What is the Minimum Step Rate Required to Achieve Moderate Intensity Walking Overground in Adolescent Girls?

Background: In order to promote walking, researchers have sought to identify the required step rate to maintain a health-enhancing intensity of walking. However, there is limited evidence regarding the stepping rate required to promote moderate intensity walking in adolescent girls. Purpose: To identify the step rate equivalent to moderate intensity physical activity (MPA) in adolescent girls and to explore the influence that different anthropometric measures may have on the step rate equating to MPA in this population. Methods: Fifty six adolescent girls (mean age 13.8(0.7) yrs) were recruited to the study. Anthropometric variables and resting metabolic rate were assessed, followed by three overground walking trials on a flat surface at approximately 2, 3 and 4 mph each lasting a minimum of 4 minutes. Oxygen uptake ( ) was assessed using a portable gas analyser, and subsequently converted into METs. Step count was assessed by real time direct observation hand tally. Results: Employing the linear regression between step rate and METs (r2 =0.20 SEE 0.003) suggests that 120 steps·min-¹was representative of MPA (3METs) equating to 7200 steps in 60 minutes. Multiple regression and mixed model regression confirmed weight related variables and maturity were significant predictors of METs (P<0.01). Conclusion: The results suggest that at population level a step rate of 120 steps·min-¹ may be advocated to achieve MPA in adolescent girls, although due to the small sample size used caution should be applied. At an individual level other factors such as age and weight should be considered.