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-second training group (15TG) consisting of 4-6x15-second sprints interspersed with 2-minute recovery, whereas eight participants (M: 5; F: 3) were assigned to 30-second training group (30TG) consisting of 4-6x30 second sprints interspersed with 4-minute recovery. Both groups performed their respective training twice per week over 9weeks and changes in peak oxygen uptake (VO2peak) and time to exhaustion (TTE) were assessed every 3weeks. Additional eight healthy active adults (M: 6; F: 2) completed the performance assessments 9weeks apart without performing training (control group, CON). Following 9weeks of training, both groups improved VO2peak (15TG: 12.1%; 30TG: 12.8%, P<.05) and TTE (15TG: 16.2%; 30TG: 12.8%, P<.01) to a similar extent. However, while both groups showed the greatest gains in VO2peak at 3weeks (15TG: 16.6%; 30TG: 17.0%, P<.001), those in TTE were greatest at 9weeks. CON did not change any of performance variables following 9weeks. This study demonstrated that while 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.