If you are exercising for health and fitness, and not training for a specific sport, you may be more susceptible to overuse injuries or stress-related or repetitive-motion injuries. These injuries usually result when joints or soft tissue (muscles, tendons, ligaments or bursae) become irritated and inflamed. Another common and bothersome overuse injury is a stress fracture, a tiny crack in a bone that has been repeatedly stressed during exercise.

Overuse injuries commonly occur when a person does an unusually large amount of exercise, stressing tendons and joints that haven't had a chance to adapt to the new workload. Whereas your muscles can adjust to new demands fairly easily, the fibrous tissue in tendons and joints adapts more slowly, increasing in size and strength gradually over weeks and months. To avoid overuse injury, you must give these soft tissues time to toughen, even if your muscles are urging you to go farther and faster.

• Begin any new type of exercise cautiously; do short, easy workouts for the first few weeks. Never increase the length of your workouts by more than 5 percent from one week to the next, and never increase both the length and the intensity of your workout at the same time.
  
• Avoid workouts that are substantially harder or farther than anything you have done before. One overly stressful workout is enough to cause painful inflammation.
  
• Be sure your shoes fit well. Before wearing them during a workout, spend time breaking them in by walking around in them.
  
• If you feel any tingling, aching or soreness in a joint, muscle or tendon — either during or after a workout, or the next day — stop that activity until all signs of discomfort are gone. Also, swelling is not normal. Pain that is not relieved by a short period of rest is not normal.