As stated above, proper bag training has many benefits but improper training may be detrimental. Two types of athletic injuries are associated with physical activity: chronic and acute.
Chronic injuries develop and last over an extended period. Training improperly, too intensely, or too often causes this injuries. When your body is stressed through exercise, it must be given time to recover and rebuild itself. When you train too hard or do not get sufficient rest between workouts, you may develop chronic injuries.
Acute injuries, like a twisted ankle or a broken bone, happen suddenly. These injuries may be minimized by using good equipment, proper form, and common sense. Always emphasize technique before speed and power. Start slowly and let your speed and power build gradually. Allow your body time to adapt and become more resilient to impact training.