THE INFLUENCE OF SICKLE-CELL TRAIT ON ENE RGY ABILITIES

The sickle cell trait (SCT) is a genetic abnormality of the red blood cell which mainly affects people of African descent. It is due to the mutation of only one parental gene (one glutamic acid of the chain bet a of the globin is substituted by one valin), The prevalence of SCT in the black US population is within the range of 8-9%. It is increasing in Europe and in Africa where it may reach up to 40% in some regions, The rate of prevalence of SCT in athletic populations was found to be similar to that of the general sedentary population in west African c ountries. SCT is usually asymptomatic, However, SCT has been associate d with a higher risk of sudden death during exercise. In fact, the sub stitution of one amino-acid modifies the properties of haemoglobin and produces physiological desorders such as sickling, less solubility of the deoxidized form and the reduction of affinity fur oxygen. The sic kling phenomenon (formation of sickle cells) mainly occurs in some con ditions related to the practise of sport (intense and/or prolonged exe rcise, exercise in hypoxic conditions, exercise in heat conditions). T hese sickled red blood cells reduce the speed of capillary flow or obs truct the blood vessels which because of the lack of oxygen, become al tered. The physical ability of sickle cell trait carriers (HbAS) who p ractise sport should be different from the physical ability of subject s with normal haemoglobin (HbAA) because of: 1) potential risks due to their haemoglobinopathy and 2) the eventual modification of their per formance ability. These two aspects have caused controversies among ma ny researchers particularly in line with their investigation methods. Nevertheless, the following results seem to be established: 1) the abi lity to perform sprint exercises is not altered in the HbAS subjects. Their performances in these events are similar to those of HbAA subjec ts; 2) The ability of HbAS subjects to perform intense and prolonged e xercise is decreased. Our former results have shown that prolonged aer obic efforts in hypobaric hypoxic conditions may be associated with a deleterious effect on the performance of HbAS subjects. The damaging c onsequences on their performance in these conditions could be due to t issue oxygen delivery limitations.