Abstract
Prolonged altitude exposure usually leads to considerable weight loss of which a large
part is from muscle tissue. This loss reduces maximum alactic anaerobic muscle power.
It was hypothesized that most of the weight loss may simply be the result of malnutrition
due to lack of palatable food in an uncomfortable environment. To test this hypothesis
eight healthy male subjects (age 33.7±4.6 S.C. yr), well acclimatized to prevent symptoms
of acute mountain sickness, were exposed for 4 weeks to an altitude of 5050 m with
access to a large choice of palatable food in comfortable conditions. Body weight
(with a scale), body composition (from skinfolds), arm muscle plus bone cross-sectional
area (Am + b) and muscle plus bone leg volume (Vm + b) (from skinfolds and circumferences),
maximum voluntary contraction force of the elbow flexors (MVC, with a load cell) and
maximum jumping height (Hmax, on a platform) were measured before departure (SL) and
in the first (ALT1), second (ALT2) and fourth week (ALT4) of their altitude sojourn.
Three-day dietary records were obtained at SL and at ALT4. Body mass had decreased
significantly at ALT2 (-3.8%) and at ALT4 (-4.6%) likely reflecting changes in body
water homeostasis. No changes were found in %fat, Am + b, Vm + b, MVC or Hmax. Average
dietary intake at SL was 8.96±1.45 MJ and had increased to 13.59±3.07 MJ at ALT4.
In conclusion, up to an altitude of 5050 m loss of body mass from fat and muscle tissue,
and hence impairment of maximum anaerobic muscle power (alactic) appears to be avoidable
by food intake matched to energy expenditure. The latter may be achieved simply by
proper acclimatization, sufficient comfort and availability of palatable food.
Key words
Nutrition - altitude - mountaineering - muscle - weight loss - alactic power
