We examined the effects of inserting 3 s recovery periods during high-intensity cycling exercise at 25 s and 10 s intervals on pulmonary oxygen uptake (V̇O2p), muscle deoxygenation (HHb), associated kinetics (τ), and energy system contributions. Eleven men (24±3 years) completed two trials of three cycling protocols: an 8 min continuous protocol (CONT) and two, 8 min intermittent exercise protocols with work-to-rest periods of 25 s-to-3 s (25INT) and 10 s-to-3 s (10INT). Each protocol began with a step-transition from a 20 W baseline to a power output (PO) of 60% between lactate threshold and maximal V̇O2p (Δ60). This PO was maintained for 8 min in CONT, whereas 3 s periods of 20 W cycling were inserted every 10 s and 25 s after the transition to Δ60 in 10INT and 25INT. Breath-by-breath gas exchange measured by mass spectrometry and turbine and vastus lateralis muscle deoxygenation ([HHb]) measured by near-infrared spectroscopy were recorded throughout. Arterialized-capillary lactate concentration ([Lac-]) was obtained before and 2 min post-exercise. The τV̇O2p was lowest (p<0.05) for 10INT (24±4 s) and 25INT (23±5 s) compared to CONT (28±4 s) whereas [HHb] kinetics did not differ (p>0.05) between conditions. Post-exercise [Lac-] was lowest (p<0.05) for 10INT (7.0±1.7 mM), was higher for 25INT (10.2±1.9 mM) and was greatest in CONT (14.3±3.1 mM). Inserting 3 s recovery periods during heavy-intensity exercise speeded V̇O2p kinetics and reduced overall V̇O2p suggesting an increased reliance on PCr derived phosphorylation during the work period of INT compared to an identical PO performed continuously.
- O2 on-kinetics
- near-infrared spectroscopy
- intermittent exercise
- energy systems
- Copyright © 2016, Journal of Applied Physiology