Effect of training in humans on off- and on-transient oxygen uptake kinetics after severe exhausting intensity runs

The purpose of this study was to examine the effect of 4 weeks of intense interval-training on the pulmonary off-transient oxygen uptake ((V) over dot O-2) after running until exhaustion at the same absolute speed. Seven physical education students ran as follows in three maximal tests on a synthetic track (400 m) whilst breathing through a portable, telemetric metabolic analyser: firstly, in an incremental test which determined maximal oxygen uptake ((V) over dot O-2max), the minimal speed associated with (V) over dot O-2max (nu(V) over dot O-2max) and the speed at the lactate threshold (nu(LT)). Secondly, in two continuous severe intensity runs at 90% (R90) and 95% (R95) of nu(V) over dot O-2max. After training, the times to exhaustion (t(lim)) at these two speeds (i.e. the time limits t(lim90) and t(lim95), respectively), were significantly increased at both speeds (+37% and +66% for t(lim90) and t(lim95), P = 0.04 and 0.01, respectively) and nu(LT) and nu(V) over dot O-2max were increased by 8% and 5%, respectively (P < 0.02). The time constants of the cardio-dynamic added to the metabolic phase (phases I + II) and of the slow phase (phase III) of oxygen kinetics in the on-transient phase decreased significantly after training (P = 0.05). However, the decrease in the time constants of oxygen kinetics in the on-transient phases II and III were not correlated with the improvement in performance (i.e. increase in t(lim)). After training the (V) over dot O-2 off-transient phase was significantly faster [off-time constant (tau(off)) decreased significantly both after R90 and R95, P = 0.03]. This decrease in Toff was correlated with the increase in t(lim90) (r = 0.795. P = 0.03). The physiological factors best correlated with the increased performance after training were nu(LT) for t(lim90) and nu(V) over dot O-2max for t(lim95).