Is anyone here not an engineer?
Is anyone here not an engineer?
fred flintstone wrote:
Here's how I explain it to the kids, and they generally get the idea. It's the difference between a square wheel and a round wheel in the caveman era. The square wheel works, but it is a clunker. It appears to stop momentarily every time it contacts the ground, then catches up and rotates over the point of contact, and wastes energy as it clunks along. The round wheel just rolls, baby. Heel vs. mid- or fore-foot stiking is not much different.
I don't understand, are my legs wheels?
I can't tell you that. It's classified.
biggus dickus wrote:
Would all you engineers agree the the less time/friction with the foot in front of your CG the better?
P.S. I'm an engineer too.
Applying principles of mechanical engineering to biomechanics is a dangerous endeavor. It's how we ended up with all the fancy shoe technology today that doesn't do a whole lot other than look nice. Impact is one example: an engineer would think that a more cushioned surface (or shoe) would decrease the impact force of a runner. However, this is not the case--the body automatically adjusts the stiffness of the legs to maintain a constant overall surface-shoe-insole-leg stiffness.
There is a lot of funny business in this thread. Here are the facts:
*No footstrike has been shown to be more efficient at all speeds than another
*At extremely fast speeds (sprinting), toe-running (forefoot striking without a heel touch) is the only viable footstrike method.
*At extremely slow speeds (a walk or slow jog), heelstriking is most efficient
*Shorter ground contact times are more efficient
*You have to land somewhat in front of your center of gravity; otherwise you'd fall flat on your face (if you're a physicist, draw the force diagram!)
And that's about it.
Now, here's my reasonably informed opinion: footstrike takes a back seat to foot placement. Landing too far out front causes longer ground contact times. You need to land a certain amount in front of your center of gravity to keep yourself upright. If you landed right underneath, your forward momentum would make you tip right over. So there is an "optimal" place for your foot to land, and anything in front of this causes excess braking.
Heelstriking or midfoot striking is probably best at slower speeds, because forefoot striking there causes unnecessary Achilles loading. But at faster speeds, a midfoot or forefoot strike is probably more efficient because it increases loading on the Achilles tendon, which can then return the energy when pushing off. Unfortunately, since the attitude in America has been "form doesn't matter at all" for so long, many runners do not KNOW HOW to comfortably run on their midfoot or forefoot. They heelstrike when they sprint! This is a result of "reaching" with the lower leg in an attempt to increase stride length. For a young runner just getting into the sport, it is probably best to LEARN midfoot striking as the standard footstrike. Coming up onto the forefoot at higher speeds is much more natural and does not feel as foreign to a midfoot striker vs. heelstriker. Widespread heelstriking is also the result of the built-up heels on today's shoes. I suspect more people would midfoot strike if they were in lower-heeled shoes.
But if you've been running healthy for years, and heelstrike, why change? It would be more prudent to learn how to "switch" to a mid/forefoot strike when necessary (in a middle distance race in spikes) than to try to change your footstrike at ALL speeds.
biggus dickus wrote:
Would all you engineers agree the the less time/friction with the foot in front of your CG the better?
Not necessarily, as the video I posted earlier shows. One of the big factors is how quickly you absorb the impact and support your weight. A softer footstrike allows you to extend your stride a bit, but introduces a bit of extra lope to your stride, which does not help a quick turnover.
There are so many factors to consider. And yes, I have an engineering degree as well.
I'm no physicist, but if one is running at a constant pace, wouldn't they fall flat on their face if their foot strike was behind their center of gravity?
Also, two more facts:
*forefoot striking is not "softer" than heelstrike running. It transfers impact forces absorbed by the knee and hips into the ankle and Achilles and thus reducing the apparent impact force and impact loading rate, but the peak ground reaction forces do not change for a given speed.
*Impact forces are not correlated with injury. In fact, higher impact forces seem to have a preventative effect.
