Thread: Muscle Efficiency

I have heard that animals other than humans have much greater strength to weight ratios; I was wondering if anyone could explain how that works?

For example, I heard about a test in which a 135lb. female human and chimpanzee took turns pulling on a force meter , I think the woman could pull about 200lb., while the chimp could pull about 1200lb.

What is different about their muscles, do they have to eat a lot more to have the energy for this, why don't humans have these muscles, and finally, how can we get them!

There are a lot of factors that effect muscle strength - total muscle cross sectional area, fiber cross sectional area (larger fibers are stronger), proportion of different types of muscle fibers (fast twitch, for quick bursts of movement, and slow twitch, for prolonged movement, and there are multiple types of fast and slow twitch), the overall efficiency with which muscles turn energy into force, differences in the molecules that create muscle action such as myosin and actin, and the lever mechanics of the muscle in question (which is more closely related to skeletal morphology than to the muscles themselves).

I tried to do some research on this but there doesn't seem to be much direct comparative research between the muscle morphology of humans and chimpanzees (nor much reliably sourced information on the subject in general). Sadly, that means we don't entirely understand where the difference is coming from.

One article I did find is this:

http://www.vetmed.ucdavis.edu/PHR/PHR292/Stedman.pdf

If you scroll down to the third page you'll see pictures of a cross section of jaw muscle (right below the skulls). The one on the left is from a macaque, and the one on the right is from a human. Notice how the individual fibers in the macaque sample are significantly larger than the fibers in the human sample. The paper contends that these differences are due to a genetic mutation in a muscle gene that is present only in humans. If that's true, it's probably safe to assume that chimps have similarly large fibers compared to humans, at least in their jaws - which would make those muscles much stronger than the human correlates.

I have heard in several places, though unfortunately I didn't find any good sources for it, that chimpanzees are strong but slow, and humans have evolved to be fast and flexible, rather than strong. A chimpanzee diet is primarily fruit, which does not need to be chased in order to be eaten. So in order to be as comparatively strong as a chimp, you might have to sacrifice a lot of your flexibility and speed. (Just think about typing - a continuous series of quick, delicate movements. Do you think a chimp could do that?)