While we all know that exercise is healthy, some research has begun to raise questions about whether its possible to overdo a good thing. A few studies have found that long-time endurance athletes can have a heightened risk for abnormal heartbeats, and even for scarring of the heart muscle. Likewise, experiments with lab animals have found possible links between prolonged, extremely strenuous running and undesirable changes in the structure and function of the heart.
But the actual incidence of runners having a heart attack during a marathon race is vanishingly small, a finding that seems to suggest that marathon training cant be excessively hard on hearts.
Such inconsistencies in the data about prolonged endurance exercise and heart health prompted researchers to wonder if past studies had been too imprecise. It is difficult to isolate the risks associated with strenuous exercise from other lifestyle factors, said Beth Taylor, an assistant professor in the health sciences department at the University of Hartford who led the new study, which was published last month in BMJ Open. Runners whose hearts seemed to have been affected by their exercise habits might also have smoked, gorged on junk food or otherwise imperiled their hearts, separately from how much they worked out.
So Dr Taylor and her colleagues decided to better control for such factors by studying marathon runners along with their domestic partners, who presumably would be sharing their lifestyles if not their physical exertions. If cardiac health differed among these couples, the scientists felt, they could reasonably conclude that training had played a role, since so many lifestyle factors would be the same.
Forty-two runners, along with their spouses or partners, agreed to participate in the study. Half of the runners were women. Their ages ranged from 33 to 59, although most were in their mid- to late 40s. Their partners were around the same age but considerably less active, averaging fewer than two sessions of moderate exercise per week. Many did not formally exercise at all, although most reported frequently walking, gardening or undertaking other types of moderate activity.
The day before the 2012 race, the racers and their partners filled out questionnaires about their exercise and health histories. Scientists then drew blood to determine the volunteers vital signs. Finally, each volunteer underwent a heart scan to reveal the buildup of arterial plaques, an indication of heart disease.
Not surprisingly, the marathon runners were significantly thinner than their partners, although few of the partners were overweight. The runners also generally had lower blood pressure, heart rates, bad cholesterol and other indicators of cardiac health.
But running did not insulate the racers altogether from heart disease, the scientists found. Some of the racers, particularly the oldest ones, carried large deposits of plaques in their arteries, a worrying sign. These older racers also tended to have the highest tallies on a numerical assessment of heart attack risk called the Framingham risk score, which considers medical and lifestyle factors that, along with genetics, can contribute to the development of atherosclerotic plaques.
Over all, Dr Taylor said, the studys data suggests that if youre training for a marathon or otherwise doing frequent and prolonged endurance exercise, youre probably not hurting your heart and are likely strengthening it. But you should be aware of your past health habits and family history.
Perhaps the more surprising takeaway of the study, Dr Taylor said, is that marathon trainings cardiac benefits may be transferable. The spouses of the runners were quite healthy, too, she pointed out. More so than many people, they walked and moved around frequently, and had generally robust cardiac risk profiles. Dr Taylors conclusion: if you want improved heart health but cant be a runner, marry one.
- GRETCHEN REYNOLDS