Significance of the Velocity at &OV0312;O2max and Time to Exhaustion at this Velocity

Abstract

In 1923, Hill and Lupton pointed out that for Hill himself, ‘the rate of oxygen intake due to exercise increases as speed increases, reaching a maximum for the speeds beyond about 256 m/min. At this particular speed, for which no further increases in O₂ intake can occur, the heart, lungs, circulation, and the diffusion of oxygen to the active muscle-fibres have attained their maximum activity. At higher speeds the requirement of the body for oxygen is far higher but cannot be satisfied, and the oxygen debt continuously increases’. In 1975, this minimal velocity which elicits maximal oxygen uptake (V̇O_2max) was called ‘critical speed’ and was used to measure the maximal aerobic capacity (max E_ox), i.e. the total oxygen consumed at V̇O_2max. This should not be confused with the term ‘critical power’ which is closest to the power output at the ‘lactate threshold’. In 1984, the term ‘velocity at V̇O_2max’ and the abbreviation ‘vV̇O_2max’ was introduced. It was reported that vV̇O_2max is a useful variable that combines V̇O_2max and economy into a single factor which can identify aerobic differences between various runners or categories of runners. vV̇O_2max explained individual differences in performance that V̇O_2max or running economy alone did not. Following that, the concept of a maximal aerobic running velocity (V_amax in m/sec) was formulated. This was a running velocity at which V̇O_2max occurred and was calculated as the ratio between V̇O_2max (ml/kg/min) minus oxygen consumption at rest, and the energy cost of running (ml/kg/sec). There are many ways to determine the velocity associated with V̇O_2max making it difficult to compare maintenance times. In fact, the time to exhaustion (t_lim) at vV̇O_2max is reproducible in an individual, however, there is a great variability among individuals with a low coefficient of variation for vV̇O_2max. For an average value of about 6 minutes, the coefficient of variation is about 25%. It seems that the lactate threshold which is correlated with the t_lim at vV̇O_2max can explain this difference among individuals, the role of the anaerobic contribution being significant. An inverse relationship has been found between t_lim at vV̇O_2max and V̇O_2max and a positive one between vV̇O_2max and the velocity at the lactate threshold expressed as a fraction of vV̇O_2max. These results are similar for different sports (e.g. running, cycling, kayaking, swimming). It seems that the real time spent at V̇O_2max is significantly different from an exhaustive run at a velocity close to vV̇O_2max (105% vV̇O_2max). However, the minimal velocity which elicits V̇O_2maxand the t_lim at this velocity appear to convey valuable information when analysing a runner’s performance over 1500m to a marathon.