Some runners have eccentric motions that have no bearing on their running. Bill Rodgers was famous for looping one arm in bigger circles than the other; it turned out to be a natural way to counterbalance having a leg-length discrepancy - though many had suggested he "correct" his form, he was running well. If he were a beginning runner with a bunch of nagging injuries, however, it might make sense to put an insert into one shoe to adjust for leg length and then try to run "correctly." Jim Ryun ran sub-4 minute miles with his head rolling in circles; the rest of his form was perfect and this eccentricity did not seem to affect him.
The first consideration is: does your running form get worse when you run faster? If it stays the same or improves, chances are that you've found what works for you. For example, I have an odd arm swing (you can imitate it by holding your elbows locked at one angle; it forces you to move your shoulders back and forth) which goes away when sprinting or running hard uphill. I can run with better form on slower runs, but it takes concentration and is tiring. You don't need fancy equipment to answer this question - you friends can tell you, if they've seen you run, if your form falls apart when running fast.
If your form does get worse when you run faster, the next question is: how much running have you done? Beginning runners often have an awkwardness that gets better with practice and without conscious effort. Veteran high-mileage runners often develop an efficient "shuffle" stride; Derek Clayton and Alberto Salazar set world records in the marathon with that stride - heel striking, no knee lift; it sometimes looks like they're almost sitting - and this stride works well for some runners at some distances. The shuffle does not work well at short race lengths, though, and a runner planning to do short races has to learn (or relearn) the "power stride." Fortunately, this is a simple task: the faster you run, the better your form has to be, so practicing fast strides and/or sprints will automatically correct flaws.
Just what is "correct" form? There are so many factors that entire books have been written on the subject. In short, if you have no biomechanical weaknesses, your form will probably be good and you'll have few problems with injury. If you have weaknesses, some can be corrected to a degree, but most have to be compensated for by altering one's form. These deviations in form from the standard will lead to injury... but only if you overtrain or make sudden changes in your training.
Learning the various elements of good form can be valuable, but more telling is learning to observe how one's own form changes. The classic example of this is "falling apart," when one has run as far as one can at a given pace and suddenly it's a struggle to keep moving (in the marathon, this is "hitting the wall"); when one falls apart, one's form alters dramatically. Knowing what the difference is between how you ran when you ran well and how you run when exhausted, sometimes you can get back into a run (albeit at a slower pace) by forcing yourself to adjust your form to what it should be. This is one of those things that I do not do well - photos of me late in ultramarathons show me with hunched shoulders, leaning forward, often staring at the ground in front of my feet. Correcting the imbalances that lead to that poor posture with specific exercises could be of use, but I think it's better to not get in that situation in the first place.
|Photomanipulation (oops, her eyes don't track!)|