LACTATE EXCHANGE AND REMOVAL ABILITIES IN SICKLE-CELL TRAIT CARRIERS DURING AND AFTER INCREMENTAL EXERCISE

Arterial blood lactate concentrations and pH were measured on seven bl ack male sickle cell trait (SCT) carriers before, during and after inc remental exhaustive bicycle exercise (25 W increments per minute) and compared with those of six control individuals of the same ethnic orig in having a similar physical fitness level. The object of the experime nt was to determine if SCT has an effect on lactate kinetics. At volit ional exhaustion which was reached at a comparable overall mean absolu te work rate for both groups, oxygen consumption expressed per kilogra m body mass was significantly lower for the SCT carriers than for the control volunteers. Lactate concentrations were higher for the SCT car riers after the 150 W exercise step but differences reached statistica l significance on ly at exhaustion. Concentrations were distinctly hig her for the SCT group during the following 40 minutes of recovery. Whi le there were no observable differences in blood pH between the SCT an d control subjects during the exercise, this variable became significa ntly lower for the SCT than for the control group 8 minutes after the end of exercise. Lactate recovery curves were fitted by a biexponentia l time function where the two velocity constants inform on the body's overall ability to exchange and remove lactate. The ability to remove lactate was comparable for the two groups. The present results do not warrant drawing a definite conclusion on impairment of the ability to exchange lactate in the presence of SCT. However, SCT carriers are lik ely to produce more lactate than control subjects reaching exhaustion at similar mean absolute work rate during exhaustive incremental bicyc le exercise.