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More efficient running style

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Canute Jan 2016 12:26pm, 16 Jan 2016 1,715 posts	Quote Pin Canute Hi everyone. It is good to see a little spark of life in the old thread. For me, the great thing about this thread in the ‘old days’ was that it was a place where debate was mostly more friendly and inclusive than in many of the other internet sites that discussed running form and efficiency, though we nonetheless did have the occasional fireworks and schisms. Although I don’t miss the fireworks, I do miss the fact that much of the passion has gone out of discussion about running efficiency. In part this is because several of the old debates have been either settled or shown to be irrelevant. But I think there are still interesting questions that have not been answered.
GlennR Feb 2016 9:43am, 17 Feb 2016 17,313 posts	Quote Pin GlennR Hello all. A useful looking research study: link.springer.com Thanks to FreshStart for digging it out.
Canute Feb 2016 11:27am, 17 Feb 2016 1,725 posts	Quote Pin Canute Thanks , Glenn and FreshStart. This is a useful review. Quite wisely the author points out that most studies consider individual factors in isolation without taking account of effects on other aspects of running mechanics. For example, she notes that landing with a small horizontal distance between point of contact and COM does decrease braking force, ( as would be expected) but does not improve efficiency. This is almost certainly because, at given cadence and speed, landing with the foot only a little in front of the COM inevitably demands a greater airborne time and there fore would in getting airborne. There has to be a trade-off to achieve optimum efficiency. Nonetheless, her conclusion that a 3% reduction in stride length improves economy does make sense because at a given speed, this requires a 3% increase in cadence, and for most recreational runners, such an increase in cadence is beneficial as it decreases both braking cost and elevation cost. It only becomes harmful at high speed when the cost of swinging the leg is high, since swing cost increase with increase in both speed and cadence. Perhaps the most important conclusion is that you need to take multiple factors into account before making recommendations.
Ceratonia Feb 2016 11:47am, 17 Feb 2016 3,098 posts	Quote Pin Ceratonia Interesting paper. My quick reading was not that a 3% reduction improves RE, but that trained runners naturally select the correct stride length, but I only glanced through. It seems clear that increased leg stiffness and light shoes are both associated with higher RE.
Canute Feb 2016 12:00pm, 17 Feb 2016 1,726 posts	Quote Pin Canute Ceratonia, I was basing my comment on her awkwardly worded statement on the second page: ‘This range appears to be the preferred stride length minus 3 % to the preferred stride length.’ However she does also draw the conclusion that ‘generalizing the principle of an optimal stride length range to all runners should be done with caution, as self-optimization appears to be a physiological adaptation resulting from greater running experience.’ I strongly agree with that. Nonetheless, I think there is very good evidence that on average recreational runners do improve their efficiency by a modest increase in cadence (or decrease in stride length).
GlennR Feb 2016 5:31pm, 22 Feb 2016 17,426 posts	Quote Pin GlennR My new Garmin gives me figures for average vertical oscillation and average ground contact time. Is there anything I can do with these in terms of training?
HappyG(rrr) Feb 2016 5:45pm, 22 Feb 2016 25,376 posts	Quote Pin HappyG(rrr) I would think that leg stiffness, while potentially improving running efficiency, might also lead to a greater injury risk. This would be especially true of those running on relentlessly hard surfaces e.g. tarmac. Running efficiency is not presumably a goal to be pursued at the expense of injury? G
Canute Feb 2016 6:25pm, 22 Feb 2016 1,727 posts	Quote Pin Canute What changes do you want to produce? There are three main energy costs of running: getting airborne (increases with to vertical oscillation); braking (increases with ground contact time) and leg swing cost (increases with cadence. Merely trying to change one of the three is likely to have effects on the other two. If you increase cadence you will probably decrease contact time and vertical oscillation, and for many inexperienced runners that is beneficial, though an experienced runner , self-selected cadence at a given speed is more likely to be optimal. However, an athlete who is trying to improve efficiency might benefit from measuring all three – but there is no simple rule for telling you what change might be beneficial. Nonetheless if cadence at a given speed matches that typical of an experience runner at that speed and ground contact time is still long, plyometrics might help decrease the ground contact time.
Canute Feb 2016 6:37pm, 22 Feb 2016 1,728 posts	Quote Pin Canute But be aware that if you decrease ground contact time at a given cadence you will increase airborne time and that will inevitably increase vertical oscillation of the COM. I do not know at which part of your body your device measures vertical oscillation; I assume it is your chest. You can alter the position of the COM relative to chest by lifting the swinging leg higher. Thus a given increase in vertical oscillation of the COM can be accommodated with a lesser increase of the vertical oscillation of the chest – but this will increase swing cost, and it is a complication that you might not want to think about because there is a risk of ‘analysis paralysis’).
GlennR Feb 2016 11:11am, 26 Feb 2016 17,574 posts	Quote Pin GlennR A question for you clever people. If I get on the Wattbike and do thirty minutes at an average of 130 Watts then, in energy terms, that is 65 Watt Hours, a number that is convertible into kilojoules or kilocalories if I could be bothered to do the maths. Why then should it make a difference to my own calorie burn if my average heart rate is (say) 130 bpm or 115 bpm? If the answer to that is "it doesn't", then why does the Garmin give different output? I appreciate that with running improved efficiency might reduce the energy required for a given distance, but on the face of it that appears less relevant to cycling. I have a feeling I'm suffering from brain fade on this one. Put me out of my misery so I don't think about it for hours