Austin L. Cooper, FACSM. University of Alabama, Tuscaloosa, AL.

Pattern Of Step Accumulation (Cadence Bands) And Relative Heart Rate Intensity During Free-Living Observation Austin Cooper1, Peixuan Zheng2, Hayley V MacDonald1, Michael V Fedewa1, Scott W Ducharme2, Elroy J Aguiar1 1 The University of Alabama, Tuscaloosa, AL2 University of Illinois Chicago, Chicago, IL3 California State University Long Beach, Long Beach, CA Background: Step-based measurement of physical activity (PA) is increasing in popularity. Steps/day provides an indication of daily volume of PA, however, it is often criticized for its inability to capture intensity. Cadence [steps/min] is a valid proxy of PA intensity, however few studies have explored the pattern of step accumulation under free-living conditions. Similarly, relative-intensity is often expressed as a percentage of maximal heart rate (%HRmax), however, few studies have examined its daily distribution. Methods: Healthy adults (n=14, 22.5±3.8 years) wore an ActiGraph GT9X+ accelerometer on their waist (30 Hz sampling rate) and a chest-worn Polar HR monitor for 24 h during free-living observation, resulting in 15,962 pairs of cadence and HR values. Cadence data was compiled into cadence bands (steps/min): non-movement (0), incidental movement (1-19), sporadic movement (20-39), purposeful steps (40-59), slow walking (60-79), medium walking (80-99), brisk walking (100-119), and all faster locomotion (≥120). For %HRmax (age-predicted using the Tanaka equation), the data was compiled into HR zones: very light (<57%), light (57-63%), moderate (64-76%), and vigorous (77-95%) according to ACSM guidelines. Median [IQR] time spent in cadence bands and relative-intensity HR zones were computed. Results: For cadence bands, the highest amount of time spent was in non-movement (805.5 [187.5] min, 69.3% of wear time) and incidental movement (274.5 [139.5] min, 23.6%). Sporadic movement (23 [23.8] min, 2.0%) and brisk walking (25 [34.0] min, 2.2%), were similar/greater, respectively, than purposeful (8 [12.8] min, 0.7%), slow (7.5 [7] min, 0.6%) and medium walking (8 [7] min, 0.7%) combined. Faster locomotion was rare (2 [13.5] min, 0.2%). Analysis of %HRmax revealed similar trends, but with varying proportions. Participants spent the majority of time at a very light intensity (1188.5 [206.8] min, 98.0%), followed by vigorous (16.0 [53.0] min, 1.3%), moderate (4.5 [4.3] min, 0.4%) and light (4.0 [4.0] min, 0.3%). Conclusions: Participants spent a majority of their time in low cadence bands and at very light intensity, and tended to skip straight to higher cadence bands and relative intensities. Future studies should examine patterns of cadence and HR using more rigorous methods (i.e., longer observation, Holter monitor, and a larger demographically diverse sample. Grant funding: The University of Alabama Office for Research and Economic Development: #RG14902

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