D. Desplanches et al., MUSCLE-TISSUE ADAPTATIONS OF HIGH-ALTITUDE NATIVES TO TRAINING IN CHRONIC HYPOXIA OR ACUTE NORMOXIA, Journal of applied physiology, 81(5), 1996, pp. 1946-1951
Twenty healthy high-altitude natives, residents of La Pat, Bolivia (3,
600 m), participated in 6 wk of endurance exercise training on bicycle
ergometers, 5 times/wk, 30 min/session, as previously described in no
rmoxia-trained sea-level natives (K. Hoppeler, H. Howald, K. E. Conley
, S. L. Lindstedt, H. Claassen, P. Vock, and E. R. Weibel. J. Appl. Ph
ysiol. 59: 320-327, 1985). A first group of 10 subjects was trained in
chronic hypoxia (HT barometric pressure = 500 mmHg; inspired O-2 frac
tion = 0.209) a second group of 10 subjects was trained in acute normo
xia (NT; barometric pressure = 500 mmHg; inspired O-2 fraction = 0.314
). The workloads were adjusted to similar to 70% of peak O-2 consumpti
on (Vo(2)peak) measured either in hypoxia for the HT group or in normo
xia for the NT group. Vo(2peak) determination and biopsies of the vast
us lateralis muscle were taken before and after the training program.
Vo(2peak) in the HT group was increased (14%) in a way similar to that
in NT sea-level natives with the same protocol. Moreover, Vo(2peak) i
n the NT group was not further increased by additional Oz delivery dur
ing the training session. HT or NT induced similar increases in muscle
capillary-to-fiber ratio (26%) and capillary density (19%) as well as
in the volume density of total mitochondria and citrate synthase acti
vity (45%). It is concluded that high-altitude natives have a reduced
capillarity and muscle tissue oxidative capacity; however, their train
ing response is similar to that of sea-level residents, independent of
whether training is carried out in hypobaric hypoxia or hypobaric nor
moxia.