Article Title



Cayla R. McAvoy1, Jose Mora-Gonzalez1, Taavy Miller1,2, Hai Yan1, Scott W. Ducharme3, Elroy J. Aguiar4, Catrine Tudor-Locke, FACSM1. 1University of North Carolina - Charlotte, Charlotte, NC. 2Hanger Institute for Clinical Research and Education, Austin, TX. 3Department of Kinesiology, California State University, Long Beach, Long Beach, CA. 4Department of Kinesiology, The University of Alabama, Tuscaloosa, AL.

BACKGROUND: A walking cadence of ≥100 steps/min has been associated with an absolutely-defined moderate intensity (≥3 metabolic equivalents or METs) in adults 21-85 years of age. Less is known about the relationship between cadence and relatively-defined moderate intensity (defined as ≥46% of maximal oxygen consumption [VO2max]), especially in older adults. PURPOSE: To identify a heuristic (i.e., evidence-based, rounded) cadence threshold associated with ≥46% VO2max in older adults. METHODS: Twenty-eight ambulatory and ostensibly healthy older adults (mean [SD], age = 67.5 [4.8], range= 61 to 76 years) completed a submaximal treadmill walking protocol consisting of 5-minute bouts (2-minute rest between bouts), progressing from 0.5 mph (13.4 m/min) up to 6.0 mph (160.9 m/min) in 0.5 mph increments. The test concluded after the bout when participants achieved 75% age-predicted heart rate max (HRmax; 220-age), naturally selected to run, and/or reported a rating of perceived exertion > 13. Cadence was directly observed and a chest-strap continuously measured heart rate. On a subsequent day, participants performed a maximal modified Balke treadmill protocol. Speed was set to elicit 70-75% age-predicted HRmax and remained constant, while grade progressively increased every 2 minutes until participants reached voluntary exhaustion. VO2 was continuously assessed with a portable indirect calorimeter and rolling 15-second averages were used to calculate maximum individual VO2max values. These identified values were then applied to the recorded data from the submaximal test and used to identify associated optimal cadence thresholds using Receiver Operating Characteristic (ROC) curve analysis, including computations for 95% confidence intervals (CI), area under the curve (AUC), sensitivity (Se), and specificity (Sp). Youden’s Index (YI) informed heuristic values. RESULTS: The optimal cadence threshold associated with ≥46% VO2max was 103.3 steps/min (CI = 95.3-106.7), with AUC = 91.7%, Se=82.9%, and Sp=88.1%. When rounding to a heuristic cadence threshold of 100 steps/min for ease of application, Se=84.1%, Sp=80.5%, and YI=164.7. When rounding to 105 steps/min, Se=78.0%, Sp=88.1%, and YI=166.2 CONCLUSION: Maximizing YI, a heuristic cadence value of ≥105 steps/min was identified as a potentially useful proxy indicator of relatively-defined moderate intensity walking in ambulatory and ostensibly healthy older adults. Funding: NIH-NIA-5R01AG049024 Keywords: Walking, Older adults, Cadence, Oxygen consumption

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