Is Running Outdoors Better Than a Treadmill?

Comparing Calories, Muscle Growth, Safety, and Moods

An athletic woman trail running.
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The treadmill has become the de facto part of any gym experience and, for some people, the only place where they do any actual running. Certainly, treadmills have their benefits in that they allow you to run year-round whatever weather or season.

But how does running on a treadmill actually compare to running outdoors? Does one burn more calories than the other, or are there any benefits that might convince us to change our workout routine?

Comparing Calories

The benefits of running are enormous whether you are running indoors or out, and, in the end, the number of calories you burn doesn’t depend so much on where you to run but how fast you do it.

With that being said, most people will tell you that running outdoors requires far more energy than doing so on a treadmill. And this seems a reasonable conceit given that you are constantly navigating terrain, fighting the wind, and making quick stops and starts, all of which increase the caloric burn.

But whether you burn more calories is the subject of debate. One well-known study published in 1996 suggested that you need at run at one percent incline on a treadmill in order for it to be equivalent to running outdoors.

While this seems to suggest that outdoor running requires more energy, the conclusion was limited by the fact that the study only included experienced runners. Even among these performance athletes, the equivalency was only reached when running at pace of over 7.09 minutes per mile (or roughly 8.5 miles per hour).

Let’s face it, most of us run at a far slower pace than this. So, the question of whether running indoors or outdoors is a better way to burn calories is largely a wash. How hard you work, on the other hand, appears to the real deciding factor.

Muscle Growth and Safety

Another popular belief is that running on a treadmill is better for your body as there is less impact on the joints and connective tissues.

And while that would suggest that treadmills are "safer," there has been no real evidence to support this. In fact, a number of studies have shown that running on a treadmill builds far less muscle needed to protect these vulnerable joints. 

One 2016 study from the Department of Sports Rehabilitation at Woosong University in Korea showed that running outdoors had more far positive effect on the lower extremities, increasing both the range of motion of the ankles and the overall strength of legs (as measured by the vertical jump).

Generally speaking, running outdoors is a far better way to build the quadricep muscles of the thighs, the gastrocnemius and soleus muscles of the calves, and the gluteus muscles of the buttocks. This is because every time your foot lands in front of you on a treadmill, the belt brings your leg back under you—something that these muscles should be doing.

From the perspective of safety, it is difficult to say whether one type of running is inherently "safer" than the other. Each poses certain hazards that can be minimized by wearing the right shoe, learning how to train properly, and knowing how to use the equipment correctly. These factors tend to influence safety risks more than where you do your running.

Running's Effect on Mood

While running in general is known to boost your energy and overall sense of well-being, there is one type that is clearly is leaps and bounds ahead of the other.

In 2012, researchers from the University of Exeter in England did an analysis of 11 major studies looking into the emotional effects of exercise performed in a natural environment versus that done indoors. What they found was that exercising outdoors was associated with increased energy levels, better moods, stronger feelings of revitalization, and decreases in tension, confusion, anger, and depression. Moreover, a person was more likely to continue exercising regularly if doing so in a natural environment.

Strangely enough, feelings of calmness were seen to decrease following outdoor exercise. Some have suggested that the changing stimulus in a natural environment may play as part when compared to the relatively static atmosphere of a gym.

While this should not suggest that treadmill running has the opposite effect, it may help bolster what your mother has long told you: that it's good to get outdoors and get some fresh air. Doing so may, in fact, give you the boost needed to make running a lasting part of your life's routine.

Sources:

Sung, E. "The effect of treadmill-based and track-based walking training on physical fitness in ankle-sprain experienced young people." J Exerc Rehabil. 2017; 13(1):84-88. DOI: 10.12965/jer.1732878.439.

Thompson Coon, J.; Boddy, K.; Stein, K. et al. "Does participating in physical activity in outdoor natural environments have a greater effect on physical and mental wellbeing than physical activity indoors? A systematic review." Environ Sci Technol. 2011; 45(5):1761-72. DOI: 10.1021/es102947t.

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