KILDING, A. E., CHALLIS, N. V., WINTER, E. M. and FYSH, M. (2004). Characterisation, asymmetry and reproducibility of on- and off-transient pulmonary oxygen uptake kinetics in endurance-trained runners. European journal of applied physiology, 93 (5-6), 588-597. [Article]
The purpose of this study was three-fold: (1) to characterise both the on- and off-transient oxygen uptake (VO2) kinetics in endurance runners during moderate-intensity treadmill running; (2) to determine the degree of symmetry between on- and off-transients; and (3) to determine the reproducibility of VO2 kinetic parameters in endurance runners. Twelve endurance-trained runners [mean (SD) age 25.2 (4.7) years, body mass 70.1 (9.7) kg, height 179.5 (7.5) cm, ventilatory threshold (VT), 3,429 (389) ml.min–1, maximal VO2 (VO2 max) 4,138 (625) ml.min–1] performed two multiple square-wave transition protocols on separate days. The protocol consisted of six (three transitions, 15 min rest, three transitions) square-wave transitions from walking at 4 km.h–1 to running at a speed equivalent to 80% of the VO2 at the VT (80%VT). To determine the reproducibility, the protocol was repeated on a separate day (i.e. a test-retest design). Pulmonary gas-exchange was measured breath-by-breath. The VO2 data were modelled [from 20 s post-onset (or offset) of exercise] using non-linear least squares regression by a mono-exponential model, incorporating a time delay. The on- and off-transient time constants (Ton and Toff), mean response times (MRTon and MRToff) and amplitudes (Aon and Aoff) were obtained from the model fit. On- and off transient kinetics were compared using paired t-tests. The reproducibility of each kinetic parameter was explored using statistical (paired t-tests) and non-statistical techniques [95% limits of agreement (LOA, including measurement error and systematic bias) and coefficient of variation (CV)]. It was found that the Ton [12.4 (1.9)] was significantly (P<0.001) shorter than Toff [24.5 (2.3) s]. Similarly, MRTon [27.1 (1.9) s] was shorter than MRToff [33.4 (2.2) s]. With respect to the reproducibility of the parameters, paired t-tests did not reveal significant differences between test 1 and test 2 for any on- or off-transient VO2 kinetic parameter (P>0.05). The LOA for Ton (1.9 s), Toff (2.3 s), MRTon (1.2 s), MRToff (3.2 s), Aon (204 ml.min–1) and Aoff (198 ml.min–1) were narrow and acceptable. Furthermore, the measurement error (range, 4.3 to 15.1%) and CV (1.3 to 4.8%) all indicated good reproducibility. There was a tendency for Toff to be more reproducible than Ton. However, MRTon was the most reproducible kinetic parameter. Overall, the results suggest that: (1) a multiple square-wave transition protocol can be used to characterise, reproducibly, both on- and off-transient VO2 kinetic parameters during treadmill running in runners; (2) the phase II time constant is independent of VO2 max, and (3) asymmetry exists between on- and off transient VO2 kinetic parameters.
Altmetric Badge
Dimensions Badge
Actions (login required)
![]() |
View Item |