Impaired oxygen uptake kinetics in the first high-level athlete with Hb Hope: a case study.

Abstract

Hemoglobin (Hb) Hope is a beta-globin chain variant with reduced oxygen (O₂) affinity, known to induce anemia. This usually leads to limitations in O₂uptake (VO₂) and exercise tolerance. We studied the case of a high-level female athlete with Hb Hope. She had been selected for cross-country races from 13 yrs onward, then was a national junior champion in 400-m race, and finally failed to win any cross-country races as an adult. Hematological analysis revealed normal red blood cell indices and Hb level (12.3 g.dL⁻¹). Incremental exercise showed peak work rate (WR), VO(2max) and gas exchange threshold (GET) within normal ranges for healthy females. Constant WR testing at 90% of GET showed that kinetics of pulmonary VO₂included the presence of a slow component. This was in disagreement with the data on VO₂kinetics response to exercise intensities below GET. Phase 2 parameters, time constant (τ2, 31 s), time delay (TD2, 39 s), amplitude (A2, 780 ml.min⁻¹), and gain in VO₂(ΔVO₂ .ΔWR-1, 9.2 ml.min-1.W⁻¹) were within normal ranges. Phase 3 showed a slow component similar to that reported in severe exercise. The absence of anemia and the normality of phase 2 suggested normal O₂delivery and oxidative metabolism in exercising muscles. In contrast, phase 3 suggested poor aerobic capacity and limited exercise tolerance. However, the lack of symptoms during testing also suggested that the slow component was due to the specific recruitment of fast-twitch fibers in this former champion athlete with Hb Hope in races requiring mainly anaerobic metabolism.

• Authors: I Touhami, D Le Gallais, S Perrey, A Bibi, D Koubaa, R Mankai, Z Bartagi, T Messaoud, S Fattoum
• Journal: The Journal of sports medicine and physical fitness (J Sports Med Phys Fitness) Vol. 55 Issue 5 Pg. 544-8 (May 2015) ISSN: 0022-4707 [Print] Italy
• PMID: 24947919 (Publication Type: Case Reports, Journal Article)

Chemical References

• Hemoglobins, Abnormal
• hemoglobin Hope
• Oxygen

Topics

• Adult
• Athletes
• Electromyography
• Exercise Test
• Female
• Hemoglobinopathies (blood, physiopathology)
• Hemoglobins, Abnormal (metabolism)
• Humans
• Muscle, Skeletal (physiology)
• Oxygen (metabolism)
• Oxygen Consumption (physiology)
• Physical Exertion (physiology)
• Pulmonary Gas Exchange (physiology)