Short-term interval training at both lower and higher intensities in the severe exercise domain result in improvements in V̇O₂ on-kinetics.

Abstract

Although high-intensity interval training (HIT) seems to promote greater improvements in aerobic parameters than continuous training, the influence of exercise intensity on [Formula: see text] on-kinetics remains under investigation. After an incremental test, twenty-one recreationally trained cyclists performed several time-to-exhaustion tests to determine critical power (CP), and the highest intensity (I HIGH), and the lowest exercise duration (T LOW) at which [Formula: see text] is attained during constant exercise. Subjects also completed a series of step transitions to moderate- and heavy-intensity work rates to determine pulmonary [Formula: see text] on-kinetics. Surface electromyography (EMG) of vastus lateralis muscle and blood lactate accumulation (∆BLC) was measured during heavy exercise. Subjects were assigned to one of two 4-week work-matched training groups: the lower [105% CP: n=11; 4×5min at 105% CP (218±39W), 1min recovery] or the upper [I HIGH: n=10; 8×100% I HIGH (355±60W), 1:2 work:recovery ratio] intensity of the severe exercise domain. The two interventions were similarly effective in reducing the phase II [Formula: see text] time constant during moderate (105% CP: 34±13 to 25±8s; I HIGH: 31±9 to 23±6s) and heavy exercise (105% CP: 25±7 to 18±5s; I HIGH: 27±7 to 16±5s) and in reducing the amplitude of [Formula: see text] slow component, EMG amplitude, and ∆BLC during heavy exercise. In conclusion, the short-term adjustments in response to step transitions to moderate and heavy exercise were independent of training intensity within the severe exercise domain.