Effects of increased intensity of intermittent training in runners with differing VO2 kinetics

The purpose of this study was to test the hypothesis that athletes having a slower oxygen uptake (V.O-2) kinetics would benefit more, in terms of time spent near V.O-2max, from an increase in the intensity of an intermittent running training (IT). After determination of V.O-2max, vV.O-2max (i.e. the minimal velocity associated with V.O-2max in an incremental test) and the time to exhaustion sustained at vV.O-2max (T-lim), seven well-trained triathletes performed in random order two IT sessions. The two IT comprised 30-s work intervals at either 100% (IT100%) or 105% (IT105%) of vV.O-2max with 30-s recovery intervals at 50% of vV.O-2max between each repeat. The parameters of the V.O-2 kinetics (td(1), tau(1), A(1), td(2), tau(2), A(2), i.e. time delay, time constant and amplitude of the primary phase and slow component, respectively) during the T-lim test were modelled with two exponential functions. The highest V.O-2 reached was significantly lower (P<0.01) in IT100% run at 19.8 (0.9) km(.)h(-1) [66.2 (4.6) ml(.)min(-1.)kg(-1)] than in IT105% run at 20.8 (1.0) km(.)h(-1) [71.1 (4.9) ml(.)min(-1.)kg(-1)] or in the incremental test [71.2 (4.2) ml(.)min(-1.)kg(-1)]. The time sustained above 90% of V.O-2max in IT105% [338 (149) s] was significantly higher (P<0.05) than in IT100% [168 (131) s]. The average T-lim was 244 (39) s, tau(1) was 15.8 (5.9) s and td(2) was 96 (13) s. tau(1) was correlated with the difference in time spent above 90% of V.O-2max (r=0.91; P<0.01) between IT105% and IT100%. In conclusion, athletes with a slower V.O-2 kinetics in a vV.O-2max constant-velocity test benefited more from the 5% rise of IT work intensity, exercising for longer above 90% of V.O-2max when the IT intensity was increased from 100 to 105% of vV.O-2max.