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a Keio University Sports Medicine Research Center, Yokohama, Japan
b Atsugi Public Health Center, Atsugi, Japan
Norimitsu Kinoshita, Sports Medicine Research Center, Keio University 4-1-1 Hiyoshi, Kohoku-Ku, Yokohama, Kanagawa, 223-0061 Japan E-mail: kinoshit{at}hc.cc.keio.ac.jp.
Decision Editor: John E. Morley, MB, BCh
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Abstract |
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Methods. Body composition, cardiac structure, and respiratory gas exchange during exercise were estimated in eight climbers with differing levels of experience (seven men and one woman, aged 54 to 63 years) 6 months before their expedition.
Results. Using supplementary O2, the four experienced climbers ascended beyond Camp 4 (7400 m) without showing any health problems and were able to attempt the summit. In contrast, the others, who had minimal experience at extreme altitude, suffered from altitude sickness on the way to Camp 4. Body mass index values were relatively high, but their low percentage of body fat (14.9%–21.4%) was indicative of the climbers' substantial lean body weight. Cardiac structures were generally normal, although three experienced male climbers had borderline hypertension and eccentric hypertrophy of the left ventricle. Peak 
O2 ranged from 30.9 to 45.6 ml/kg/min, and no significant relationship between fitness level and the success or failure of the ascent was evident.
Conclusions. Even sexagenarians are capable of safely climbing 8000-m peaks with supplementary O2. An exceptionally high fitness level, as is seen in elite older athletes, does not appear to be required. What is essential, however, is moderate fitness, good health, and extensive experience.
ONLY the most tenacious and experienced mountaineers are capable of scaling the 8000-m Himalayan peaks (1). Although research providing a better understanding of the local meteorology of Himalayan peaks (2) and of the physiological characteristics of elite alpinists (3)(4)(5) has encouraged other climbers to challenge extremely high altitudes, one might consider such an ascent unwise. This is especially true for older persons in whom agility, fitness, or cognitive function may have declined somewhat and in whom the incidence of morbidity due to chronic disease has increased. Nevertheless, because many climbers, not all of them young, are fascinated by these famous and challenging peaks, recreational mountaineering at moderate altitude is popular even among older individuals (6)(7).
To date, there has been little research on the relationship between aging and altitude tolerance (8). In particular, attempts by older people to climb 8000-m peaks has been scarcely mentioned in the medical literature. The purpose of the present study was to investigate the physiological characteristics of middle-aged and older climbers, both expert and amateur, who ascended Gasherbrum II, an 8035-m peak in the Karakoram Range of the Himalayas.
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Methods |
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Base Camp was situated at an altitude of 5100 m on Gasherbrum II, and the highest camp (Camp 4) was established at 7400 m. Although all eight climbers attempted to ascend to Camp 4 without supplementary O2, only four were sufficiently acclimatized to consider challenging the summit (group M1). The remaining four were forced to give up their ascent either on the way to Camp 4 or once they arrived because they failed to sufficiently acclimatize (group M2). Three of the M1 climbers then attempted to ascend to the summit using supplementary O2; the fourth, who was the leader of the expedition (subject 2, Table 1 ), descended with an M2 climber who had fainted just after reaching Camp 4 (subject 3). Of the three climbers who challenged the summit, one (subject 1) was a member of the first ascent team and was successful. The others (subjects 3 and 4) were members of the second team and were forced to give up the ascent at a point 235 m below the summit (7800 m above sea level) because of bad weather conditions.
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Body Composition
Percent body fat and lean body mass were determined using underwater weighing (AD-6204; A&D, Tokyo, Japan). Density was calculated using the equation of Broæek (9).
Echocardiography
Two-dimensional echocardiography was carried out in conjunction with M-mode imaging using a Hewlett-Packard (model-7020A, Andover, MA) imaging system equipped with a 3.5-MHz phased array transducer. Serial M-mode recordings were made in a left lateral decubitus position using the standard technique employed in our laboratory (10). M-mode echocardiographic measurements were obtained according to the guidelines of the American Society of Echocardiography (11). To minimize the effect of respiration on the measurements, the values were reported as the means of at least five representative cardiac cycles. All measurements were performed by the same investigator (NK). Blood pressure was recorded prior to echocardiography using a sphygmomanometer. Left ventricular (LV) mass was calculated using the formula of Devereux and Reichek (12) and indexed to body surface area, which was calculated according to the formula of DuBois and DuBois (13).
Exercise Testing
Maximal exercise tolerance was assessed using a treadmill. For the climbers, the protocol for determining peak oxygen uptake (O2) consisted of a series of 2-minute stages, starting at 4.8 km/h on a 3% grade. The speed was increased to 6 km/h at the second stage, after which it was held constant while the grade was progressively increased by 3% at each stage until reaching 15% (stage 5). After completion of the stage 5, the grade was held constant at 15%, and the speed was progressively increased by 1.2 km/h at each successive stage until volitional exhaustion. For the other subjects, the duration at each stage remained 2 minutes, but the starting point was 3.2 km/h at 0% grade. The grade was then increased by 3% up to 12% (stage 5) while the speed was held constant, after which the speed was increased in increments of 0.8 km/h at a constant 12% grade.
During the exercise, a 12-lead electrocardiogram was interfaced with the subject, and heart rate (HR) was recorded continuously. Blood pressure (BP) was measured every minute during the exercise and throughout the recovery period.
Respiratory Gas Analysis
Minute ventilation, O2, and CO2 production were determined using a breath-by-breath MMC Horizon System 4400 tc (SensorMedics, Anaheim, CA). The gas analyzers were calibrated before and after each test with two commercial gases of known composition, as described in the manual. Peak O2 (averaged over three consecutive 15-second intervals) was defined as the point at which O2 uptake plateaued, despite increasing work rate (leveling-off criterion), with a respiratory quotient >1.10 (14). O2 pulse (O2/HR) was for subjects exercising maximally.
Statistical Analyses
All statistical analyses were carried out using the Statistical Package for Social Science (SPSS) (SPSS Inc., Chicago, IL) Base 10.0J for Windows. Values are expressed as means ± SD.
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O2 and O2 pulse values were lower among the climbers than among the actively training subjects, although the three male M1 climbers had higher O2 and O2 pulse values than were seen among the M2 climbers. Still, the relationship between fitness level and success (M1) or failure (M2) was not necessarily obvious. For instance, the one woman climber (subject 3 of M1) accomplished the ascent despite her lower peak O2 and O2 pulse, whereas another climber with higher O2 (subject 4 of M2) came down with altitude sickness at a comparatively low altitude (Table 1 and Table 2 ). |
Discussion |
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3000 m), and as the authors of one report suggested (7), elderly individuals who visit high altitudes for recreational activities may curtail their activities upon arrival.
In contrast, all of the climbers in the present study were in their mid-fifties to early sixties, and ascending an 8000-m peak is a challenge far beyond recreation. Consequently, the impact of aging on physical and mental functioning at extreme altitude was likely to be a significant factor among this group. For example, pulmonary diffusing capacity, hypoxic ventilatory response, and peak O2, all of which should contribute to maintaining oxygenation and exercise performance in the hypoxic environment of high altitude (18)(19)(21), are all known to decline with age (22)(23). Moreover, some evidence suggests that age-related decreases in vital capacity increase the likelihood of developing high-altitude pulmonary edema (24). The partial pressures of oxygen at the altitudes between Camp 2 (5900 m) and Camp 4 were estimated to be about 40% to 50% of those at sea level. At that level of hypoxia, decreases in cognitive function or neuromuscular performance that could lead to an increased risk of lethal accidents or health deterioration would seem likely (20)(25), particularly among older climbers. Nevertheless, four climbers, aged 58 to 62, reached Camp 4 with no significant deterioration in health, indicating that age itself was not a limitation for mountaineering to these high altitudes. Instead, the level of experience appeared to be the key factor determining final success or failure.
One might anticipate that being overweight would be a precipitating factor for acute mountain sickness (26), yet the four climbers who succeeded in reaching the summit all had relatively high BMIs, and one of the elite male climbers would be regarded as overweight according to this parameter. It is notable, however, that their percent body fat was low and that more lean body weight—i.e., greater muscle mass—should contribute to their capacity to endure the arduous trek while bearing heavy equipment.
The LV mass indexes of the three male M1 climbers were larger than those of well-trained, active subjects. The climbers' condition may have been due in part to their borderline hypertension. The doctor accompanying this expedition (MH) frequently monitored the pulses, BPs, and blood O2 saturations of these climbers, and no deleterious hemodynamic responses were observed, suggesting that mild hypertension does not adversely affect older climbers mountaineering on 8000-m peaks. It should be emphasized that these climbers exhibited no other complications of hypertension, and no abnormal hemodynamic responses were observed during the exercise tests carried out prior to the climb.
Better exercise performance and greater peak O2 might be expected to increase the likelihood that a climber could successfully ascend to extremely high altitudes. But the success of the female climber, who exhibited a relatively low peak O2 and O2 pulse, runs contrary to this notion and might encourage older climbers with lower peak O2 to attempt such a challenge. In fact, none of the three elite M1 climbers had peak O2 levels as high as the average among the actively training athletes of corresponding age. Furthermore, the success of the female climber might imply that peak O2 is even less important when climbing at altitudes below 7400 m. It should be recognized, however, that the lifestyle of the female climber was not a sedentary one; she was an expert mountaineer with extensive experience in alpine ascent. This is made apparent by the fact that her peak O2 was greater and her percent body fat was lower than the average among the sedentary males of corresponding age. A sedentary lifestyle contributes not only to a decline in peak O2, but also to a decline in the level of physical performance at high altitude. Thus, an individual's capacity to perform at high altitude is likely to be better reflected by their background than by peak O2 itself.
All of the climbers in this study utilized supplementary O2 above 7400 m. Consequently, the effect of peak O2 level on the capacity of older climbers to ascend beyond that altitude without supplementary O2 was not determined.
In summary, our findings demonstrate that even sexagenarians are capable of safely climbing 8000-m peaks with supplementary O2. An exceptionally high fitness level, as is seen in elite older athletes, does not appear to be required. What is essential, however, is moderate fitness, good health, and extensive experience.
Received April 18, 2000
Accepted April 20, 2000
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  J. E. Morley Editorial: The Aging Athlete J. Gerontol. A Biol. Sci. Med. Sci., November 1, 2000; 55(11): 627M - 629. [Full Text]
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