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

Abstract

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

Pulmonary O2 uptake on-kinetics in sprint- and endurance-trained athletes

“…The ENT athletes (comprising runners, cyclists, and tri-athletes) in our study had _ V O 2 peak values measured during cycle ergometer exercise of approximately 60 mLÁkg -1 Ámin -1 . This is similar to that reported by Kilding et al (2005) for endurance runners tested on a motorized treadmill (~59 mLÁkg -1 Ámin -1 ), but somewhat lower than that reported by Koppo et al (2004a) for elite cyclists performing cycle ergometer exercise (~67 mLÁkg -1 Ámin -1 ). The SPT athletes had relative _ V O 2 peak values of approximately 47 mLÁkg -1 Ámin -1 , slightly higher than those previously reported for age-matched subjects who were not specifically trained (i.e., 41-45 mLÁkg -1 Ámin -1 ; Jones and Carter 2004;Koppo et al 2004a), but somewhat lower than those reported previously by Fukuoka et al (1995) for American football players (53 mLÁkg -1 Ámin -1 ) and by Granier et al (1995) for track sprint runners (52 mLÁkg -1 Ámin -1 ).…”

“…In the present study, the ENT subjects had phase II val- ues of~17-20 s. Although these values are considerably shorter (i.e., the kinetics are faster) than those reported for sedentary or recreationally active subjects (i.e., phase II of 25-32 s for moderate-intensity exercise; e.g., Brittain et al 2001;DeLorey et al 2003;Koppo et al 2004b;Roberts et al 2005;Wilkerson et al 2005;Berger et al 2006a), they are somewhat longer than those that have been reported previously for highly trained endurance cyclists and runners (phase II of~12 s; Koppo et al 2004a;Kilding et al 2005). This difference is likely a function of the higher fitness of the cyclists studied by Koppo et al (2004a) and the use of treadmill as opposed to cycle ergometry by Kilding et al (2005).…”

“…This difference is likely a function of the higher fitness of the cyclists studied by Koppo et al (2004a) and the use of treadmill as opposed to cycle ergometry by Kilding et al (2005). The phase II in the SPT athletes was 32 s, on average, for both moderate-and severe-intensity exercise.…”

Pulmonary oxygen uptake and muscle deoxygenation kinetics during recovery in trained and untrained male adolescents

“…on-off symmetry (Cleuziou et al 2004;Ozyener et al 2001;Paterson and Whipp 1991). However, previous studies in trained subjects have demonstrated on-off asymmetry in the pulmonary oxygen uptake kinetic response (Fukuoka et al 2002;Kilding et al 2005;Kilding et al 2006;Kilding et al 2007). Of particular note is the study by Fukuoka et al (Fukuoka et al 2002) where previously untrained adults undertook a 90 day training programme.…”

Oxygen uptake kinetics during exercise in adults with Down syndrome

“…As a double square-wave was conducted and this may limit the accurate determination of the phase 2 time constant, we also calculated the MRT. Kidling et al (2005) demonstrated no significant differences in test-retest MRT values derived from a treadmill running protocol on two separate days. Evidence also exists to confirm that the MRT can be used as more reliable oxygen uptake kinetic modeling tool than peak cross-correlation time for a pseudorandom binary sequence exercise test (Edwards et al 2005).…”