Demographic characteristics (e.g. age, gender, family status and comorbidity) and information on experience with computers, tablets and smartphones will be collected at baseline. Also, written informed consent will be completed at baseline. In addition to the monitoring data, standardised measurements will be taken at baseline (T0), at 3 months (T1) and at 6 months (T2).
Primary outcome measure
Adherence: Adherence to the intervention will firstly be assessed based on adherence to the exercise program and wearing of the sensor. Adherence to the exercise program will be calculated based on completion of exercise bouts. Adherence to wearing the sensor will be calculated based on the number of days the sensor is worn and the successful collection of data. Adherence will be considered sufficient when adherence to the exercise program and to the wearing of the sensor exceeds 70%.
Additional information on factors that may influence adherence will be collected by means of a questionnaire. The user evaluation questionnaire is an adapted version of the SensAction-AAL subject evaluation form [
21]. The questionnaire contains questions about the perceived burden of the intervention, wearing of the sensor, and acceptability of the technology. Information will be collected at T
1 and T
2.
Secondary outcome measures
Objective daily physical activity based on sensor data: Baseline (T0) information on time spent “active” (standing and walking) will be collected while wearing the sensor for a week before starting the exercise program. A week of wearing will also be used as intermediate and follow-up information on daily activity at T1 and T2.
Self-reported daily physical activity: In addition to objective daily physical activity, self-reported daily physical activity will be measured by questionnaire at T
0, T
1 and T
2. The Short Questionnaire to Assess Health-enhancing physical activity (SQUASH) gives an insight into habitual physical activity [
22]. The SQUASH consists of four domains: A) commuting activities, B) leisure-time activities, C) household activities, and D) activities at work and school. The questions within the four domains are prestructured into frequency, duration and intensity of an activity. Reproducibility and relative validity of the SQUASH for assessing physical activity have been evaluated [
22,
23].
Functional performance: Functional performance is assessed by means of several clinical tests for physical functioning at T
0, T
1 and T
2. First, subjects are requested to stand up from a chair at a self-selected pace (Sit-To-Stand; STS). STS is commonly used as a test to assess lower-limb strength and balance [
24,
25]. Slower test scores are associated with higher fall risk in older adults [
26]. Subjects are instructed to sit still for several seconds, stand up from the chair at their preferred pace and then stand still for several seconds. The STS movement has good inter-rater and test-retest reliability in healthy older adults [
27]. The test is repeated three times if possible.
Second, the Timed Up-and-Go test (TUG) will be used to measure balance and functional mobility. The TUG is a widely used clinical test and is known to be associated with fall risk in older adults [
28,
29]. The test protocol includes standing up from a chair, walking 3 m at a preferred speed, turning 180°, walking back and sitting down again. Intra-rater reliability ICC as well as inter-rater reliability ICC of the TUG are excellent [
30]. The test is deemed to be a valid measure of dynamic balance and functional control in older adults [
31]. This test will be repeated two times if possible.
Third, the Five-Times-Sit-to-Stand test (FTSS) will be used to indicate postural control and lower extremity strength. The FTSS has been associated with postural control, lower extremity strength and fall risk in older adults [
26]. Slower test scores have been related to more functional impairments in daily living among older adults [
32]. Subjects are instructed to stand up from a chair consecutively five times as fast as possible, preferably without using their hands for support. Test-retest reliability of the FTSS in community-dwelling older adults is adequate [
33,
34]. The FTSS is deemed to be a valid measure of dynamic balance and functional ability in community-dwelling older adults [
31]. Inter-rater reliability is good to excellent [
34,
35]. The test will be repeated twice if possible.
In addition, subjects follow a weekly functional performance self-assessment protocol independently while wearing the sensor. The protocol consists of one STS, one TUG and one FTSS test. Subjects are asked to shake their sensor five times before and after performing their self-assessment, to mark the self-assessment in their daily life data.