Does cost of running depend on speed?

Abstract

Two series of experiments were carried out with similar techniques to assess the gross cost of running (CR), i.e. the ratio between O2 demand and speed. The two groups of male subjects differed in average maximal O2 uptake and variation coefficient (VO2 max = 70.9 ± 4.7 ml O2 • min –1 • kg–1 , VC = 6.6%; and 61.1±10.1 ml O2 • min–1 • kg–1, VC =16.5%). In the first series the O2 demand (VO2, mlO2 • min–1 • kg–1) was measured in the final 30 s of 4-min runs at 7 treadmill speeds (V, 166.7 to 366.7 m • min–1) in 12 well trained male marathon runners. After having added the anaerobic component of O2 demand, a mean linear regression was computed: VO2 = -11.5±4.0 + 0.232±0.018 * V , R2 = 0.992±0.004 (mean ± standard deviation). The intercepts (i.e. the apparent VO2 corresponding to V=0 or VO2 V0) were linearly related to the slopes (ΔVO2/ΔV; R=-0.71, p=0.0007). CR increased on average from 0.163±0.013 to 0.198±0.010 mlO2 • kg–1 • m–1 in the range of 166.7–333.3 m • min–1. The percent increase ranked from 10.1% to 37.4%. In the second series of experiments (18 subjects), VO2 V0 was inversely related to VO2 max while the opposite was true for ΔVO2/ΔV. Subjects with the lowest (VO2 max) presented positive values of VO2 V0. In conclusion, the widespread idea that gross CR is speed independent does not apply to all distance runners. Therefore, gross CR should be measured at race speed whenever gross CR is utilized to predict running performance.