What Is Quadriceps?
Quadriceps muscle is located at the front of your thigh bone. It consists of three muscles: vastus medialis (vastus longus), vastus intermedius (vastus lateralis) and soleus (soleus). Vasti medii is the largest muscle, which is responsible for lifting your leg up off the ground. Vasti lateralis is the smallest one, which helps in bending your knee. Soleus is the middle muscle, which assists with extending your foot upward. These muscles are all connected together through tendons and ligaments.
The quadriceps muscles have two main functions:
1) They assist in raising your legs when running or jumping; and 2) they help you bend your knees during walking or sitting down.
How Does Quadriceps Work?
Quadriceps work by contracting and relaxing the muscles in order to raise your legs. When you run, jump or perform other movements involving your legs, these muscles contract. When they relax, it means that the movement stops. If you try to lift yourself up with only one leg while keeping the other straightened out, then your body will fall over if not properly supported.
When you stand up and lift your leg, the quadriceps need to contract in order to keep your body stable. If you want to extend your leg, then these muscles need to relax. The act of extending your straightened leg causes the muscles to tire out.
If you fail to do that, then your body will fall over as well.
Quadriceps Work by Shortening and Lengthening
The rectus femoris, vastus medius and vastus lateralis are all involved in straightening your knee. They also help in extending your leg. This happens when your knee bends at a right angle to your shin bone.
Your body weight pulls down the kneecap, which pivots on a hinge supported by the thighbone (femur). The lower end of the thighbone slides in a groove at the top of your shinbone. The movement of knee bending is mainly powered by the muscles in the front part of your thigh. During this process, the vasti muscles separate or spread out to create space for your thighs to move closer to each other.
The rectus femoris, vastus medius and vastus intermedius are involved in both knee bending and straightening. They all help in stretching your leg back by extending your knee. This happens when the knee is bent back and the lower part of the thigh slides over the shinbone.
During this process, the vasti muscles contract and shorten to move your thigh backward.
The rectus femoris
The rectus femoris is the only quadriceps that starts at the hipbone (ilium). It runs straight down the middle of your thigh. It is the only muscle that actually crosses both the hip and knee joints.
It straightens your hip and bends your knee.
The Vastus Medii Muscle
The vastus medii is a quadriceps muscle that starts at the top front of your hipbone (ilium) and runs down to the upper front part of your shinbone. It is involved in bending your knee as well as stretching your leg backward.
The Vastus Lateralis Muscle
The vastus lateralis is a quadriceps muscle that starts at the side of your hipbone and runs down to the upper part of your shinbone. It is involved in bending your knee and stretching out your leg sideways.
The Vastus Intermedius Muscle
The vastus intermedius is a quadriceps muscle that starts at the side of your hipbone and runs down to the upper part of your shinbone. It is involved in straightening your knee as well as stretching out your leg sideways.
Sources & references used in this article:
Developments in the use of the hamstring/quadriceps ratio for the assessment of muscle balance by R Coombs, G Garbutt – Journal of sports science & medicine, 2002 – ncbi.nlm.nih.gov
Biomechanical considerations in patellofemoral joint rehabilitation by LA Steinkamp, MF Dillingham… – … American journal of …, 1993 – journals.sagepub.com
Maximal voluntary force of bilateral and unilateral leg extension by PG Schantz, T Moritani, E Karlson… – Acta Physiologica …, 1989 – Wiley Online Library
The effects of gender on quadriceps muscle activation strategies during a maneuver that mimics a high ACL injury risk position by GD Myer, KR Ford, TE Hewett – Journal of Electromyography and …, 2005 – Elsevier
The effect of concentric isokinetic strength training of the quadriceps femoris on electromyography and muscle strength in the trained and untrained limb by TK Evetovich, TJ Housh, DJ Housh… – … Research, 2001 – journals.lww.com
Patellofemoral stresses during open and closed kinetic chain exercises: an analysis using computer simulation by ZA Cohen, H Roglic, RP Grelsamer… – … American journal of …, 2001 – journals.sagepub.com
Electromyographic and kinematic analysis of cutting maneuvers: implications for anterior cruciate ligament injury by S Colby, A Francisco, Y Bing… – … American journal of …, 2000 – journals.sagepub.com