Background The change of anaerobic exercise abilities during and after a high-altitude expedition or hypoxic exposure is not well studied.To evaluate the effects of an extreme-altitude expedition on anaerobic performance,the 10-second supramaximal test and endocrine hormones were evaluated before and after an expedition to Peak Lenin.Methods Four subjects (3 male and 1 female,age (30.5+16.5) years) were recruited into the study.Three sets of tests were performed,including a basic test at sea level and 20 days before first arrival at the base camp (3600 m),a middle test done at day after returning from the summit to the base camp and the post test at the 10th day after return to the sea level.Both the supramaximal test,performed by a cycle ergometer,and body composition,performed by bioelectrical impedance analysis,were completed before the basic test and post test.The endocrine hormones including cortisol,growth hormone,testosterone,noradrenaline,adrenaline,dopamine,glucagon and β-endorphin were measured at all tests.Results Comparing the conditions before and after the expedition,the body measurement parameters were decreased after the expedition,i.e.,body weight (-4.22%,P ＜0.05),fat-free mass (-2.09%,P ＜0.01 ) and body fat (-8.95%,P=0.172).The peak power relative/body weight ratio (PP/BW) was similar ((9.70+1.97) vs (9.11+1.80) W/kg,P=0.093),while mean power/body weight ratio (MP/BW) was reduced significantly after the expedition ((9.14+1.77) vs (8.33+1.74) W/kg,P ＜0.05).Peak power/fat-free mass (PP/FFM),mean power/fat-free mass (MP/FFM) and fatigue index (FI) were significantly lower after the expedition (PP/FFM:(11.95+1.71) vs (10.99+1.59) W/kg,P ＜0.05;MP/FFM:(11.26+1.50) vs (10.04+1.55) W/kg,P＜0.O05;FI (85.55±4.17)% vs (77.25±4.40)%,P＜0.05).Hormone assays showed a significant increase of noradrenaline (basic vs middle,P＜0.05) as well as decrease of adrenaline (P＜0.05).Meanwhile,a trend towards an increase in dopamine (basic vs middle) and a decrease of β-endorphin (basic vs post) were also noted.Conclusions These results suggested that an expedition to an extreme altitude may have negative effects on anaerobic performance.It showed that a significant increase of noradrenaline (basic vs middle) as well as decrease of adrenaline after the expedition to Peak Lenin had occurred.The real physiological significance needs to be further investigated.