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Comment by davyjones | Hacker News Reader

Human muscles are capable of much...(comparable to chimpanzees?). But there is some sort of a governor in place to ensure safety. In extreme circumstances, the governor can be "turned off" (adrenalin?) and we have cases of mothers lifting cars to save her child, etc.

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Essentially. IIRC there are a couple of negative feedback loops, one local and one involving the brain, and they usually limit you to about a 1/3 duty cycle for each muscle fiber. There are certainly ways that ratio can be increased, just yelling can increase the maximum force you can consciously exert by about 15%. I have no idea what the maximum is, but I'd imagine that going much further than what you're normally limited to drastically increases your odds of tearing something during exertion.

The reason chimpanzees can exert more force is anchoring, their muscles are anchored to the bone further form the joint so they have better mechanical advantage. A human has a much wider range of movement, though, and I believe we better maintain force under movement. So which a chimp might be able to lift themselves more easily, a human ends up being able to throw a rock or spear much further.

EDIT: Also, ekianjo is right that lifting cars is an exaggeration.

It's probably best not to compare human and chimp ROM, since that has less to do with muscle attachment sites, and isn't really that consistent, joint to joint. For example, a chimp shoulder has fabulous overhead ROM... as expected for a tree climber and swinger.

The flip side of having crappier levers for force, is that we have better levers for precision.

> lifting cars to save her child, etc.

Lifting cars is often an exaggeration in terms of wording, the reality is usually lifting up one side of the car, which is very different in terms of weight.

Muscle is not the only tissue involved with moving a weight around. Obviously you need a skeleton that can bear the load, and a heart & lungs fit enough to pump adequately oxygenated blood. But don't underestimate the large role a strength-adapted central nervous system plays.

no safety governor, just fine motor skills by addressing small specific muscle groups, hence unfortunate 'retard strength' myth (trading fine motor skills for blunt force)

no safety governor, just fine motor skills by addressing small specific muscle groups

I'm pretty sure the safeguard here is the Golgi tendon organ

http://en.wikipedia.org/wiki/Golgi_tendon_organ

http://en.wikipedia.org/wiki/Golgi_tendon_reflex

The Golgi tendon reflex operates as a protective feedback mechanism to control the tension of an active muscle by causing relaxation before the tendon tension becomes high enough to cause damage.

Chimpanzee doesnt damage itself while having more strenght using same muscle mass as weaker human.

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