Now, to get that additional edge, an increasing number of athletes, including those in high school, are turning to sports supplements. Doctors and nutritional experts are beginning to warn athletes about potential long-term side effects. Such supplements might enhance endurance, but the untrained 'weekend warrior' can face muscle injuries or bone damage by exercising beyond his or her endurance limit. Over the last five years, the nutritional supplement industry has exploded in popularity, growing at a 10-percent annual rate. It allows you to exercise a little longer to sustain performance.
Creatine protects muscles by drawing water inside muscle cells.
It also reduces lactic acid, which naturally builds up in overworked muscles and leads to cramping. But Dr. Lyle Lundblad, president of the Midwest Institute of Urology in Minneapolis, warns that it may not be good for all muscles. One side effect with creatine is erectile dysfunction in some men. Lundblad estimates about 10 percent to 20 percent of his patients have supplement-related erection or virility problems. Health professionals agree that adolescents under age 18 should not use creatine.