Darcy Ummels

The validation of a pocket worn activity tracker | 97 5 pocket, attached with a clip, to secure a fixed orientation of the device with respect to axial mobility of the upper leg. This wear location is shown in Figure 5.1. Two commonly used activity trackers, the activPAL 30 and the Fitbit Alta HR (Fitbit; Fitbit Inc., San Fransisco, CA, US) were used as reference for a more relevant interpretation of the validation results. Based on the recommendations of the manufactures the activ ‐ PAL is worn on the dominant leg ten centimetres above the patella (activPAL) and the Fitbit is worn on the nondominant wrist. 31 Figure 5.1 MOX wear location. Data collection and procedure Participants were measured at the Human Performance Laboratory of Maastricht University (Maastricht, NL) or at Zuyd University of Applied Science (Heerlen, NL). Both laboratories are comparable in size (about 120 m 2 ) and facilities. Demographic data were collected (gender, age, body weight, and body length) by two researchers, either DU (physiotherapist) or WB (application engineer). Thereafter, the participants performed the 10 MWT to calculate their average walking speed. After the 10 MWT, participants were fitted with the MOX, the activPAL, and the Fitbit. The same MOX, activPAL, and Fitbit were used for all participants. The activity protocol was recorded on video and observed to use as a gold standard to determine the actual step count, dynamic, standing, and sedentary time in seconds performed by the participants. Step count was counted manually by two independent observers using the counter application Counter +. 32 A step was defined as: “when the entire foot is lifted from the floor and when the participants replaced their foot (forward, backward, sideways or upwards)”. 33 After manually counting the step count,