Blood lactate concentrations during incremental exercise in subjects with sickle cell trait

Abstract

The aim of the present study was to assess blood lactate concentrations ([LA], mmol x L(-1)) and oxygen uptake (VO2, L x min(-1), mL x kg(-1) x min(-1)) during incremental exercise in subjects with sickle cell trait (SCT) only, i.e., sedentary subjects with SCT without anemia and/or associated alpha thalassemia. Anemia was ruled out using hemoglobin (Hb) level, and alphathalassemia was ruled out using hemoglobin S (HbS) percentage and concomitant Hb level and mean corpuscular volume (MCV). Comparison was made with control subjects with normal Hb, matched for physical fitness, anthropometric data, and hematological parameters. All subjects underwent an incremental exercise test (IET) using an electromagnetic cycle ergometer. Ventilatory data, i.e., minute ventilation (VE, L x min(-1)), oxygen uptake (VO2, mL x min(-1), mL x Kg(-1) x min(-1)) carbon dioxide production (VO2, mL x min(-1)), ventilatory equivalent for O2(VE x VO2(-1))and for CO2 (VE x VO2(-1)), and respiratory exchange ratio (RER, VO2 x VO2(-1)), were collected every minute during IET and the recovery period using a breath-by-breath automated system. Heart rate (HR, beats x 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 period, and then every 5 min until the 20th minute of recovery. [LA] were determined by an enzymatic method with a spectrophotometer. Comparisons of all mean cardioventilatory variables showed no significant differences in subjects with SCT versus controls during IET and recovery. In contrast, analysis of variance revealed significantly lower time courses 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 [LA] exhibited by subjects with SCT during incremental exercise and the subsequent recovery was not associated with concomitant oxygen uptake impairment.

Physical fitness indices and anthropometrics profiles in schoolchildren with sickle cell trait/disease

“…In the Gulf region, including Oman, the SCD is the most prevalent genetic blood disorder and it has been reported that 6% of the population are sickle cell gene carriers (traits) [10]. Although previous studies showed a normal exercise tolerance in adult and adolescent HbS carriers [11][12][13], meager data are available on children. Furthermore, although children with sickle cell disease (SCD) or sickle cell trait (SCT) are usually encouraged to be physically active and participate in sport and exercise on a regular basis, no information exists on the anthropometrical characteristics and exercise performance in these children in Sultanate of Oman.…”

Faster lactate transport across red blood cell membrane in sickle cell trait carriers

“…Other investigations have reported higher [La] during the last two increments of a graded test (12), but this contrasting result may be explained by a heterogeneous training status and differences in physical fitness between the tested subjects (12). Bile et al (1) and Sara et al (24) noted a significantly lower blood [La] during a ramp exercise test in sedentary and trained AS, respectively. In these studies, AS were carefully matched with a control group for physical activity and physiological performance (1,24).…”

“…Bile et al (1) and Sara et al (24) noted a significantly lower blood [La] during a ramp exercise test in sedentary and trained AS, respectively. In these studies, AS were carefully matched with a control group for physical activity and physiological performance (1,24). Based on the "lactate shuttle" mechanism (4, 5), the pathophysiological process involved in the lowered lactate in AS subjects during incremental exercise could be due to both greater uptake by RBCs and greater utilization by muscles.…”

“…The physical and physiological behavior of exercising SCT carriers (AS) remains equivocal, and controversial data have been documented. Although the presence of Hb S should result in lower aerobic capacity, most studies have reported similar aerobic performances in AS and controls (1,13,20,24). Impaired O 2 delivery to muscles from AS RBCs during exercise could result in a greater participation of anaerobic metabolism in exercising muscles.…”

“…This should lead to an earlier rise in blood lactate concentration ([La]) as noted in subjects with abnormal O 2 transport (34). However, most studies matching AS and normal Hb (AA) subjects in terms of both physical performance and physical activity demonstrate lower blood [La] in AS during incremental exercise (1,13,24).…”