Your heart is racing, after all.

Photo: Getty/Randy Risling 

Amusement parks, with their death-defying rides and delicious treats, are one of the best parts of summer. We know spending time outside is definitely good for you, but does the whole going on rides thing count as a workout? Even a little bit? After all, your heart is pounding on every roller coaster you ride and that's got to count for something cardiovascular, right?

Not really, says Nicole Weinberg, M.D., a cardiologist at Providence Saint John's Health Center in Santa Monica-coincidentally just an hour away from three of the country's most popular amusement parks.

"Your heart is racing after a scary ride because of adrenaline and that can actually be bad for your heart," she says. "There's a reason for all those signs warning people with heart problems and pregnant ladies to stay off."

When your heart rate increases suddenly due to a rush of adrenaline, it can feel fun. But it actually puts a lot of stress on your heart-and not in the good way that, say, running or biking does, she explains. Adrenaline is a "stress hormone" released only in times of danger, causing a fight-or-flight response that is helpful in the short term but can cause long-term damage. When your heart rate increases from cardiovascular exercise (rather than from adrenaline), that strengthens the heart muscle over time, making it stronger, healthier, and better able to withstand stress. (Still, cardio does add extra work to the heart. So if you are at risk for any heart problems, you should talk to your doctor before starting an exercise program.)

For healthy people, a burst of adrenaline is not a big deal and your heart can handle the occasional roller coaster–induced jolt. But for others with health problems, particularly those who already have extra pressure put on their heart from cardiovascular disease, high blood pressure, or pregnancy, it can be very harmful. It's not super common, but there have been reported instances where riding a ride has triggered a heart event in someone, she adds.

Plus, even if the heart-rate increase was beneficial in some way, most rides last less than two minutes-not exactly a workout, she says.

But that doesn't mean your day at Disney can't be good for you in other ways. "Walking all day around the park is a great way to get in some extra exercise," Dr. Weinberg says. You can easily end up walking 10 to 12 miles over the course of the day-almost a half marathon!

In addition, the combination of being on vacation and riding some relaxing rides can help you de-stress big time, which is one of the best things you can do for your heart health, she says.

Bottom line? Walk whenever you can, skip the fast food, and make time to ride the giant swings and you can totally count your amusement park experience as a workout (mostly).