BLOOD LACTATE CONCENTRATIONS DURING INCREMENTAL EXERCISE IN SUBJECTS WITH SICKLE-CELL TRAIT

The aim of the present study was to assess blood lactate concentration s ([LA], mmol.L-1) and oxygen uptake (VO2, L.min(-1), mL.kg(-1).min(-1 )) during incremental exercise in subjects with sickle cell trait (SCT ) only, i.e., sedentary subjects with SCT without anemia and/or associ ated alphathalassemia. Anemia was ruled out using hemoglobin (Hb) leve l, and alphathalassemia was ruled out using hemoglobin S (HbS) percent age and concomitant Hb level and mean corpuscular volume (MCV). Compar ison was made with control subjects with normal Hb: matched for physic al fitness, anthropometric data, and hematological parameters. All sub jects underwent an incremental exercise test (IET) using an electromag netic cycle ergometer. Ventilatory data, i.e., minute ventilation (VE, L.min(-1)), oxygen uptake (VO2, mL.min(-1), mL.Kg(-1).min(-1)) carbon dioxide production (VO2, mL.min(-1)), ventilatory equivalent for O-2 (VE.VO2-1) and for CO2 (VE.VO2-1), and respiratory exchange ratio (RER , VO2.VO2-1), were collected every minute during IET and the recovery period using a breath-by-breath automated system. Heart rate (HR, beat s min(-1)) was measured every minute using an EKG. Blood sampling was done every minute during IET and the first 5 min of the recovery perio d, and then every 5 min until the 20th minute of recovery. [LA] were d etermined by an enzymatic method with a spectrophotometer. Comparisons of all mean cardioventilatory variables showed no significant differe nces in subjects with SCT versus controls during IET and recovery. In contrast, analysis of variance revealed significantly lower time cours es of [LA] during IET (P < 0.05) and recovery (P < 0.05), whereas time courses of VO2 were similar (P < 0.05). We conclude that the lower [L A] exhibited by subjects with SCT during incremental exercise and the subsequent recovery was not associated with concomitant oxygen uptake impairment.