The effects of weekly or daily oral cholecalciferol use on muscle strength, muscle thickness, and functional independence in patients with spinal cord injury

Objectives: This study aims to evaluate the effects of vitamin D supplementation at different doses and dose intervals on upper extremity muscle strength, muscle thickness, and functional independence of patients with paraplegic spinal cord injury (SCI). Patients and methods: This prospective controlled clinical trial included 64 paraplegic patients (45 males, 19 females; mean age: 39.7±11.5 years; range, 18 to 64 years) with serum 25-hydroxyvitamin D (25[OH]D) levels <20 ng/mL between June 2020 and June 2021. Participants were divided into three groups: control (n=20), daily supplementation with 6000 IU cholecalciferol (n=23), and weekly supplementation with 50,000 IU cholecalciferol (n=21) for eight weeks. Hand grip strength was assessed with a dynamometer, muscle thickness was measured using ultrasonography, and functional independence was evaluated with the Spinal Cord Independence Measure III. Results: Serum 25(OH)D levels significantly increased in both supplementation groups compared to baseline (p=0.001). Nondominant hand grip strength significantly improved in both groups (daily, p=0.025; weekly, p=0.038). Muscle thickness of the biceps brachii significantly increased in the daily group (p<0.05), while triceps brachii thickness significantly improved in both groups (p<0.001). Spinal Cord Independence Measure III scores, encompassing self-care, respiratory-sphincter control, and mobility, showed significant improvements in the supplementation groups (p<0.05), but no changes were observed in the control group. No significant differences were found between daily and weekly supplementation regimens. Conclusion: Vitamin D supplementation, whether daily or weekly, improved muscle performance and functional independence in individuals with SCI. While these findings support the inclusion of vitamin D replacement in rehabilitation programs, larger and longerterm studies are needed to confirm the benefits.