1. Plan to train. Your body needs to build endurance and strength to be able to handle a distance you've never attempted. "If the athlete's body is not conditioned for the physical requirements of a race, injuries can certainly occur," says Dr. Desai, who has completed several triathlons and is currently training for an Ironman, which includes a half-marathon at the end of the race.

"Musculoskeletal injuries can range from strained muscles to fractures," he says. "And just as the athlete's musculoskeletal system must be prepared for the race so does the cardiovascular system. Serious conditions such as heat stroke and heart attack can occur if the athlete neglects proper training."

2. Look at a calendar. Training will vary based on the experience and condition of the athlete, Dr. Desai says. He says that for a beginner who is training three days a week, preparing for a 5K should take about eight weeks.

3. Have a schedule. "An athlete should have a training schedule with clearly set obtainable goals," he says. "Training schedules can easily be found in running books and online."

4. Build gradually. Regardless of the distance, start slow. If you've never run a mile, don't try to run three on your first day out. Start with a slow and short jog, working to build your distance and speed over time.

5. Rest. "Rest days are just important as the training days," Dr. Desai says. "It is a fine balance between overtraining and risking burnout or injury, and not training enough to be adequately prepared." Rest days in between training days let the body recover.

For more information, Baylor Health Care System