ENERGY-EXPENDITURE DURING BICYCLING

This study was designed to measure the O2 uptake (V̇O2) of cyclists while they rode outdoors at speeds from 32 to 40 km/h. Regression analyses of data from 92 trials using the same wheels, tires, and tire pressure with the cyclists riding in their preferred gear and in an aerodynamic position indicated the best equation (r = 0.84) to estimate V̇O2 in liters per minute where rider and wind speed are expressed in kilometers per hour and rider weight in kilograms. Following another rider closely, i.e., drafting, at 32 km/h reduced V̇O2 by 18 ± 11%; the benefit of drafting a single rider at 37 and 40 km/h was greater (27 ± 8%) than that at 32 km/h. Drafting one, two, or four riders in a line at 40 km/h resulted in the same reduction in V̇O2 (27 ± 7%). Riding at 40 km/h at the back of a group of eight riders reduced V̇O2 by significantly more (39 ± 6%) than drafting one, two, or four riders in a line; drafting a vehicle at 40 km/h resulted in the greatest decrease in V̇O2 (62 ± 6%). V̇O2 was also 7 ± 4% lower when the cyclists were riding an aerodynamic bicycle. An aerodynamic set of wheels with a reduced number of spokes and one set of disk wheels were the only wheels to reduce V̇O2 significantly while the cyclists were riding a conventional racing bicycle at 40 km/h. Thus drafting and using aerodynamically designed equipment can alter the energy expenditure of cyclists at speeds similar to those encountered in competitive events (32-40 km/h).