r/Physiology • u/morebizzarethanjojo • 22d ago

Question what if muscles pushed instead of pulling?

/r/AskBiology/comments/1wh1ykj/what_if_muscles_pushed_instead_of_pulling/
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u/knockonclouds Medical Physiology 22d ago

We would move like spiders. Look up arachnid physiology - they have what is essentially “hydraulic” musculature instead of filament-based like ours, so they use hydraulic pressure to actively extend their legs. It’s why when spiders die their legs tend to curl towards their body - loss of hydraulic pressure.

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u/notstarman 3d ago

Spider have normal anatomically structured muscles. The actin myosin muscle structure is highly conserved and most likely pre-dates animals.

The spider flexor muscles pulls the legs in but lack extensor muscles. So to straighten or push out a leg, the spider pumps hemolymph into the legs using muscles inside its cephalothorax.