Body composition & cardiovascular functions in healthy males acclimatized to desert & high altitude.

BACKGROUND & OBJECTIVES: Several physiological changes affecting physical fitness occur in humans whenever they are exposed to extremes of environments such as heat, cold and high altitude (HA). The present study was undertaken to evaluate effect of stay in desert and HA on physical fitness and body composition of physically active individuals. METHODS: Study was conducted on three groups of male soldiers (n=30 in each group) at different climatic conditions i.e., temperate (plains of north India), hot desert (Rajasthan), and HA (3600 m) in Western Himalayas. Subjects were acclimatized to hot and HA environments and had similar BMI (body mass index). Body fat, lean body mass, haemoglobin levels were determined along with, blood pressure and physical fitness index (PFI). RESULTS: The body fat of subjects at temperate, desert and HA was found to be 15.4, 12.8 and 16.9 per cent respectively. The resting heart rate and blood pressure were higher in altitude group in comparison to others. PFI score of volunteers at temperate, desert and HA were found to be 97.4 +/- 10.3, 92.4+/- 14.4 and 83.8 +/- 6.2 respectively. INTERPRETATION & CONCLUSION: A combination of different factors i.e., higher resting pulse rate, increased blood pressure and body fat may be responsible for lower PFI at HA. The observed differences in body fat content of different groups could be an adaptive feature to the environment.

Hydration and tissue solid content of the lean body on prolonged exposure to altitude.

Using densitometric, hydrometric and anthropometric techniques, body fat, tissue solids, water and mineral content were quantitatively measured on two groups each of 26 young and healthy Indian soldiers of mixed ethnic composition. The experimental group was exposed to 3500 m altitude for 2 years and the experiments were carried out after 48 h and 3 weeks rehabilitation in Delhi (300 m). The control group was never exposed to high altidues. Inspite of the experimental group being fed with superior rations at high altitude, this group showed significantly hyperhydrated lean body with reduced tissue solids in comparison to the control group which was fed with identical rations in Delhi. The calculated mean density of the fat free body had declined to 0.092 x 10(3) kg/m3. The 3 week stay at low altitude had little influence on body composition. Hyper-hydration, with reduced tissue solids, would cause reduction in the density of fat free body, and would thus interfere with the estimates of total body fat based on densitometric procedures alone. In the hyperhydrated state, Siri's formula overestimated fat by 22.8% of the true value.

Variations in skinfold thickness during de-acclimatisation and re-acclimatisation to high altitude. Relation to body fat content.

Skinfold thickness, body weight, body water, anthropometric measurements and segment volumes were determined in 28 young and healthy Indian soldiers on return to Delhi (200 m) after staying for more than 24 months at high altitude (3500 m). The measurements were made on the 2nd day and after 3 weeks. Ten subjects were then randomly selected from this group and returned by air to the high-altitude station, and the measurements were repeated on the 3rd and 12th day of their reinduction. Though body weight and total body water increased marginally on transfer to the lower altitude, body density remained more or less unchanged. There were significant increases in the thickness of skinfolds, even when body density had increased. During this period hand and foot volumes decreased significantly. Despite significant increases in thoracic skinfold thickness, the torso volume decreased slightly. On returning to high altitude, the soldiers lost body weight, were hypohydrated and showed reduced skinfold thickness. Fat losses calculated on the basis of reduction in skinfold thickness were far in excess of those calculated from losses in body weight and in total body water. As the reduced skinfold thickness was unrelated to changes in body water content at high altitude, it seems that such reductions are due to redistribution of blood in the skin. From the results of these investigations it is concluded that variations in skinfold thickness during acclimatisation to high altitude do not accurately represent the changes in body fat content.

Prediction of body volume by a stepwise linear regression technique.

Body volume and 35 anthropometric measurements were obtained from 88 active soldiers using standard techniques. These anthropometric measurements were examined for their possible relationships to body volume using stepwise linear regression analysis. Four measurements (Body weight, anterior thigh skinfold thickness, subscapular skinfold thickness and suprailiac skinfold thickness) accounted for 99.7% of the variation in body volume and the introduction of each of these measurements in the equation was significant. The regression equation for predicting body volume from these 4 anthropometric measurements had a multiple correlation coefficient of 0.9987 (P less than 0.001). Body weight alone was correlated with body volume to the extent of 0.9966. An attempt has therefore been made to develop a multiple linear regression equation without incorporation of body weight in the regression analysis. Nine measurements were selected by stepwise linear regression analysis for predicting body volume. These nine measurements accounted for 97.1% of the variation in body volume. These equations have been validated on another small sample of 22 soldiers. The analysis has also revealed that a direct regression of body density from the anthropometric variables gives more accurate results than when estimated body volumes are utilized for calculating body density.

Relationship of body density and lean body mass to body measurements: application to Indian soldiers of relationships developed for people of European descent.

Body density was measured directly in 90 young Indian soldiers from the Gurkha, Rajput and South Indian regiments. Body density was also predicted on the same subjects using skinfold thicknesses as well as other anthropometric measurements. Validity of the regression equations of Pascale, Grossman, Sloan and Frankel (1956), Sloan (1967) and Wilmore and Behnke (1969) was also tested on these Indian soldiers. Lean body mass was estimated directly from another equation of Wilmore and Behnke (1969), where skinfold thicknesses were not involved. The results indicate that all the body density predicting equations underestimate the measured body density, with the equation of Sloan (1967) approximately more closely to the actual value in these ethnic groups. The equation of Wilmore and Behnke (1969) regresses lean body weight from body measurement satisfactorily in all the ethnic groups of this study.

Estimation of body density and lean body weight from body measurements at high altitude.

Body density and other anthropometric data were obtained on 101 Indian soldiers who were continously staying at high altitude (3920 m) for more than 10 months. Use was made of a human body volumeter, and body density was calculated from observed body weight and volume. Measurements were taken on the body using standard techniques. A stepwise linear regression analysis was performed to establish possible relationships of 36 body measurements with density and lean body weight. Thigh anterior, juxta-nipple skin folds and forearm and ankle circumference were selected in the regression equation predicting body density. Multiple correlation coefficient (R) equal to 0.765 was obtained for this equation. For the predicted lean body weight, R equalled 0.930. The regression equations included body weight, thigh, anterior and juxta-nipple skin fold thicknesses, and forearm circumference. Contribution of other body measurements in the regression of these parameters was not significant. The analysis also revealed that a new set of coefficients is required for the measurements included in the published regression equations.