Virtual Assistant for Exercise Adherence in Older ADULTS

Exercise Adherence (% of prescribed sessions completed)

Exercise adherence will be defined as the percentage of prescribed exercise sessions completed during the 12-week intervention. A single adherence value will be calculated for each participant as: \\text{Adherence (%) = (Sessions completed / Sessions prescribed) × 100} Measurement method: Virtual Assistant/BOT Group: Adherence will be recorded automatically by the virtual assistant (BOT), which logs session completion in real time. Municipal Exercise Group: Adherence will be calculated from attendance records routinely collected in the Enguera se saludable municipal program, using the same formula (completed / prescribed × 100). Although adherence is obtained from different data sources, the measurement itself is identical in both groups, expressed as a percentage (%).

Physical performance assessed by the Short Physical Performance Battery (SPPB)

Lower-limb functional performance will be assessed using the Short Physical Performance Battery (SPPB), a validated instrument for older adults. The SPPB includes three components: balance tests, gait speed, and the 5-times sit-to-stand test. Each component is scored from 0 to 4, yielding a total score from 0 to 12, with higher scores indicating better physical performance. Unit of measurement: SPPB total score (0-12 points).

Accelerometry-Based Physical Activity (Moderate-to-Vigorous Activity Levels)

Moderate-to-vigorous physical activity (MVPA) will be quantified using a wrist- or hip-worn triaxial accelerometer. MVPA will be calculated according to established cut-points for older adults, expressed as minutes per day accumulated at moderate or vigorous intensity. Devices will be worn during the monitoring period, and raw acceleration data will be processed using standardized algorithms to derive daily MVPA time. A single MVPA value will be generated for each assessment period. Unit of measurement: Minutes/day of MVPA (moderate-to-vigorous physical activity).

Risk of falls measured by the FallSkip® system (Fall Risk Index, 0-100)

Risk of falls will be assessed using the FallSkip® system, an instrumented device that evaluates fall risk in older adults through a standardized functional protocol. The device records parameters such as reaction time, postural stability, gait acceleration/deceleration patterns, and sit-to-stand performance. These variables are integrated automatically by the device software to generate a Fall Risk Index on a 0-100 scale, with higher values indicating greater risk of falls. A single Fall Risk Index score will be obtained for each participant at every assessment time point. Unit of measurement: FallSkip® Fall Risk Index (0-100 points).

User experience and usability of the virtual assistant measured with a Visual Analog Scale (VAS)

User experience and usability of the virtual assistant (BOT) will be evaluated using a Visual Analog Scale (VAS), an anchored numerical scale ranging from 0 to 10, in which 0 represents the worst possible user experience/usability and 10 represents the best possible user experience/usability. Participants will rate their overall experience and perceived usability of the virtual assistant on this single-item scale. A single VAS score will be obtained for each assessment period. Unit of measurement: Score on the Visual Analog Scale (0-10), where higher scores indicate better user experience/usability.