Effect of Lower-Limb Blood Flow Restriction-Enhanced Multicomponent Exercise on Functional Performance and Peripheral Vascular Endothelial Function in Frail Older Adults: a Randomized Controlled Trial

INTERVENTION: Intervention group (Lower limb blood flow restriction enhanced multi‐component exercise):12‐week lower limb blood flow restriction enhanced multi‐component exercise (3 times per week, 45‐60 minutes per session; including resistance, aerobic, balance, gait, and flexibility training);Control group (Health education + routine follow‐up):Health education and routine follow‐up (elderly health, exercise safety, fall prevention, nutritional support, chronic disease self‐management; no structured supervised exercise training provided, no lower limb blood flow restriction training scheduled); CONDITION: Frailty PRIMARY OUTCOME: Change in Short Physical Performance Battery (SPPB) total score at 12 weeks;Ankle‐brachial index and peripheral arterial stiffness parameters (ABI, baPWV, cfPWV);Central arterial pressure and wave reflection indices (central systolic/diastolic pressure, augmentation index);Brachial artery flow‐mediated dilation (FMD) and shear rate–normalized FMD;Middle cerebral artery blood flow velocity and dynamic cerebral autoregulation indices (phase, gain via transfer function analysis);Montreal Cognitive Assessment–CHINA version (MoCA‐BC) total score;Heart rate variability (HRV) parameters in time and frequency domains;SF‐36 health‐related quality of life scores (domain and summary scores); SECONDARY OUTCOME: Senior Fitness Test (SFT) component performance;6‐minute walk distance and spatiotemporal gait parameters; INCLUSION CRITERIA: 1. Age >=60 years old; 2. Gender is not limited; 3. Residence status: Elderly residents in the community, who can travel to and from the experimental site by themselves or with assistance. 4. Frailty status: Fried frailty phenotype score >=1 point (including pre‐frailty and frailty). 5. There are no acute phase diseases or severe decompensation states. The current condition has been evaluated by clinical doctors as relatively stable 6. No contraindications for exercise; 7. No color blindness, mental illness, etc. 8. Be able to understand the research content, be willing to participate in this study and sign the written informed consent form