Effects of reduced-volume of sprint interval training and the time course of physiological and performance adaptations

This study sought to determine the time course of training adaptations to two different sprint interval training programmes with the same sprint: rest ratio (1:8) but different sprint duration. Nine participants (M: 7; F: 2) were assigned to 15-s training group (15TG) consisting of 4 to 6 x 15-s sprints interspersed with 2-min recovery, whereas eight participants (M: 5; F: 3) were assigned to 30-s training group (30TG) consisting of 4 to 6 30-s sprints interspersed with 4-min recovery. Both groups performed their respective training twice per week over 9 weeks and changes in peak oxygen uptake (V̇O2peak) and time to exhaustion (TTE) were assessed every 3 weeks. Additional 8 healthy active adults (M: 6; F: 2) completed the performance assessments 9 weeks apart without performing training (control group, CON). Following 9 weeks of training, both groups improved V̇O2peak (15TG: 12.1%; 30TG: 12.8%, P < 0.05) and TTE (15TG: 16.2%; 30TG: 12.8%, P < 0.01) to a similar extent. However, while both groups showed the greatest gains in V̇O2peak at 3 weeks (15TG: 16.6%; 30TG: 17.0%, P < 0.001), those in TTE were greatest at 9 weeks. CON did not change any of performance variables following 9 weeks. This study demonstrated that whilst the changes in cardiorespiratory function plateau within several weeks with sprint interval training, endurance capacity (TTE) is more sensitive to such training over a longer time frame in moderately-trained individuals. Furthermore, a 50% reduction in sprint duration does not diminish overall training adaptations over 9 weeks.