Sickle cell trait in Ivory Coast athletic champions, 1956-1989

In vivo muscle function and energetics in women with sickle cell anemia or trait: a 31P-magnetic resonance spectroscopy study

Sickle cell anemia (SCA) is a genetic hemoglobinopathy associated with an impaired oxygen delivery to skeletal muscle that could alter ATP production processes and increase intramuscular acidosis. These alterations have been already reported in the Townes mouse model of SCA but the corresponding changes in humans have not been documented. In the present study, we used 31-phosphorus magnetic resonance spectroscopy to investigate in vivo the metabolic changes induced by a moderate-intensity exercise in twelve SCA patients, eight sickle cell trait (SCT) carriers, and twelve controls women. The rest-exercise-recovery protocol disclosed slight differences regarding phosphocreatine (PCr) consumption and lactate accumulation between SCA patients and controls but these differences did not reach a statistical significance. On that basis, the in vivo metabolic changes associated with a moderate-intensity muscle exercise were slightly altered in SCA patients and SCT carriers but within a normal range. The present results strongly support the fact that a moderate-intensity exercise is safe and could be recommended in stable SCA patients and SCT subjects.NEW & NOTEWORTHY The main finding of the present study was that the metabolic changes associated with a moderate-intensity muscle exercise were slightly modified in stable sickle cell anemia patients and sickle cell trait carriers as compared to controls but still in the normal range. The present results strongly support the safety of a moderate-intensity exercise for stable sickle cell anemia patients and sickle cell trait carriers.

Moderate and intense muscular exercises induce marked intramyocellular metabolic acidosis in sickle cell disease mice

Sickle cell disease (SCD) is associated with an impaired oxygen delivery to skeletal muscle that could alter ATP production processes. The present study aimed to determine the effects of sickle hemoglobin (HbS) on muscle pH homeostasis in response to exercise in homozygous (HbSS, n = 9) and heterozygous (HbAS, n = 10) SCD (Townes) mice in comparison to control (HbAA, n = 10) littermates. Magnetic resonance spectroscopy of phosphorus 31 enabled to measure intramuscular pH and phosphocreatine (PCr) concentration during rest-stimulation-recovery protocols at two different intensities. Maximal activity of some enzymes involved in muscle energetics and content of proteins involved in pH regulation were also investigated. HbSS mice presented a more pronounced exercise-induced intramuscular acidosis, whatever the intensity of exercise. Moreover, the depletion of PCr was also exacerbated in HbSS mice in response to intense exercise as compared with both HbAA and HbAS mice ( P < 0.01). While no difference was observed concerning proteins involved in muscle pH regulation, the activity of enolase (a glycolytic enzyme) was higher in both HbSS and HbAS mice as compared with controls ( P < 0.05). Interestingly, HbAS mice presented also metabolic impairments as compared with their control counterparts. This study has identified for the first time an exacerbated exercise-induced intramuscular acidosis in SCD mice.

NEW & NOTEWORTHY The main finding of the present study was that the exercise-induced intramuscular acidosis was systematically more pronounced in sickle cell disease (SCD) mice as compared with their control counterparts. This result is important since it has been demonstrated in vitro that acidosis can trigger hemoglobin polymerization. From that point of view, our results tend to support the idea that high-intensity exercise may increase the risk of hemoglobin polymerization in SCD.

ACSM and CHAMP summit on sickle cell trait: mitigating risks for warfighters and athletes

INTRODUCTION

An estimated 300 million people worldwide have sickle cell trait (SCT). Although largely benign, SCT has been associated with exertional rhabdomyolysis and exercise-related sudden death in warfighters/athletes (WA). The National Collegiate Athletic Association's policy to confirm a student athlete's SCT status during their preparticipation medical examination prompted reaction from some organizations regarding the rationale and ethical justification of the policy.

METHODS

On September 26 and 27, 2011, a summit, composed of military and civilian experts in sports medicine and SCT, was convened at the Uniformed Services University in Bethesda, MD. The expert panel was charged with two objectives: 1) to provide specific recommendations to further mitigate the apparent risk with strenuous exercise in WA with SCT and 2) to develop clinical guidelines to identify, treat, and return to duty/play WA suspected to have incurred nonfatal sickle cell collapse.

RESULTS

New terminology is introduced, areas of current controversy are explored, consensus recommendations for mitigating risk and managing the WA with SCT are reviewed, and important areas for future research are identified.

CONCLUSION

Further research is needed before conclusions can be drawn regarding the etiology of the increased death rate observed in WA with SCT, and the possibility exists that SCT is a surrogate for as yet another contributing factor for the unexplained deaths.

Skeletal muscle structural and energetic characteristics in subjects with sickle cell trait, α-thalassemia, or dual hemoglobinopathy

Previous studies have shown that subjects with sickle cell trait (SCT), α-thalassemia (α-t), and the dual hemoglobinopathy (SCT/α-t) manifest subtle, albeit significant, differences during exercise. To better understand such differences, we assessed skeletal muscle histomorphological and energetic characteristics in 10 control HbAA subjects (C), 5 subjects with α-t (α-t), 6 SCT carriers (SCT) and 9 SCT carriers with α-t (SCT/α-t). Subjects underwent a muscle biopsy and also performed an incremental maximal exercise and a time to exhaustion test. There were no observable differences in daily energy expenditure, maximal power output (Pmax), or time to exhaustion at 110% Pmax ( Tex) among the groups. Blood lactate concentrations measured at the end of the Tex, muscle fiber type distribution, and mean phosphofructokinase (PFK), lactate dehydrogenase (LDH), β-hydroxyacyl-CoA-dehydrogenase (HAD), and citrate synthase (CS) activities were all similar among the four groups. However, SCT was associated with a lower cytochrome- c oxidase (COx) activity in type IIa fibers ( P < 0.05), and similar trends were observed in fiber types I and IIx. Trends toward lower creatine kinase (CK) activity ( P = 0.0702) and higher surface area of type IIx fibers were observed in SCT ( P = 0.0925). In summary, these findings support most of the previous observations in SCT, such as 1) similar maximal power output and associated maximal oxygen consumption (V̇o2max) values and 2) lower exercise performances during prolonged submaximal exercise. Furthermore, performances during short supramaximal exercise were not different in SCT. Finally, the dual hemoglobinopathy condition does not seem to affect muscle characteristics.

The epidemiology of abnormal hemoglobins in Mediterranean high-level athletes

The aim of this study was to determine the prevalence and nature of hemoglobin (Hb) defects in a Mediterranean high-level (HL) athlete population. Five hundred and ninety-four HL male and female athletes were recruited during the annual follow-up of the members of Tunisian national teams. Hematological data, Hb electrophoresis, and DNA analysis were assessed using conventional techniques. Sporting discipline, type of sport, and performance levels were assessed using a questionnaire. The results showed that 32 HL athletes had abnormal Hb (5.4%): beta-thalassemia (2.2%), alpha-thalassemia (0.5%), HbAS (1.5%), HbAC (0.5%), and rare Hb variants (0.7%). Of the 32 defect carriers, all but one (a alpha-thalassemia) were heterozygous. All the detected hemoglobinopathies but one (an Hb Hope) had already been reported in the country. The prevalence of Hb defect in the HL athletes was similar to that described in the general Tunisian population (P > 0.05). The percentage of Hb defect in the athletes was not dependent on gender, or performance level (P > 0.05). Within each type of sport the percentages of athletes with normal and abnormal Hb were similar (P > 0.05). The hematological data revealed the diversity of anemia, microcytosis, and hypochromia in thalassemic HL athletes. We concluded that HL athletes in Tunisia were a representative sample of the general Tunisian population regarding the prevalence and nature of benign abnormal Hb. The hematological data of the thalassemia carriers exhibited high variability and raised the question of genetic and sporting counseling, as well as biological follow-up for these carriers.

Sports haematology

While the crucial role of haemoglobin in aerobic exercise has been well accepted, there is still a great deal of controversy about the optimal haematological parameters in the athletic population. The initial part of this review will examine the question of anaemia in athletes. The most common finding in athletes is a dilutional pseudoanaemia that is caused by a plasma volume expansion, rather than an actual blood loss. It is not a pathological state and normalises with training cessation in 3 to 5 days. This entity should be distinguished from conditions associated with lowered blood counts, such as intravascular haemolysis or iron deficiency anaemia. The evaluation of true anaemia states in the athlete must take into account not only blood losses secondary to exercise, such as foot strike haemolysis or iron losses through sweat, but non-athletic causes as well. Depending on the age and sex of the athlete, consideration must be given to evaluation of the gastrointestinal or genitourinary systems for blood loss. Finally, a comprehensive nutritional history must be taken, as athletes, especially women, are frequently not consuming adequate dietary iron. The second section of the paper will deal with the very contentious issue of sickle cell trait. While there have been studies demonstrating an increased risk of sudden death in people with sickle cell trait, it is still quite rare and should not be used as a restriction to activity. Further, studies have demonstrated that patients with sickle cell trait have an exercise capacity that is probably normal or near normal. However, in the cases of sudden death, it has been secondary to rhabdomyolysis occurring among sickle cell trait athletes performing at intense exertion under hot conditions, soon after arriving at altitude. The recommendations are that athletes with sickle cell trait adhere to compliance with the general guidelines for fluid replacement and acclimatisation to hot conditions and altitude. The final section of the paper examines the issue of haematological manipulation for the purposes of ergogenic improvement. Although experiments with blood doping revealed improvements in running time to exhaustion and maximal oxygen uptake, the introduction of recombinant erythropoietin has rendered blood doping little more than a historical footnote. However, the improvements in performance are not without risk, and the use of exogenous erythropoietin has the potential for increased viscosity of the blood and thrombosis with potentially fatal results. Until a definitive test is developed for detection of exogenous erythropoietin, it will continue to be a part of elite athletics.

Exercise-induced death in sickle cell trait: role of aging, training, and deconditioning

The pathophysiological process of exercise-induced death in subjects with sickle cell trait (SCT) remains unclear. Concerning the cause of death, authors have suggested stressful environmental conditions such as altitude, heat and humidity, or abnormal patient conditions such as deconditioning, fatigue, and disease. These conditions are thought to lead to hypoxemia, hyperlactatemia, acidosis, dehydration, hyperthermia, or exercise-induced rhabdomyolysis, all of which may initiate sickle cell crisis, disseminated intravascular coagulation, myoglobinuria, and renal failure. We report the case of a 41-yr-old, healthy, and apparently well-conditioned subject with SCT who died during a cross-country race under normal environmental conditions in good weather (in terms of temperature and humidity). The medical and athletic history of the subject were unremarkable. We refer to an epidemiological study that reported a relation between age and exercise-induced sudden death in subjects with SCT. We then review the pathophysiological effects of aging in association with deconditioning and high-level training reported in the literature, particularly the decrease in aerobic metabolism in deconditioned subjects, and the exercise-induced hypoxemia in highly trained subjects. We discuss the consequences of deconditioning and high-level training in subjects with SCT during exercise, and conclude that these factors may be involved in the age-dependent risk of exercise-related sudden death in subjects with SCT.

Hyperoxia during recovery from consecutive anaerobic exercises in the sickle cell trait

The sickle cell trait (HbAS) does not affect anaerobic exercise performance. However, lower blood lactate concentrations ([La-]) are consistently found during repeated anaerobic exercise in HbAS, and could be related to type of recovery. To study this, on three different occasions 17 HbAS and 17 matched control athletes (HbAA) underwent a series of three maximal cycle exercise tests of approximately 2-min duration, separated by 10-min recovery periods of rest, breathing either room air (P) or 100% oxygen (H), or of light pedaling (A). In all tests, work performed, heart rate, blood hematocrit, and [La-] were measured. Despite similar evolution of performance in each series of three anaerobic exercises, significantly lower [La-] were consistently found in HbAS in P and A, compared to HbAA (P < 0.0001). However, in H, similar [La-] was found in HbAS and HbAA. Higher mean heart rates were consistently measured in HbAS at exhaustion, and during the first 4 min of recovery, these differences being unrelated to type of recovery. We conclude that type of recovery does not influence subsequent performance in HbAS or HbAA. We speculate that improved regional oxygen availability in exercising muscle is associated with marked modification of lactate kinetics in highly trained HbAS, but not in similarly fit HbAA athletes.

Sickle Cell Trait, Heroic Exercise, and Fatal Collapse

In brief Although sickle cell trait is generally benign and consistent with peak athleticism, it poses a small risk of gross hematuria and splenic infarction at altitude. More alarming is the growing evidence that, in some people with sickle cell trait, maximal exercise-especially in hot weather or when new at altitude-can evoke a life-threatening syndrome of sickling, fulminant rhabdomyolysis, lactic acidosis, collapse, acute renal failure, and hyperkalemia. More than 30 such cases are described, along with practical tips for recognition and prevention.