During 3 yr, 274 exertion injuries in middle-aged keep-fit athletes were collected. A keep-fit athlete was a person who regularly took part in non-competitive sports activities. Exertion injury was a nontraumatic pain syndrome in the musculo-skeletal system. In the material, there were 35 women and 239 men. Most of them were 30-39 yr old. Most exertion injuries took place in July, Aug. and Sept. About 80% of the patients were joggers. 80% of them had been training regularly for more than 1 yr. At the moment of occurrence of the symptoms, 68% of the patients trained 3-5/wk. Joggers ran approximately 40 km/wk. About 30% of the injuries took place in the knee, 24% in the ankle, heel and foot, 17% in the leg and 9% in the achilles tendon. Almost 1/5 of the pain syndromes were chronic in nature. The majority responded well to rest and to conservative treatment. Fifteen cases were treated surgically. Most of the exertion injuries were typical exertion syndromes seen also in competitive athletes. Others were degenerative changes, organic anomalies, etc., which revealed their 1st-symptoms during regular keep-fit activities.