Serial casting is primarily used when a muscle is too short to allow functional movement. The joint is typically casted so that tension is applied to the muscle. Over time the muscle may become longer and allow for improved range of motion. What is the primary mechanism of serial casting?

• A. To lengthen a shortened muscle by applying repetitive passive stretching
• B. To strengthen the antagonist muscle
• C. To increase bone density
• D. To improve aerobic endurance

Answer: (A)

Serial casting works by applying a low-load, prolonged stretch to a shortened muscle-tendon unit. The cast holds the joint in a lengthened position, causing viscoelastic creep and gradual remodeling of connective tissue, which can include adding sarcomeres in series. Over time this lengthening allows a greater range of motion and enables functional movement. This mechanism is distinct from strengthening, bone density changes, or aerobic endurance improvements, which are not the goals of serial casting.