I have been doing a bit of research on the whole running cadence concept and I have found out some interesting results.
Apparently the number of steps per minute (cadence in cycling terms) that an elite athlete will take on average doesn’t vary as much as I would expect. For any elite distance runner (over about 3000m) you can predict that they will be running at about 180 steps per minute (90 left foot and 90 right foot) regardless of how fast they are running.
It seems that even as a runner does slow miles in a warm up or fast miles in an all out 5k race, the thing that varies is not the stride rate but the stride length. If the runner is out for a cruisy jog around the block to warm up, they will hit the ground at about 90 steps for each leg each minute. But each stride will take them only perhaps 1.1m if they are running at 5 minute klm pace (8min03 mile). However when they pick it up to 4 minute klm pace (6min26 mile) and stride at 180 per minute then each step will take them approximately 1.4m. Further more when they go racing at 3 minute klms pace (4min50 mile) then their stride stretches out to about 1.85m each time a foot hits the ground.
Now that 1.85 metres is taller than me (a little over 6 foot), and this makes me wonder how on earth do we propel ourselves that far while we spring from one foot to the next (and do it over and over about 20-40,000 times in a marathon).
It seems clear that if someone is able to spring themselves from one foot to the next picking up that much distance, then the more of these steps that they can fit into each minute, the further they will travel (and thus the faster they will be flying).
There is a sensible limit to how fast you should turn over your strides. While the advantages of a fast turn over is a high potential speed, relatively low impact shock sent through the runner’s body and apparent biomechanical advantages, there are also disadvantages associated with pushing the stride rate too high. The first of these is that increasing stride rate can lead to an excessive reduction in stride length if it is found that the runner hasn’t got the time or focus to fire all the various propulsive muscles fully leading up to take-off each time. The second, and probably ultimately limiting, factor is the higher loads placed on the cardiovascular system at progressively higher stride rates. This is the same phenomenon experienced by racing cyclists. They find that although higher pedal revolutions per minute (cadence) can be more efficient at generating continuous high speeds (for most cyclists), there is a limit that varies between individuals. An excellent example is in time trials of the Tour de France. Most cyclists have traditionally geared up and pushed heavy gears (big chain rings and small cogs) slowly at maybe 70-90 revs per minute for the entire time trial (subsequently imitated by triathletes and all forms of time-trialers). However Lance Armstrong and some other members of the pro peleton began time trialling at higher and higher cadences reaching over 100 revs (closer to criterium cadence). Apparently this higher revolutions per minute suits best the rider who is limited in muscle bulk but has an excellent aerobic capacity. It is this high aerobic capacity that allowed Lance Armstrong to continually spin his pedals faster than the rest but cross the line faster than them also. So it remains that the highest cadences in cycling are reserved for those with low muscle mass (and so are inefficient “pushers”) but high aerobic capacity to keep up with the demand created by the extreme turnover rate. This, to me, sounds like the physiology of a distance runner and so it is no surprise that we too benefit from high turnover.
The last point I would like to make here is that practically all elite distance runners stride at about 180 per minute and this makes me wonder if that is the optimal rate or just a popular rate. Apparently we all tend towards this rate as we get more efficient, but is it possible that by notching it up even further we may may experience even higher speeds that are still sustainable? I haven’t found any research on this yet so if anyone else does, please let me know.