Brief, intense exercise training may induce metabolic and performance adaptations comparable to traditional endurance training. However, no study has directly compared these diverse training strategies in a standardized manner. We therefore examined changes in exercise capacity and molecular and cellular adaptations in skeletal muscle after low volume sprint-interval training (SIT) and high volume endurance training (ET). Sixteen active men (21 ± 1 years,V O 2 peak = 4.0 ± 0.21 min −1 ) were assigned to a SIT or ET group (n = 8 each) and performed six training sessions over 14 days. Each session consisted of either four to six repeats of 30 s 'all out' cycling at ∼250%V O 2 peak with 4 min recovery (SIT) or 90-120 min continuous cycling at ∼65%V O 2 peak (ET). Training time commitment over 2 weeks was ∼2.5 h for SIT and ∼10.5 h for ET, and total training volume was ∼90% lower for SIT versus ET (∼630 versus ∼6500 kJ). Training decreased the time required to complete 50 and 750 kJ cycling time trials, with no difference between groups (main effects, P ≤ 0.05). Biopsy samples obtained before and after training revealed similar increases in muscle oxidative capacity, as reflected by the maximal activity of cytochrome c oxidase (COX) and COX subunits II and IV protein content (main effects, P ≤ 0.05), but COX II and IV mRNAs were unchanged. Training-induced increases in muscle buffering capacity and glycogen content were also similar between groups (main effects, P ≤ 0.05). Given the large difference in training volume, these data demonstrate that SIT is a time-efficient strategy to induce rapid adaptations in skeletal muscle and exercise performance that are comparable to ET in young active men.

No abstract

Reactive oxygen species (ROS) generated by mitochondria are produced as by-products of normal oxidative metabolism. The fate of these species is governed by a number of factors that vary from tissue to tissue in mammals and may be involved in the pathogenesis of disease. Reactive oxygen species are also invoked as agents that are important in the processes which become active in cells undergoing apoptosis. Integration of knowledge surrounding these different aspects of ROS generation is difficult and reveals considerable gaps in our understanding.