From the August 2004 issue of Runner's World
Discomfort in the Upper Body
The symptoms of a heart attack can be subtle (an ache or feeling of pressure in the chest, arms, neck, and jaw), and they won't necessarily drop you to your knees. Don't assume it's heartburn. Seek immediate medical attention.
Faintness, Lightheadedness, Nausea
Take a time-out and reassess the situation. It might be that you skipped breakfast, or it could be something more serious like a heat-related illness. Cut your workout short. If you don't feel better after resting and eating, see your doctor.
Shortness of Breath
If you are wheezing or if you have trouble catching your breath within five minutes, take a break. Pay particular attention to whether you are using ancillary muscles--lifting your shoulders to try and increase capacity, forcing air into your lungs. If the symptoms persist after five minutes of rest, seek immediate medical attention.
Pain in Joints
Expect muscle aches as you challenge yourself, but never accept pain in joints during or after exercise. This can lead to serious injuries of bones, tendons, and ligaments. See your doctor.
Unspecified Pain
Pain is your body's way of identifying an injury and wrenching you away from the stressor to protect you from further harm. To run through it, you're going to have to override your body's natural instincts to protect itself, which isn't smart. Pain is injury. See your doctor.
