Walking briskly, playing golf and mowing a lawn are sufficient for most people to reach a moderate level of exercise intensity. (bigstockphoto/GETTY IMAGES)

Our bodies are built for physical activity. Movement and regular exertion can trigger healthful changes in almost every cell type, tissue and organ system. Yet most American adults don’t get the minimum amount of aerobic exercise recommended by health and fitness experts and government guidelines. They suggest the equivalent of 30 minutes of moderate exercise, such as brisk walking, or 15 minutes of vigorous exercise, such as jogging or swimming, five days a week, plus two sessions of strength training to build muscle. Here’s how to conquer six obstacles that can get in the way of being active.

‘I never have enough time’

An easy way to begin is by making everyday routines more physically active. For example, try walking or bicycling to work, even if only partway, and take the stairs instead of the elevator.

If you join a gym, choose one that’s close to your home or workplace. To save even more time — not to mention money — skip the health club and set up a home gym. You don’t need fancy equipment: A few dumbbells or resistance bands, a stability ball and some exercise DVDs will do nicely.

‘I’m too old to start now’

It’s never too late to start exercising for aerobic fitness and muscular strength. No matter how old you are, your muscles will respond quickly to training.

If you’re a man over 45 or a woman over 55 and have been sedentary, get a physician’s clearance before jumping into a vigorous workout routine. Even for moderate exercise, it’s best to consult a physician first if you have arthritis, diabetes or another ongoing health problem, or if you’ve had symptoms such as chest pain, dizziness or shortness of breath.

‘My health isn’tgood enough’

Exercise is a proven treatment for diabetes, depression, high blood pressure, osteoarthritis, peripheral vascular disease and other problems common in older age. Many frail, chronically ill people and their caregivers assume, incorrectly, that exercise isn’t safe. But only a handful of health problems make exercise out of the question, such as retinal detachments, spinal instability, a recent heart attack and extremely advanced heart failure.

‘I’m too tired for exercise’

Expending energy to increase energy might seem like a contradiction, but dozens of clinical trials have found that starting a regular exercise routine can combat feelings of exhaustion, even among people suffering from chronic conditions associated with fatigue, such as cancer, fibromyalgia and multiple sclerosis. Aerobic activity helps rev up your metabolism, elevate your mood and improve your sex life. It can also help you sleep more soundly.

‘I’m not overweight.What’s the point?’

Sedentary living can make you more vulnerable to cancer, heart disease, osteoporosis, Type 2 diabetes and premature death, even if you’re lean. As a risk factor for heart disease, inactivity ranks about as high as smoking.

Exercise works in many ways to boost health and life span. Aerobic training and resistance exercise improve the body’s ability to manage blood sugar, which helps control diabetes. Exercise can lower blood pressure, in part by keeping artery walls supple, and weight-bearing exercise builds bones to help them resist osteoporosis.

‘It’s too painful’

Exercise doesn’t have to be overly ambitious to build aerobic fitness and muscle strength. Walking briskly is sufficient for most people to reach the moderate level of intensity recommended by fitness experts, as are playing golf, mowing a lawn and biking at a leisurely pace.

To trigger significant muscle growth, you need to work muscles at only 60 percent of their maximum capability. For most people, that means using a weight you can lift about 15 times. If joint pain is an issue, water aerobics can lighten the load and make it possible to move in ways that otherwise might be too painful.

Copyright 2011. Consumers Union of United States Inc.

Coming Thursday in Local Living

3Is strength training dangerous for pregnant women? MisFits columnist Lenny Bernstein digs into the research. And the Checklist offers health advice for September, including how to manage during the peak of asthma season and vitamins you’ll need more of as the sun shines less.