HHH- Look up the studies your self off the meta-analysis. I don't care enough to look them up for you. They're all there. A meta-analysis looks at the studies done on the subject. Each is cited in the journal article and the majority say what I've been saying. I should know, I've published on the subject of GRF and injury risk.
Malmo- You said "
This is not true, otherwise heelstrikers would have higher injury rates than FFstrikers."
We have no idea whether heel striking causes more injuries or not because it has NEVER been studied. That doesn't mean it does or not. It has been studied that an impact transient leads to increased injury risk. So the statement is true. We don't know whether we can connect that to heel striking yet.
The reason it never has been studied is because a bunch of scientist 30yrs ago decided that (despite a few studies to the contrary) that heel striking was how EVERYONE should run.
So if you read studies on biomechanics, GRF, or whatever from the 80s through early 2000's most have a clause in the methods that say "All non heel strikers were eliminated from this study."
So no one has studied injury rates of heel vs. other foot strike.
What has been studied is injury risk of those with an impact transient and those without a large one. And that's shown that those with increase impact transient are at an increased risk.
We HAVE studied peak GRF (what you say occurs at 100ms). It's been studied a ton because initially people thought exactly what you did that it must relate to injuries. Well all the research shows it really doesn't.
The theory on the initial impact peak has NOTHING do with footstrike.
Researchers noted that all these studies showed that those who had a high impact transient were at a higher risk for getting injured. ALl these shoe innovations were designed to decrease that transient.
It just so happens that foot strike changes it. That's when people started wondering if foot strike could reduce injury risk.
That's where we are now. No one has done a comparitive study.
We don't know for sure if footstrike effects injuries. We have theory saying that it probably does. But it hasn't been studied.
We don't know the answer because a bunch of people ASSUMED that heel striking is correct and never tested that hypothesis to be true. Similar to what many people are doing in this thread.
Keep an open mind.
Also- why could the first 50ms/the initial peak be so important? Probably because of where the impact force is transmitted.
Look at where the body is when you reach the true peak at around 100ms. You are directly vertical. The peak forces are transmitted straight up basically.
During the initial touching of the ground, the foot is in front of the center of gravity and in a heel strike vs. a forefoot strike the direction of the force is different. Perhaps this plays a big role. We're trying to figure that out.
How the lower leg absorbs the force is important.