RESUMEN
Today the Kenyan dominance in middle- and long-distance running is so profound that it has no equivalence to any other sport in the world. Critical physiological factors for performance in running include maximal oxygen consumption (VO2max), fractional VO2max utilization and running economy (energetic cost of running). Kenyan and non-Kenyan elite runners seem to be able to reach very high, but similar maximal oxygen uptake levels just as there is some indication that untrained Kenyans and non-Kenyans have a similar VO2max. In addition, the fractional utilization of VO2max seems to be very high but similar in Kenyan and European runners. Similarly, no differences in the proportion of slow muscle fibers have been observed when comparing Kenyan elite runners with their Caucasian counterparts. In contrast, the oxygen cost of running at a given running velocity has been found to be lower in Kenyan elite runners relative to other elite runners and there is some indication that this is due to differences in body dimensions. Pulmonary system limitations have been observed in Kenyan runners in the form of exercise-induced arterial hypoxemia, expiratory flow limitation, and high levels of respiratory muscle work. It appears that Kenyan runners do not possess a pulmonary system that confers a physiological advantage. Additional studies on truly elite Kenyan runners are necessary to understand the underlying physiology which permits extraordinary running performances.
Asunto(s)
Rendimiento Atlético/fisiología , Músculo Esquelético/metabolismo , Consumo de Oxígeno , Resistencia Física/fisiología , Carrera/fisiología , Amoníaco/sangre , Arterias , Humanos , Hipoxia/etiología , Kenia , Ácido Láctico/sangre , Pulmón/fisiología , Músculo Esquelético/irrigación sanguínea , Músculo Esquelético/citología , Oxígeno/metabolismo , Músculos Respiratorios/fisiologíaRESUMEN
BACKGROUND: The clinical significance of an incidental finding of bone marrow edema (BME) on MRI in professional runners is poorly understood. PURPOSE: To investigate the prevalence and clinical and radiological progression of BME lesions in professional runners who consider themselves to be asymptomatic. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Sixteen athletes (13 men and 3 women; mean age, 22.9 ± 2.7 years) were recruited from the Dutch National Committee middle-distance and long-distance running selection. All athletes had been injury free for the year before the study. Magnetic resonance imaging scans were obtained before the start of the season and at the end of the season. Both pubic bones, hips, knees, and ankles were scanned in a single session. Preseason and postseason Lysholm scores were obtained. RESULTS: Fourteen of the 16 athletes had BME lesions before the start of the season (45 BME lesions in total). Most BME lesions (69%; 31/45) were located in the ankle joint and foot. More than half of the lesions (58%; 26/45) fluctuated during the season, with new lesions occurring (20%; 9/45) and old lesions disappearing (22%; 10/45). The few clinical complaints that occurred throughout the season were not related to the presence of BME lesions. CONCLUSION: Almost all asymptomatic athletes showed BME lesions, with more than half of the lesions fluctuating during the season. These data suggest that the incidental finding of a BME lesion on MRI of professional runners should not immediately be related to clinical complaints or lead to an altered training program.