Resistance-Based Multicomponent Training Plus Nutrition Supplementation for Intrinsic Capacity and Disability Risk in Chinese Rural Older Adults

This study aims to determine whether resistance-dominant multicomponent training combined with leucine-enriched whey protein and vitamin D supplementation can improve intrinsic capacity and reduce disability risk in rural Chinese older adults. The study focuses on the locomotion and vitality domains of intrinsic capacity, which are closely related to mobility function, nutritional status, muscle reserves, and the ability to maintain independent daily living. Eligible participants will be rural community-dwelling adults aged 60 years or older who present at least one of the following risk characteristics: reduced physical performance, low gait speed, nutritional risk, sarcopenia risk, or pre-frailty/frailty. After baseline assessment, participants will be randomly allocated in a 1:1:1:1:1 ratio to one of five study groups: control group, nutrition supplementation group, resistance training group, resistance training plus nutrition supplementation group, and resistance-dominant multicomponent training plus nutrition supplementation group. The traditional resistance training program will include progressive functional resistance exercises such as chair sit-to-stand, chair-assisted squat, calf raise, elastic-band knee extension, elastic-band hip abduction, elastic-band rowing, wall push-up, and shoulder press. The resistance-dominant multicomponent training program will use resistance training as the core component and will additionally include balance, gait, aerobic, flexibility, and breathing relaxation exercises. Exercise sessions will be conducted three times per week for 12 weeks. The nutritional supplementation will consist of approximately 20 g/day whey protein, 2.5-3.0 g/day total leucine, and 800-1000 IU/day vitamin D3. The supplement will be administered twice daily. On training days, one dose will be taken within 30 minutes to 2 hours after exercise, and another dose after breakfast. On non-training days, the supplement will be taken after breakfast and dinner. Outcome assessments will be performed at baseline and at week 12. The primary outcomes are the Short Physical Performance Battery score, FRAIL score, and activities of daily living/instrumental activities of daily living scores. Secondary outcomes include 4-meter gait speed, Timed Up and Go test, five-times sit-to-stand test, 30-second chair stand test, handgrip strength, Mini Nutritional Assessment Short Form score, daily protein intake, serum 25-hydroxyvitamin D, body mass index, calf circumference, appendicular skeletal muscle mass index, and quality of life. Safety outcomes include renal function, blood calcium, falls, musculoskeletal injury, gastrointestinal symptoms, and other adverse events.