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 V˙O₂ 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 V˙O₂ at the ventilatory threshold (V˙O₂vt) and V˙O₂max 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 % V˙O₂max for 30 minutes to the HR associated with 75 % V˙O₂max 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 V˙O₂vt (R^{2 =} 0.26, p < 0.0001). 2) The absolute intensity of training in watts (W) accounted for approximately 56 % of the training effect at VT (R^{2 =} 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 ΔV˙O₂max. These data clearly show that as a result of aerobic training both the V˙O₂ 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 V˙O₂vt but not in V˙O₂max.

Key Words:

Submaximal exercise, submaximal fitness, V˙O₂, race, sex.

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