There are reasons runners should slow 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, Colorado.
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: 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 said for a typical 60-year-old, 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."
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.