There are several pros and cons of running outdoors versus on a treadmill. It is hard to say which is ‘better,’ nevertheless they are not equal. The treadmill is a beautiful piece of cardio machinery, but I can’t help but feel like some overgrown gerbil when I’m on one. There are many different kinds of designs. The high-end gym models cost upwards of 9k. It is the most popular piece of equipment in health clubs for a reason; it burns a lot of calories and produces a great workout. However, it is not equivalent to running outdoors. Biomechanically these are two very different activities. In fact, when comparing similar speeds and grades, some studies show outdoor running burns more calories and more recent studies show no difference. Let’s examine why free-range running may be superior (in many but not all ways) to treadmill running.
Running on the treadmill is like running in place. The belt rolls underneath your feet, causing you to run directly down, not forward. It is common for the belt to ‘grab’ your feet and pull them back as you are running, which increases the stress on your knees, back and hips. In contrast, free range running is a type of controlled forward falling. Literally, all your stabilizing muscles around your joints have to struggle to keep you from face-planting. Outdoor ground surfaces are nowhere near a homogeneous (flat) as a treadmill’s smooth belt. Running on uneven surfaces taxes the stabilizing muscles and increases your gross neural demand (metabolic and caloric output). Varied road conditions offer your joints some relief (wear patterns are more diverse- which is a good thing) and optimize proprioception while strengthening the muscles in your feet, legs and core.
Outdoor running also exposes you to air resistance. Have you ever run into a headwind and felt you were hardly moving (this is a recurring dream of mine!)? How about running with the wind at your back, giving you the feeling you could beat Prefontaine? These things don’t happen on the treadmill unless you put your treadmill outside! Having to overcome variable wind and weather conditions increases the neuromuscular and caloric demand of the routine. Moreover, the air quality and oxygen content are usually better when running outdoors, not to mention the copious amounts of healthy vitamin D radiating from the sun.
The treadmill is not without its benefits: absolute control of your pace and incline; consistent environment – no freak hail storms to outrun; no traffic or bears to encounter; you can watch TV; large real-time data in front of you; and it may be a time saver (you don’t have to leave the house) and the most important benefit is you can stop whenever you want and won’t be miles from your home (in the rain or snow). A 2008 study comparing running outdoors and treadmill running at the same speed confirmed what earlier studies concluded: Treadmill running typically produces shorter strides with increased frequency. Furthermore, earlier studies found an increased period where the foot is in contact with the treadmill belt. Shorter and more frequent strides have been associated with fewer impact forces. However, since the treadmill belt ‘gives’ unlike the hard road, the indoor workout has a smaller amount of healthy skeletal impact – which is needed to increase bone density. So you take the good with the bad…with the ugly.
However, the 2019 meta-analysis study found that oxygen consumption was equal between treadmill running and outdoor running, at no incline and even at speeds as fast as six minutes per mile.
A 1% grade recommendation while running on a treadmill (above 6 mph) will more accurately reflect the energy cost of outdoor running. The treadmill is a great tool to use while at the gym or home, but it may not be a total replacement for outdoor running for the serious athlete. However, many athletes swear by their treadmill workouts. In the end, if you like one or the other better than do that. It won't make a huge difference.
"When you put all this together, the sense I’m left with is that the biggest differences between treadmill and outdoor running aren’t in how you run, but rather in how you respond to the experience. It’s probably true that people run slightly differently on treadmills: when you look in detail at the biomechanics, you find subtle differences in things like knee angles and peak ground forces, but the overall pattern (as one such study concluded) is that the two movements are close enough that you don’t have to worry about the differences—as long as the belt is properly calibrated and not too soft." - Alex Hutchinson
Sources:
1- Riley, P. O., Dicharry, J. A. Y., Franz, J., Croce, U., Wilder, R. P., & Kerrigan, D. C. (2008). A kinematics and kinetic comparison of overground and treadmill running. Medicine & Science in Sports & Exercise, 40 (6), 1093. 2- Schache, A. G., Blanch, P. D., Rath, D. A., Wrigley, T. V., Starr, R., & Bennell, K. L. (2001). A comparison of overground and treadmill running for measuring the three-dimensional kinematics of the lumbo-pelvic-hip complex. Clinical Biomechanics, 16 (8), 667-680. 3- Frishberg, B. A. (1983). An analysis of overground and treadmill sprinting. Medicine & Science in Sports & Exercise, 15 (6), 478. 4-Heiderscheit, B. C.; Chumanov, E. S.; Michalski, M. P.; Wille, C. M.; Ryan, M. B., Effects of Step Rate Manipulation on Joint Mechanics during Running. Medicine & Science in Sports & Exercise 2011, 43 (2), 296-302. 5-Jones, A. M., & Doust, J. H. (1996). A 1% treadmill grade most accurately reflects the energetic cost of outdoor running. Journal of sports sciences, 14 (4), 321-327.
