Characterisation, asymmetry and reproducibility of on- and off-transient pulmonary oxygen uptake kinetics in endurance-trained runners

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.

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<p>The purpose of this study was three-fold: (1) to characterise both the on- and off-transient oxygen uptake (VO<sub>2</sub>) 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 VO<sub>2</sub> 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 (V<sub>T</sub>), 3,429 (389) ml.min<sup>–1</sup>, maximal VO<sub>2</sub> (VO<sub>2 max</sub>) 4,138 (625) ml.min<sup>–1</sup>] 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<sup>–1</sup> to running at a speed equivalent to 80% of the VO<sub>2</sub> at the V<sub>T</sub> (80%V<sub>T</sub>). 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 VO<sub>2</sub> 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 (T<sub>on</sub> and T<sub>off</sub>), mean response times (MRT<sub>on</sub> and MRT<sub>off</sub>) and amplitudes (A<sub>on</sub> and A<sub>off</sub>) 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 T<sub>on</sub> [12.4 (1.9)] was significantly (P<0.001) shorter than T<sub>off</sub> [24.5 (2.3) s]. Similarly, MRT<sub>on</sub> [27.1 (1.9) s] was shorter than MRT<sub>off</sub> [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 VO<sub>2</sub> kinetic parameter (P>0.05). The LOA for T<sub>on</sub> (1.9 s), T<sub>off</sub> (2.3 s), MRT<sub>on</sub> (1.2 s), MRT<sub>off</sub> (3.2 s), A<sub>on</sub> (204 ml.min<sup>–1</sup>) and A<sub>off</sub> (198 ml.min<sup>–1</sup>) 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 T<sub>off</sub> to be more reproducible than T<sub>on</sub>. However, MRT<sub>on</sub> 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 VO<sub>2</sub> kinetic parameters during treadmill running in runners; (2) the phase II time constant is independent of VO<sub>2 max</sub>, and (3) asymmetry exists between on- and off transient VO<sub>2</sub> kinetic parameters.</p>

Item Type: Article
Research Institute, Centre or Group: Centre for Sport and Exercise Science
Identification Number:
Depositing User: Ann Betterton
Date Deposited: 18 Dec 2008
Last Modified: 27 Sep 2010 14:58

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