Why Are High-Altitude Natives So Strong at Altitude? Maximal Oxygen Transport to the Muscle Cell in Altitude Natives

Abstract

In hypoxia aerobic exercise performance of high-altitude natives is suggested to be superior to that of lowlanders; i.e., for a given altitude natives are reported to have higher maximal oxygen uptake (VO2max). The likely basis for this is a higher pulmonary diffusion capacity, which in turn ensures higher arterial O2 saturation (SaO2) and therefore also potentially a higher delivery of O2 to the exercising muscles. This review focuses on O2 transport in high-altitude Aymara. We have quantified femoral artery O2 delivery, arterial O2 extraction and calculated leg VO2 in Aymara, and compared their values with that of acclimatizing Danish lowlanders. All subjects were studied at 4100 m. At maximal exercise SaO2 dropped tremendously in the lowlanders, but did not change in the Aymara. Therefore arterial O2 content was also higher in the Aymara. At maximal exercise however, fractional O2 extraction was lower in the Aymara, and the a-vO2 difference was similar in both populations. The lower extraction levels in the Aymara were associated with lower muscle O2 conductance (a measure of muscle diffusion capacity). At any given submaximal exercise intensity, leg VO2 was always of similar magnitude in both groups, but at maximal exercise the lowlanders had higher leg blood flow, and hence also higher maximum leg VO2. With the induction of acute normoxia fractional arterial O2 extraction fell in the highlanders, but remained unchanged in the lowlanders. Hence high-altitude natives seem to be more diffusion limited at the muscle level as compared to lowlanders. In conclusion Aymara preserve very high SaO2 during hypoxic exercise (likely due to a higher lung diffusion capacity), but the effect on VO2max is reduced by a lower ability to extract O2 at the muscle level.

Endurance Training in Normobaric Hypoxia Imposes Less Physical Stress for Geriatric Rehabilitation

“…The rehabilitation intervention included physical strength training, gait training, balance training and other common physical therapy methods. The relatively lower HR observed in HG during the post-test may be an early signal of an emerging higher stroke volume and improved O 2 utilization that has been demonstrated in other studies (Levine and Stray-Gundersen, 1997 ; Vissers et al, 2015 ; Lundby and Calbet, 2016 ; Moon et al, 2016 ). These positive outcomes may be attributed to the combined effects of the endurance training with an impactful target HR as well as the O 2 deprivation.…”

Altitude and Endurance Performance in Altitude Natives versus Lowlanders: Insights from Professional Cycling

“…In this regard, several classic studies with nonathletes have compared physiological responses to endurance exercise in lowlanders and altitude natives (e.g., from the Andes) (14,15,29), and there is evidence that, compared with the former, altitude natives can attenuate the detrimental effects of hypoxia on performance (7,9,11). An important mechanism seems to be an enhanced pulmonary gas exchange under hypoxic conditions in altitude natives, which ensures preservation of arterial oxygen saturation and thus a higher oxygen delivery to working muscles (8,15). There is also laboratory evidence that altitude-acclimatized humans have a potentially preserved endurance performance capacity (expressed as VO 2max ) compared with sea-level human in those types of exercise that do not compromise oxygen delivery to working muscles (i.e., one-leg pedaling) versus those with an oxygen delivery that might be limited owing to the involvement of more muscle mass (i.e., two-leg cycling) (30).…”

“…An interesting question is whether the magnitude of physiological impairment induced by hypoxic environments differs between lowlanders and altitude natives as well as the mechanisms responsible for potential differences (7,8). In general, high-altitude native populations have evolved to resist the depressive effects of hypoxia on physical capacity, as these people successfully lived and reproduced at high altitude for hundreds of generations with hypoxia as a constant evolutionary pressure (9).…”