Objective Daily Physical Activity Assessment

Daily PA will be assessed using ActiGraph GT3X triaxial accelerometers [48 (link)], successfully used in previous clinical trials including patients with knee and/or hip OA [49 (link)]. Participants wear the accelerometer attached to a waist belt for ten consecutive days throughout their waking hours, except for showering or swimming. Additionally, participants will be asked to complete a short activity diary including wearing time, unusual activities, or activities difficult to detect, as well as reasons and duration for removal of the device. Data will be recorded at a sampling rate of 100 Hz. After returning the accelerometer and diary, data will be downloaded, processed, and analysed, for which the Freedson thresholds will be used. 0–99 counts per minute (CPM) indicate sedentary behaviour, while values between 100 and 1951, 1952–5724, 5725–9498, and values ≥9499 CPM indicate light, moderate, vigorous, and very vigorous PA, respectively [50 (link)]. Valid PA assessments require a minimum wear time of at least 7 days, 10 h per day [51 ].
Additionally, we will use a questionnaire on daily PA focusing on leisure and work, comprising nine items that are part of the “German Health Update” (GEDA) study of the Robert Koch Institute [52 ], and a single question derived from the Global Physical Activity Questionnaire developed by the WHO on daily sitting time [53 (link)].