Definition of the Quadriceps Muscles

Man on muddy bike
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The quadriceps muscles consist of four large muscles at the front of the thigh: the rectus femoris, vastus intermedius, vastus lateralis, and vastus medialis. The "quads" are powerful muscles involved in movement and propulsion. Exercises that improve the quadriceps muscles are leg presses, squats, and leg extensions.

Anatomy

The rectus femoris has its origin on the iliac spine of the hip bone.

The other quadriceps muscles have their origins on the femur. The vastus lateralis originates on the lateral surface of the femur, the vastus intermedius on the anterior surface, and the vastus medialis on the medial surface. All four quads insert on the patella (the kneecap) via the quadriceps tendon and on the tibial tuberosity via the patellar ligament. The rectus femoris partially covers the other three quadriceps. The femoral nerve innervates the quads and they get their blood supply via the lateral femoral circumflex artery.

What the Quadriceps Muscles Do

The quadriceps all work to extend (straighten) the knee. The rectus femoris also flexes the hip, The vastus medialis adducts the thigh and also extends and externally rotates the thigh and stabilizes the kneecap.

You use the quads whenever you straighten a bent knee. In everyday life, they help you get up from a chair, walk, climb stairs and squat.

They are used in walking and running at the onset of a stride and get used significantly when going downhill. They get a real workout with cycling, and cyclists have well-developed quads. The quads are used in jumping and sports like basketball that requires jumps.

The quadriceps are antagonists to the hamstring and gluteal muscles, which do more of the heavy work in running and walking.

Tight quads can have an effect on those antagonistic muscles.

Exercises

Sprinting, cycling, and stair climbing will give the quads a natural workout. Compound exercises for the quadriceps include sprints, squats, lunges, deadlifts, leg press, and Smith Machine squats. Isolation exercises for the quads include leg extensions and exercise machines for the inner thigh and outer thigh.

Stretches

Tight quadriceps can cause an imbalance with the hamstrings and gluteal muscles. Runners and cyclists may experience tight quads. Warming up at an easy pace can help relieve tight quads, but using stretches is common.

Injuries

Runners often develop an imbalance between strong hamstring muscles and less developed quadriceps. A pulled or strained quad muscle may result, often during a sudden acceleration, sprint, or kicking action.