More Than an Exercise in Vanity

“Healthy muscles, researchers say, are those that have been worked, stressed and pushed to their limit so that they have enough power and strength to get you through life, especially as you grow older. And keeping muscles fit takes effort, which means regular training with weight lifting and cardiovascular exercise even if the results are not a sculptured look, these experts add. If you don’t work your muscles, they will atrophy, especially as you grow older. Older people often fall because they are too weak to brace themselves, and they have trouble with steps and opening jars because their muscles have lost so much strength. There are two aspects to healthy muscles: endurance and strength, said Robert H. Fitts, an exercise physiologist at Marquette University and chairman of the biology department there. Those who try to lift at the gym can end up using weights that are not heavy enough to fully stimulate their muscles. That is especially true of women, Dr. Kraemer said, even those who work with personal trainers. While women often say they are afraid they will bulk up, this fear is unfounded, Dr. Kraemer and others say. Acquiring muscle mass requires testosterone levels that women don’t have. Instead, the toning that many women say they want comes from lifting heavy weights.”

http://www.nytimes.com/2008/05/13/health/13muscles.html?ref=health