Roller coasters can be hard on the heart

When a roller coaster advertises heart-stopping action, it may not be an empty boast.

On average, four people die each year from roller coaster rides. About half of the deaths are caused by accidents, inebriation or foolish behavior, and mechanical failure. The other half are due to medical conditions, mostly heart attacks, lethal arrhythmias, bleeding into the brain or ruptured blood vessels.

Two studies of roller coaster riders showed that the heart starts pounding almost as soon as the cars begin their first climb. Peak heart rates among the generally young and healthy volunteers averaged 155 beats per minute, with some riders hitting 90 percent of their maximum heart rates in under a minute. Blood pressure also spikes.

In one of the studies, published in 2007 in The Journal of the American Medical Association, about half the volunteers had irregular but harmless heartbeats for several minutes after the ride had ended. Whether the irregularities would be harmless in people with heart disease is an open question.

It's conceivable, though unknown, whether newer rides might have even greater effects on the cardiovascular system. Some of the newest rides top 100 miles an hour and reach G-forces similar to those experienced at liftoff by space shuttle astronauts.

The vast majority of people who loop-the-loop walk away from the ride with a thrill and nothing more. But there's a reason why roller coasters and other rides prominently post a warning for folks with heart disease.