Treadmill Running – Friend or Foe, Safe or Dangerous?
Most of the runners I meet do not particularly enjoy running on a treadmill. They would rather be outside taking in the scenery or running with their friends. However, at certain times of the year (which, in Alabama, might be 0° in January, or 100°+ in July!), and at certain life stages (babies/toddlers in the house?), it might be the “dreadmill” or no running at all. Most people will find when they run on a treadmill that it feels a bit different and that they often have to add a little incline to make it feel like running on the road. Even then, the surface of some treadmills have quite a spring to them. This different feeling is another reason why many don’t like the treadmill. The final reason I hear is that some have a fear of being spat backward off of it!
When I do a running analysis, I am sensitive to these factors as I am videoing somebody on a treadmill. But unfortunately, doing an outdoor analysis would require some very expensive equipment that typically would be used in the research setting. Up till now, our knowledge of any potential biomechanical differences between outdoor and treadmill running has been limited. However, in the latest journal to come through my door was an interesting article with preliminary data that may affect our practice.
Rich Willy is a professor at East Carolina University, whose work was featured in a previous blog. Rich and his team studied 18 injury-free runners age 18-35. They limited age to limit the effect of age on gait variations. Each runner ran for 6-minutes to get used to the treadmill before 10 seconds of 3-dimensional mechanics from 56 markers were sampled. After 10-minutes of rest they then ran at the same speed along a 25m runway and 3D mechanics were again sampled.
The study confirmed some knowledge we already had: stride was typically shortened when running on a treadmill. They found it took an extra 23 steps to complete a kilometer on the treadmill, but they did not see an increase in patellofemoral (anterior knee) joint stress. Along with this, they found no significant differences in measures such as peak knee flexion and peak knee extension moment. So, there was relatively little effect at the knee when running on a treadmill versus road. The ankle though was a different story! They found that achilles tendon force and loading rate were significantly greater during treadmill running.
What does this mean?
For a clinician, this means that we have some confidence in studies produced about knee joint mechanics in running that were studied on the treadmill. It gives us some caution on studies of the achilles on a treadmill.
For the clinician and athlete, it means that running on a treadmill is likely a safe place for someone with knee issues to return to running. In athletes with Achilles tendon problems such as tendinopathy, rupture, repair, some caution may need to be exhibited; running on the road may be more appropriate. They estimated that per kilometer the Achilles tendon was exposed to 45 more cycles of bodyweight when running on the treadmill. Increases in these cycles increase collagen turnover in the tendon and can lead to the development of tendinopathy.
I used the words “preliminary data” earlier as there are limitations to this research. Limitations do not mean the research is not of good quality, but merely underline the fact that research is a journey and this is a step towards a better understanding. The main limitations were the sample group was of a certain age range, injury-free, and had a wide range of habitual running volume. Therefore we do not really know if these results fit for a 55-year-old male who has had on/off problems with his Achilles in the past.
Every month new papers are released, some are good and some bad, that affect our understanding of the runner and athlete. I am focused on runners and athletes so I take the time to read and assess the quality of this evidence and make the changes to my practice that are needed. My practice continues to evolve and I feel this is what helps me give my athletes what they need. If you need help with a running injury, I would love to help you, please contact me!
If someone wants to use a treadmill, and it is their way to get/keep moving, we should encourage its use!
Willy RW, Halsey L, Hayek A, Johnson H, Willson JD. Patellofemoral Joint and Achilles Tendon Loads During Overground and Treadmill Running. J Orthop Sports Phys Ther. 2016;:1-31.
Gif: via Giphy