Effects of wind assistance and resistance on the forward motion of a runner.

The aerobic energy cost (delta VO2) of running at different speeds (V) with and against a range of wind velocities (WV) has been studied in a wind tunnel on three healthy male subjects and the results compared with downhill and uphill gradient running on a motor-driven treadmill. In terms of equivalent horizontal and vertical forces, comparison showed that the two forms of exercise were physiologically identical for gradients and WV ranging from -10 to +5% and 1.5 to 15 m . s-1, respectively. The apparent mechanical efficiencies of the work performed with a head and following wind were approximately +0.35 and -1.2. At WV greater than 15 m . s-1 it was more efficient to run against the wind and the corresponding gradient on the treadmill. At high WV the subjects altered their posture and "leaned" into the wind, thus possibly converting potential drag into body lift. The energy cost of overcoming air resistance on a calm day outdoor was calculated to be 7.8% for sprinting (10 m . s-1), 4% middle-distance (6 m . s-1), and 2% marathon (5 m . s-1) running.