There are four muscles that extend the leg. vastus lateralis, vastus medialis, vastus intermedius and rectus femoris.
The quadricepts (a group of four) are voluntary muscles that extend the leg at the knee.
The dorsiflexors include the extensorum longus, the tibialis anterior, and the peroneus.
Flexing the thigh, extending the leg, adducts leg
You extend the muscles neccisary, and contract others.
The quadriceps femoris group extends the leg at the knee joint. It is responsible for straightening the knee and kicking movements.
the muscles that extends the lower leg are vastus lateralis, vastus medialis and vastus intermedius. These muscles collectively make up the quadriceps..
Triceps
An inability to extend the leg would result from a loss of function of the common peroneal nerve, a branch of the sciatic nerve. This nerve provides motor function to the muscles that extend the leg and dorsiflex the foot. Injury or compression of the common peroneal nerve can lead to weakness or paralysis in these muscles, resulting in difficulty extending the leg.
The Hamstrings consist of three muscles that have the same action: the Biceps Femoris, Semitendinosus and Semimembranosus. Their actions are to flex the knee joint, adduct the leg, and extend the thigh. The Quadriceps femoris is four muscles of the femur. They are the Rectus femoris, Vastus lateralis, Vastus medialis, and Vastus intermedialis. As a group (the quads) they extend the leg at the knee.
The gluteal muscles.
The muscles that flex and extend your finger are not as large as those in your leg. As a result, the biochemical processes that cause muscles to flex are limited. Trying to exert leg-force with your hands is a bit like using a moped to haul a boat.
No, they can also contract, they do every time you use them to move an arm, a leg, etc..