Changes in ventilatory threshold with exercise training in a sedentary population: The heritage family study

The purpose of this study was to evaluate the effect of exercise training intensity relative to the ventilatory threshold (VT) on changes in work (watts) and V̇O₂ at the ventilatory threshold and at maximal exercise in previously sedentary participants in the HERITAGE Family Study. We hypothesized that those who exercised below their VT would improve less in V̇O₂ at the ventilatory threshold (V̇O₂vt) and V̇O₂max than those who tained at an intensity greater than their VT. Supervised cycle ergometer training was performed at the 4 participating clinical centers, 3 times a week for 20 weeks. Exercise training progressed from the HR corresponding to 55% V̇O₂max for 30 minutes to the HR associated with 75% V̇O₂max for 50 minutes for the final 6 weeks. VT was determined at baseline and after exercise training using standardized methods. 432 sedentary white and black men (n = 224) and women (n = 208), aged 17 to 65 years, were retrospectively divided into groups based on whether exercise training was initiated below, at, or above VT. Results: 1) Training intensity (relative to VT) accounting for about 26% of the improvement in V̇O₂vt (R²⁼0.26, p < 0.0001). 2) The absolute intensity of training in watts (W) accounted for approximately 56% of the training effect at VT (R²⁼0.56, p < 0.0001) with post-training watts at VT (VT_watts) being not significantly different than W during training (p > 0.70). 3) Training intensity (relative to VT) had no effect on ΔV̇O₂max. These data clearly show that as a result of aerobic training both the V̇O₂ and W associated with VT respond and become similar to the absolute intensity of sustained (3 × /week for 50 min) aerobic exercise training. Higher intensities of exercise, relative to VT, result in larger gains in V̇O₂vt but not in V̇O₂max.