A comparison of pulmonary oxygen uptake kinetics in middle- and long-distance runners

The purpose of this study was two-fold: 1) to compare the on- and off-transient pulmonary oxygen uptake (VO2) kinetics, in the moderate-intensity domain, of middle-distance (MD) and long-distance (LD) runners and 2) to determine the relationship between the volume of training and VO2 kinetics. With institutional ethics approval, 16 competitive male MD (800/1500 m) and 16 competitive male LD runners (5000/10 000 m) participated in the study. Each runner completed a series of tests to assess maximal VO2 (VO2max), ventilatory threshold (V(T)), and both the on- and off-transient primary time constants (tauon and tauoff, respectively) in response to moderate-intensity treadmill exercise. The results showed that tauon was significantly shorter in LD (12.3 +/- 0.5 s) than MD runners (16.4 +/- 1.0 s, p = 0.002). During recovery from exercise, tauoff was shorter in LD than MD runners (tauoff, 24.3 +/- 0.6 s vs. 26.9 +/- 0.8 s, p = 0.017). The volume of training was greater in LD (66.6 +/- 3.5 km x wk(-1)) than MD runners (43.5 +/- 3.9 km x wk(-1), p < 0.001) and was related to tauon in both groups of runner (MD: r = - 0.63, p = 0.009; LD: r = - 0.68, p = 0.004). Collectively, the results show that MD and LD runners can be differentiated on the basis of their on- and off-transient VO2 kinetics, despite similarities of VO2max and V(T). This is attributable to the greater volume of training performed by LD runners. Further investigations into adaptation(s) to training in muscle in MD and LD runners is required to determine the functional significance of such differences and the response of VO2 kinetic parameters to different training stimuli.