Relative Intensity-associated Cadence (steps/min) Thresholds In 61-85 Year Olds, The Cadence-adults Study

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A cadence of 100 steps/min has been associated with absolutely-defined moderate intensity (3 metabolic equivalents [METs; where 1 MET = 3.5 mLO2/kg]) in young and middle-aged adults. However, less is known about how cadence corresponds with relative intensity indicators, especially in older adults. PURPOSE: To investigate cadence thresholds associated with the lower thresholds of relatively-defined indicators of moderate intensity provided in the 2011 ACSM Position Stand (i.e., 40-59% of heart rate reserve [%HRR], 64-76% of maximum heart rate [%HRmax], and a Borg scale rating of perceived exertion [RPE] of 12-13) in healthy older adults. METHODS: Ninety-eight older adults (mean [SD]; age = 72.6 [7.0] years, BMI = 25.9 [3.5] kg/m2) completed a progressive treadmill walking protocol consisting of 5-minute bouts separated by 2-min rests increasing from 0.5 to 6.0 mph in 0.5 mph increments. The protocol concluded following the bout during which the participants naturally selected to jog or run, reached 75% age-predicted HRmax, or reported a Borg scale RPE >13. Cadence was calculated by dividing directly observed step counts by bout duration (5 min). Heart rate (HR) was measured using a chest-worn Polar HR monitor, and HR was averaged over the final 2-min of each bout. HRmax was estimated using the standard equation of 220 – age. Intensity indicators were analyzed using Receiver Operating Characteristic (ROC) curves and optimal cadence thresholds associated with moderate intensity were determined using Youden’s Index. RESULTS: The cadence threshold associated with 40% HRR was 103 steps/min (sensitivity = 78%, specificity = 75%, area under the ROC curve [AUC] = 0.83), and that associated with 64% HRmax was 104 step/min (sensitivity = 66%, specificity = 75%, AUC = 0.77). Additionally, an RPE ≥12 was associated with a cadence threshold of 101 steps/min (sensitivity = 63%, specificity = 73%, AUC = 0.79). CONCLUSION: Cadence thresholds of 100 - 104 steps/min were associated with relative indicators of moderate intensity in ostensibly healthy older adults. These results are consistent with the commonly reported heuristic (i.e., practical, rounded, evidence-based) threshold of 100 steps/min associated with absolutely-defined moderate intensity walking in healthy adults. Supported by NIH/NIA Grant 5R01AG049024.