The relation of oxygen intake and speed in competition cycling and comparative observations on the bicycle ergometer.

1. The relation of V(O2) and speed was determined on six competition cyclists riding at speeds ranging from 12 km/hr to 41 km/hr on the runway of an airfield. Comparative measurements were made on the bicycle ergometer to determine the corresponding work rates, and from this information rolling resistance and air resistance were derived.2. V(O2) was a curvilinear function of cycling speed, and increased from 0.88 l./min at 12.5 km/hr to 5.12 l./min at 41 km/hr, mean body weight being 72.9 kg.3. On the ergometer, V(O2) was a linear function of work rate; maximum values up to 5.1 l./min (74.4 ml./kg min) and work rates up to 425 W (2600 kg m/min) were observed.4. Data are presented on the relation of pedal frequency and speed in cycling, and on the relation of mechanical efficiency and pedal frequency, as determined on the ergometer.5. The estimated rolling resistance for four subjects was 0.71 kg f. The drag coefficient was 0.79 and the drag area 0.33 m(2). The values agreed well with results obtained by other methods.6. The energy expenditure (power developed) in cycling increased approximately as the square of the speed, and not as the cube of the speed as expected. This was explained by the varying contribution of rolling resistance and air resistance to over-all resistance to motion at different speeds.