the same in LSES and HSES children [1.2 (SD 0.2) l.min-1]; Pmax and P were lower in LSES subjects [154.0 (SD 33.2) vs 174.6 (SD 38.4) W and 116.3 (SD 23.3) vs 128.2 (SD 28.0) W, respectively]; the linear relationships between VO2max and fat free mass were the same in LSES and HSES boys but, in the girls, the LSES group had lower values. For anaerobic performance, the relationships were significantly different: the slopes were the same but LSES values for the both sexes were lower. These results would suggest that factors other than differences in body dimensions alone were responsible for the lower performance of LSES girls and boys. Cultural factors and motor learning, structural and functional alterations of muscle induced by marginal malnutrition have been discussed.

The effect of acute hypoxia at low altitude and acute normoxia at high altitude on performance during a 30-s Wingate test in children.

The effect of acute hypoxia (FIO2 = 0.137 +/- 0.001) at Low Altitude (LA: Clermont-Ferrand, 330 m) and acute normoxia (FIO2 = 0.306 +/- 0.006) at High Altitude (HA: La Paz, 3600 m) on performance during a 30-s Wingate test has been investigated in prepubertal children (Tanner stage 1). Twenty five boys (LA, n = 10; HA, n = 15) aged from 10.6 to 12.7 years performed two Wingate tests at random: at LA, one in normoxia (ambient air) and one in acute hypoxia and at HA, one in chronic hypoxia (ambient air) and one in acute normoxia. The subjects performed the two tests using the same calibrated cycle ergometer. Peak Power (PP), Mean Power (MP), O2 uptake during the 30 s (VO2) and blood lactate accumulation (delta [L]s) were measured. Compared to normoxia, acute hypoxia at LA did not alter PP (8.0 +/- 1.1 vs 7.9 +/- 1.3 W.kg-1 BW) and MP (6.1 +/- 0.7 vs 6.1 +/- 1.1 W.kg-1 BW). Similarly, compared to chronic hypoxia, acute normoxia at HA did not modify these parameters (PP: 7.4 +/- 1.5 vs 7.3 +/- 1.8; MP: 5.4 +/- 1.2 vs 5.5 +/- 1.1; W.kg-1 BW). VO2 and delta [L]s were neither significantly changed by acute hypoxia at LA (520 +/- 50 vs 550 +/- 60 ml O2; 5.3 +/- 1.7 vs 4.8 +/- 1.7 mmol.l-1) nor by acute normoxia at HA (530 +/- 110 vs 500 +/- 90 ml O2; 3.4 +/- 1.3 vs 3.3 +/- 1.0 mmol.l-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood lactate after maximal and supramaximal exercise in 10- to 12-year-old Bolivian boys. Effects of altitude and socioeconomic status.

The aim of this paper was to analyze the effects of chronic hypoxia and socioeconomic level on blood lactate concentrations obtained after maximal exercise and a 30-s Wingate test in 145 Bolivian boys (mean age: 10.8 years). Among the boys studied at high altitude (HA) (La Paz, 3600m) and at low altitude (LA) (Santa Cruz de la Sierra, 420m), 23 (HAHSES) and 48 (LAHSES) were from a high socioeconomic status (HSES), and 44 (HALSES) and 30 (LALSES) from a low socioeconomic status (LSES). The pubertal development was evaluated by salivary testosterone level ([T]). Blood samples were collected from the earlobe for blood lactate determination 2 min after cessation of maximal exercise ([L]v) and of a 30-s Wingate test ([L]w). Results (means +/- SD) showed: (1) [T] was significantly lower at HA: HA (HSES + LSES): 139.0 +/- 46.6 vs LA (HSES + LSES) = 186.2 +/- 53.7 pmole.1-1 (p = 0.0001). There was no significant difference between HAHSES and HALSES but LALSES was significantly lower than LAHSES. When the four groups were pooled, significant positive correlations between [L] and [T] were found; (2) for a same level of socioeconomic conditions, [L]v and [L]w were significantly lower at HA: HAHSES = 4.9 +/- 1.5 vs LAHSES = 7.4 +/- 2.1 and HALSES = 4.8 +/- 1.4 vs LALSES = 6.3 +/- 1.5 mmole.l-1 for [L]v; HAHSES = 5.1 +/- 1.0 vs LAHSES = 6.2 +/- 1.4 and HALSES = 4.6 +/- 1.0 vs LALSES = 5.3 +/- 1.4 mmole.l-1 for [L]w; (3) except for [L]v at HA, the HSES boys exhibited higher [L]v and [L]w than the LSES children for a same altitude; (4) there were significant linear relationships between the power developed during the 30-s Wingate test and [L]w.(ABSTRACT TRUNCATED AT 250 WORDS)

The importance of socioeconomic and nutritional conditions rather than altitude on the physical growth of prepubertal Andean highland boys.

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.

Effect of chronic hypoxia and socioeconomic status on VO2max and anaerobic power of Bolivian boys.

The aim of this work was to analyze the effects of altitude and socioeconomic and nutritional status on maximal oxygen uptake (VO2max) and anaerobic power (P) in 11-yr-old Bolivian boys. At both high (HA) (3,600 m) and low (LA) (420 m) altitudes, the boys were divided into high (HA1, n = 23, LA1, n = 48) and low (HA2, n = 44, LA2, n = 30) socioeconomic levels. Anthropometric characteristics, VO2max, and P [maximal P (Pmax) during a force-velocity test and mean P (P) during a 30-s Wingate test] were measured. Results showed that 1) anthropometric parameters were not different between HA1 and LA1 and HA2 and LA2 boys, but HA2 and LA2 boys were two years behind HA1 and LA1 boys in development; 2) VO2max was not different in boys from the same altitude, but at HA VO2max was 10% lower than at LA (HA1 = 37.2 +/- 5.6, HA2 = 38.9 +/- 6.4, LA1 = 42.5 +/- 5.8, LA2 = 42.5 +/- 5.3 ml.min-1 x kg-1 body wt); and 3) Pmax and P were higher in well-nourished than in undernourished boys, but there was no difference in Pmax and P between HA1 and LA1 and HA2 and LA2 boys (HA1 = 6.8 +/- 1.0, HA2 = 5.5 +/- 0.8, LA1 = 7.1 +/- 1.0, LA2 = 5.3 +/- 0.9 W/kg for Pmax; HA1 = 5.2 +/- 0.8, HA2 = 4.5 +/- 0.9, LA1 = 5.2 +/- 0.7, LA2 = 4.0 +/- 0.6 W/kg for P).(ABSTRACT TRUNCATED AT 250 WORDS)

Physical fitness of children resident at high altitude in Bolivia.

In 7-15-yr-old children living in La Paz (Bolivia, altitude 3,700 m) (HA): 1) Maximal oxygen consumption (VO2max) varies from 35 to 45 ml.min-1.kg-1 and maximal heart rate from 188 to 194 beats.min-1. These values are lower than those of their counterparts at low altitude (LA) by 10-20% and 10-15 b.min-1, respectively. 2) The anaerobic metabolism is not affected by chronic hypoxia if the nutritional conditions and pubertal development of HA and LA boys are the same. When related to percent of VO2max, submaximal O2 debts are similar at HA and LA. After supramaximal exercise, maximal O2 debts (45.7 +/- 2.7 vs 45.9 +/- 3.8 ml.kg-1) and blood lactate concentrations (7.6 +/- 0.6 vs 6.5 +/- 0.6 mmol.l-1) are also the same at HA and LA. No differences are observed between the 2 altitudes in ventilatory (60 vs 56% VO2max) and lactate (60 vs 65% VO2max) thresholds. The altitude of La Paz does not alter the anaerobic performance of a force-velocity test (from 6 to 10 W.kg-1) between the ages of 7 to 15 years but reduces by 14-17% the mean anaerobic power developed during a 30-s Wingate test. This decrease could be linked to a lower participation of glycolysis and aerobic metabolism at HA during this test. 3) Poor socio-economic and nutritional conditions do not modify the aerobic performance of boys living in La Paz but lead to lower maximal anaerobic power (from -17% to -25%) when compared with HA boys from a high socio-economic background.(ABSTRACT TRUNCATED AT 250 WORDS)