Brisk walk really may be just as good as a run…

Walking really is just as good for you as running – but only if you compare it in terms of calories burned and not merely on time spent, researchers reported on Thursday.

Studies have gone back and forth on the question for years – is a stroll as good as a run? Does a brisk walk strengthen your heart as much as a pounding jog?

Paul Williams of Lawrence Berkeley National Laboratory in California and Paul Thompson of Hartford Hospital in Connecticut think they’ve answered the question, finally. They did it in the best way possible, by comparing tens of thousands of runners to tens of thousands of walkers.

The answer is what common sense would dictate – it’s how much a person exercises in terms of energy spent, not how long he or she spends exercising, that matters.

“It takes longer to walk a mile than to run a mile. But if you match them up on the energy expended, they are comparable,” Williams said in a telephone interview. “If you do the same amount of exercise – if you expend the same number of calories – you get the same benefit.”

They studied 33,060 runners taking part in the National Runners’ Health Study and 15,045 walkers in the National Walkers’ Health Study. They measured their blood pressure, blood sugar and cholesterol at the beginning, and then watched for six years to see who got diagnosed with high blood pressure, unhealthy cholesterol or diabetes.

People who exercised equally in terms of energy output got the same benefit, regardless of whether they ran or walked, Williams and Thompson report in the American Heart Association journal Arteriosclerosis, Thrombosis and Vascular Biology.

Williams said it made sense to study dedicated walkers and runners, because they usually keep careful track of distance and time spent running or walking. Most other people have trouble accurately estimating how much time and effort they spend exercising, he says.

They used a measurement called a MET. “One MET is how much energy you expend when you are sitting,” Williams said. Walking at a brisk pace burns 3.8 METS, or 3.8 times as much energy spent sitting for the same time. Running burns anywhere between 7 and 12 METS.

One MET of walking is roughly equivalent to a kilometer, or just over half a mile, Williams estimates. But running is less efficient than walking, so runners do tend to burn more calories over the same time.

“A person would need to walk 4.3 miles at a brisk pace to expend the same amount of exercise as running 3 miles, and it would take about twice as long (an hour and 15 minutes by walking instead of 38 minutes by running),” Williams says.

In general, the runners were younger and fitter than the walkers were. The male runners were 48 on average, versus 62 for the walkers; female runners were about 41 on average versus 53 for the walkers. The runners were 38 percent less likely to develop high blood pressure, 36 percent less likely to have high cholesterol and 71 percent less likely to develop diabetes than the walkers.

But this all seemed to be because the runners actually exercised more than the walkers did, Williams said.

“We have sort of known this all along,” said Dr. Gerald Fletcher, a cardiologist at the Mayo Clinic in Jacksonville, Fla., who was not involved in the study.

Running can burn more calories in a shorter time, so it’s good for people who are crunched for time. “But walking is certainly easier than running,” Fletcher said. “As long as people get out there and do it.”

The Institute of Medicine says Americans should try to get at least an hour of moderate exercise such as brisk walking every day to stay healthy. The Heart Association has similar guidelines.

Maggie Fox, Senior Writer         NBC News

April 4, 2013 at 4:03 PM ET