Lactate Removal Ability and VO2 Recovery Kinetics in Sickle Cell Trait Carriers Compared with Normal Haemoglobin Subjects: Preliminary Data

ABSTRACT

Because of the reduced affinity of haemoglobin S to oxygen and the altered blood rheological profile of sickle cell trait carriers (AS), it is often thought that exercise physiological responses should differ between AS and subjects with normal haemoglobin (AA). The present study aimed to compare the ability to remove blood lactate and the characteristics of oxygen uptake (VO2) recovery kinetics after supramaximal exercise in eight AS and eight matched AA. All subjects performed a supramaximal exercise test consisting of pedalling for 1 min at 110% maximal VO2 Following exercise, venous blood samples were obtained from AS and AA at different times to assess blood lactate concentrations. Mathematical modelling was applied during recovery to assess the blood lactate removal ability (time constant τ2) and the kinetics for VO2 . recovery (amplitude A2 and time constant γ2). Lactate removal ability and the VO2 . recovery kinetics were not significantly different between the two groups (P > 0.05). No significant relationship was observed between γ2 and VO2 (r = 0.04; P > 0.05) or between γ2 and τ2 (r = -0.44; P > 0.05) in all groups. It seems that the ability to recover or to remove lactate after a short supramaximal exercise does appear unaltered by sickle cell trait. It is possible that the elevated blood viscosity reported several times in AS could have promoted greater vasodilatation which in turn may favour exercise recovery to a similar level observed in subjects with normal haemoglobin. Our findings may suggest that AS and AA subjects need similar recovery after exhausting exercise. However, it is also known that AS may be prone to medical complications in response to exercise. So, the presence of clinical sign should justify to prolong recovery or to stop exercise in AS.