The V˙o ₂ slow component for severe exercise depends on type of exercise and is not correlated with time to fatigue

Abstract

The purpose of this study was to examine the influence of the type of exercise (running vs. cycling) on the O2 uptake V(O2) slow component. Ten triathletes performed exhaustive exercise on a treadmill and on a cycloergometer at a work rate corresponding to 90% of maximal VO2 (90% work rate maximal V(O2)). The duration of the tests before exhaustion was superimposable for both type of exercises (10 min 37 s +/- 4 min 11 s vs. 10 min 54 s +/- 4 min 47 s for running and cycling, respectively). The V(O2) slow component (difference between V(O2) at the last minute and minute 3 of exercise) was significantly lower during running compared with cycling (20.9 +/- 2 vs. 268.8 +/- 24 ml/min). Consequently, there was no relationship between the magnitude of the V(O2) slow component and the time to fatigue. Finally, because blood lactate levels at the end of the tests were similar for both running (7.2 +/- 1.9 mmol/l) and cycling (7.3 +/- 2.4 mmol/l), there was a clear dissociation between blood lactate and the V(O2) slow component during running. These data demonstrate that 1) the V(O2) slow component depends on the type of exercise in a group of triathletes and 2) the time to fatigue is independent of the magnitude of the V(O2) slow component and blood lactate concentration. It is speculated that the difference in muscular contraction regimen between running and cycling could account for the difference in the V(O2) slow component.

Componente lento do VO2 em crianças durante exercício pesado de corrida: análise com base em diferentes modelos matemáticos

“…The majority of work conducted with the purpose to verify and quantify the SC gives priority to exercise performed in cycle ergometer. However, the found indices in this ergometer in adults are always higher than the ones obtained during running exercise (2)(3)(4) . Besides the theoretical implications, the comprehension and determination of the SC may be extremely important in the exercise prescription, once some authors have been proposing that the maximal tolerance of the performed exertion above the lactate steady maximal phase or critical power (~80-85%VO 2 max), may be dependent on the SC behavior (5) .…”

“…Billat et al (2) characterized the SC as the difference in VO 2 between the third and sixth minute of exercise of heavy intensity, assuming that close and from that time, it is possible to observe the appearance of the SC. Some studies used hence, the criterion of time interval 6-3 minutes in order to estimate the magnitude of the SC (10)(11) .…”

“…increased significantly between the 10,6 and 12,6 years during heavy exercise (40%∆) performed in cycle ergometer. Interestingly, some studies conducted in adults with different aerobic training levels, have verified that the SC (absolute and relative) is higher during heavy exercise in cycling than in running (2,4) . Therefore, one may also hypothesize that the SC seems to be dependent on the interaction between the exercise type and the chronological age.…”

“…Specifically, the difference of the VO 2 between the sixth minute and the third minute (∆VO 2 6-3 min) of exercise is used as index for that matter (2,(10)(11) . In this criterion, it is assumed that the VO 2 would only reach the index corresponding to the load after three minutes of exercise.…”

Slow component of V̇O2 kinetics: the effect of training status, fibre type, UCP3 mRNA and citrate synthase activity

“…Mathematical modelling based on both linear and double exponential models 21,22 has been used, as well as subtracting the V O 2 obtained after 3 min of exercise from either the V O 2 measured after 6 min of exercise or the end-exercise V O 2 . 1,23 Using the mathematical modelling procedures the start of the SC has been observed to occur after approximately 90 -120 s of exercise. 22 The magnitude of the relative SC is calculated as the difference between the end-exercise V O 2 and the V O 2 value occurring at the start of the SC divided by the difference between end-exercise V O 2 and baseline V O 2 .…”