Search the forums for related threads. It is useful to understand how the wrist works. It's just a joint; it doesn't have any muscles. The movement of the wrist joint is controlled by the muscles in the forearm. The wrist can move in several different ways; some are weak compared to others. For example, the strongest wrist movement comes from pronation or supination of the forearm (unlike other wrist movements, the forearm moves "with" the wrist for this one). Pronation is the best way to hit a powerful smash. Many players use wrist flexion instead, which is much weaker. There is a common myth that badminton is "all in the wrist". It's not. The wrist, fingers and forearm all work together to produce that sudden, sharp and deceptive power that good badminton players develop. Don't forget the role of the fingers!