Associated with the increase in bone length are epiphyseal cartilage, calcium, vitamin D, and exercise. 1. Epiphyseal cartilage: The increase in bone length is mainly due to the growth of epiphyseal cartilage, which is the main condition for bone growth and development. When the epiphyseal cartilage fuses, it marks the end of bone growth. 2. The intake of calcium and protein in food can increase the concentration of calcium in the body, thus promoting the longitudinal growth of bone, and also increase the strength of bone by utilizing calcium deposition. 3. Vitamin D: Vitamin D, also known as the anti-rickets vitamin, is absorbed by the gastrointestinal tract, liver and kidneys and under a series of effects such as ultraviolet irradiation, 1,25(OH)2 vitamin D3, which promotes the absorption and deposition of calcium, and thus helps bone growth. 4. Appropriate exercise can promote the proliferation of osteoblasts, bone density growth, in the growth period can also promote the growth of long bones.