MAXIMAL OXYGEN DEFICIT OF SPRINT AND MIDDLE-DISTANCE RUNNERS

Anaerobic energy capacity was evaluated by maximal oxygen deficit (MOD ) as well as by blood gas and muscle biopsy variables during short exh austing running in six recreational (RR) and eight competitive sprint and middle distance runners (SMDR). On 3 days runs to exhaustion were executed. Two runs were performed at a treadmill gradient of 15% at sp eeds which resulted in exhaustion after approximately 1 (R(15%,1min)) and 2-3 min (R(15%,2-3min)), respectively. On the 3rd day, the subject s ran with the treadmill at a gradient of 1% at a speed which caused e xhaustion after 2-3 min (R(1%,2-3min)). The runner performance was ass essed from 400 m [RR, median 64.8 (range 62.2-69.6) s; SMDR, median 49 .4 (range 48.5-52.0) s] and 800 m [RR, median 158.8 (range 153.3-170.2 ) s; SMDR, median 115.2 (range 113.3-123.3) s] track times. Muscle bio psies from gastrocnemius muscle were obtained before and immediately a fter R(15%,2-3min,) from which muscle lactate and creatine phosphate ( CP) concentrations fibre type distribution, capillaries per fibre, tot al lactate dehydrogenase (LDH) activity and the LDH isoenzyme pattern were determined. The MOD increased with the treadmill gradient and dur ation. During both treadmill and track runs, SMDR performance was supe rior to that of RR, but no significant differences were observed with respect to MOD, muscle fibre type distribution, total LDH activity, it s iso-enzyme pattern, changes in muscle lactate or CP concentrations. However, after treadmill runs, peak venous lactate concentration and p artial pressures of carbon dioxide were higher, and pH lower in SMDR. Also the number of capillaries per muscle fibre and the maximal oxygen uptake were larger in SMDR. These findings would suggest that the sup erior performance of SMDR depended more on their aerobic than on their anaerobic capacity.