Low Testosterone levels in men are common, but did you know that many men with low testosterone have no symptoms.

Low testosterone levels are associated with reduced muscles and bone mass, sexual dysfunction, depression, coronary artery disease, abdominal fat deposition and insulin resistance. About 25 percent of men in the United States have low testosterone, but only about 6 percent of men under age 70 have significant symptoms, according to scientists from the New England Research Institute, Inc.

Their conclusions are typical of the medical model of health: people are healthy if they do not have disease. Many men over 30 insist on optimal health and performance. They want strong bones and muscles, efficient metabolism, confident emotional outlook and low body fat consistent with optimal quality of life.

Studies by researchers such as Tom Storer and Shalender Bhasin showed that strength, muscle mass and physical performance were proportional to blood testosterone levels. Men with low testosterone may not have significant symptoms of disease, but are not functioning optimally.

Active men want to ride the crest of the wave and are not satisfied to mire in the Whitewater. [sources: Journal of Clinical Endocrinology and Metabolism, Fitness RX]