Low haemoglobin concentration in Tibetan males is associated with greater high-altitude exercise capacity.
J Physiol
; 593(14): 3207-18, 2015 Jul 15.
Article
em En
| MEDLINE
| ID: mdl-25988759
ABSTRACT
Tibetans living at high altitude have adapted genetically such that many display a low erythropoietic response, resulting in near sea-level haemoglobin (Hb) concentration. We hypothesized that absence of the erythropoietic response would be associated with greater exercise capacity compared to those with high [Hb] as a result of beneficial changes in oxygen transport. We measured, in 21 Tibetan males with [Hb] ranging from 15.2 g dl(-1) to 22.9 g dl(-1) (9.4 mmol l(-1) to 14.2 mmol l(-1) ), [Hb], ventilation, volumes of O2 and CO2 utilized at peak exercise (VÌO2 and VÌCO2), heart rate, cardiac output and arterial blood gas variables at peak exercise on a cycle ergometer at â¼4200 m. Lung and muscle O2 diffusional conductances were computed from these measurements. [Hb] was related (negatively) to VÌO2 kg(-1) (r = -0.45, P< 0.05), cardiac output kg(-1) (QT kg(-1) , r = -0.54, P < 0.02), and O2 diffusion capacity in muscle (DM kg(-1) , r = -0.44, P<0.05), but was unrelated to ventilation, arterial partial pressure of O2 (PaO2) or pulmonary diffusing capacity. Using multiple linear regression, variance in peak VÌO2 kg(-1) was primarily attributed to QT, DM, and PCO2 (R(2) = 0.88). However, variance in pulmonary gas exchange played essentially no role in determining peak VÌO2. These results (1) show higher exercise capacity in Tibetans without the erythropoietic response, supported mostly by cardiac and muscle O2 transport capacity and ventilation rather than pulmonary adaptations, and (2) support the emerging hypothesis that the polycythaemia of altitude, normally a beneficial response to low cellular PO2, may become maladaptive if excessively elevated under chronic hypoxia. The cause and effect relationships among [Hb], QT, DM, and PCO2 remain to be elucidated.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Hemoglobinas
/
Adaptação Fisiológica
/
Tolerância ao Exercício
/
Altitude
Tipo de estudo:
Risk_factors_studies
Limite:
Adult
/
Humans
/
Male
País/Região como assunto:
Asia
Idioma:
En
Revista:
J Physiol
Ano de publicação:
2015
Tipo de documento:
Article
País de afiliação:
Estados Unidos