Mark Cucuzzella, M.D., has never been one to chase records, but at the age of 51, the runner and family physician from Shepherdstown, West Virginia, now finds himself in the hunt. On the line? Beating a 33-year streak of sub-3:00 marathons.

Races - Places We earn a commission for products purchased through some links in this article That applies to running.

From Runners World for New Balance.

“My times today may not be the fastest among 50-year-olds,” he said. “But fast times mean nothing if you’re injured. There aren’t many others my age still out there hitting consistent times, year after year.”

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Even if he hits goal at the Marine Corps Marathon and ends up breaking the streak, that’s just icing on the cake for the unassuming physician.

There was a time when Cucuzzella thought he might not ever run again. Back in 2000, he underwent surgery for arthritis in his feet. While the procedure brought pain levels down some, he still struggled. Other doctors kept telling him to stop running, but Cucuzzella knew that wasn’t the answer. Undeterred, Cucuzzella began a journey to find pain-free running.

Cucuzzella’s head-first leap “down the rabbit hole,” as he says, led to years of research and learning, and with the release of his upcoming book Health & Injuries , the now pain-free runner shares what he’s learned to date. His mission, he says, is to make running safer and more fun for anyone who wishes to participate. Here are three key takeaways that you should use in your training right now.

Posture and Form Matter

That applies to running and in regular life, says Cucuzzella. Since adopting more sedentary lifestyles, many runners suffer chronic back pain, poor posture, and incomplete breathing, or breathing from your upper chest rather than from your diaphragm and abdomen.

But you can fix it: “Even if you have a full-time desk job, you can reverse the damage caused by sitting for hours on end,” he says.

To begin, Cucuzzella recommends a standing—or even a treadmill—desk. But that doesn’t mean staying locked into those positions all day either.

“Mix things up. Walk around, stand on one leg, squat, kneel—anything to vary your positions,” he says.

Hand-in-hand with movement throughout your day is better breathing, says Cucuzzella. “You can’t have good posture if you’re not belly breathing,” he says.

In the end, your posture should involve hips over ankles, shoulders over hips, ears over shoulders and most of your weight in your heels. You shouldn’t slouch at the shoulders or stand with your knees bent.

Enough work on this when not running will carry over to the sport. And that’s important, since proper form and breathing will result in relaxed running.

Build Endurance

Learning to become a “butter burner” should be an endurance athlete’s goal, says Cuccuzella. His recommendation? Build a firm base of endurance that allows your body to tap into fat, its most plentiful and efficient form of fuel.

To get there, Cucuzzella says, you need to start by spending all your running time in a true aerobic zone. Long a fan of Phil Maffetone’s “180 minus your age” heart rate formula, the physician recommends using this baseline for all your running, until you’ve reached a proficient speed at that low heart rate. This is generally a period of few months and without question, requires patience.

Then, if you want, you can add on some speedwork. Cucuzzella himself, however, sticks mostly to short sprints and drills, often daily. Four to six weeks out from a race day, he will add in some marathon race pace, although this still occupies a very small percentage of his overall training.

Nail Your Nutrition

Going hand-in-hand with fat-burning development is your nutrition approach. Cucuzzella is a proponent of rethinking our culture’s established dietary principles. In his book, his chapters on nutrition aim to arm runners with knowledge, awareness and discipline when entering a grocery store.

His guidelines? Avoid added sugars; add plenty of healthy fats and protein like avocado, quality meats, eggs and nuts; eat the rainbow of colorful vegetables; eliminate processed foods and refined grains or flours; remove all trans fats and vegetable seed oils; and abandon all complicated or overly restrictive diet regimens.

And then there’s quantity: “Don’t go hungry. Eat until you are nearly full and not more,” he said.