Ever had a panic attack followed by very achey legs? At first I thought it was just me but then I found its actually very common and there's science behind it. The geek in me loves stuff like this!
So when you feel stress the body enters its fight or flight mode. This was amazing back in the days of early man. You hear a mountain lion roar behind you, that stresses you out slightly and your body reacts by running like crazy. Its a built in mechanism that was meant for survival. There's also freeze which in some cases can help too. Another cave man screams 'ah buh argghhh ah' which roughly translates to 'whose in my patch of forest, I'm going to cave your head in with my club', you feel slightly stressed and you freeze. He can't hear you rustling in the bushes and goes back to his hobby ot painting crude drawings of animals on his cave wall. But for those of us with panic disorders and anxiety we have found that that response can trigger when it doesn't quite need to or be overactive in situations that are mildly stressful but don't need a life or death response.
The body preparing to flight will send a surge or adrenaline through the body, especially to our legs that will help us to run. Ever heard someone say I didn't know they could move that fast. They usually mean a person moving or reacting very quickly when startled or in perceived danger. Such as your elderly grandparent with a fear of anything creepy crawly dashing across the kitchen when somebody shouts 'spider'. In that case they have used their adrenaline to protect themself from perceived danger. This is very useful in the body as danger may happen when you are already extremely tired, injured, unwell and less able to move more freely. You don't hear people say I saw the bus coming towards me but I didn't attempt to move because my knees a little sore. Their body takes over to protect them. The same with freeze mode. If somebody shouted poisonous snake and pointed beside you, some people would run and some when stand completely still with fear. They are in freeze mode. And to help with this the body tenses all your muscles. This can also be caused by an adrenaline surge that sits in the muscle making them feel sore later.