To the Editor.— The article by J. R. Murphy (225:981, 1973) concerned the prevalence of sickle cell hemoglobin (Hb AS) in football players and offered the hypothesis that men with sickle cell trait would not have limited physical capabilities. During a mission performed in Dahomey by the Institute of Anthropology of Rome University, the energy expenditure of two groups of 15 adults in apparent good health was examined, one group with normal adult hemoglobin (Hb A) and the other with Hb AS. The two groups were selected to show similar somatometric values, also similar to the average values of the examined population as a whole. The energy expenditure was measured at rest and at the cycloergometer, with power levels of 483 and 790 kg/meter, respectively. Respiratory gas analysis was carried out by means of an open-circuit Hartmann and Braun apparatus. Data of the Table show that the energy expenditure under