In a recent study posted in the Journal of Orthopedic & Sports Physical Therapy 18 healthy runners were studied running overground and on a treadmill. They ran at their natural running speed and the values were adjusted to make up for individual differences.
The findings were interesting. The treadmill running showed greater Achilles tendon loading compared to overground running.
What this study may be telling us is that something occurs on treadmills that increases the load on the Achilles tendon. These values were 12-14% higher compared to overground running. This can lead to overuse and tendinitis. A nagging problem that can take months to heal.
So here’s some food for thought. If you are mainly an outdoor runner and you need to do a session or two on the treadmill you might want to keep your speed a bit slower and avoid any significant elevations.
Slower running and less elevation during running on a treadmill will decrease the workloads on the Achilles tendon.