Better VO2 max has previously been linked to lower all-cause mortality independent of other health factors such as obesity and to improved cognitive function in old age. In this study, the 24 sessions were done either over the course of 3 weeks or 8 weeks. VO2 max improved by 7.5% in the 3-week group and by 12% in eight-week group suggesting that efficient recovery is needed in order for adaptations to occur that improve VO2 max.

For those interested in the exercise protocol: Each training session consisted of 10 minutes warm-up followed by 4×4-minute intervals at 90–95% of HRmax, alternating with 3-minute of active recovery at 70% of HRmax, ending with a 5-minute cool-down, giving a total exercise time of 40 minutes per session.