The knee helps your leg flex and extend.
extend
It is still sitting!
There are four muscles that extend the leg. vastus lateralis, vastus medialis, vastus intermedius and rectus femoris.
Quadriceps will extend your lower leg.
You extend the muscles neccisary, and contract others.
if your sitting down
Extend from the groin to the end of the foot.
extends leg; straightens knee joint
Quadriceps' units and sartorius
you wont lose a leg
From a crouching position, wrap your left leg around your right ankle like a snake. With your hands on the gound, jump and extend both of your legs as you spin your torso and legs a little counter-clockwise to land in a sitting position facing another direction. However, after you extend your legs and are still in midair, tuck your left leg in, so you land on your left foot instead of your bottom with your right leg sticking out. The five-step is a good transition from a six-step to a four-step.