'Left uppercut! Left uppercut!" yells Joey DeMalavez, Philly tough guy and former pro boxer, as seven neophyte pugilists advance, slicing the air with gloved fists at Joltin' Jabs, the trainer's Main Street Manayunk gym.

Their opponents: in the mirrors in front of them.

"Jab!" DeMalavez orders. For some, there's a bit of hand tremor, a shuffle to their gait. DeMalavez marvels at their determination. "Amazing."

All have Parkinson's disease. For them, noncontact boxing is exercise as weapon.

"Feeling in control of your body," said Bonnie Queen, 69, a psychotherapist in her day job, "translates into feeling in control of your life."

With or without Parkinson's.

Exercise, we've long been told, is good for your health. But how much to get? And what kind?

The short answer: Federal guidelines advise adults of all ages to get 150 minutes or more of moderate- intensity aerobic activity a week or 75 minutes of vigorous aerobics. Twice as much total aerobic activity will yield greater benefits.

Moderate- or high-intensity muscle-strengthening activity involving all major muscle groups should be done at least twice weekly.

Children age 6 to 17 should engage in 60 minutes of physical activity a day - mostly moderate or vigorous aerobics but also muscle-strengthening and bone-stretching activities at least three days a week.

"The human body is supposed to do things," said Alfred Bove, emeritus professor of medicine at Temple University. "We're not supposed to just sit around all day."

Daniel Edmundowicz, cardiology chief at Temple University Hospital, said he tells patients to park in a far spot of the supermarket lot or do a pre-shopping lap around the aisles.

Have trouble sleeping? Take a brisk walk a few times a week.

"Sleep is used by your body for rest and recovery," said Fredric Jaffe, the hospital's medical director for pulmonary rehabilitation. "If you give it something to recover from, it will sleep better."

Even limited exercise has some benefits. Getting at least the recommended 2½ hours a week will likely lead to lower blood pressure and "bad" cholesterol, both key to cardiovascular health. Physical activity at various levels can also cut risks for cancer, diabetes, depression, and cognitive loss.

Losing weight, you may have noticed, is absent from the list.

Experts say that exercise alone is not apt to result in as much weight loss as many seek.

To shed pounds, cut calories, too.

Thomas Wadden, director of the University of Pennsylvania's Center for Weight and Eating Disorders, advises cutting 500 to 750 calories a day. Most women who want to lose weight should aim for 1,200 to 1,500 calories daily; most men should go for 1,500 to 1,800.

And when you've reached your goal, be ready to exercise more. If you got to 150 minutes a week, increase it to 225, Wadden said: "Your body is more fuel-efficient after weight loss - about 20 to 30 percent more."

Do the work, reap the rewards.

"Exercise is medicine," said Kathryn Schmitz, an exercise physiologist at Pennsylvania State University.

Her research has shown that progressive resistance training can prevent and relieve breast cancer survivors' lymphedema, the painful swelling of arms and shoulders due to removal of lymph nodes, and aerobic exercise may reduce breast cancer risk.

Schmitz, a former Martha Graham dancer, believes that medical science has been slow to embrace exercise's curative powers.

"We are a pill and surgery culture," she said. It's what doctors prescribe, and what patients are used to.

"Exercise is like a pill," said Schmitz, who plans to make exercise, diet, and sleep a focus of her work at the Penn State Cancer Institute in Hershey, which recently named her associate director of population science.

As for the old caveat about consulting with your doctor first, well . . .

"If you want to help people, don't say that," Schmitz said. "Then they give up before they've even started."

To get the benefits of exercise while minimizing risks it is important to get the intensity right: not too hard, not too easy. Schmitz advises a simple "talk but not sing" rule. If you're too breathless to talk, you are working too hard. If you can hold a note, you aren't working hard enough.

It can add up to:

Stronger bones. Research at Children's Hospital of Philadelphia found higher bone density in children who engaged in high levels of physical activity. Especially useful are high-impact, weight-bearing activities such as gymnastics and soccer.

For adults, "walking, stair climbing, running, and dancing in combination with weightlifting can increase the strength of your bones," said Kate E. Temme, an assistant professor of women's sports medicine at Penn Sports Medicine Center.

For defense against falls, others advocate such balance exercises as yoga and tai chi, as well as such flexibility exercises as stretching.

Healthier pregnancies. In times past, pregnancy was often considered a no-exercise zone. No more - as long as the pregnancy is healthy.

With their doctors' guidance, many women can follow the same national guidelines for all adults, Temme said. The benefits: less back pain, healthy weight gain during pregnancy, faster weight loss afterward, and lower risk of gestational diabetes.

Lower cancer risk. Exercise, especially at higher levels, is linked to reduced risk of colon, endometrial, breast, and lung cancers, according to the National Cancer Institute.

Some evidence suggests lowered risk for cervical and ovarian cancers, as well.

Improved mental health. Research has found that exercise may help ward off and even reduce cognitive loss.

In one study, people with Alzheimer's disease who did aerobics experienced less depression and irritability. In another, they performed better in tests of executive function - such abilities as planning and organizing - than those who did not.

And, of course, aerobic exercise can lift your spirits by releasing endorphins. Think "runner's high."

Rutgers University researchers Brandon Alderman and Tracey Shors found that aerobics plus meditation brought substantial relief to clinically depressed adults. Other studies credited weightlifting with curbing depression. Ditto for yoga.

Exercise can also ease anxiety - a possible boon for your skin. Aside from the rosy glow, alleviating anxiety may lessen flare-ups of acne and eczema, according to the University of Cincinnati's sports dermatology clinic.

Picking up the pace

Jay Alberts, a Cleveland Clinic neuroscientist, was riding a tandem bicycle across Iowa in 2003 and picked up the pace to 80 to 90 rpms. That was double what his cycling partner, who had Parkinson's, did on her own.

To his surprise, she remarked: " 'When I'm on the bike, it doesn't feel like I have Parkinson's.' " And her handwriting - the tiny script that is typical of people with Parkinson's - became more normal during the multiday trip, Alberts said.

Back in the lab, Alberts studied how other Parkinson's patients responded to forced increases in activity. His team eventually found increased connectivity between parts of the brain responsible for motor ability.

"Parkinson's robs someone of control," Alberts said. Exercise "allows them to have some control."

Rock Steady Boxing started in Indianapolis in 2006, and the nonprofit now trains therapists around the country in its technique.

The Bala Cynwyd-based Parkinson Council funded training for therapists at Penn's Parkinson's Rehabilitation Center, which began its program two years ago, and for Joey DeMalavez more recently. The personal trainer to celebrities and athletes started working with Parkinson's patients at his Joltin' Jabs gym in May.

No one is saying that boxing is a cure. No one even knows for sure how it works. But as the fighters persevere, many report less depression and more mobility; their facial muscles, frozen masklike by the disease, form smiles.

"Every time I punch the bag, I feel like I'm fighting Parkinson's," said retired gym teacher Fred Rosenfeld, 70, a few weeks into his training at Joltin' Jabs.

Bryna Spinell, 68, another retired teacher with Parkinson's, has been training in Penn's program since shortly after it began. She has her own boxing gloves. Pink. She wishes she'd started sooner.

"I tell my kids," Spinell said, " 'You have to be active. It will save your life.' "