Anthropometric changes associated with high altitude acclimatization in females.код для вставкиСкачать
Anthropometric Changes Associated with High Altitude Acclimatization in Females JOHN P. HANNON, J. L. SHIELDS AND CHARLES W. HARRIS Physiology Division, U.S. Army Medical Research and Nutrition Laboratory, Fitzsimons General Hospital, Denver, Colorado 80240 ABSTRACT The anthropometric effects of prolonged high altitude exposure were studied in eight college women who lived on the summit of Pikes Peak (14,100 f t . ) for 2.5 months. Acclimatization to altitude was associated with a decrease of skinfold thickness and a reduction in limb circumference, but little change in body weight. It was concluded that these changes reflected a loss of subcutaneous fat during the period of altitude exposure. Altitude exposure did not produce any alterations in trunk circumference at the umbilicus or buttocks, but it did cause an increase in the inspiratory chest circumference at the axillary level and a reduction in expiratory chest Circumference at the subscapular level. The first anthropometric study of high altitude natives, the Aymara Indians of Bolivia and Peru, was reported in 1870 by Forbes. Only a few individuals were actually measured, yet Forbes described these Indians reasonably correctly as being short and robust, relatively long-bodied but shortlegged, never corpulent and possessing large chests. This latter characteristic, although based upon linear and circumference measurements not volume measurements, was concluded to be an altitude adaptation, “affording space for an immense development of the breathing organs.” Later, x-ray measurements of the thorax by Keith (’23) and pulmonary function measurements by Barcroft et al. (’23) and Hurtado (’32) confirmed Forbes’ original descriptions and conclusions. In Europe, Loewy and Marton (’34) found an elevated vital capacity in children residing at the comparatively low altitude of Davos (5,240 ft.) while Rengger-Perlmann (’28) observed the same change in adults of this locality. Loewy and Wittkower (’37) noted that most high altitude residents and animals were smaller than the same species at low elevations and felt that this size difference, as well as a reduction in body fat and muscle mass was ascribable to an increased amount of physical work. Some of the foregoing characteristics can be seen when low altitude residents are brought to high altitude. In this respect, the thoracic enlargement has been extenAM. J. PHYS. ANTHBOP., 31: 77-84, sively studied (Barcroft et al., ’23; Keith, ’23; Tenney et al., ’52; Verzar, ’45) and evidence showing a loss of body fat has been gradually accumulating (Hannon and Chinn, ’66; Surks, Chinn and Matoush, ’66). Insofar as we can determine, there are only two reports containing quantitative anthropometric data on women exposed to high altitude. One of these is the above indicated article of Forbes’ which includes extensive measurements on one Aymara female. The other is Heber’s report (’21) of his experience in the Ladak province of Kashmir, wherein he describes a few casual chest measurements which were obtained from one woman, first at 5,000 feet and later after three weeks’ exposure to an elevation of 11,500 feet. He found that her chest circumference had increased by 0.5 cm at the higher elevation, but does not indicate whether this was an inspiratory or expiratory volume. In this same article, Heber states that his wife observed a two-inch increase in her chest circumference after living in Ladak for two years. The present report contains anthropometric data collected from eight college women who lived for 2.5 months at the summit of Pikes Peak, Colorado. METHODS Eight University of Missouri female students, without prior high altitude exposure, were selected on the basis of nor77 78 J. P. HANNON, J. L. SHIELDS AND C. W. HARRIS ma1 medical history, physical examination, hematocrit and hemoglobin levels, electrocardiogram, chest roentgenograms, and exercise tolerance tests. In addition, they were screened for past work experience, physical fitness as determined on a bicycle ergometer, as well as general appearance and personality. These latter criteria were pertinent to their employment at the tourist concession on Pikes Peak, where they would be working long hours and meeting the public. Over a three month period, prior to altitude exposure, the subjects were required to engage in sports activities, intramural and otherwise, to raise their level of physical activity to approximate that expected on Pikes Peak. After completion of low altitude measurements they were flown from Columbia, Missouri (elevation 700 ft.) to Denver, Colorado where they remained overnight. The next morning, they were taken to the summit of Pikes Peak (elevation 14,000 ft.) by automobile, a trip requiring 2.5 hours. For the following two and a half months, the women lived and worked in the tourist house atop the Peak except for one day per week, their day off, when they descended to Colorado Springs (elevation 6,000 ft.) or surrounding mountain areas. In all of our determinations, at least one week had elapsed since their last trip to lower elevations. Experimental measurements were made after an overnight fast in Missouri one week prior to departure, after an overnight stay in Denver and after 1, 7, 30 and 65 days’ exposure on Pikes Peak. On the indicated days, body weights were determined in the morning shortly after arising, with the subjects in a fasting state. They wore shorts and lightweight shirts. The overall accuracy of the weight measurements was f 10 gm. Skinfold thicknesses were determined with a Lange anthropometric caliper placed parallel to the normal cleavage line in the respective areas. A pressure of 10 g/mmz was employed. Five of the anatomical locations described in the study of Skerlj et al., ( ’ 5 3 ) were included in these skinfold measurements. These were : brachial, halfway between the shoulder and elbow over the right triceps brachii; subscapular, approximately 3 cm below the inferior angle of the right scapula; suprdiac, midway between the lower margin of the ribs and the iliac crest on the right side; umbilical, approximately 3 cm to the right of the umbilicus and thigh, over the right rectus femoris midway between the ilium and the knee. Body circumferences were determined with a flexible, non-stretch tape using bony landmarks to insure uniformity of placement. Since most of these anthropometric measures, particularly skinfold determinations, can vary greatly with technique, the same investigator performed each measure throughout the study. The data were statistically evaluated with Analyses of Variances and Critical Differences at the 0.05 level of confidence computed (Lindquist, ’56). The actual magnitude of these Critical Differences are shown in the various figures that follow. RESULTS Although it would appear (fig. 1 ) that altitude exposure was associated with a progressive and apparently linear loss of body weight, the changes were small and not statistically significant. In fact, four of the subjects exhibited either no loss or an actual gain of weight during the 65 days they lived at Pikes Peak. Skinfold thicknesses, as seen in table 1, were obtained at five locations. In all of these, except the suprailiac region, altitude exposure was associated with a thickness reduction ( P I 0.05) which averaged from as little as 1 mm in the subscapular re- BODY WEIGHT J 56L ’ Y D ’ 0 10 20 30 mIvs RT 40 50 60 A\K!=d@a = l Y Fig. 1 Body weight changes during altitude acclimatization. Weight on the ordinate, is expressed in kilograms. The abbreviation “D” refers to Denver and “C. D.” to Critical Difference at PL0.05. 79 ALTITUDE ANTHROPOMETRY TABLE 1 Effect of altitude exposure on skinfold thicknesses o f women - Skinfold Brachial Subscapular Suprailiac Umbilical Thigh Days at Pikes Peak n 7 13.2k2.64 13.4C2.61 11.3k0.91 11.0C1.22 10.122.44 12.0C3.37 13.01-3.19 12.422.57 16.33~2.19 13.21-2.62 -- Rn 10.923.08 9.7k1.41 9.4i2.51 12.2k1.52 12.4f2.66 .-- RS 11.421.71 10.121.42 9.2C2.60 11.542.16 12.943.14 Critical difference 1.84 1.06 n.s.c. 1.75 1.96 Values indicate mean skinfold thicknesses, in mm, + standard deviations for eight subjects. Critical Difference indicates minimum difference between means -where P C 0.05, as computed from an Analysis of Variance of the data (see Methods). gion to almost 4 mm in the thigh region. In some areas the reduction in skinfold thickness was reflected in a similar reduction in body circumferences (fig. 2). In the upper arm, for example, an average loss of about 1.5 cm was recorded over the course of the summer. The thigh, which showed a large skinfold reduction, also showed a large reduction ( 2 cm) in circumference. On a percentage basis, howBODY H/ CIRCUMFERENCES , , 27 UPPER ARM -5 25 ] C.D. = 1.04 24 UMBlLl CUS 71 70 BUTTOCKS 94 ever, both limbs exhibited similar losses in circumferences, that is, about 6% over the period of altitude exposure. Trunk measurements at the level of the umbilicus and the buttocks failed to show any statistically significant altitude effects, although there is a suggestion of an increase in umbilicus circumference during the first week of exposure. At the level of the thorax, two rather interesting alterations in body circumference were observed (fig. 3). One of these was an early and sustained increase in axillary circumference measured during maximum inspiration. With maximum expiration, chest circumference at this level was unaffected by altitude exposure. An opposite picture was obtained when the measurements were made at the subscapular level. Here altitude exposure had no effect on chest circumference during maximum inspiration but produced an abrupt and sustained decrease in circumference when measured during maximum expiration. DISCUSSION This study shows that some women lose weight during altitude exposure, others gain and still others are unaffected. THIGH If the data are averaged, a slight, but 34 statistically, insignificant reduction is ob33 served. Men, on the other hand, character’ -D b Ib 2b $0 40 o; 6b ’ istically show a large weight loss when DAYS AT PIKES PEAK taken to high elevations. For example, if we compare the average weight change Fig. 2 Effects of altitude acclimatization on the circumference of the upper leg, upper arm, in women with that described for males and lower trunk. Circumferences, on the ordinate, by Consolazio et al. (’68) we see (fig. 4) are expressed in centimeters. The abbreviation about a nine-fold greater loss in males “ D refers t o Denver, “C. D.” t o Critical Difference at P 40.05, and “N. S.C.” to No Signifi- than in females over similar periods of exposure. Thus, after one month men excant Change. 93 80 J. P. HANNON, J. L. SHIELDS AND C. W.HARRIS hibit an average loss of 3,900 g, which is a typical value, while women exhibit an average loss of 440 g. The greater loss in 87r AXILLARY MAX. 1 men can not be attributed to a greater level of physical activity; if anything, they ] C.O. 1.32 were less active than the women since the latter were required to work in the Concession atop the Peak. In both sexes, however, a concerted effort was made to match as closely as possible the low and high 78 altitude activity levels. A greater degree of anorexia in men may be responsible 78 for this sex difference, but unfortunately, SUBSCAPULAR MAX. it was not feasible for us to evaluate I N S.C) 76 caloric balance directly in the present 75 study of women. It is to be noted, however, that these women experienced less moun71 tain sickness than normally seen in males SUBSCAPULAR M IN. C.D.= 1.75 (Harris et d.,'66) which would favor better appetites and hence a lower de68 crement in food intake. 67L In this study of women we found no 0 0 10 20 30 40 50 60 evidence of dehydration as has been reDAYS AT PIKES PEAK ported for Himalayan climbers (Pugh, '64). In small mammals, various estimates Fig. 3 Effects of altitude acclimatization on of body water content have shown hypoxic chest circumferences during maximum inspiration and maximum expiration. Circumferences, exposure to be associated with marked on the ordinate, are expressed in centimeters. dehydration. For instance, Swann et al. The abbreviation "D" refers to Denver, "C. D ('42, '43) found insensible water loss to to CriticaI Difference at P L 0.05 and "N. S. C." be increased 50 to 100% in rats exposed to No Significant Change. to a simulated altitude of 18,000 feet for 6 to 23 hours. Also in rats, Stickney reported ('46) significantly increased fecal, BODY WEIGHT LOSS (kilogmmr) urine and insensible water loss while calculations by Picon-Reategui et al. ('53) showed that dehydration could account for 94% of the body weight loss seen during acute exposure to a simulated altitude of 15,000 feet. Lawless and Van Liere ('47) studied the effects of hypoxia on tissue water content and found a significant reduction in striated muscle and skin hydration at 18,000 feet, an observation which is somewhat confused by the fact that similar dehydration was not observed in the animals exposed to 8,000 or 28,000 feet. In humans, many investigators have attributed the weight losses observed in mountain climbers or other sojourners to I dehydration. Pugh ('62), Balke ('59) and t 2 3 4 5 10 20 X I 40 M 60 DAYS AT PIKES PEAK Buskirk and Mendez ('67), for example, Fig. 4 Comparative weight losses, in kilo- feel such dehydration is due to an ingrams, of men and women during high altitude creased respiratory water loss. There are also reports (Consolazio et al., '68) of exposure on Pikes Peak. BODY CIRCUMFERENCES Hf , - I " " 1 , 4 I ALTITUDE ANTHROPOMETRY negative water balances of men during acute exposure. But, unfortunately, there is a paucity of actual data on the changes in body water content, if any, which accompany high altitude exposure. Available data fail to support the conclusion that altitude exposure produces substantial dehydration, even during acute stages where body weight declines rather markedly. Nevison ('66) showed an increased turnover of body water in Himalayan climbers, but he found no statistically significant changes in the total body water content as estimated by the DzO dilution technique. Similar data have been reported by Buskirk and Mendez ('67). Recent measurements by Surks et al., ('66) and Hannon and Chinn ('66) have shown relatively normal levels of hydration in soldiers exposed for one to two weeks on Pikes Peak as estimated by body densitometry and antipyrine dilution. In both of the foregoing studies, measurement of body water by DzO dilution was also attempted, but the technique was found to be highly unreliable, particularly during the first few days of altitude exposure. In native populations of the Andes, Siri et al. ('54) PiconReategui ('61 ) and Picon-Reatgui and coworkers ('61 ) employing, respectively, antipyrine and tritiated water dilution techniques observed little or no relationship between altitude and body water content. If anything, the data of Siri et al. ('54) indicate a slight increase in the hydration of high altitude natives. Altitude-induced changes in body fat content have only been assessed indirectly in humans. In the present study, the reductions in skinfold thickness suggest a loss of subcutaneous lipid. Data on soldiers reported by Surks et al. ('66), and Hannon and Chinn ('66), which were obtained by body densitometry before and after exposure on Pikes Peak, indicate a large fat loss also occurs in males. On the basis of D20 measurements, Gill and Pugh ('64) reported reduced body fat levels in Himalayan climbers. Native residents of the Andes, however, generally exhibit normal or slightly reduced body fat levels (PiconReategui, '61; Siri et al., '54). Direct measurements have only been made in laboratory rodents, and these show a reduction 81 in body fat content under conditions of simulated (Cullumbine, '52) and actual (Chinn, '67) altitude exposure. Thus, it would seem reasonable to conclude that only the acute stages of altitude exposure are associated with a loss of body fat, and this loss probably accounts for most of the body weight reduction. The causes of these fat losses are not known with certainty. In men the loss is no doubt related to the anorexia which accompanies acute exposure, and may be enhanced by an increased rate of lipid catabolism (Klain and Hannon, '68). In women, as indicated above, anorexia does not seem like a probable cause. It may be related to their physical activity at high altitude in spite of our attempts to regulate activity levels. Thus, similar decreases in skinfold are seen during the training of athletes (Thompson et al., '56). The changes in thoracic circumference seen in this study are somewhat difficult to interpret. It should be pointed out that while axillary maximum and subscapular minimum values are significantly altered after one week of exposure, these alterations are quite small in magnitude. They do suggest the ability for enhanced thoracic volume displacement if maximum inspiratory and expiratory reserves are used. However, since these subjects exhibited a decrease in forced vital capacity during altitude exposure (Shields et al., '68) the functional significance of the changes in thoracic circumference are nebulouse. Conceivably, hypoxia-induced changes in tidal volume and minute volume, which have been observed in man at various levels of oxygen consumption (Grover, '63) could exert a training effect on the musculo-skeletal aparatus of the thorax, thus imparting greater capacity for volume displacement. An enlargement of the pectoral muscles might also be a factor. Such alterations are indeed observed in physical training programs (Morehouse and Miller, ' 5 3 ) , but it is doubtful whether the alterations seen in the present study could contribute materially to high altitude acclimatization, at least in females. The direction of the change, nevertheless, is toward the anatomical characteristics of high altitude na- a2 J. P. HANNON, J. L. SHIELDS AND C. W.HARRTS tive, and in this respect we should note that the enlarged chest capacity of the native is considered to be an acquired, not a genetic, characteristic (Monge, '53). ACKNOWLEDGMENTS The authors would like to express their appreciation to the Helen Stewart Co., particularly Mr. William Carle, manager of the Pikes Peak Summit House who agreed to employ the subjects of this study for the entire course of the summer. The data on weight losses of men exposed to altitude on Pikes Peak were kindly provided by Mr. C. F. Consolazio of the Bioenergetics Division of this laboratory. LITERATURE CITED Balke, B. 1959 Man in space. In: Bioastronautics, Advances in Research, p. 161. Randolph AFB, Texas. USAF School of Aviation Medicine. Barcroft, J., C. A. Binger, A. V. Bock, J. H. Doggart, H. S. Forbes, H. Harrop, J. C. Meakins and A. C. 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