‘I’m an Ironman Athlete and Heart Doctor—Here’s How I Design My Workouts for the Greatest Cardio Benefits’

Ironman races and heart surgeries have a lot in common. At least that’s according to likely one of the few people in the world who would know: Jeffrey H. Newman, MD, a cardiothoracic surgeon with the Palm Beach Health Network and a retired triathlete.

“Our operations are anywhere from two to five hours, and you have to remain focused on the task at hand and be efficient,” says Dr. Newman, who last completed an Ironman in 2010. “So with triathlon, it was very easy to hone that concentration and that focus.”

Another thing he’s honed over years of heart surgeries and Ironman triathlons? How to design a training plan—or even just a workout routine—for maximum cardio benefits. Here, Dr. Newman shares how his expertise in heart health has shaped his approach to exercise, and his advice for optimizing your workouts to strengthen your heart, whether you’re an Ironman or a casual gym-goer.

Consistency is key

Ironman triathlons consist of a 2.4-mile swim, a 112-mile bike ride, and a 26.2-mile run (yep, that’s a literal marathon tacked on to the end). While training for his races—including the exclusive Ironman World Championships in Kona, Hawaii—Dr. Newman would exercise twice a day on weekdays, and go for long runs, bike rides, or swims on weekends. “Training for an endurance race means you have to prepare your body to be in that slogging state of exercising all day,” he says.

You definitely don’t need to be logging 20-plus hours of exercise a week to boost your heart health. But, says Dr. Newman, you do need to be consistent. Five to seven hours a week over four to five days, with a mix of aerobic and strength work, “is probably adequate to keep your heart strong,” he says. “If you exercise intermittently, or if you are a weekend warrior, you’re not really getting the benefits you think you are.”

Most days, keep things easy

One tenant of Ironman training that everyone can learn from? The vast majority of workouts are done in heart rate zone two, meaning they should feel relatively easy and sustainable for a long period of time. Zone two work builds endurance and aerobic capacity, gradually making your heart more efficient in carrying oxygen to your muscles, which allows you to accomplish more in your workouts with less effort.

While Dr. Newman says higher-intensity training has a time and a place, he says zone two training will be more beneficial long-term for the heart than workouts that have your heart rate spiking and then resting.

The heart needs rest days, too

Though the heart is technically an organ, it primarily consists of muscular tissue that keeps it pumping. So just like your other muscles, which need time after workouts to rest and rebuild, the heart needs recovery days, too, says Dr. Newman.

A rest day doesn’t have to mean doing absolutely nothing, he says, but it shouldn’t involve anything intense that gets your heart rate anywhere above a low zone two. This is for the same reason that you don’t want to overtrain your other muscles—especially if you have a race on the horizon: “If you don’t allow your heart or your legs to recover from hard training days, you end up bonking,” says Dr. Newman, “or not going as fast as you want to because you never achieved the maximum benefit from your exercise.”

Because remember: It’s when we rest that our muscles rebuild and actually grow stronger. So if you never let your heart rest, you’ll never get the max benefit of the time and work you put into strengthening it.