Determination of Step Rate Thresholds Corresponding to Physical Activity Intensity Classifications in Adults

Background: Current recommendations call for adults to be physically active at moderate and/or vigorous intensities. Given the popularity of walking and running, the use of step rates may provide a practical and inexpensive means to evaluate ambulatory intensity. Thus, the purpose of this study was to identify step rate thresholds that correspond to various intensity classifications. Methods: Oxygen consumption was measured at rest and during 10 minute treadmill walking and running trials at 6 standardized speeds (54, 80, 107, 134, 161, and 188 m.min(-1)) in 9 men and 10 women (28.8 +/- 6.8 yrs). Two observers counted the participants' steps at each treadmill speed. Linear and nonlinear regression analyses were used to develop prediction equations to ascertain step rate thresholds at various intensities. Results: Nonlinear regression analysis of the metabolic cost versus step rates across all treadmill speeds yielded the highest R(2) values for men (R(2) = .91) and women (R(2) = .79). For men, the nonlinear analysis yielded 94 and 125 step.min(-1) for moderate and vigorous intensities, respectively. For women, 99 and 135 step-mini corresponded with moderate and vigorous intensities, respectively. Conclusions: Promoting a step rate of 100 step.min(-1) may serve as a practical public health recommendation to exercise at moderate intensity.