The aim of the present study was to examine whether improvements in pulmonary V̇O2 kinetics following a short period of high-intensity training (HIT) would be associated with improved skeletal muscle mitochondrial function. Ten untrained male volunteers (age: 26 ± 2; mean ± SD) performed six HIT sessions (8-12 x 60 s at incremental test peak power; 271 ± 52 W) over a 2-week period. Before and after the HIT-period, V̇O2 kinetics was modelled during moderate intensity cycling (110 ± 19 W). Mitochondrial function was assessed with high-resolution respirometry (HRR) and maximal activities of oxidative enzymes citrate synthase (CS) and cytochrome c oxidase (COX) were accordingly determined. In response to HIT, V̇O2 kinetics became faster (τ: 20.4 ± 4.4 vs. 28.9 ± 6.1 s; P<0.01) and fatty acid oxidation (ETFP) and leak respiration (LN) both became elevated (P<0.05). Activity of CS and COX did not increase in response to training. Both before and after the HIT-period fast V̇O2 kinetics (low τ values) was associated with large values for ETFP, electron transport system capacity (ETS) and electron flow specific to complex II (CIIP) (P<0.05). Collectively these findings support that selected measures of mitochondrial function obtained with HRR are important for fast V̇O2 kinetics and better markers than maximal oxidative enzyme activity in describing the speed of the V̇O2 response during moderate intensity exercise.
- High intensity training
- oxygen uptake
- enzyme activity
- cycling economy
- Copyright © 2015, Journal of Applied Physiology