Boxing is an intermittent combat sport that requires repeated high-intensity actions, sustained punching output, and rapid post-exercise recovery. This single-arm field-based study will examine the effects of a nine-session high-intensity intermittent training program on sport-specific punching output, heart-rate responses, and accelerometer-derived movement responses in youth amateur boxers. Participants will complete a standardized boxing-specific test before and after the intervention. The primary outcome will be the total number of punches completed during the test. Secondary outcomes will include round-by-round punching output, heart rate immediately after the test, heart rate one minute after the test, one-minute heart-rate recovery, and the accelerometer-derived sum of absolute acceleration peaks recorded during each round. The study is designed to provide ecologically valid evidence on feasible monitoring strategies for training adaptation in amateur boxing.