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1. The relation of 
O2 and speed was measured on seven athletes running on a cinder track and an all-weather track. The results were compared with similar observations on four athletes running on a treadmill.
O2 and speed was measured on seven athletes running on a cinder track and an all-weather track. The results were compared with similar observations on four athletes running on a treadmill.2. In treadmill running the relation was linear and the zero intercept coincided with resting O2.
O2.3. In track running the relation was curvilinear, but was adequately represented by a linear regression over a range of speeds extending from 8·0 km/hr (2·2 m/sec) to 21·5 km/hr (6·0 m/sec). The slope of this line was substantially steeper than the regression line slope for treadmill running.
4. The influence of air resistance in running was estimated from measurements of O2 on a subject running on a treadmill at constant speed against wind of varying velocity.
O2 on a subject running on a treadmill at constant speed against wind of varying velocity.5. The extra O2 intake (ΔO2) associated with wind increased as the square of wind velocity. If wind velocity and running velocity are equal, as in running on a track in calm air, ΔO2 will increase as the cube of velocity.
O2) associated with wind increased as the square of wind velocity. If wind velocity and running velocity are equal, as in running on a track in calm air, ΔO2 will increase as the cube of velocity.6. It was estimated that the energy cost of overcoming air resistance in track running is about 8% of total energy cost at 21·5 km/hr (5000 m races) and 16% for sprinting 100 m in 10·0 sec.
