For instance, if you are a devoted runner who spends hours jogging, your upper body may wither unless you give it a reason not to. At the same time, your achilles, hamstrings, knees and lower back muscles may protest those miles after miles. As Frank Jobe, MD, Neal EllAttrache, MD, and Karen Mohr, PT, point out in Athletic Forever (Contemporary), "Dedicated runners are among the most injury-prone of all athletes. If running is your main form of exercise, you have a 37 to 56 percent chance of sustaining an injury each year and your chances for a recurrence of that injury are as high as 70 percent."

Simple Principle
The basic principle of cross training is simple: take part in various activities that supplement each other. Runners should lift some weights or at least shoot a few hoops to keep those arms and shoulders toned. Bikers should walk or run now and then to keep their bones healthy. (Bicycling, since it is not a weight bearing exercise, does little to promote bone strength.) Swimmers should find something to do on dry land so that their bones react to gravity and grow stronger. And, no matter what your sport, you should stay well-nourished and supplied with plenty of antioxidants.

As Stephen T. Sinatra, MD, points out in Optimum Health (Bantam), while athletes may enjoy health benefits from exercise, "The vigorous training pursued by competitive athletes renders them more prone to catabolic stress-a situation in which tissues are constantly broken down."

He goes on to point out that the low fat diet many athletes follow may be short of antioxidant nutrients. Unfortunately, that shortage can lead to injury. The metabolic acceleration caused by athletic activity may increase potentially harmful oxidative stress at the cellular level. Without antioxidant nutrients to help quell that stress... Well, the results may not be pretty. Potentially, that kind of oxidative damage may, theoretically, lead to cancer or heart disease. As Dr. Sinatra says, in those circumstances, "the supplemental use of glutathione, vitamins C and E, coenzyme Q10 and magnesium seems reasonable. Some athletes, such as menstruating women, may also need iron supplementation."

In addition, water is crucial for athletes to stay adequately hydrated during activity. According to Daniel Gastelu and Fred Hatfield, PhD, in Dynamic Nutrition for Maximum Performance (Avery), when you run short of water "this can adversely affect performance and, in the long run, can cause peaks and valleys in the athlete's performance." In addition, they advise using sports drinks to stay adequately supplied with electrolytes. "The major electrolytes found in bodily fluids are chloride, magnesium, potassium and sodium."

Electrolytes serve a host of duties, including keeping the heart muscle functioning properly. Gastelu and Hatfield explain, "An electrolyte is an ion that is required by the body to regulate the electric charge and flow of water between the cells and the bloodstream."

Getting Better All the Time
Even if you cross train religiously and try to avoid overdoing one particular sport, sooner or later you may incur injury. If you do (or even before you hurt yourself), the trio of Stanley W. Jacob, MD, Ronald M. Lawrence, MD, PhD, and Martin Zucker, authors of The Miracle of MSM (Putnam), believe that methylsulfonylmethane (MSM) can provide reliable relief for pain and suffering.

"Many people experience rapid relief after starting MSM," say this trio. They go on to claim that "this nutritional supplement has real potential to make a significant impact on the quality of life."

"Your main enemy in the hours following an injury is inflammation," warns Athletic Forever. For injury, they recommend RICE: rest, ice, compression and elevation. In other words, put the injured body part in a firmly wrapped bandage (don't cut off the circulation!) Keep the injury cold but don't put ice directly on it (watch out for frost bite). Rest a while and keep the injury elevated. Then, don't exercise again until you've fully recovered.