The work rate (WR) corresponding to ventilatory threshold (VT) is an appropriate intensity for regenerative and low-intensity training sessions. During incremental ramp exercise, VO2 increase lags behind WR increase. Traditionally, a VO2 time delay (td) of 45 seconds is used to calculate the WR at VT from such tests. Considerable inaccuracies were observed when using this constant td. Therefore, this study aimed at reinvestigating the temporal relationship between VO2 and WR at VT.
20 subjects (VO2peak 49.9 to 72.6 mL · min–1 · kg–1) performed a ramp test in order to determine VT and a subsequent steady-state test during which WR was adjusted to elicit the VO2 corresponding to VT. The difference in WR and heart rate at VT was calculated between the ramp and the steady-state test (WRdiff, HRdiff) as well as the time delay corresponding to WRdiff during ramp exercise.
Mean values were td = 85 ± 26 seconds (range 38 to 144), WRdiff = 45 ± 12 W (range 23 to 67), HRdiff = 1 ± 9 beats/min (range –21 to +15). The limits of agreement for the difference between WR at VT during ramp and steady-state exercise were ± 24 W. No signifi cant influence on td, WRdiff, or HRdiff from differences in endurance capacity (VO2peak and VT; P > .10 for all correlations) or ramp increment (P = .26, .49, and .85, respectively) were observed.
The wide ranges of td, WRdiff, and HRdiff prevent the derivation of exact training guidelines from single-ramp tests. It is advisable to perform a steady-state test to exactly determine the WR corresponding to VT.
The authors are with the Institute of Sports and Preventive Medicine, University of Saarland, Faculty of Clinical Medicine, 66041 Saarbrücken, Germany.