With the recent changes due to COVID19, treadmills have been selling out in stores and online as more people start to utilise treadmill running more than ever before. But how similar is treadmill running really to overground (outdoor) running? In this blog article, I’ll summarise the findings of the research regarding the differences between the two, then I’ll make practical recommendations so you can maximise your physiological benefit and progress on a treadmill.
Kinematics & Kinetics
Kinematics and kinetics refer to the motion of limbs and joint angles during movement, and how forces work to cause those movements.
The main thing you need to know: The mechanics between treadmill and overground running are similar (Riley et al., 2008; Van Hooren et al., 2020).
There are only a few features that are noticeably different between treadmill and overground running. Many of these are related to each other, for example a change to one feature will naturally have an effect on another.
They are listed in the table below (Riley et al., 2008; Van Hooren et al., 2020):
|Feature||Treadmill mechanics vs overground|
|Forwards propulsion required||Reduced|
|Vertical displacement and time in the air||Reduced|
|Ground contact time||Higher|
|Ground reaction force||Reduced|
|Knee flexion in stance||Reduced|
|Knee flexion at foot strike||Higher|
Williams (1985) also suggested these differences were mainly present when running faster than 18km/hr on a treadmill (3 min 20 pace). Anything slower and the mechanics are more comparable.
Physiological and metabolic demands
Mimicking the cardiovascular demands of overground running is very important, because these parameters are what determines physiological stimulus and adaptations, that ultimately lead to aerobic endurance and capacity improvements. Common parameters to measure these demands include running economy and VO2 (How much oxygen is consumed per minute), RPE (Rate of perceived exertion) and HR (Heart rate).
One of the most well-known factors that reduce effort levels on a treadmill is the lack of air resistance (Jones & Doust, 1996). In addition to lack of air resistance, there is reduced forward propulsion required from the runner as the belt moves for them.
On the other hand, there are other factors that can increase effort levels on a treadmill. The mental resilience of running on one spot compared to seeing different scenery outside and lack of fresh air are a couple of factors that can increase RPE for long distance treadmill running. However, there needs to be more research to look into these factors.
According to a recent review by Miller et al (2019):
- At slower submaximal speeds, HR and RPE were lower than overground running
- At faster submaximal speeds, HR and RPE were higher than overground running
- At near maximal and maximal speeds, HR and RPE were similar to overground running
- Endurance performance lower but sprint performance similar on a treadmill compared to overground running
Other factors (Riley et al., 2008)
In reality, there are many different factors that will affect treadmill running. Some of these variables include:
- Quality, size and power of a treadmill
- Individual running technique
- Familiarity of running on a treadmill
If your goals are for general health and fitness, you can self-elect treadmill speeds to your desired pace and still reap fitness benefits.
However, if your goals are to improve running performance, then you should make your treadmill sessions reflect as accurately as possible to race conditions, which will always be outdoors overground running.
If you had the patience to read through the research findings, you will notice there are conflicting findings whether treadmill running causes similar, lower or higher levels of VO2 and HR than overground running. These are dependent on treadmill running speed, and the other individual variables. For this reason, the practical recommendations are unfortunately not a definitive, one size fits all recommendation, but also require a level of trial and error to find what works best for you.
The first thing you can do is to get the best quality treadmill that your budget allows. Commercial treadmills in gyms are perfect for running, but now that gyms in Australia are closed, many people are turning to purchasing their own treadmills.
The first thing to look out for is a treadmill power (CHP). This will allow more consistent belt speed and power. Aim to get a treadmill with a CHP of at least 1.5, and above 2 is ideal. Any less and it’ll be weak for running, but appropriate for walking.
The larger the running platform is, the more comfortable you will be to run naturally without modifying your technique. Aim for a treadmill that is about 140cm long and 50cm wide. The bigger the better, depending on how much space you have.
To make-up for lack of air resistance, it has been suggested by Jones and Doust (1996) that increasing treadmill incline can accurately mimic the energetic cost of overground running.
- If running at 5 min 42 sec pace or slower, then keep your treadmill at 0% incline.
- If running between 3 min 20 sec pace and 5 min 41 pace, then you should increase your treadmill to 1% incline.
- If running faster than 3 min 20 pace, then you should increase your treadmill to 2% incline
Note that increasing treadmill incline will more accurately simulate cardiovascular demands, but also change the muscular demands such as increasing calf input. For this reason, it’ll be best to vary how you run on a treadmill, to avoid overuse to muscle groups that are not adapted to running in that way.
Another way to simulate cardiovascular demands to overground running on a flat treadmill is to increase the speed.
Interval running (Panasci et al., 2017)
Interval running at high speeds on a flat treadmill has been shown to have lower metabolic cost than overground running by 6.3%. It is suggested in a 30 sec on, 30 sec off running protocol, a 15% increase in speed is required to match the physiological responses of VO2, RPE and HR of overground running. However, more research is required to conclude whether this speed increase is relevant for other running protocols and speeds.
With the varied findings in the research, there is no single perfect way to emulate overground running on a treadmill. Observe how your HR and RPE response in a treadmill session compared to the same overground session, then modify the treadmill incline or speed according to the recommendations and see if it’s more similar. Vary the changes you make over different sessions to expose your body to different stimuli. Where you can, run outdoors as we are still very lucky to have the capacity and space to do so!
Trang Nguyen is a Physiotherapist and Strength and Conditioning Coach helping endurance athletes achieve their greatest potential. Through coaching, programming and rehab, Trang strives to help individuals minimise injury and maximise performance. Have any questions? Trang is always happy to chat. Feel free to get in touch at [email protected]
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
Monte, L. (1976). A cinematographic analysis of overground and treadmill running by males and females. Medicine and science in sports, 8(2), 84-87.
Miller, J. R., Van Hooren, B., Bishop, C., Buckley, J. D., Willy, R. W., & Fuller, J. T. (2019). A systematic review and meta-analysis of crossover studies comparing physiological, perceptual and performance measures between treadmill and overground running. Sports Medicine, 49(5), 763-782.
Panascì, M., Lepers, R., La Torre, A., Bonato, M., & Assadi, H. (2017). Physiological responses during intermittent running exercise differ between outdoor and treadmill running. Applied Physiology, Nutrition, and Metabolism, 42(9), 973-977.
Riley, P. O., Dicharry, J., Franz, J. A. S. O. N., Della 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), 1093-1100.
Van Hooren, B., Fuller, J. T., Buckley, J. D., Miller, J. R., Sewell, K., Rao, G., … & Willy, R. W. (2020). Is Motorized Treadmill Running Biomechanically Comparable to Overground Running? A Systematic Review and Meta-Analysis of Cross-Over Studies. Sports Medicine, 50(4), 785-813.
Williams, K. R. (1985). Biomechanics of running. Exercise and sport sciences reviews, 13(1), 389-442.