Ball machine usage in tennis: Movement initiation and swing timing while returning balls from a ball machine and from a real server

Practicing with the use of a ball machine could handicap a player compared to playing against an actual opponent. recent studies have shown some differences in swing timing and movement coordination,when a player faces a ball projection machine as opposed to a human opponent. we focused on the time of movement initiation and on stroke timing during returning tennis serves (simulated by a ball machine or by a real server). receivers' movements were measured on a tennis court. in spite of using a serving ball speed from 90 kph to 135 kph,results showed significant differences in movement initiation and backswing duration between serves received from a ball machine and serves received from a real server. players had shorter movement initiation when they faced a ball machine. backswing duration was longer for the group using a ball machine. that demonstrates different movement timing of tennis returns when players face a ball machine. use of ball machines in tennis practice should be limited as it may disrupt stroke timing. © journal of sports science and medicine.