engleski

Comparison of VO2 kinetics in walking and running at the gait transition speed

Walking and running, as two distinctive patterns of locomotion, may be considered the most natural forms of physical activity in humans. It is surprising, therefore, that no attempts have been made, to our knowledge, to compare the VO2 kinetics in walking and running.The aim of this study was to examine VO2 kinetics during walking and running at the preferred gait transition speed (PTS). Twenty-two physical education students (21.4&#177; ; 2.4y, 182&#177; ; 7cm), performed treadmill tests for determination of the aerobic gas exchange thresholds (for walking, ATw, and running, ATr), VO2max and PTS. Thereafter, they completed two square-wave 30-minute walking (W30) and running (R30) tests at the PTS ; VO2 was determined breath-by-breath, and computorised non-linear regression techniques were used to describe either a mono-, bi- exponential or exponential+linear VO2 response. ANOVA for repeated measurements was used to test for differences between walking and running parameters. The PTS had the same average value as ATw and ATr (7.1&#177; ; 0.4 km/h). The time constant for the fast VO2 component ("tau") in the 30- minute tests was significantly smaller for running than for walking (29.1&#177; ; 8.4 s vs 33.0&#177; ; 8.2 s, p<0.01), while the amplitude of the primary VO2 response (A1) was smaller in the walking test (10.9&#177; ; 1.6 vs 15.7&#177; ; 2.1 ml O2/min/kg). The parameters of the VO2 slow component did not differ significantly between tests, although the VO2 slow component was greater (170&#177; ; 94 ml/min vs 123&#177; ; 25 ml/min) and more often present (19/22 vs 6/22) during running. The time delay for the slow component (td2) was greater for walking (343&#177; ; 220 s vs 194&#177; ; 116 s, p>0.05). The mean time to achieve stable state (tss) and the aerobic energy cost (Css) were significantly lower for walking (tss = 316&#177; ; 306 s and 588&#177; ; 419 s ; Css = 157&#177; ; 20 ml O2/kg/km and 218&#177; ; 20 ml O2/kg/km, for W30 and R30, respectively). In W30, the aerobic energy cost centered at the 3rd minute of exercise (C3=153&#177; ; 18 ml O2/kg/km) and Css did not differ significantly (p> 0.05), while in the R30 test, C3 was significantly lower than Css (C3=197&#177; ; 21 ml O2/kg/km, p<0.05), although explaining effectively the variability of Css (r2 = 0.93). Oxygen uptake kinetics ("tau") are significantly faster in running compared to walking at the preferred gait transition speed in young healthy subjects. Although all tests were equally distributed within the moderate and heavy intensity domains, walking at the PTS is characterized by a monoexponential VO2 response, while a VO2 slow component is present during running at the PTS, in most subjects. References. 1. Barstow TJ, Mole&#8217; PA (1991). Linear and nonlinear characteristics of oxygen uptake kinetics during heavy exercise. J Appl Physiol 71(3):2099-106.

VO2 kinetics; gait transition speed; walking; running

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