Oxygen (O2) uptake kinetics reflect the rate at which an individual’s oxygen consumption (VO2) changes to meet a new metabolic demand, such as an increase or decrease in exercise intensity. O2 uptake kinetics can indicate cardiovascular and metabolic fitness and are described by the time variable, τ (tau), of the exponential equation describing the change in VO2. With training τ decreases, indicating a more rapid increase in VO2 to meet the new metabolic demand. Interval training at supramaximal (>100% VO2max) intensities has been shown to elicit similar improvements in O2 uptake kinetics to traditional endurance training. This study looked to determine the optimal intensity of interval training for eliciting improvements in O2 uptake kinetics. Fifteen recreationally active individuals (males: n=9, age = 23.3±3.3 years, VO2max = 44.2±6.5 ml O2•min-1•kg-1; females: n=6, age = 21.5±0.7 years, VO2max = 39.7±5.4 ml O2•min-1•kg-1) participated in 12 training sessions over 4 weeks. To measure O2 uptake kinetics subjects completed three step transitions from loadless (~25W) to low work-rate (~80W) cycling, prior and following training. Each subject was randomly assigned to one of three intensities - high-intensity interval training (HIIT ~120% VO2max), moderate-intensity interval training (MIIT ~90% VO2max), and low-intensity interval training (LIIT ~65% VO2max). Each session consisted of 8-12 intervals of 1-minute duration with 1-minute recovery on a stationary bicycle at the prescribed relative intensity. No significant differences between groups were observed in changes in τ (Δτ: LIIT: 3.1±8.3s; MIIT: -0.59±12.4s; HIIT: 6.2±6.0s).
Effect of prior heavy exercise on O2 uptake kinetics in the upper regions of the moderate‐intensity domain
