Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

If you wanted to at least semi-realistically model the key components of Human running, what are the factors that determine the top running speed of an individual? The primary things to consider would be the 'thrust' provided by the legs, with significant components in the vertical and horizontal, and also wind resistance and energy dissipated by muscles and bones during the 'landing' half of each step, before the thrust part kicks in.

If a human was running in a vacuum (somehow...) would they be able to run much quicker, or is the wind resistance part negligible compared with the losses involved in the running action itself?

If anyone has references great, but I'd be happy with a well reasoned back of the envelope calculation.

share|improve this question
1  
free body diagram will get a +1 –  Magpie Apr 24 '13 at 4:42
    
See Wikipedia and the references in its "Notes" section as well. (Only somewhat related, also: physics.stackexchange.com/q/61174/17609) –  Glen The Udderboat Apr 24 '13 at 6:30
add comment

2 Answers 2

up vote 11 down vote accepted

The horizontal component of running is believed to be fairly negligible for humans. Some research suggests that the limit isn't strength related at all, but design --- in particular, based solely on power, humans could theoretically run up to almost 40 mph. The issue is two fold: first, our limbs are actually too heavy, for big strength (e.g. climbing in trees) - and weight us down for fast running. The second component is that we're in contact with the ground for far too short a time on each step. For comparison, consider cheetah's - who's long, forward-alternating strides significantly extend contact time.

share|improve this answer
    
The first article you linked to actually says the horizontal component isn't negligible but accounts for more than a third of the metabolic cost. (I'm not qualified to judge whether that's true, but it's what it says in the abstract.) –  Nathaniel Apr 24 '13 at 4:41
    
@Nathaniel, that's a good point - but if you look at their data its more like, 'up to one-third' -- and this result (while a good study) has, to my knowledge, been ascribed to the artificial nature of the additional horizontal force (AHF). I'm not up to date on the literature - I would be interested to hear more recent results. –  zhermes Apr 24 '13 at 4:52
    
+1, a good answer will some very interesting info, but doesn't quite answer the whole question. I'll hold off accepting for a few days to see if anyone can give a better answer. –  Bogdanovist Apr 25 '13 at 5:45
add comment

In regards to wind resistance, it is negligible at running speeds in comparison to its value as air conditioning. The reason bicyclists can cycle for much longer than runners can run is from the much better cooling obtained from greater wind resistance!

The increased drag is of course more than made up for by the vastly greater efficiency of cycling.

share|improve this answer
1  
So running in a freezer would allow you to run faster? –  RhysW Apr 24 '13 at 9:46
    
Not faster, longer. –  nnevala Apr 24 '13 at 11:02
    
Then why can I use the bike machines at the gym far longer than I could run on a treadmill? –  Jim Apr 24 '13 at 17:29
    
The prohibitive factor in running distance is not overheating. Note that runners cannot run significantly further when its very cold out. –  zhermes Apr 25 '13 at 1:07
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.