Sickle cell trait performance in a prolonged race at high altitude.

The limitation of aerobic exercise capacity of athletes with the sickle cell trait (SCT), under conditions of limited oxygen availability, is still controversial. To study this, we took advantage of an unique setting, the International Mount Cameroon Ascent Race, a 34.1-km race over difficult terrain, slopes ranging from 7 to 40%, and altitudes varying from 615 to 4095 m, combined with high prevalence rates of SCT among the African runners. Of 266 Cameroonian runners, SCT was detected in 33 athletes (12.4%), a prevalence similar to that of the ethnically corrected general population. However, in runners of the Bakoueri tribe whose performance is contingent with social stature, SCT was present in only 1 of 41 runners (2.4%), as compared with 15.6% in the general population of the Bakoueri tribe (P < 0.03). In general, performance times of SCT runners were not different from non-SCT runners, except during the portion of the race at altitudes ranging from 3800 to 4095 m, where significantly longer times were clocked by SCT subjects (P < 0.02). We conclude that prolonged aerobic efforts in hypobaric hypoxic conditions may be associated with a detrimental effect on performance in SCT carriers. If this is true, it might account for the reduced prevalence of SCT among those runners representing the Bakoueri tribe, provided an objective measure of performance at altitude was employed to select these representatives.