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More efficient running style

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Jhuff Dec 2013 1:22am, 17 Dec 2013 3,732 posts	Quote Pin Jhuff Yes big dog does appear to lift his paws
Canute Dec 2013 8:40pm, 19 Dec 2013 827 posts	Quote Pin Canute If you ask runners whether it is more efficient to spend a shorter time on the ground, many will say yes because short time on the ground results in less braking. However if you ask whether it is better to bounce higher in the air, most will say no because bouncing higher requires more work against gravity. Of course these two apparently rational answers are somewhat contradictory because if you spend a shorter time on the ground you must bounce higher (assuming constant cadence). During the second half of airborne time you are falling freely under the influence of gravity, so the higher you are at mid-flight, the longer you will stay airborne, and the less the proportion of time you spend on the ground. There is a trade-off between braking costs and elevation costs. As braking cost decreases, elevation cost increases. So what is the optimum? A recent study of trained athletes (‘good’ club runners; typically 32 min for 10 K) found that those who bounced higher were more efficient. ncbi.nlm.nih.gov The range of take-off angles extended up to 5 degrees. An increase in take-off angle from 2.5 to 5 degrees was associated with about a 10% increase in efficiency. Of course, at much higher take off angle, the costs of elevation will become too high. However, the evidence indicates that trying to keep low to the ground is likely to be inefficient. But it does require a strong upwards push to get ariborne, and at most, about half of energy for this push can be obtained from elastic recoil
Boab Dec 2013 8:45pm, 19 Dec 2013 7,422 posts	Quote Pin Boab That's interesting Canute, but how is elastic recoil measured?
Canute Dec 2013 9:10pm, 19 Dec 2013 828 posts	Quote Pin Canute Boab, The proportion that can be obtained from recoil can be estimated by measuring the oxygen consumption during repeated vertical jumping to a specified height. The proportion obtained from elastic recoil does depend on the duration of ground contact, and the proportion obtained when running is not likely to be quite as high as can be achieved during simple vertical bouncing.
FenlandRunner Dec 2013 9:38pm, 19 Dec 2013 32 posts	Quote Pin FenlandRunner For a 10k you can waste energy being bouncy. Can't see that working for a marathon?
SPR Dec 2013 10:11pm, 19 Dec 2013 18,928 posts	Quote Pin SPR If you are efficient, you aren't wasting energy.
Boab Dec 2013 10:27pm, 19 Dec 2013 7,424 posts	Quote Pin Boab Canute, I am probably being very stupid here. You say that "The proportion that can be obtained from recoil can be estimated by measuring the oxygen consumption during repeated vertical jumping to a specified height". i am confused (easily done) but how can the studies know how much was down to elastic recoil and, say, muscle strength, and say how the subjects felt on the day and say, how much alcohol the subjects had drunk(silly variable, but a variable just the same). I am not trying to be obtuse, I am just curious as to how these things are subjectively measured?
SPR Dec 2013 11:09pm, 19 Dec 2013 18,930 posts	Quote Pin SPR Article on the study Canute is talking about
SPR Dec 2013 11:09pm, 19 Dec 2013 18,931 posts	Quote Pin SPR runnersworld.com
Canute Dec 2013 11:37am, 20 Dec 2013 829 posts	Quote Pin Canute FR, this picture suggests that it might work for the marathon. en.wikipedia.org