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, 569 (Pt 2), 667-75

Economy of Locomotion in High-Altitude Tibetan Migrants Exposed to Normoxia

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Economy of Locomotion in High-Altitude Tibetan Migrants Exposed to Normoxia

Claudio Marconi et al. J Physiol.

Abstract

High-altitude Tibetans undergo a pattern of adaptations to chronic hypoxia characterized, among others, by a more efficient aerobic performance compared with acclimatized lowlanders. To test whether such changes may persist upon descent to moderate altitude, oxygen uptake of 17 male Tibetan natives lifelong residents at 3500-4500 m was assessed within 1 month upon migration to 1300 m. Exercise protocols were: 5 min treadmill walking at 6 km h(-1) on increasing inclines from +5 to +15% and 5 min running at 10 km h(-1) on a +5% grade. The data (mean +/- S.E.M.) were compared with those obtained on Nepali lowlanders. When walking on +10, +12.5 and +15% inclines, net V(O2) of Tibetans was 25.2 +/- 0.7, 29.1 +/- 1.1 and 31.3 +/- 0.9 ml kg(-1) min(-1), respectively, i.e. 8, 10 and 13% less (P < 0.05) than that of Nepali. At the end of the heaviest load, blood lactate concentration was lower in Tibetans than in Nepali (6.0 +/- 0.9 versus 8.9 +/- 0.6 mM; P < 0.05). During running, V(O2) of Tibetans was 35.1 +/- 0.8 versus 39.3 +/- 0.7 ml kg(-1) min(-1) (i.e. 11% less; P < 0.01). In conclusion, during submaximal walking and running at 1300 m, Tibetans are still characterized by lower aerobic energy expenditure than control subjects that is not accounted for by differences in mechanical power output and/or compensated for by anaerobic glycolysis. These findings indicate that chronic hypoxia induces metabolic adaptations whose underlying mechanisms still need to be elucidated, that persist for at least 1 month upon descent to moderate altitude.

Figures

Figure 1
Figure 1
Pulmonary oxygen uptake formula image, heart rate (HR) and respiratory gas exchange ratio (R) of Tibetan migrants and Nepali walking at 6 km h−1 on increasing slopes.
Figure 2
Figure 2
Absolute (upper panel) and specific (expressed per unit of BSA, middle panel) pulmonary ventilation and breathing rate (lower panel) of migrants and Nepali as a function of the slope of the treadmill, during walking at 6 km h−1.
Figure 3
Figure 3
Net (steady state – standing value) formula image of Tibetan migrants during walking at a constant speed (6 km h−1) on a +5, +10, +12.5 and +15% grade as a function of the days at 1300 m.
Figure 4
Figure 4. Metabolic power output as a function of the corresponding mechanical external power output in Tibetan migrants and Nepali lowlanders during walking at a constant speed (6 km h−1) on a +5, +10, +12.5 and +15% grade and during running (10 km h−1 on a +5% grade)
Metabolic power output was calculated from aerobic energy sources, assuming the extreme caloric equivalents for formula image of 20.9 kJ l−1 (R = 1) and 19.7 kJ l−1 (R = 0.7). Mechanical external power output during walking and running was calculated from data by Minetti et al. (1993, , respectively).

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