MAXIMAL OXYGEN-UPTAKE AND AEROBIC-ANAEROBIC TRANSITION ON TREADMILL AND BICYCLE IN TRIATHLETES

The maximal aerobic capacity and the aerobic-anaerobic transition were analyzed on 14 triathletes performing an incremental work load on a b icycle ergometer and on horizontal or inclined treadmills. To compare the cardiorespiratory responses between cycling and running, the subje cts were divided into 2 groups of 7 with similar aerobic capacity dete rmined from cycle runs. The first group ran on horizontal treadmill wh ile the second group performed similar exercise on inclined treadmill at constant grade (1.5%). Heart rate was recorded by electrocardiogram . Oxygen uptake (V(O2)), CO2 production (V(O2)), respiratory frequency , and pulmonary ventilation were monitored at 30 s intervals through a Rudolph valve connected to a calibrated Oxycon V. Tidal volume, respi ratory exchange ratio, equivalent O2 and CO2 were calculated from on-l ine computer. Aerobic and anaerobic thresholds were determined by a no n-invasive method from pulmonary ventilation curves. The results showe d that maximum oxygen uptake (V(O2max)) did not differ between the 2 t ypes of ergometers. Pulmonary ventilation, heart rate and V(O2) record ed at aerobic and anaerobic thresholds depended on the mode of exercis e and reached the highest values on inclined treadmill. The amount of muscle mass, the type and the distribution of active motor units invol ved in each exercise test might be at the origin of these differences. This indicates that, when assessing a training program from anaerobic threshold values, it is necessary to take into consideration the type of ergometer used and the protocol performed.