The primary purpose of this study was to document the physiological responses of level walking and running (LW/R) at various speeds, and grade walking (GW) at various grades on a treadmill. Twenty-four young untrained Japanese women performed 2 tests on the specially designed treadmill for a higher grade exercise. The first test was the LW/R with increase of speeds, 33.3, 66.7, 91.7, and 116.7 m[middle dot]min-1. The first 3 progressions were for walking and the last progression was for running. The second test was the GW with increase of grades 0, 10, 20, and 30% with the velocity of 33.3 m[middle dot]min-1 in all progressions. The different combinations of speeds and grade for the progressions used in this study were selected based on the results of preliminary pilot studies, so that the percent heart rate maximim (%HRmax) was reached at the minimum intensities recommended to allow improving cardiorespiratory fitness by the American College of Sports Medicine (ACSM). Significant (p <= 0.05) differences were found for [latin capital V with dot above]O2 (l[middle dot]min-1 and l[middle dot]kg-1[middle dot]min-1), HR, %HRmax, percent heart rate reserve, and rating of perceived exertion between all 4 progressions in LW/R and GW. However, no significant differences in all variables except step rate between each progression for LW/R and GW. There were significant differences between measured [latin capital V with dot above]O2 and [latin capital V with dot above]O2 calculated from ACSM metabolic equations on all progressions in LW/R and GW (p <= 0.05). These results indicated that the walking at the slower speed of 33.3 m[middle dot]min-1 at a higher grade of 30% is effective as much as the level running at 116.6 m[middle dot]min-1, and more effective than brisk level walking at 91.7 m[middle dot]min-1 to improve cardiorespiratory fitness in untrained young women. The ACSM equation for walking and running underestimates [latin capital V with dot above]O2 for young untrained Japanese women. Population characteristics (e.g., body size and age) should be considered when designing cardiorespiratory fitness programs based on the ACSM equation.
(C) 2007 National Strength and Conditioning Association