The Latest The National Academy of Sciences (NAS) dropped a bombshell last summer, saying the longstanding prescription of 30 minutes of daily exercise wasn't enough and that Americans needed twice as much moderate-intensity exercise to prevent weight gain and maximize health benefits. To qualify, a walk requires a minimum pace of 4 mph. The fitness community generally applauded the new standard but worried it would further discourage those who already make excuses about not having enough time.

One solution? Breaking that hour up. A study in the journal Medicine & Science in Sports & Exercise (MSSE) found that several 10-minute bouts of exercise provided as much cardiovascular and tension-reducing benefit as a solid 30- or 60-minute workout.

Functional fitness -- exercises focused on enhancing the body's ability to handle activities central to one's lifestyle, such as playing tennis or lifting a grandchild -- continued to spread through the health clubs in 2002, with experts urging people to focus on building muscle strength at the body's core: the abdomen, back and buttocks. The trend filled health clubs with weighted medicine balls, balance boards and inflatable balls used in building balance and core strength.

A study in the Journal of the American Medical Association showed for the first time that human growth hormone -- often prescribed off-label to older people to combat slowing metabolism -- increased lean body mass and muscle strength while decreasing fat mass in healthy elderly men and women. But adverse effects like diabetes and glucose intolerance were frequent. Starting in middle age, adults lose 6 to 8 percent of muscle per decade, experts say. Loss of skeletal muscle is linked to diseases such as obesity and insulin-resistant diabetes.

Muscle strength and aerobic fitness were more achievable for older adults who used water-based exercise, found another MSSE study. Researchers found that the buoyancy and resistance of water force higher energy expenditure than similar land exercises without straining joints or causing pain.

It's well known that vitamin E protects against certain muscle damage after aerobic exercise, but a third MSSE study showed the supplement is of no use in battling soreness after weight-resistance training.

In case there was doubt, 2002 piled on evidence that exercise does more for your health than keep you limber. Research showed that regular workouts can help ward off heart attack and stroke, osteoporosis, breast and colon cancer, constipation, depression and impotence, as well as reduce weight and the risk of age-related dementia, and lower cholesterol levels while increasing metabolism and alleviating muscle imbalances that can contribute to lower-back pain.

Can there be too much of a good thing? You bet. A study in the journal Psychology of Addictive Behaviors showed that men were twice as likely as women to exercise to excess and were more prone to becoming irritable, tense, anxious and depressed if they missed a workout. Exercise-dependent study participants often gave up social relationships in order to hit the gym.

Researchers announced last fall that a naturally occurring antioxidant called coenzyme Q10, sold over-the-counter as a dietary supplement, may help fight Parkinson's disease and amyotrophic lateral sclerosis (ALS), or Lou Gehrig's disease -- both neuromuscular disorders. More definitive trials are underway.

The Next Thing Findings later this year may clarify how much exercise the body needs. This is unlikely to deliver comforting news to the 97 percent of Americans who don't meet the new NAS recommendation -- or, for that matter, the 75 percent who don't even meet the old half-hour standard.

New genetic techniques and computer modeling are helping to create a deeper understanding of muscle systems. Researchers hope this will improve knowledge of how to retain healthy function while providing more clues for the prevention and treatment of diseases such as muscular dystrophy, polio and Guillain-Barre syndrome.

Hype-O-Scope Home ab machines continue to get the hard sell on late-night TV, and growing sales show some folks are tuning in. Experts aren't impressed. In a study published in late 2002, exercise scientists at Kansas State University found that the unassisted crunch or sit-up is as good for the abdominal muscles as any exercise you'd get using typical exercise equipment.

Worry Index The percentage of Americans who are overweight (60) far exceeds the percentage (3) who exercise an hour daily.

About 5,000 people in the United States are diagnosed with ALS each year and as many as 30,000 Americans may have the disease at any given time, according to government data. Initial symptoms are usually muscle weakness or stiffness.

Muscular dystrophy (MD), the common name for several progressive hereditary diseases that cause muscles to weaken and degenerate, is estimated to affect as many as 250,000 Americans annually.

For More Information American College of Sports Medicine: www.acsm.org

Amyotrophic Lateral Sclerosis Association: www.alsa.org

The Cooper Institute: www.cooperinst.org

Muscular Dystrophy Association: www.mdausa.org

National Institute of Neurological Disorders and Stroke: www.ninds.nih.gov

Shape Up America: www.shapeupamerica.org

-- Suz Redfearn

You thought a daily half-hour was enough exercise. Try an hour.