Exercise Helps the Heart, But Can Manual Labor Hurt? By Batya Swift Yasgur, MA May 12, 2021 -- All exercise is not created equal, and the exercise you get during leisure time is better for your heart health than on-the-job exercise. In fact, on-the-job physical exercise may actually be harmful to heart health, according to a study published in April. The difference in leisure-time exercise and workplace exercise is a phenomenon sometimes called the “physical activity paradox,” lead study author Andreas Holtermann, PhD, of the National Research Center for the Working Environment in Copenhagen, Denmark, tells WebMD. “Our findings suggest that clinicians, patients, and managers ought to be aware that having a manual physical activity-demanding job might not improve fitness and health of the workers, while health-enhancing leisure-time physical activity ought to be promoted,” he says.