The assumption that if someone is a world class runner, then they must have perfect or at least very good technique
This assumption is often an unstated part of many arguments which basically say something like, "Since there is so much variability in the running styles of world class runners, then there must not be a single optimal technique for all runners." There are many examples of people who have run at world class level despite having very bad technique. Alberto Salazar had his career cut short in part because his technique was so bad. The real question is, "Could some of these runners improve their performance if they improved their technique?" Performing at high level does not necessarily mean that one's technique is optimal or even very good. It may just mean that the runner has exceptional ability that allows him or her to perform well despite having poor technique.
People naturally run at different cadences when running at different speeds, therefore there is no "magic cadence" for running.
It has been observed by me and many others, that when people run at an easy pace, their technique falls apart, and their cadence slows down below 180 steps per minute. I don't think there is any great mystery about why. Let me explain with an analogy. When I lift a very heavy weight over my head, I'm very aware of my technique, mostly because without proper technique, I may not get the weight up. When I lift a 10 lbs weight over my head, I'm hardly aware of my technique at all; because the weight is so trivial I can use extremely suboptimal lifting technique and still easily succeed in getting the weight overhead.
My point is that just because people naturally adopt a lower cadence when they run more slowly that does not mean that they are running optimally for that pace. It may just mean that the pace is so trivial that subconsciously they have stopped bothering to try running with good technique.
Everyone is proportioned differently, so everyone must have a different optimal technique
Regardless of what theory of running movement you subscribe to, the primary force acting on a runner is gravity. Gravity is a downward force that must be redirected using gravitational torque, and to manage that force properly, everyone must do a minimum of two things. First they must land as close to their center-of-gravity as possible and second they must reduce counterbalance by getting their trailing leg off the ground as quickly as possible. Every running technique I've studied that was devised by a track coach has these two elements in common (Pose, Explosive Running, BK Running and Evolution Running). I doubt that this is a mere coincidence. All of these techniques were designed for high performance running, and the fact that they are so similar leads me to believe that there is not much variation in optimal technique from one person to the next.
To convince me that everyone has a unique optimal running technique, someone would have to explain two things to me in very precise detail.
- How does landing further away from one's center of gravity increase efficiency for some people and not for others?
- How does leaving the trailing leg behind one's center of gravity (creating counterbalance) increase efficiency for some people and not for others?
- Just because someone is doing something well, and maybe even better than everyone else, that does not mean he or she is doing it optimally.
- Variation may be normal and natural, but normal and natural does not mean optimal. In fact, what is normal and natural is usually very suboptimal.