for an ad-free Fetcheveryone experience!

More efficient running style

2 lurkers | 183 watchers

Canute Dec 2013 11:39am, 20 Dec 2013 830 posts	Quote Pin Canute Opps, that lin might not work because the colon generated an emiticon. You can find the picture at en.wikipedia.org
Canute Dec 2013 11:51am, 20 Dec 2013 831 posts	Quote Pin Canute Boab, If you know the height of the jump and the weight of the athlete you can calculate the energy required for each jump. If you know how much oxygen was used and you also measure the respiratory exchange ratio (the ratio of CO2 produced to O2 consumed) you can calculate the energy the athlete used for jumping . Respiratory exchange ratio tells you what type of fuel was being used. If the exchange ratio is 1, you know the fuel was carbohydrate, because when carbohydrate is burned, 1 molecule of oxygen yields one molecule of CO2. Fat produces less CO2 for each litre of oxygen consumed. We know how many calories are generated when a litre of oxygen is used to burn carbohydrate, and we can do a similar calculation for various proportions of fat and carbohydrate. You also need to measure resting energy consumption and subtract that from energy consumption when jumping.
Hills of Death (HOD) Dec 2013 1:43pm, 20 Dec 2013 29,305 posts	Quote Pin Hills of Death (HOD) Basically if your skinny you can run faster
Gobi Dec 2013 2:01pm, 20 Dec 2013 53,148 posts	Quote Pin Gobi LOL, true in my case Fatter, Older and slower (C) 2013
SPR Dec 2013 5:29pm, 21 Dec 2013 18,935 posts	Quote Pin SPR Was bounce explicitly measured? Russ Tucker (of The Science of Sport) has said (on twitter) stride angle is not necessarily bounce. Russ reviewed the paper so seems to suggest that it wasn't measured?
Canute Dec 2013 1:30pm, 22 Dec 2013 832 posts	Quote Pin Canute For a given speed and cadence, stride angle does predict peak elevation reasonably accurately. Speed was fixed for each trial, but cadence was not. However, variation in cadence between experienced runners is usually fairly small. Nonetheless, contrary to the authors claim, I think that stride angle is probably not a very useful measurement, because I doubt that it can be measured very precisely. The authors also measured time on stance. They found that this was strongly correlated with stride angle, and also correlated with efficiency (short contact corresponds to better efficiency). I think time on stance can be measured more reliably. For a given cadence, time on stance does predict peak elevation exactly. The principle conclusion from the study is still that keeping low to the ground is inefficient. The one important additional feature to note is that at higher cadence, the peak height for optimum efficiency is lower, but there is a upper limit to the desirable cadence at any given speed, because the energy cost of repositioning the leg during swing increases with increasing cadence. My point in drawing attention to this study was to emphasize that there is a trade-off between braking cost and elevation cost, so simply trying to avoid elevation is a mistake. This study does confirm that conclusion, though I think the data for time on stance provides the more convincing illustration of the point.
richh Dec 2013 1:52pm, 22 Dec 2013 652 posts	Quote Pin richh zCould someone explain exactly what "take off angle" means in this paper? Thanks!
SPR Dec 2013 2:08pm, 22 Dec 2013 18,938 posts	Quote Pin SPR Is take off angle the same as stride angle From reading the runnersworld article I get stride angle as the angle at which the foot (and only the foot) leave the ground, so the triangle is heel, toe, floor.
SPR Dec 2013 2:17pm, 22 Dec 2013 18,939 posts	Quote Pin SPR ^ nope that's defo wrong!!! Canute - the question is do those with higher stride angle usually have higher cadence and vice versa. There was enough difference in cadence between Haile, Kennesia, and Mo.
SPR Dec 2013 2:24pm, 22 Dec 2013 18,940 posts	Quote Pin SPR "Stride angle isn’t the easiest term to understand, so prepare yourself for this one. According to the study, stride angle is “the angle of the parable tangent derived from the theoretical arc traced by a foot during a stride and the ground.” If you’re good at math it’s not as bad as it sounds. Essentially, it’s an interplay between how high your foot gets when it leaves the ground, and how far it travels." breakingmuscle.com