Cadence (steps/min) Associated With Moderate Intensity Walking In Older Adults: The CADENCE-Adults Study

Abstract

Cadence (steps/min) is an accessible and understandable metric for communicating physical activity intensity. Studies in younger and middle-aged adults consistently report ≥100 steps/min associated with walking at an absolutely-defined moderate intensity (i.e., 3 metabolic equivalents [METs]) or higher. However, few studies have quantified the cadence-intensity relationship in older adults. PURPOSE: To identify a reasonable heuristic (i.e., evidence-based, practical, rounded) cadence threshold associated with absolutely-defined moderate intensity in ambulatory older adults. METHODS: Ninety-eight older adults 61-85 years of age (49% women; age=72.6±6.9 years; BMI=25.9±3.5 kg/m2) completed a series of 5-min treadmill walking bouts. Bouts began at 0.5 mph and increased in 0.5 mph increments until participants: 1) naturally selected to run, 2) reached >75% of their age-predicted maximum heart rate (220 - age), or 3) reported a Borg scale rating of perceived exertion (RPE) >13. Oxygen uptake (VO2; mlˑkg-1ˑmin-1) was measured using indirect calorimetry and cadence was derived by dividing directly-observed steps by bout duration. VO2 was averaged over the last two minutes of each bout and divided by 3.5 mlˑkg-1ˑmin-1 to determine METs. Moderate intensity (3 METs) cadence thresholds were identified with two analytic approaches: 1) using Youden’s index in a Receiver Operator Characteristic (ROC) curve and 2) by estimating a segmented (i.e., ‘hockey-stick’) regression model that accounted for repeated measures for the cadence-intensity relationship. RESULTS: Eighty participants (82%) reached 3 METs. The ROC curve displayed an area under the curve (AUC) of 0.93. The segmented regression model indicated that cadence explained 70% of the variance in METs. The cadence thresholds associated with absolutely-defined moderate intensity were 100.3 steps/min in the ROC analysis (accuracy = 85.5%, sensitivity=86.8%, specificity=84.5%) and 103.1 steps/min in the regression analysis (95% prediction interval=70-114 steps/min). CONCLUSION: Consistent with previous evidence collected from younger and middle-aged adults, 100 steps/min serves as a reasonable heuristic threshold to communicate absolutely-defined moderate intensity walking in ambulatory older adults. Funding: NIH NIA 5R01AG049024