Working hard is not the same as working out

Let’s say your daily routine has you hauling 50-pound bags of mulch, laying railroad ties, mowing lawns and bending over to weed gardens from dawn to dusk. As you load your truck and head home to collapse on the couch, a middle-aged guy in spandex streaks by on his bike, going home after a day of taking meetings, talking on the phone and staring into a computer screen.

Who’s more likely to have a heart attack?

Health doesn’t always play fair, a group of German investigators recently found: It’s the landscaper-by-day, couch-potato-by-night who’s more likely to develop coronary heart disease, not the bicycling desk jockey. And it’s not a case of rich man, poor man -- the well-established relationship between income and health. In interpreting their results, the researchers took into account differences in their subjects’ socioeconomic status.

The authors said their study provides further evidence that when it comes to protecting the heart from inflammation and disease, working hard is no substitute for working out. Working hard may burn more calories and work the muscles harder, because most job-related physical strain calls for short bursts of strength and activity. But only working out strengthens the muscle that matters most -- the heart. Most leisure-time exercise, such as bicycling, swimming or walking, will raise the heart rate moderately and keep it up for a longer time.

The study, which builds upon growing research on different paths to fitness, suggests that for people whose jobs involve hard physical labor, the heart may be among the muscles strained, with bad consequences for its health. Across the spectrum of physically demanding jobs, however, the value of leisure-time physical activity was clear: It reduced the odds of coronary heart disease.

Two cardiologists and two epidemiologists looked at nearly 800 people 40 to 68 years of age, about 40% of them with confirmed heart disease, to discern the relationship between heart disease and exercise, either job-related or off the clock. They found that among those who experienced heavy work-related physical strain, the odds of having coronary heart disease approached 5%, a rate almost five times higher than among those with jobs that involved no physical strain.

But among all the workers, regular leisure-time physical activity -- even just one to two hours a week -- lowered the odds of developing heart disease. A brief walk or bike ride helped lower the heart-disease risk among those engaged in hard daily labor.

The leisure-time exercisers also showed far lower levels of blood chemicals that indicate existing or developing heart disease: C-reactive protein, serum amyloid A, interleukin 6 and intercellular adhesion molecule 1, the researchers found. The study is published in the May 26 issue of Archives of Internal Medicine, a medical journal.

Although even a little exercise -- less than an hour a week -- drove down the odds of heart disease, more was clearly better. Those reporting leisure-time physical activity for more than two hours a week showed the greatest reduction in the odds of heart disease and its ominous markers.

Dr. Wolfgang Koenig, a cardiologist at the University of Ulm in Germany and one of the study’s authors, observed that there seemed to be a crucial difference between the exercise that the study’s “strenuous job” subjects got during their work day and the extracurricular exercise done by others. “One explanation is that, usually, physical activity outside of work is endurance training,” said Koenig. “Physical activity at work is different: It’s isometric work.”

Generally, working out seems to deliver the strongest benefits to those who are at greatest risk of heart disease, Koenig said. But his study could not determine whether it actually leveled the playing field among all workers.

The research confirms the findings of a study on Finnish male twins published in 2000, which first suggested that only leisure-time physical activity prevented coronary heart disease; occupational physical activity did not.

Dr. Michele Hamilton, a UCLA cardiologist, said the study has important take-home messages for all workers. First, she said, don’t get intimidated. Build an exercise program that gets your heart rate up for at least 20 minutes, four or more times a week, whether you have a job sitting at a computer or one that keeps you moving all day. Don’t make the mistake of thinking that a physically demanding job alone will keep heart disease at bay, Hamilton said. You need the sustained heart-pumping activity that you get during a brisk walk or a bike ride on a regular basis.

Also, keep up the routine, she said: Fitful bouts of exercise don’t do much good, and they can strain the heart and cause a heart attack, even if you regularly lift steel girders or run up staircases carrying heavy equipment.

Perhaps exercise done outside of work may just be more fun, Hamilton and Koenig say, and thus may count more than work-related exertions when it comes to protecting the heart.

“We know that continuing physical leisure-time activity affects your mood,” said Koenig, and that, in turn, boosts the immune system.