Can 'strength snacking' offset losses of muscle mass and strength with physical inactivity in older adults?

INTERVENTION: After one week of daily step count monitoring during their usual activities, participants will be randomly allocated to one of three study groups: Group 1: Reduced steps During the inactivity (step reduction) period, participants will be asked to reduce their daily step count by around 65% (to less than 1500 steps per day) compared to their normal daily values. Participants will be asked to remain as inactive as possible during this period and engage in indoor activities at home requiring minimal physical activity (e.g., reading, watching television). As per the baseline period, the daily step counts of participants will be monitored using a pedometer worn on their wrist (which you will be asked to record in a logbook), and participant physical activity levels will also be measured using an ActivPAL accelerometer device. Group 2: Reduced steps plus "strength snacking” For participants allocated to the "strength snacking” group, "strength snacks” will be performed twice‐daily (once in the morning, once in the evening) for 14 days during the reduced steps period. The "strength snacks” will consist of five bodyweight exercises (such as chair sit‐to‐stand, single‐leg squats, calf raises, step‐ups, standing balance, etc.) that will be standardised across all participants. Each exercise will be completed continuously for one minute, and participants will be asked to perform the maximum number of repetitions possible in one minute. One minute of rest will be allowed between each exercise. Each "strength snacking” session will therefore involve only 5 min of exercise (10 minutes total duration). The "strength snacking” intervention will be delivered to participants and monitored by the research team using a commercial smart dev CONDITION: Musculoskeletal ‐ Other muscular and skeletal disorders Physical Medicine / Rehabilitation ‐ Other physical medicine / rehabilitation Sarcopenia;Physical inactivity; ; Sarcopenia ; Physical inactivity PRIMARY OUTCOME: Bilateral maximal isometric knee extensor strength assessed via isokinetic dynamometry.[Immediately before and after the 2‐week reduced steps period (primary timepoint), and immediately after the 4‐week follow‐up exercise program (secondary timepoint).] INCLUSION CRITERIA: Participants must be: 1) English‐speaking, 2) non‐smoking, 3) able to walk unaided or with minimal assistance for at least 50 m, 4) cognitively intact as indicated by a score of 2 or less on the Short Portable Mental Status Questionnaire (SPMSQ), and 5) identified as not being at a higher risk of an adverse event during exercise, as determined by the ESSA Adult Pre‐exercise Screening System (APSS). SECONDARY OUTCOME: 5 times sit‐to‐stand (STS) test performance.[Immediately before and after the 2‐week reduced steps period, and immediately after the 4‐week follow‐up exercise program.] Adherence (number of sessions completed, and number of exercises, sets and repetitions completed within each session). The program will be considered feasible if adherence to the program (number of sessions completed as planned) was at least 66%. [Throughout the 2‐week exercise program completed during the reduced steps period and 4‐week follow‐up exercise program.] Adverse events (defined as an intervention‐related event resulting in absence from, or modification to, the exercise intervention). Examples of adverse events include an intervention‐related musculoskeletal injury (e.g., muscle or joint injury).[During and at the end of the 2 week step reduction intervention, and at the end of the 4 week re‐training period.] Bilateral grip strength assessed via a handheld dynamometer.[Immediately before and after the 2‐week reduced steps period, and immediately after the 4‐week follow‐up exercise program.] Four square step test performance.[Immediately before and after the 2‐week reduced steps period, and immediately after the 4‐week follow‐up exercise program.] Markers of depression, anxiety and stress (assessed via DASS‐21 questionnaire).[Immediately before and after the 2‐week reduced steps period, and immediately after the 4‐week follow‐up exercise program.] Perceived usability of the Physitrack exercise programming system [assessed via the System Usability Scale (SUS)].[Immediately before the 2‐week reduced steps period, and immediately after the 4‐week follow‐up exercise program.] Perception of the "strength snacking" exercise program (assessed via a customised Post‐Intervention Evaluation Questionnaire).[Immediately before the 2‐week reduced steps period, and immediately after the 4‐week follow‐up exercise program.] Retention [recorded as the number (proportion) of participants that completed the 2‐week step reduction intervention and the 4‐week follow‐up re‐training program]. The program will be considered feasible if at least 90% of participants completed the trial.[Throughout the 2‐week reduced steps and 4‐week follow‐up exercise program.] Subjective health‐related quality of life [assessed via the Short Form 36 (SF‐36) version 2 and assessment of Quality of Life ‐ 6D questionnaires].[Immediately before and after the 2‐week reduced steps period, and immediately after the 4‐week follow‐up exercise program.] Timed up‐and‐go (TUG) test performance.[Immediately before and after the 2‐week reduced steps period, and immediately after the 4‐week follow‐up exercise program.] Total body and regional lean mass and fat mass (assessed via DXA).[Immediately before and after the 2‐week reduced steps period.] Total body fat‐free and fat mass [assessed via bioimpedance spectroscopy (BIS)].[Immediately before and after the 2‐week reduced steps period, and immediately after the 4‐week follow‐up exercise program.]