Treadmills are very popular pieces of equipment, especially as the weather starts to get cooler. In fact, most people think of the treadmill as one of their "go-to" cardiovascular activities. But should it be?
Treadmill walking/running is very different, biomechanically, from walking/running on a track or outside. When we are on solid ground, we must utilize our hamstrings to help pull ourselves forward when our foot first hits the ground and our gluts to propel our body forward when our leg is behind us. Our arms are also free to swing which helps us to utilize momentum while moving.
A treadmill changes these mechanics. Instead of pulling and pushing our bodies off of a stable surface, we are essentially trying not to fall forward as the ground is pulled out from underneath us. This makes the effort of walking much more passive. We will not need to utilize our hamstrings, gluts, or core muscles as much due to the machine doing a greater amount of the work. When our locomotive and stabilizing muscles are not fully functioning, we may overextend certain joints, our low back or knees, for example. It also teaches us poor walking mechanics that can carry over into walking on flat surfaces.
Additionally, as we increase our speed, we tend to hang on the handrails and not swing our arms. Not only does this make the activity even more passive, but the rotational forces and stresses on our bodies are not able to be distributed throughout our joints to be absorbed adequately. This can cause back or leg pain, as well as malposition/malalignment of the spine and/or pelvis.
Walking outdoors is the best option. Not only does this restore our natural mechanics, but it offers a natural interval training - hills! We're also able to look around at the sites around us which is relaxing for the neurological system.
Walking on a track is a close second as proper mechanics are still intact, but it becomes harder to visually appreciate the world around you. Also, if you always walk counterclockwise, you'll be using your joints and muscles asymmetrically as you walk around in a continuous circle.
If you have to walk on the treadmill, try increasing the incline to 1-2%. This will help restore the push/pull mechanics that are missing from walking on a flat treadmill. Be sure not to make the incline so steep that you'll need to hang on to the handrail which, as mentioned before, is not a good plan. It is also easy to stare at one object - a book, TV, calorie counter, etc. Be sure to look around to keep your visual system relaxed and active. If you're going to use a treadmill, it's best to place it in front of a window so you can still be aware of the world around you.
No matter what form you choose - get out there and get active!