Jogging is one of those activities that seems to embody the concept of healthy physical activity. A new study from Denmark may prompt a rethinking of the benefits of strenuous jogging. Researchers with the ongoing Copenhagen City Heart Study found that, compared to healthy but inactive non-joggers, the death rate of light joggers was 90% lower. No surprise there. But the death rate for strenuous joggers was no different than that of sedentary non-joggers. In this study, the most beneficial exercise was jogging at a slow or moderate pace two to three times a week for a total of 60 to 145 minutes. This one study certainly shouldn’t change the current recommendations for physical activity. But it helps debunk the “no pain, no gain” myth of exercise and supports the idea that any activity is better than none—but there may be an upper limit.

If you are a sociable soul, here’s some interesting news about exercising with others: A study published online in the British Journal of Sports Medicine shows that being part of an outdoor walking group can improve health in many ways, including improvements in blood pressure, resting heart rate, total cholesterol, body weight, body fat, physical functioning, and risk of depression. In addition, people who were part of a walking group tended to keep exercising and not slack off. The findings are interesting because walking group participants reaped health benefits even though many of the groups did not meet international guidelines for moderate activity. This supports the idea that any activity is better than none.

The standard recommendation for exercise is at least 150 minutes of moderate-intensity activity each week. But that may not be the best recommendation for everyone, especially those who are older and have trouble exercising, or those who don’t exercise at all. If we think of exercise as a spectrum, with no activity on one end and 150 minutes or more a week on the other end, there’s a continuum in between. Getting individuals to move along that continuum, from no exercise to a little, a little to more, and so on, is an important goal. New research on the hazards of sitting for prolonged periods should get all of us to sit less and stand or move more.

More than half of the average person’s waking hours are spent sitting: watching television, working at a computer, commuting, or doing other physically inactive pursuits. But all that sitting could be sending some to an early grave. That’s the conclusion of a Canadian study published in this week’s Annals of Internal Medicine. People in the study who sat for prolonged periods of time had a higher risk of dying from all causes — even those who exercised regularly. The negative effects were even more pronounced in people who did little or no exercise. In addition to premature death, the study documented higher rates of type 2 diabetes, cancer, and cancer-related deaths in very sedentary people. If you sit for work, try standing or moving around for one to three minutes every half hour. Better yet, think about working at a standing desk. At home, stand when watching TV or talking on the phone.

Even if you don't swim, exercising in the water can improve your strength, balance, and cardiovascular fitness. And it's easier on your joints.

Quick-start strength-training program

Work out at home or in your office to improve muscle mass.

Muscle mass tends to diminish with age, so making strength training part of your overall exercise regimen is very important. And while many people assume that effective strength-training programs require joining expensive fitness clubs and lifting heavy weights, there are plenty of strength-building exercises you can do at home and at work with little or no special equipment. "You really can strength train without the big machines and get effective results, without spending a lot of money," says Elissa Huber-Anderson, a physical therapist at Harvard-a-ffiliated Massachusetts General Hospital.

Try some low-impact activities to ease into an exercise routine.

You know that regular exercise is good for your heart. But only about half of American adults manage the 2.5 hours per week of moderate exercise (such as brisk walking) recommended by the federal physical activity guidelines. Being too busy is a common excuse, but there are bona fide reasons for not exercising. If you're recovering from a heart attack, are overweight, or are simply out of shape, 30 minutes of exercise a day may feel out of reach.

Q. What is better for my heart—a fast run on the treadmill for 10 minutes or 30 minutes of light cycling on a machine?

A. The benefit of exercise on heart health depends on the dose; in other words, the more the better. So, my answer to your question is "Why not do both?" Exercise of virtually any kind prevents heart attacks, strokes, high blood pressure, and diabetes.

Strength or resistance training challenges your muscles with a stronger-than-usual counterforce, such as pushing against a wall or lifting a dumbbell or pulling on a resistance band. Using progressively heavier weights or increasing resistance makes muscles stronger. This kind of exercise increases muscle mass, tones muscles, and strengthens bones. It also helps you maintain the strength you need for everyday activities — lifting groceries, climbing stairs, rising from a chair, or rushing for the bus.

The current national guidelines for physical activity recommend strengthening exercises for all major muscle groups (legs, hips, back, chest, abdomen, shoulders, and arms) at least twice a week. One set — usually 8 to 12 repetitions of the same movement — per session is effective, though some evidence suggests that two to three sets may be better. Your muscles need at least 48 hours to recover between strength training sessions.