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POINT-COUNTERPOINT

Rebuttal from Dr. Connes

The authors tried to convince us that SCT is not a limiting factor to practice sports activities at high level. However, as already demonstrated by the same authors more than one decade ago (6, 7), it is not right for endurance performance. These authors demonstrated that although the percentage of participation of SCT carriers in the first Abidjan semi-marathon was similar to the percentage of SCT in the general Ivory Coast population, no SCT carrier (without alpha-thalassemia) was internationally ranked (7). Moreover, when arguing that SCT carriers are not prone to exercise tolerance, Le Gallais et al. (8) do not refer to recent data showing lower aerobic capacity in that population (2).

Le Gallais et al. (8) also based their argument on experimental data collected on lactate metabolism during exercise showing normal lactic response in SCT carriers. Red blood cells (RBCs) from SCT carriers are able to uptake lactate more rapidly than RBCs from noncarriers (9). Although this adaptation could constitute an advantage during exercise, higher RBC lactate transport activity could be responsible for lower RBC deformability and therefore increased risk for blood microcirculation impairment (1).

At least, using the data published by Scoville et al. (10), Le Gallais et al. (8) tried to demonstrate that SCT carriers are not prone to substantially higher risk of exercise-related sudden death. However, Scoville et al. (10) found 35% of idiopathic sudden death (ISD) associated with SCT: it is not negligible. Eckart et al. (3) reinforced the analysis conducted by Scoville et al. (10) and reported 26 deaths in US Army recruits with SCT between 1977 and 2001 for a total of 126 nontraumatic sudden deaths related to exercise (3). Of 126 deaths, 44 were classified as ISD and 27% (i.e., 12 subjects) of ISD was associated with SCT. However, of 44 ISD, 24 occurred in African American recruits. Therefore, 50% of the ISD related to exercise that occurred in black recruits was associated with SCT. That supports previous studies showing high prevalence of SCT in black military basic trainees with exertional sudden death (4, 5).

In conclusion, it is clear that SCT should not be considered asymptomatic and as a benign condition during physical activity.

REFERENCES

1. Connes P, Sara F, Hardy-Dessources MD, Etienne-Julan M, Hue O. Does higher red blood cell (RBC) lactate transporter activity explain impaired RBC deformability in sickle cell trait? Jpn J Physiol 55: 385–387, 2005.[CrossRef][Web of Science][Medline]
2. Connes P, Monchanin G, Perrey S, Wouassi D, Atchou G, Forsuh A, Debaud J, Djoda B, Owona FX, Francina A, Banga PE, Massarelli R, Thiriet P, Martin C. Oxygen uptake kinetics during heavy submaximal exercise: effect of sickle cell trait with or without alpha-thalassemia. Int J Sports Med 27: 517–525, 2006.[CrossRef][Web of Science][Medline]
3. Eckart RE, Scoville SL, Campbell CL, Shry EA, Stajduhar KC, Potter RN, Pearse LA, Virmani R. Sudden death in young adults: a 25-year review of autopsies in military recruits. Ann Intern Med 141: 829–834, 2004.[Abstract/Free Full Text]
4. Kark JA, Posey DM, Schumacher HR, Ruehle CJ. Sickle-cell trait as a risk factor for sudden death in physical training. N Engl J Med 317: 781–787, 1987.[Abstract]
5. Kark JA, Ward FT. Exercise and hemoglobin S. Semin Hematol 31: 181–225, 1994.[Web of Science][Medline]
6. Le Gallais D, Prefaut C, Dulat C, Macabies J, Lonsdorfer J. Sickle cell trait in Ivory Coast athletic champions, 1956–1989. Int J Sports Med 12: 509–510, 1991.[Web of Science][Medline]
7. Le Gallais D, Prefaut C, Mercier J, Bile A, Bogui P, Lonsdorfer J. Sickle cell trait as a limiting factor for high-level performance in a semi-marathon. Int J Sports Med 15: 399–402, 1994.[Web of Science][Medline]
8. Le Gallais D, Lonsdorfer J, Bogui P, Fattoum S. Point: Sickle cell trait should be considered asymptomatic and as a benign condition during physical activity. J Appl Physiol; doi:10.1152/japplphysiol.00338–2007.
9. Sara F, Connes P, Hue O, Montout-Hedreville M, Etienne-Julan M, Hardy-Dessources MD. Faster lactate transport across red blood cell membrane in sickle cell trait carriers. J Appl Physiol 100: 437–442, 2006.
10. Scoville SL, Gardner JW, Magill AJ, Potter RN, Kark JA. Nontraumatic deaths during U.S. armed forces basic training, 1977–2001. Am J Prev Med 26: 205–212, 2004.[CrossRef][Web of Science][Medline]

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