Reasons Why Running on a Treadmill Feels Slower

The best thing about treadmill aerobic exercises is you can do them under any weather element. So whether it's rainy, snowy, or sun high, running indoors will get you closer to your fitness goals. But why do I run slower on a treadmill?

Running outdoors is unpredictable, and the terrain changes with every stride. In addition, you can run against the wind, making you cool down or have wind assist. All these changes make it challenging to determine which form is faster.

What Do the Records Say?

Many online web results lean towards treadmill running being harder and hence slower. Most of these people offering reviews are treadmill owners. But no one can know for sure because professional athletes use treadmills for speed training.

But let's compare the half marathon treadmill time and the half marathon record time outdoors. The fastest time over the half marathon distance (13.1 miles) is 57:31.

The fastest time over the half marathon distance on a treadmill is 1:10:07. According to a 2015 study by Biology of Sport Journal, treadmill runners don't have air resistance when running at the same velocity as outdoor runners. This makes indoor runners gain a better running economy. But with a slight 1% treadmill incline, you can compensate for the difference in energy cost, which changes the tide towards outdoor runners, giving them a better running economy.

So, what makes treadmill running harder?

Treadmill Calibration

Machines are efficient but only sometimes reliable. An overused treadmill may tend to be off on the measurements, making it slightly inaccurate. When running at the same pace on the treadmill as outside, some runners feel they work harder indoors.

To prove this notion, various athletes tried running at the exact calibration on different treadmill models, both new and used. Even though the results were inconclusive, most reported a difference in pace for all the models.

Treadmill calibration

Running Form

A treadmill run is nothing like running outside. There is just so much limited freedom. Also, on a treadmill, everything relies on balance because you are running on a small deck, and your strides might be unnatural.

Your running form is low on a treadmill because you lack the freedom to exert yourself on the belt as you would outside. Treadmill running requires you to adhere to user weight and height to resemble the run outdoors.

While this sounds petty, it's true in so many ways.

Speed Variation

Treadmill runners can only change their speed slowly as they would outdoors. Yes, there is a speed button, and the change would be almost immediate, but nothing compares to free running.

Treadmills lack natural inclines and declines as you would get when running downhill or having the wind on your back assist you to power through. But treadmills are consistent, and you can set a specific speed and maintain it for a specified period as you wish with zero interruptions by the terrain or weather.

treadmill Speed variation

Running Muscles

Even though treadmill running and outdoor running are all forms of running, they don't target the same muscle groups. The advantage of running outdoors is that you work many different muscles because of the constantly changing terrain.

Treadmill workouts target the same muscles all the time. Because of this difference, treadmill running isn't the best for competitive athletes looking to become efficient runners. Seeing that you don't use all your muscles on the treadmill, it makes sense that your speed will go down.

There's also a risk of running an injury on the treadmill because of overusing the same muscles when running every time. The more muscles you work, the better the running efficiency.


Running indoors feels uncomfortable because you tend to get hot faster than outdoors. Even with a fan to cool you, your heart rate will rise more quickly, making it different from the cool breeze outdoors.

Heat affects runners in different ways and can slow you down when you can't take it anymore. You can't control the heat when running outside, but you can dress for the weather, making it easier to push through. Likewise, running in chilly weather makes you run faster.

treadmill Running muscles


After running on the treadmill for the first time in a gym, you feel the excitement and want to do it again. But treadmill owners are used to the equipment and attest that it gets boring fast.

Even though you can make your running experience lively by switching on the TV or listening to your favorite podcast or music as you run, treadmill running is physically and mentally tasking.

According to a 2016 study by IJERP, it's easier to stay focused on running outdoors than on a treadmill. Even though the study is about the difference between outdoor and indoor cycling, the dynamics remain the same for running.

The good news is you can make treadmill exercises better by incorporating different training programs. For example, you can join group training and interact with others to cope with mental boredom or try HIIT treadmill routines that work you hard, so you don't have the time to get bored.

Other runners change the boredom to their advantage by using it to build mental toughness. For example, running a marathon is easier to maintain a steady pace when running in a group. But you will need mental toughness to run at a steady pace when isolated from the pack. 


If we rely on science to answer, why do I run slower on a treadmill? We will incline towards the affirmative. Yes, science shows that it's advantageous and way faster to run outdoors than on a treadmill.
But there is a lingering doubt because for science to be accurate, we should consider the world outdoors record holder to run on the treadmill and see the difference. However, one constant in the running is you need running shoes whether training indoors or outdoors. So always protect your feet whether running on the soft padded treadmill belt or the rough trail outdoors.

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