Men can't build muscle after the age of 40?

That is absolutely false. "You can replace fat with muscle at any age," says Wayne Westcott, Ph.D., fitness director for the South Shore YMCA in Quincy, Massachusetts, and author of Strength Training Past 50. "I've worked with older men—some as old as sixty—who shed three to four pounds of fat and meanwhile gained that same amount in muscle within two to three months of a regular strength training program," he says. The quote that you read in the book may have been referring to a very specific situation that affects only a very small population, Westcott explains. "For example, if someone has been a bodybuilder his entire life and is in elite physical shape, he probably won't build any new muscle once he reaches a certain age." This does not, however, apply to 99 percent of the population, because most people do not reach their genetic peak. That is, they don't build the maximum muscle mass possible with the raw materials they were given. Weight training is essential for middle-aged and older adults, because the aging process causes a loss of skeletal muscle, which in turn leads to decreased muscle strength. These age-related effects, however, can be reversed: A study conducted at Pennsylvania State University found that "resistance training is an effective means of preserving or increasing" muscle mass in aging adults. And training goes above and beyond building muscle; it increases energy, bone density, and overall strength.