All competitive athletes will, at some time, run out of energy and be unable to get through a workout. Over the years, scientists have offered many explanations and treatments for this "chronic fatigue."
Most of them have been wrong.
Until 20 years ago, athletes were often told their tiredness was caused by low levels of minerals such as potassium, magnesium, sodium and/or calcium. Researchers have since shown that healthy athletes rarely suffer from such deficiencies.
Then, viruses and other infectious agents were blamed. But most of the time, doctors couldn't -- and still can't -- find these problems in athletes.
The most likely explanation for chronic fatigue in competitive athletes is muscle damage.
When you train hard for competition, you damage the microscopic fibers in your muscles. You need to allow time for your muscles to heal; ease up on your workouts for a day or so. Many athletes are so obsessed that they attempt another hard workout before their muscles have recovered. They suffer additional damage that prevents the muscle fibers from adequately storing the muscle sugar needed for fuel.
If you're a competitive athlete and suddenly find you can't get through a normal workout, you're probably training too much. Rest a few days. If you don't recover, ask your doctor to look for a hidden infection.
Q: My foot ached when I ran; it got worse each day until it ached even when I was lying in bed. My doctor X-rayed my foot and found nothing. But he says I have a stress fracture. What can you tell me about this injury?
A: Stress fractures are small cracks in a bone's surface. Since X-rays are often not sensitive enough to detect the cracks, you may need a test that involves injecting a radioactive material into your veins to see if it collects over the fracture site.
The usual treatment for a stress fracture is to stop running. You can continue walking, although your doctor may put a cast on your leg to slow you down and make sure you can't run.
Resume running when it doesn't hurt to do so. Whole recovery usually takes about 12 weeks, although in some cases, it can take more than two years.
The most common sites for stress fractures are the bones of the lower leg and foot. If you have a stress fracture in one leg or foot, you have a 20 percent chance of suffering a fracture in the other leg or foot.
Women are more likely to develop stress fractures than men because their bones are less dense. And although a majority of stress fractures are not associated with high mileage or running on hard roads, runners develop stress fractures nearly 10 times more frequently than aerobic dancers do.
And, high-arched feet are poor shock absorbers. Therefore, people who have this condition tend to have the most foot stress fractures.
Dr. Mirkin is a practicing physician in Silver Spring specializing in sports medicine and nutrition.