A 35-year-old male presents to the orthopedic clinic 6 weeks after sustaining a closed fracture of the mid-shaft humerus managed conservatively with a functional brace. On examination, there is minimal swelling, no tenderness over the fracture site, and the patient reports pain-free active range of motion of the shoulder and elbow. Plain radiographs show early callus formation with bridging across the fracture line. What is the most appropriate next step in management?