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Exercise physiology - Mechanical Efficiency during running

Could someone please discuss the practical implications for testing and knowing that someone has significantly lower economy of movement (mechanical efficiency) during running than they should?

[This is the second time I have posted this problem because I did not understand the first response which stated ATP. But what does it mean by "practical implacations for tesing. Does 'lower economy of movement during running imply incorrect form, wasted energy, bad shoes... I am having a hard time understanding this concept.]

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You do seem to have a good understanding as to what the implications of lower mechanical efficieny are. As you stated this can be due to:
<br>1) Poor form - ie. excessively flailing arms
<br>2) Bad footwear (for example if you are running on wet grass and don't have something that will give you good traction you will expend more energy because you are having to do an extra "push" as your foot slips, OR imagine the difference between a shoe that provides a little cushion and spring as you step down vs a solid hit)
<br>3) Improper biomechanics of running
<br> - this can be because of things like a collapsed arch which as you run will result in excess movements (ie. typically falling on a collapsed arch would cause your knee to go into valgus briefly and there would be a compensatory correction of this before push off - all wasted muscle activity as it does not contribute significantly to your driving forward)
<br> - you could also have torn or lax ligaments in your knee that would allow more translation of your joint and require more muscle activity to stabilize (ie. someone who is ACL deficient will require more activity of their hamstrings to stabilize them)
<br> - there could also be improper recruitment / inhibition of muscles. When you contract an agonist the antagonist should relax. With training we get better at doing this, improving efficiency. There are some pathological conditions of the nervous system that would not allow you to relax properly even with training (for example someone with spasticity after a stroke)
<br>4) Another minor contributor may be wasted energy from excessive heat loss (ie. you will require slightly more energy if you run in -20 degree weather)
<br>Once you know someone has decreased efficiency you should do two things:
<br>1) Try to find out why and correct it if possible (ie. change shoes, orthotics, knee brace, etc.)
<br>2) When you are designing a program you need to take into account their altered efficiency. Any formulas you use to determine what someone's desired training speed should be won't be accurate because these are based on the assumption that the person has "normal" mechanical efficiency and that for prescribed speed of X their energy required (and consequently cardiac demands) is Y. However in your patient it is really Y + whatever your correction factor is. If someone has 80% efficiency (relative to normal) then you should use the formulas to calculate their desired training speed, convert that to energy expenditure, multiply by 0.8 and convert back to a running speed. (You can't always assume that you can just multiply the speed by 0.8 because for instance running has a different energy expenditure per km than jogging which is different than walking).
<br>Hope that clarifies things for you,
<br>Gerald Wolff
<br>BSc. Kinesiology, MD (2004)