title: The metabolic and ventilatory response to exercise in Tibetans born at low altitude.
abstract: The exercise response of 20 Tibetans (T) born and living in Kathmandu, Nepal (1300 m) was compared to that of 21 age- and sex-matched local lowlanders. The subjects carried out an incremental exercise protocol on a bicycle ergometer (30 watt steps every 4 min) until exhaustion. The kinetics of readjustment of VO2 measured as half time (t-on) upon a 90 watt constant load exercise was also determined. Breath-by-breath gas exchange, heart rate (HR) and blood lactate concentration ([La]) were measured at rest, at the end of each load and during recovery. The slope of the straight line relating VO2 to work load was 10.8 ml.watt-1 in both groups which corresponds to a mechanical efficiency of 0.26 (assuming a RQ of 0.89 and an energy equivalent of 20.9 kJ.L-1 O2). At submaximal loads T were characterized by higher VE (P < 0.05), VE.VO2(-1) (P < 0.01) and VCO2 levels (P < 0.001) than N. The found higher VE in T, resulting from a lower tidal volume coupled to a higher respiratory frequency, led to higher PETO2 (P < 0.001) and SaO2 (P < 0.001) at all work levels. Absolute VO2max in the two investigated groups were 1977 +/- 72 (T) and 2095 +/- 80 (N) ml.min-1 (NS). Specific (i.e. per kg body weight) VO2max were identical (37.0 +/- 1.1 [T] vs. 36.7 +/- 1.1 ml.kg-1.min-1 [N]). [La]max were 11.4 +/- 0.4 (T) vs. 12.3 +/- 0.4 (N) mM (NS). [La] accumulation in blood as a function of workload and its rate of disappearance during recovery were similar. t-on at 90 watt was 30.7 +/- 2.4 sec in T and 28.9 +/- 2.3 sec in N (NS). The corresponding average contracted O2 deficit were 971 ml for T and 994 ml for N (NS). In conclusion, Tibetans born at low altitude do not seem to differ from lowlanders with regard to their metabolic response whereas their ventilatory response to exercise is greater.
authors: Département de Physiologie, Centre Médical Universitaire, Genève, Switzerland.
authors: B
authors: B
authors: Kayser
authors: C
authors: C
authors: Marconi
authors: T
authors: T
authors: Amatya
authors: B
authors: B
authors: Basnyat
authors: A
authors: A
authors: Colombini
authors: B
authors: B
authors: Broers
authors: P
authors: P
authors: Cerretelli
mesh_terms: D000293:Adolescent; D000328:Adult; D000332:Aerobiosis / Q000502:physiology; D000531:Altitude; D001823:Body Composition / Q000502:physiology; D001827:Body Height / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006801:Humans; D007773:Lactates / Q000097:blood; D019344:Lactic Acid; D008297:Male; D008660:Metabolism / Q000235:genetics / Q000502:physiology*; D009390:Nepal; D010101:Oxygen Consumption / Q000502:physiology; D011659:Pulmonary Gas Exchange / Q000502:physiology; D015656:Respiratory Mechanics / Q000502:physiology*; D018609:Tibet / Q000208:ethnology
chemical_list: D007773:Lactates; D019344:Lactic Acid