The work rate corresponding to ventilatory threshold during steady-state and ramp exercise.

PURPOSE: The work rate (WR) corresponding to ventilatory threshold (VT) is an appropriate intensity for regenerative and low-intensity training sessions. During incremental ramp exercise, VO(2) increase lags behind WR increase. Traditionally, a VO(2) time delay (t(d)) 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 VO(2) and WR at VT.

METHODS: 20 subjects (VO(2peak) 49.9 to 72.6 mL x min-1 x 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 VO(2) corresponding to VT. The difference in WR and heart rate at VT was calculated between the ramp and the steady-state test (WR(diff), HR(diff)) as well as the time delay corresponding to WR(diff) during ramp exercise.

RESULTS: Mean values were td = 85 + or - 26 seconds (range 38 to 144), WR(diff) = 45 + or - 12 W (range 23 to 67), HR(diff) = 1 + or - 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 + or - 24 W. No significant influence on td, WR(diff), or HR(diff) from differences in endurance capacity (VO(2peak) and VT; P > .10 for all correlations) or ramp increment (P = .26, .49, and .85, respectively) were observed.

CONCLUSION: The wide ranges of td, WR(diff), and HR(diff) 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.