Therapeutic Research

Abstract

To examine a method to save time and money with empirical equations representing the relationship between oxygen uptake（V・O2）, walking speed（v）, step frequency（SF）,and step length（SL）, we recorded the V ・O2 and SF of 7 young male volunteers walking at an increasing speed from 16.7 to 131.7 m min−1 with 5 m min−1 increments every 1 min,and at a decreasing speed from 106.7 m min−1 for 5 min to 16.7 m min−1 with 5 m min−1 decrements every 1 min on a level treadmill. SL was also computed by dividing walking speed by SF. The V・O2 during decremental−speed walking was significantly greater compared to that during incremental−speed walking at corresponding speeds. The SF and SL could be expressed as a function of speed by SF＝13.18 and SL＝0.076 , respectively, regardless of the different modes of walking with respect to speed. To estimate the V ・O2 during walking at different speeds, the results of the increments and decrements were combined by averaging them with respect to speed（V・O2＝1.454×10−4v2−6.5×10−3v＋0.663, r＝0.999, n＝7）. In a mathematical model of the cardiorespiratory system, the average values of V・O2 at a given speed, even though there were on− and off−phase responses, could be predicted within 7.4％ of the theoretical steady−state value. These results suggest that the V ・O2 against walking speed can be estimated by averaging the responses between the increments and decrements of moderate speeds. This could improve exercise tests for V・O2 estimates in terms of time and money. In addition, by using the closerelationship between SF and v, V・O2 can be also expressed as a function of SF.