Because your muscles are low on oxygen and they fill with an acid that causes the hormone of pain. That is what I learned in science yesterday actually so haha.
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To get your legs to strengthen by running and running because this is using your muscles and that helps your legs to strengthen.
When you run on the treadmill, the muscles in your legs work harder than usual, causing microscopic damage to the muscle fibers. This can lead to inflammation and soreness, known as delayed onset muscle soreness (DOMS). Additionally, the impact and repetitive motion of running can also put strain on your joints and ligaments, contributing to the discomfort in your legs.
It does not hurt because you are not running hard enough. You have to exert yourself.
Your legs may hurt when you sleep because you are experiencing growing pains. You may also have restless leg syndrome which can cause sore legs.
Not entirely, no. It'd be better to say "there's a pain in my legs". To say "my legs are painful", is to say "my legs can hurt people", pretty much.
Does it hurt?
You've probably slept with you legs in an awkward position.
Because you move your legs so much and they are not used to the pressure.
by running
lay down and alleviate your legs
Look up sciatica.