I am wondering why elliptical and bike are considered to be low impact and better for people with bad knees. To me, these two seem to be using the knee joints more? Compared to walking or running on a treadmill
In: 7
When running or walking you are impacting the ground every time you take a step. On a static bike there is no impact its just motion
When you’re running, your entire bodyweight lands on one leg at a time, which exerts a lot more force on your knee. If you’re sitting on a seat and just moving your legs without putting your body weight on them, you’re putting a lot less force on your knee.
Impact is just that – impact. A sharp, sudden force which puts a high amount of acute stress on the joints.
When you jog or run, your body leaves the ground for a moment, and the entire weight of your body is put on your knees/ankles/etc. suddenly. That creates stress on those joints and can lead to injury.
Things like biking or ellipticals don’t have that sudden jolt of force. There is a lesser, but more constant, force that is applied to the joints. This is less jarring, which means less chance of injury.
To clarify a bit further —
Unlike a treadmill, on a bike or elliptical your foot never leaves “the ground” (the surface of the equipment), so there is no resulting impact as there is when you are walking or running on a treadmill. Walking/running on a treadmill requires you to lift your foot off the ground for each step. When your foot touches the ground again, there is an impact. Regardless of how minor it may seem.
Ok, take your hand and put it up against your cheek and push as hard as your can. You’re applying pressure, but the hand stays on the surface of your cheek. There’s no moment of “impact”. Now move your hand a foot away from your cheek and slap your cheek as hard as you can. That’s impact.
The momentary force created when your foot returns to the ground and suddenly stops can be multiples of your own body weight. This impact can damage or wear down your knees and hips.
Constantly moving your joints without excessively loading them is actually beneficial.
It is literally less impact. On a treadmill your feet are constantly hitting/impacting a surface which can be jarring to your joints. On an elliptical or bike your feet are not impacting anything, but smoothly pushing the skis or pedals.
The woman “running” next to me on the treadmill today sounded like she was trying to slam her entire leg through the crust of the earth with each footfall. She was not a large woman either, just had the running form of a person who believes their entire body must leave the planet and come down with 3x the force of gravity in order to produce propulsion. I cannot fathom the impact that was having on her legs.
Oh ELI5 – if your body leaves the ground and comes back down there is impact, if it is just moving without leaving the surface of the earth, there is little/no impact. There are still forces being produced, but they are friction and rotational force.
Sorry for being a dick but if you thought about this for 30 seconds how could you not figure it out? There’s no fucking repetitive impact or pounding with a bike or elliptical.
Latest Answers