Very short (15s-15s) interval-training around the critical velocity allows middle-aged runners to maintain VO2 max for 14 minutes

The purpose of this study was to compare the effectiveness of three very short interval training sessions (15-15s of hard and easier runs) run at an average velocity equal to the critical velocity to elicit VO2 max for more than 10 minutes, We hypothesized that the interval with the smallest amplitude (defined as the ratio between the difference in velocity between the hard and the easy run divided by the average velocity and multiplied by 100) would be the most efficient to elicit VO2 max for the longer time, The subjects were middle-aged runners (52 +/- 5 yr, VO2 max of 52.1 +/- 6 ml x min(-1) x kg(-1), vVO(2) max of 15.9 +/- 1.8 km x h(-1), critical velocity of 85.6 +/- 1.2% vVO(2) max) who were used to long slow distance-training rather than interval training. They performed three interval-training (IT) sessions on a synthetic track (400m) whilst breathing through the COSMED K4b(2) portable metabolic analyser. These three IT sessions were: A) 90-80% vVO(2), max (for hard bouts and active recovery periods, respectively), the amplitude =(90-80/85) 100=11%, B) 100-70% vVO(2) max amplitude=35%, and C) 60 x 110% vVO(2) max amplitude = 59%. Interval training A and B allowed the athlete to spend twice the time at VO2 max (14 min vs, 7 min) compared to interval training C. Moreover, at the end of interval training A and B the runners had a lower blood lactate than after the procedure C (9 vs, 11 mmol x l(-1)). In conclusion, short interval-training of 15s-15s at 90-80 and 100-70% of vVO(2) max proved to be the most efficient in stimulating the oxygen consumption to its highest level in healthy middle-aged long-distance runners used to doing only long slow distance-training.