This four-arm randomized pilot trial (N=48-60) compares four fragmentation patterns of a three-exercise resistance snack (sit-to-stand, squat, heel raise; 15 repetitions/exercise/day) in pre-frail older adults (Fried score 1-2, ≥70 years). Groups differ by repetitions/bout×bouts/day: G1=1×15, G2=3×5, G3=5×3, G4=15×1. Outcomes (lower limb strength, balance, executive function) are assessed at baseline, week 4, and week 8. The study will determine the optimal fragmentation pattern and provide effect sizes for a future definitive trial.
1. Age 65 years or older 2. Community-dwelling (living independently, not in a nursing home or long-term care facility) 3. Pre-frail status confirmed by Fried Frailty Phenotype score of 1-2 4. Mini-Mental State Examination (MMSE) score ≥24 5. Able to walk independently with or without a cane 6. No regular lower limb strength training (less than 2 times per week) in the past 3 months 7. Willing to adhere to the 8-week exercise intervention and complete all assessments 8. Provide written informed consent before any study-related procedures
1. Lower limb fracture or joint replacement surgery within the past 6 months 2. Unstable angina or uncontrolled hypertension (resting systolic blood pressure ≥160 mmHg) 3. Severe osteoporosis (T-score <-2.5 with history of fragility fracture) 4. Neurological disorders affecting motor function (e.g., Parkinson's disease, post-stroke hemiplegia) 5. Severe cognitive impairment (MMSE score <24) 6. Unstable cardiac or pulmonary disease (e.g., recent myocardial infarction, severe COPD exacerbation) 7. Severe visual or hearing impairment that limits ability to follow instructions or perform exercises safely 8. Participation in another interventional clinical trial within the past 30 days 9. Any other medical or psychological condition that, in the opinion of the principal investigator, would compromise participant safety or study adherence
Parallel
Highly Fragmented Exercise Snack
BehavioralParticipants in Arm 1 perform a resistance-based exercise snack consisting of three exercises: sit-to-stand, squat, and heel raise. Each bout contains 1 repetition of each exercise (1-1-1 structure). Participants complete 15 bouts per day, with each bout taking approximately 30 seconds. The total daily volume is 15 repetitions per exercise (45 total repetitions). The intervention period is 8 weeks. Participants are instructed to use event-based triggers (e.g., after each bathroom visit or after drinking water) to initiate each bout. A demonstration video and a daily exercise log are provided.
Moderately Fragmented Exercise Snack
BehavioralParticipants in Arm 2 perform a resistance-based exercise snack consisting of three exercises: sit-to-stand, squat, and heel raise. Each bout contains 3 repetitions of each exercise (3-3-3 structure). Participants complete 5 bouts per day, with each bout taking approximately 90 seconds. The total daily volume is 15 repetitions per exercise (45 total repetitions). The intervention period is 8 weeks. Participants are instructed to perform bouts at fixed time points (e.g., morning, mid-morning, noon, afternoon, evening). A demonstration video and a daily exercise log are provided.
Lowly Fragmented Exercise Snack
BehavioralParticipants in Arm 3 perform a resistance-based exercise snack consisting of three exercises: sit-to-stand, squat, and heel raise. Each bout contains 5 repetitions of each exercise (5-5-5 structure). Participants complete 3 bouts per day, with each bout taking approximately 2.5 minutes. The total daily volume is 15 repetitions per exercise (45 total repetitions). The intervention period is 8 weeks. Participants are instructed to perform bouts at three fixed time points (e.g., morning, noon, evening). A demonstration video and a daily exercise log are provided.
Consecutive Exercise (Active Control)
BehavioralParticipants in Arm 4 perform a resistance-based exercise session consisting of three exercises: sit-to-stand, squat, and heel raise. Each bout contains 15 repetitions of each exercise (15-15-15 structure). Participants complete 1 bout per day, with the bout taking approximately 7.5 minutes. The total daily volume is 15 repetitions per exercise (45 total repetitions). The intervention period is 8 weeks. Participants are instructed to perform the bout at a fixed time each day (e.g., 10:00 AM). A demonstration video and a daily exercise log are provided.
Lower Limb Muscle Strength
Measured by the 30-Second Chair Stand Test (30-CST). The number of times a participant can stand up from a sitting position and sit back down within 30 seconds. A higher score indicates better lower limb strength.
Dynamic Balance and Mobility
Measured by the Timed Up and Go (TUG) test. The time (in seconds) taken to stand up from a chair, walk 3 meters, turn around, walk back, and sit down. A shorter time indicates better dynamic balance and mobility.
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