{'fraction_non_alphanumeric': 0.028527763627101375, 'fraction_numerical': 0.007131940906775344, 'mean_word_length': 5.680272108843537, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Single Versus Multiple Monitoring Periods for Accelerometer-Measured Physical Activity in Medial Knee Osteoarthritis and Asymptomatic Controls

Purpose: 1) To compare group-level physical activity calculated from a single versus multiple non-consecutive, one-week accelerometer monitoring periods in individuals with medial-compartment knee osteoarthritis and asymptomatic controls; and 2) to examine agreement among these estimates of physical activity at the individual-level. Methods: Accelerometer data from 38 individuals with knee osteoarthritis and 47 asymptomatic individuals was collected during three non-consecutive monitoring periods over one year. General linear models examined the effects of number of sessions averaged (one, two, or three) and group on light and moderate-to-vigorous intensity physical activity, step count, and sedentary behavior. Bland Altman analyses examined agreement between one-, two-, and/or three-session averages. Results: There were no sessions by group interactions. There was a main effect of sessions for sedentary behavior that was borderline significant when expressed as percent wear time. Limits of agreement indicated that two-session average versus single-session metrics could differ by ±50 minutes for light physical activity, ±20 minutes for moderate-to-vigorous physical activity, and ±2100 steps per day. Conclusions: These data suggest that objective physical activity monitoring practices might differ between clinical research, where group data are compared, and clinical decision making, where individual data are compared. Good estimates of group level differences in step count, light, and moderate-to-vigorous physical activity were found using a single session of accelerometer data, but a single session of sedentary behavior data should take wear time into account. The large limits of agreement indicate that multiple sessions may be needed to compare these metrics among or within individuals.