engleski

Oxygen consumption and perceptual response to walking and running at the preferred transition speed

The preferred transition speed (PTS) is the velocity at which humans change gait from walking to running, or vice versa. It is a complex phenomenon, brought about by a number of different factors. Besides the commonly explored anthropometric, metabolic and biomechanical factors, the perception of exertion can influence the onset of gait transition. As the perception of exertion arguably represents the externalization of different physiological factors, the aim of this study was to analyze the relationship between the oxygen consumption and ratings of perceived exertion (RPE) during continuous tests of walking and running at the PTS. The sample consisted of 22 male PE students (21.4±2.4 yrs ; 182.2±6.9 cm ; 78.1±8.2 kg). After the determination of their PTS (7.15±0.44 km/h), the participants completed two square-wave 30-minute walking (W30) and running (R30) treadmill tests at the intensity of their PTS. During the tests, VO2 was measured breath-by-breath (Quark b2, COSMED), and the Borg scale was used to rate the perceived exertion. Ratings were made at the end of the following minutes of the tests: 1-6, 9, 12, 15, 18, 21, 24, 27, and 30. ANOVA was used to determine whether there were significant differences in RPE and VO2 values between W30 and R30. Pearson’s correlation coefficient was used to determine the relationship between mean VO2 and RPE. Results RPE values increased progressively throughout both tests. Starting with the 2nd min, RPE was significantly higher for walking compared to running (p<0.001). RPE remained significantly higher for walking throughout the test, except in the 5th, 9th, and 30th min, when, albeit being higher, the difference was not significant (p=0.06–0.07). The difference was, on average, 0.53 RPE category. VO2 in running was higher than in walking throughout the test. In both tests, there was a high correlation between the RPE and VO2 values (r2=0.82 and r2=0.98 for walking and running, respectively). Discussion The higher RPE values in walking compared to running at PTS might be related to local fatigue of the foot dorsiflexor muscles. Interestingly, the shape of the RPE curve corresponded to the shape of the VO2 kinetics curve in both tests. After the 5th min, an exponential rise of RPE occured, corresponding to the onset of the slow component of VO2 kinetics. The perceptual response very closely followed the changes in oxygen consumption and the VO2 slow component. Activation of additional muscle fibres within the working muscles, as a probable cause of the VO2 slow component, brings about the rise in oxygen consumption and other physiological variables that may be faithfully registered by RPE. References Šentija D. (2002). VO2 kinetics at the gait transition speed. PhD thesis. Chiu MC et al. (2007). Gait Posture 25:385-92. Segers V et al. (2007). Gait Posture 25:639-47.

oxygen consumption; ratings of perceived exertion; walking; running; gait transition

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