The Vo(2) slow component for severe exercise depends on type of exercise and is not correlated with time to fatigue

The purpose of this study was to examine the influence of the type of exerc ise (running vs. cycling) on the O-2 uptake ((V) over dot O-2) slow compone nt. Ten triathletes performed exhaustive exercise on a treadmill and on a c ycloergometer at a work rate corresponding to 90% of maximal (V) over dot O -2 (90% work rate maximal (V) over dot O-2) The duration of the tests befor e 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, respect ively). The (V) over dot O-2 slow component (difference between (V) over do t O-2 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) ov er dot O-2 slow component and the time to fatigue. Finally, because blood l actate 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 dissociati on between blood lactate and the (V) over dot O-2 slow component during run ning. These data demonstrate that 1) the (V) over dot O-2 slow component de pends on the type of exercise in a group of triathletes and 2) the time to fatigue is independent of the magnitude of the (V) over dot O-2 slow compon ent and blood lactate concentration. It is speculated that the difference i n muscular contraction regimen between running and cycling could account fo r the difference in the (V) over dot O-2 slow component.