Want to run faster? Start by slowing down.

Running slowly allows your body to improve the energy system that is most essential to running: your aerobic energy system, said Claire Bartholic, a coach at Runners Connect, an online community of runners and coaches.

Your body relies on several energy systems to get you up and moving. For any sustained movement, it uses your aerobic energy system, meaning it creates energy with oxygen. Oxygen helps the muscles convert fat, protein and glycogen (the form of glucose stored in your liver and muscles, which your body generates from the carbohydrates you eat) into energy.

If you want to be able to finish a marathon — or even a 5K or a run around the block — this is the energy system you want to develop, Bartholic said. And to develop it, you should run at a pace where your muscles can get plenty of oxygen.

When you’re running so fast that your body runs out of oxygen, it switches over to another energy system — the anaerobic energy system. Without enough oxygen, your muscles convert glycogen into energy less efficiently, and, as a result, you fatigue more quickly. Having this happen day after day can impede your training.

Lifelong distance runner and Road Runners Club of America coach William Etti was never a fast runner, he said. But through slow running training, he was able to improve his marathon time from five hours and 51 minutes in 2014 to three hours and 57 minutes in 2016.

“You think you have to do a lot of speed work to get faster,” he said, “but after doing most of my runs at a slow pace, my marathon finish time was much faster.”

Of course, “slow is highly individualized and varies a lot between people,” said Carwyn Sharp, chief science officer at the National Strength and Conditioning Association in Colorado Springs. That means you need to calculate the pace you need to run to maximize your aerobic capacity or, in other words, to maximize the amount of oxygen your body can use before it switches to anaerobic energy.

First, Sharp suggests this updated method for estimating your maximum heart rate (forget the old 220-minus-your-age equation): Multiply your age by 0.7 and subtract the result from 208, which would then be your estimated heart rate maximum.

From there, you can look at your heart rate during exercise. For a slow run, most recreational runners will want to stay within about 60 to 70 percent of their maximum heart rate, Sharp said. For a typical 60-year-old, whose maximum heart rate is 166, a slow run means keeping the heart rate between 97 and 116.

A less-scientific approach would be to use the “talk test,” Sharp said.

“It’s like the tale of ‘Goldilocks and the Three Bears.’ If you can’t have a conversation with your running buddy, then you’re running too fast. If you can talk easily but are barely sweating, then you’re probably too slow. If you can talk fairly easily as you are running but have to pause occasionally in the conversation to catch your breath, that’s going to be fairly spot on.”

One of the biggest obstacles to running slow is the time factor, said Jennifer Sacheck, chairwoman of the exercise and nutrition sciences department at the Milken Institute School of Public Health at George Washington University in Washington, D.C. Running slower means you need more time to cover the same amount of distance as when you run faster, and with many of us struggling to fit workouts into busy schedules, that can be difficult.

Another factor, especially with men, is the thinking that running slow is “less manly,” Sacheck said. “For guys especially, who stereotypically turn to ‘manly’ activities such as speed workouts, I’ll tell them they can ‘man it up’ by wearing a backpack or by going out for a long adventure hike.”