Why the Treadmill May Seem Much Easier Than Running Outside (but It Really Isn’t)
Is a treadmill harder or easier than running outdoors? Survey runners, and you’ll get a variety of opinions about which seems harder or easier, but the basic physical principles of running are the same in both. (I assure you.) So why do people accustomed to treadmills suddenly start running slower outdoors? I’ll explore the factors at play here and how to adapt to enjoy both treadmill and outdoor running.
Why running on a treadmill sometimes seems harder than running outside
If you find running on a treadmill more challenging than working out, you probably already know the reason: it’s boring . There’s nothing to distract you from your own efforts and the glittering numbers showing how little progress you’ve made. This is a problem we can, over time, train our brains to solve for us , whether through distractions, mindfulness, or simply gratitude for not being outside in bad weather.
The treadmill does not move your legs.
From a physics perspective, running on a treadmill is virtually identical to running outdoors under identical conditions. The runners’ claim that a treadmill “moves your legs” is incorrect. Running is the act of pushing off the ground to propel yourself forward relative to the ground. If the theory that “a treadmill moves your legs” were true, wouldn’t we have to consider the rotating Earth a kind of treadmill? And therefore, running west would be 2,000 times harder than running east?
In reality, staying in place on a treadmill moving at 6.5 mph requires the same amount of effort as moving forward at 6.5 mph on a level, stable surface. In other words, in both cases, your muscles must push with enough force to propel you 6.5 mph faster than the ground. The difference in the sensation of running on a treadmill isn’t due to physics.
If you run very fast, you need to add 1% incline.
Then there’s the issue of air resistance. Some runners claim that to simulate outdoor wind resistance, they need to set the treadmill incline to 0.5% or 1%. Even on a windless day, the body has to exert effort to keep moving. A slight incline on the treadmill is intended to simulate this additional effort.
But this is only true at a pace of 7:30 minutes per mile (8.0 mph) or higher. At slower speeds, “the difference is so small it doesn’t matter,” a scientist who studied the issue told Runner’s World . So, if you’re running at 6 mph, you don’t need to worry about accounting for air resistance. Now that we understand the physics, let’s talk about why running on a treadmill often feels easier than running outdoors.
The treadmill may feel easier because it regulates the pace of your workout.
Pace is perhaps the most important factor (besides weather) that explains why outdoor running feels harder for someone accustomed to treadmill running. On a treadmill, you choose a pace, input it into the system, and then continue running at that pace, whether you think about it or not.
But outside, you don’t know your starting speed. Even if you rely on your watch to show your current pace, it may take a while for it to react and give you the correct number. It’s easy to start too fast, especially if good music is playing or you’re eagerly anticipating the start (or end) of your workout.
So, you, a treadmill runner, head out for an outdoor run without a clear idea of your speed, and you might feel tired after a few minutes. Meanwhile, outdoor runners learn to sense their pace out of necessity. They know to listen to their body, not just look at the numbers, to determine if they can run at a pace they can maintain throughout the entire workout. Luckily, this skill is learnable! Just run outdoors at least occasionally and pay attention to your breathing and effort level.
The treadmill is not affected by the weather.
If all your treadmill workouts take place in a gym at 20 degrees Celsius, the experience will be roughly the same. But outdoors, we often face heat, wind, humidity, rain, snow, ice, and other unpleasantries.
Heat slows us down significantly , especially if we’re not used to it. (We develop a certain adaptation to heat over the summer.) Humidity combined with heat makes things even worse. Your body doesn’t cool down as well through sweating, so you get hot and continue to overheat . On a hot day, it’s normal to slow down with each mile.
Strong winds can also slow you down (when you’re running against the wind) or speed you up (when you’re running downwind). Ice can force you to slow down and watch your step. Snow can make you work harder because your feet sink into the ground and you have to fight to get them back up.
On the other hand, a cool, dry day is better for your performance than a stuffy gym. Ideal running weather (in my opinion) is around 10 degrees Celsius, windless, and overcast. Most people will run much faster and feel better in these conditions than on a treadmill at room temperature.
There are no unexpected hills on the treadmill.
If you live in a completely flat area, you can skip this section. But many of us live in areas with hills—large ones, small ones, maybe even mountains. On a treadmill, you can choose the incline. Outdoors, your options may be limited.
I live in a hilly area, so even my “flat” outdoor routes aren’t exactly flat. A standard treadmill is my only truly flat option. Even gentle hills can add extra strain on a long run, forcing you to work harder on the climbs but never quite returning to your previous speed on the descents.
The treadmill has a more predictable surface.
A treadmill has only one surface. Every step is on a flat surface. Each step has the same softness or hardness. Outdoors, however, there’s a much greater variety of surfaces.
Even during a typical city run, you’ll have to navigate curbs, slightly sloped pavement, uneven road edges, pebbles, scattered debris, and the occasional patch of grass or dirt. If you run along forest trails, you’ll encounter hard-packed dirt, mud, soft grass, fallen leaves, rocks, branches, logs, small streams to jump over, ruts carved by mountain bike wheels—you get the idea. Each of these obstacles requires your feet to land and push off slightly differently.
Various types of outdoor running are good for your legs, but can cause fatigue in the small muscles of your feet and calves if you’re not used to it.
How to train for an outdoor race if you prefer to run on a treadmill.
It’s perfectly acceptable to train on a treadmill even if you’re training for an outdoor race, and in some situations, it may be necessary. A treadmill allows you to train even in bad weather, when childcare isn’t available at the scheduled time, or for a variety of other reasons.
It’s important to run outdoors at least occasionally . If you’re training for a marathon, try to do long runs outdoors, even if some short runs and speed workouts require a treadmill. Get outside whenever possible. This way, you’ll adapt to the weather, train your legs on different surfaces, and develop the muscles and mental strength needed to tackle hills .