But as I researched the issue, I learned that there are reasons runners should slow down. I don’t mean slowing down during this hot, humid weather, when the moisture in the air makes it difficult to breathe and the heat makes it difficult to regulate body temperature. And I don’t mean slowing down to avoid injury or aid recovery. I mean slowing down with the goal to make yourself a better and even faster runner.
“When you’re running slowly, and your injury risk is lower, you can run more often, more miles, and build up slowly,” according to Claire Bartholic, a coach at Runners Connect, an online community of runners and coaches. But running slowly also allows your body to improve the energy system most essential to running: your aerobic energy system.
Your body relies on a few different 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, for example, or even a 5K or a run around the block, this is the energy system you want to develop, says Bartholic, who is a competitive masters athlete herself. And to develop it, you should run at a pace where your muscles can get plenty of oxygen.
When you’re sprinting, or running so fast that you’ve reached your aerobic threshold, or, based on your level of conditioning, when your body runs out of oxygen, it switches over to another energy system — your anaerobic energy system. Without enough oxygen, your muscles convert glycogen into energy less efficiently, and you fatigue more quickly, which eventually forces you to slow down or stop. So if all your runs are too fast, according to Bartholic, you’re not developing the power system that you need for 97 percent of a race. “Your maximum aerobic benefit is going to be running slowly.”
Of course, “ ‘slow’ is highly individualized and varies a lot between people,” according to Carwyn Sharp, chief science officer at the National Strength and Conditioning Association in Colorado Springs. That means you need to calculate how slowly 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 .7 and subtract this number from 208, which would then be your estimated heart rate maximum, or the number of beats per minute that your heart is likely to be able to beat at its fastest.
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 says. For a typical 60-year-old like me, whose maximum heart rate is 166, a slow run means keeping my heart rate between 97 and 116.
A less-scientific approach would be to use the “talk test,” Sharp says. “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.”
In summer when it’s hot and humid, you’re putting the same amount of stress on your body when you run slow as you would if you were running fast in ideal, cool conditions, according to Bartholic, so you’ll want to slow down even more to avoid overstressing your body and risking injury. Running in hot weather is sometimes called “the poor man’s altitude training,” Bartholic says, because it can simulate the kind of stress your body experiences running in high altitudes. The benefit of this kind of training is that when you’re back at sea level, or back in cooler temperatures, your pace tends to be faster with less effort.
This can be helpful if one of your goals is to participate in a fall race. And, according to Sharp, there is research showing that aerobic training can increase both ligament and tendon strength, which could help prevent injury, especially during marathon training.
Still there are obstacles — mostly societal — to running slow, according to Jennifer Sacheck, chair of the exercise and nutrition sciences department at the Milken Institute School of Public Health at George Washington University. The time factor is the biggest hurdle to doing slow runs, Sacheck says. “Physical activity has been engineered out of our day, so people have to plan their physical activities. So, planning an hour or an hour and half is much more difficult than saying, ‘I’m going to bang out 10 minutes.’ ” Sacheck suggests that one way to fit in a long, slow run might be to run to work or home after work.
Another hurdle is thinking that running slow might be “less manly,” according to Sacheck, or that you can’t get an endorphin rush from taking it slow. “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.” And, she says, most people can get the same endorphin rush from about 35 minutes to an hour of slow running as they can from 10 minutes of sprinting.
Lifelong distance runner and Road Runners Club of America certified distance coach, William Etti, 41, of Burtonsville says he was never a fast runner, but through slow running training was able to improve his marathon time from 5 hours and 51 minutes in 2014 to 3 hours and 57 minutes in 2016. He thinks this is because he began doing more medium- to long-distance runs when he ran at a conversational pace with the Montgomery County Road Runners Club and when he ran on his own without looking at his pace. “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.”
After a car accident injured his knees in 2017, Etti says now he runs slow for longevity in the sport. His hope is that “by running slower, I would be able to keep pain down and keep running in my life, because it’s a part of me I do not want to lose.”