Overtraining places a demand on the musculoskeletal system that may lead to damage to the musculoskeletal system, as well as to clinical, functional, and biomechanical adaptations that may be detrimental to sport performance. The types of injuries identified range from overt, which are obvious injuries that will usually prevent athletic performance for some period of time, to the subclinical, which decrease performance, but may be seldom recognized. These injuries apparently may be avoided or lessened in severity by a combination of several methods. A thorough preparticipation evaluation is important to detect subtle adaptations in strength and flexibility that can result from overtraining and may increase the athlete's chances of injury. A good sport-specific conditioning program is necessary to give the athlete a strong musculoskeletal base on which to build athletic skills and to decrease the risk of overtraining adaptation. In many sports, prehabilitation exercises can be performed for those musculoskeletal areas that are under high stress in a particular sport. Also, a maintenance conditioning program that extends through the season may be important to maintain fitness throughout the season. Following proper principles of conditioning, including specificity, recovery, and progression, are important. A complete and accurate diagnosis of the injuries that do occur is necessary so that proper treatment may follow. This can be facilitated by understanding the types of clinical presentations of injuries, and the different anatomical and functional alterations that may be acting to cause or to continue the clinical presentation. By following these general guidelines, safe participation in sporting activities as well as performance will be enhanced. The exact point where "training" becomes "overtraining" is difficult to define, especially prospectively. An exciting area of sports medicine research will be to define the anatomic parameters and exercise doses that will cause overtraining, and to devise fitness examinations and training programs that will allow maximal performance with minimal overload risk. At the present time, retrospective studies do indicate that adaptations occur in muscles, tendons, and bones in response to high training loads, and these particular adaptations are not beneficial to performance and may be associated with increased injury risk. Since the optimal exercise dose is not known, provision for evaluation of these adaptations and prehabilitation of all noninjured areas or proper rehabilitation of all injured areas will best prepare the musculoskeletal system for training.