Effect of Alfacalcidol on Muscle Function in Osteoporosis Patients

Inclusion Criteria: * 1\) Females aged 65 and above. 2) Individuals with osteoporosis who are either currently on denosumab or planning to initiate denosumab treatment. 3\) Participants committed to a minimum of 1-year denosumab treatment. 4) Those who have not taken any active vitamin D supplements within 3 months prior to the baseline visit (Visit 2). 5\) Participants capable of walking. 6-1) Individuals with SPPB ≤ 9 meeting the criteria for low physical performance. 6-2) Individuals with SPPB scores of 10 or 11 and concurrently exhibiting low muscle strength (hand grip strength \< 18kg) or gait speed \< 1.0 m/s or chair stand test \> 11s (sitting position) or a history of fractures (excluding skull, cervical spine, fingers, toes, and rib fractures) or a fall within the past year. 7\) Individuals who have undergone DXA (Dual-energy X-ray Absorptiometry) within 6 months of the baseline visit (Visit 2). 8\) Participants who, after receiving a detailed explanation of the clinical trial, have fully understood it, voluntarily decided to participate, and provided written consent to participate while agreeing to adhere to the precautions Exclusion Criteria: 1. Individuals contraindicated for active vitamin D supplementation: * Patients with hypercalcemia or hyperphosphatemia. ② Those with a history of urolithiasis/nephrolithiasis. 2. Individuals contraindicated for denosumab treatment: ① Those planning or with unresolved invasive dental procedures such as extractions, dental implants, or oral surgery. * Individuals with hypoalbuminemia-corrected serum calcium outside the normal range. 3. Individuals with vitamin D deficiency, defined as a serum 25(OH)D concentration below 12 ng/mL (30 nmol/L). 4. Participants who have received continuous prednisolone (or equivalent glucocorticoid) at a dose of 5 mg or higher per day for at least 90 days within 6 months of the screening visit (Visit 1). 5. Individuals with severe malnutrition, indicated by a serum albumin level of 3.0 mg/dL or below. 6. Those in an acute immobility state due to reasons such as fracture, hospitalization, or surgery within 1 month of the baseline visit (Visit 2). 7. Individuals with severe underlying conditions: ① Patients with metastatic cancer. ② Those with severe renal impairment (estimated Glomerular Filtration Rate; eGFR) less than 15 mL/min/1.73m² or undergoing dialysis. ③ Individuals receiving oxygen therapy due to chronic obstructive pulmonary disease (COPD). ④ Those with decompensated liver cirrhosis and severe liver disease with complications due to portal hypertension 8. Individuals with physical limitations due to specific conditions other than muscle decline: ① Those incapable of communication, including severe dementia. ② Individuals undergoing drug therapy for neuro-muscular disorders such as Parkinson's disease or severe myasthenia. 9. Individuals with an SPPB score of 12, indicating no impairment in physical function