Rabu, 11 Januari 2012

Range of Motion

Uh oh
What has this picture got to do with the title of this post? For that matter, what does "range of motion" refer to?

The picture is of my Mac charger after my father-in-law's dog chewed through it at the weekend. Incredibly, I was able to find a replacement charger the next day in a shop on the way home from work. Incredible, because I both work and live "in the sticks". However, yesterday, as I was getting ready to do my series of 20 minutes hard running on the treadmill, the new charger started acting up. Rob needs the charger to charge my Mac, to play the film that Rob needs, to be able to suffer the run. The days when I leave my workout until the evening I tend to get a little nervous; for me, the best time is at lunch time when I am neither straight out of bed nor am I spending time when I could otherwise be with my family. I got especially nervous that I wouldn't be able to do my workout unless I could watch some kind of slasher-flick to distract me as I have been doing lately. In the end, not only did I manage to solve the problem but I had the best workout I have perhaps ever had.

I need to qualify that. The thing is, either I was running much faster for less effort than usual, or the treadmill was broken. I'm really not sure which. It felt as though I was running fast but the difference was (and here the title of the post will become clear) that I was kicking my legs up much higher under my butt. The back of my hamstrings started to get warm from the contact with my lower leg and it felt like the leg was rebounding of my bum. I ran the first set of twenty minutes at 16 kph and didn't even go over 160 bpm (for comparison, my recommended heart rate for running a Marathon is 163 bpm). The next set I did at 16.5 kph and the last 20 I did half at the same speed before dropping down to 16 kph for the end (my heart rate was now where it should be, just below the anaerobic threshold at 178 bpm).

By kicking my leg up higher (larger range of motion) my cadence was lower than it would usually be running at that speed. I may try to measure it to see whether it was lower than my cadence at my cruising speed of 13.5 kph. All the schools of efficient running advocate a high cadence of around 180 footsteps per minute - some even suggest you run with a metronome, others simply say that the high cadence is the result of doing everything else right. The Pose Method, which I followed in order to run more efficiently, talks a lot about the range of motion and essentially says that the drills help us find an optimal range of motion. Too high a range of motion and you are wastefully moving your legs; too low and the cadence becomes too high and the extra steps taken are similarly wasteful. This is also related to the stride length and how much we bounce up and down in each stride. Much has been made of the importance of not bouncing up and down too much - this is needless work done against gravity - but it is also clear that this up and down movement muust be optimized not necessarily minimized. A study that was cited in the "Iron War" book that I read over the weekend came to the conclusion that the "bounce" wasn't a determining factor in the efficiency of the runners it tested but, what was critical, was the acceleration / deceleration of each footstep. In other words, the braking effect which is especially exacerbated by heel striking but is also determined by your skill and elasticity as a runner. So maybe I was bounding more by lifting my leg higher, maybe I was bouncing up and down a little more as a result, but perhaps I was running more efficiently. After all, I have long, powerful (and heavy) legs.

If I get a chance I may try a little scientific experiment of one on myself in order to determine my optimal cadence (the measurable consequence of running with one range of motion or another). The problem, of course, is that many other factors influence the heart rate, in particular, how tired you are. Anyway, something to think about...

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