Just to add a bit more color here: most flexor muscles in your body are a lot stronger than the corresponding extensors, so when an external command comes in telling both to contract, for example from electricity in the thing you're working on, gripping wins. You can't let go. Great for grabbing a branch as you fall out of a tree. Not so great for repairing a power line.
Late edit: I've heard you can use this factoid to your advantage to avoid being eaten by an alligator or crocodile. Wrap your arms around its snout and hold on for dear life. Their jaws are strong enough to snap you in two, but not enough to force themselves open when you're holding them shut. I don't know what Step Two is, unfortunately.
Late edit: I've heard you can use this factoid to your advantage to avoid being eaten by an alligator or crocodile. Wrap your arms around its snout and hold on for dear life. Their jaws are strong enough to snap you in two, but not enough to force themselves open when you're holding them shut. I don't know what Step Two is, unfortunately.