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.

This is a four-arm, parallel-group, randomized controlled pilot trial. Forty-eight to sixty community-dwelling pre-frail older adults (Fried frailty phenotype score 1-2, aged ≥70 years) will be randomly assigned to one of four groups (1:1:1:1 ratio). All groups perform a fixed total daily volume of 15 repetitions per exercise (sit-to-stand, squat, and heel raise), resulting in 45 total repetitions per day. The only difference between groups is the fragmentation pattern (i.e., repetitions per bout × bouts per day):

G1 (highly fragmented): 1 repetition of each exercise per bout, 15 bouts/day (~30 seconds per bout)

G2 (moderately fragmented): 3 repetitions of each exercise per bout, 5 bouts/day (~90 seconds per bout)

G3 (lowly fragmented): 5 repetitions of each exercise per bout, 3 bouts/day (~2.5 minutes per bout)

G4 (consecutive control): 15 repetitions of each exercise per bout, 1 bout/day (~7.5 minutes per bout)

The intervention period is 8 weeks. Outcomes are assessed at baseline, mid-intervention (week 4), and post-intervention (week 8). Primary outcomes include lower limb strength (30-second chair stand test) and dynamic balance (Timed Up and Go test). Secondary outcomes include comprehensive physical function (Short Physical Performance Battery), executive function (Stroop Color-Word Test and Trail Making Test), falls efficacy (modified Falls Efficacy Scale), adherence, acceptability, and adverse events.

Inclusion Criteria:

• 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

Exclusion Criteria:

• 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

The individual participant data (IPD) from this study, including anonymized performance metrics, physiological responses, and metabolic data, will be shared with other researchers upon reasonable request. Data will be provided in accordance with applicable ethical and regulatory guidelines to ensure the privacy and confidentiality of study participants. Requests for data access can be made by contacting the principal investigator,Fanyongzhao, at fanyongzhao@cupes.edu.cn.

The IPD and supporting information will be made available starting from 6 months after the publication of the study results and will remain available for 5 years.

The IPD and supporting information will be available to qualified researchers upon request. Access will be granted after a data-sharing agreement is signed to ensure the data will be used responsibly and in accordance with ethical guidelines. Researchers can request access by contacting the Principal Investigator at fanyongzhao@cupes.edu.cn.

This is a four-arm, parallel-group, randomized controlled pilot trial. Sixty community-dwelling pre-frail older adults (Fried frailty phenotype score 1-2, aged ≥70 years) will be randomly assigned to one of four groups (1:1:1:1 ratio). All groups perform a fixed total daily volume of 15 repetitions per exercise (sit-to-stand, squat, and heel raise), resulting in 45 total repetitions per day.