Muscle: 

Quadriceps: The quadriceps are made up of four muscles:

1. Rectus Femoris

2. Vastus Medialis

3. Vastus Intermeduis

4. Vastus Lateralis

Muscle: Rectus Femoris

Origin:                       

At the anteroinferior iliac spine and the brim of the acetabulum (above the thigh bone on the pelvis).

Insertion:

At the superior surface of the patella (the inferior patellar ligament then inserts into the tibial tubercle), (top of the shin bone below the knee).

Function:

Since the rectus femoris effectively crosses two joints (origin: above the hip and insertion: below the knee) it has varied functions. The rectus femoris extends the lower leg (as in leg extensions) and assists in flexing the thigh on the pelvis (as in a hanging leg raise). When the thigh is fixed (as in the contra-indicated movement: straight legged – feet fixed in position sit up) it assists in flexing the trunk on the thigh (this is the reason why the straight-legged sit-up is contra-indicated. This position places high stress on the lumbar spine, while creating the hip-flexor response that activates the tibialis anterior – rectus femorus – illipsoas and effectively by passes the rectus abdominus – the rectus abdominus stays in isometric contraction during the hip-flexor response).

The rectus femoris is the “showy” muscle in the center of the front thigh, but it provides only about 20% of the total extension force of the quadriceps group. It cannot fully extend the knee without the aid of the other vastus muscles, specifically, the vastus medialis (tear-drop shaped thigh muscle located above and inside the knee).

Indication of Weakness:

Weakness of the rectus femoris on one side may result in posterior rotation of the ilium. You can check for indication of weakness by assessing hip levels. You can put your hands on the top of the standing athlete’s ilium, the pelvis will appear relatively lower on the weaker side. You can double-check your assessment with single-leg extensions. Watch to make sure the foot remains neutral. If the athlete’s rectus femoris is weak, they may try to pronate their foot in order to utilize the stronger vastus medialis. Less likely, but still possible, is for the athlete to internally rotate the feet to use the vastus lateralis for help.

Muscle: Vastus Medialis

Origin:

At the posteromedial femur and the tendons of the adductor longus and magnus, (inner side of the femur, starting just below the top of the femur coming down the upper 2/3’s of the intercondylar line -  inner thigh bone).

Insertion:

At the superior surface of the patella (along with the rectus femoris and the other vastus muscles). The inferior patellar ligament then inserts into the tibial tubercle. 

Function:

The vastus medialis is a primary stabilizer of the patella (along with the vastus lateralis). The lowest fibers of the vastus medialis are the vastus medialis oblique (VMO). The VMO’s muscle fibers run almost horizontally and contract maximally during the final stage of knee extension. The primary function of the VMO is to keep the patella in the patellar groove of the femur.

Indication of Weakness:

Weakness of the VMO, vastus medialis or vastus laterals muscles can manifest as an abnormal position or abnormal movement of the patella with chronic instability of the knee. With any indication of weakness in any of the quadriceps muscles – avoid OPEN CHAIN EXERCISES, such as leg extension. Instead, have the athlete perform CLOSED CHAIN EXERCISES, such as squats, leg presses and dead lifts.

Muscle: Vastus Intermeduis

Origin:

At the anterior and lateral two-thirds of the upper femur

Insertion:

At the superior surface of the patella (along with the other quadriceps muscles). The inferior patellar ligament then inserts into the tibial tubercle.

Function:

The vastus intermeduis extends the lower leg. It lies underneath the rectus femoris.

Indication of Weakness:

If the vastus intermeduis become shortened or too tight it can cause pain under the patella. Actually, if any of the quadriceps muscles become shortened, it could cause pain under the patella due to the abnormal compression of the patella into the patellar groove.

Muscle: Vastus Lateralis

Origin:

At the greater trochanter (upper thigh bone), gluteal tuberosity, and lateral aspect of the upper three-fourths of the femor.

Insertion:

At the superior surface of the patella, (along with the other quadriceps muscles); the inferior patellar ligament then inserts into the tibial tubercle.

Function:

The vastus lateralis is the largest quadriceps muscle and when fully developed adds the “SWEEP” to the thighs when viewed from the front. The vastus lateralis extends the knee.

Indications of Weakness:

Weakness of the vastus lateralis muscles can manifest as an abnormal position or abnormal movement of the patella with chronic instability of the knee.

Optimal Training Principles

Pre-exhaustion programs are not recommended for the quadriceps, primarily as a result of numerous dysfunctions present or that can occur. The quadriceps are powerful muscles and when the quadriceps incorporate the equally powerful gluteals, very heavy loads can be placed on the entire body. Therefore, it is recommended that you begin training with the compound movements (such as: squats, dead lifts and leg presses) in order to enhance the normal movement patterns of the body. 

The safest squat with excellent overall benefit is the IFPA Recommended Squat Rules:

Rule 1:   Head neutral

Rule 2:   Shoulders back

Rule 3:   Bar resting on top of the scapula and posterior deltoid.

Rule 4:   Maintain “weight-lifters arch”

Rule 5:   Descend – 4 counts – inhale

Rule 6:   Do not exceed “knee-toe-line”

Rule 7:   Do not exceed “knee-hip-line”

Rule 8:   Do not bounce at bottom

Rule 9:   Feet positioned slightly wider than shoulder-width

Rule 10: Toes pointing outward for comfort 10-20 degrees

Rule 11: Nothing under heels

Rule 12: Knees track directly over toes

Rule 13: Ascend – 2 counts – exhale

Rule 14: Don’t lock the knees

According to research from the NSCA, if your athlete uses the GPO Principle (Gradual Progressive Overload) and performs deep barbell squats (hips go below “knee-hip-line”: violating Rule #7) starting out very light and gradually increases the load used in the deep squat, there will be little chance of injury. Powerlifters are required in competition to go below the “knee-hip-line” it is well known that this movement places high stress on the joint capsule. Therefore the IFPA recommends caution when using the deep squat and good judgment on whether the movement is appropriate for your athlete.

Now that the cautions are out-of-the-way, the benefit to performing deep barbell squats is to strengthen the VMO. The VMO is the primary muscle in the quadriceps for full-knee extension and knee stability. Deep squats cause much greater muscle activation of the VMO than any other exercise. If your concern for your athlete is care and prevention of potential knee athletic injuries, you can begin with NO resistance and a SUPER-SLOW technique to limit the chance of a problem developing.

The wide-stance-squat provides greater leverage and therefore is used to increase overall strength. The wide stance shifts the center of gravity slightly backward, this allows the powerful hip and gluteal muscles greater muscle activation, while decreasing stress on all but the vastus medialis muscle of the quadriceps. This exercise is best used to increase overall strength and to increase stress on hips, gluteals and vastus medialis. This wide stance squat position is referred to as the Powerlifter Squat. To optimally perform the Powerlifter Squat follow the IFPA Rules – except: position the feet fairly wide apart with toes pointed outward between 10 – 30 degrees. It is imperative that you maintain the “weight-lifters-arch” (Rule #4). During the descent, allow the hips to come back and down as if sitting in a chair and shift the weight naturally to the heels. During the ascent drive the weight through the heels while driving the hips up and forward.

The narrow stance squat is referred to as the “bodybuilder squat”. This is not recommended for the ordinary athlete because the barbell is positioned higher on the neck with much of the weight coming down on C-7 (Cervical vertebrae – 7). C-7 does not like this! The narrow stance makes it difficult to maintain a “weight-lifters-arch” and impossible not to exceed “knee-toe-line”. Bodybuilders use this high-risk exercise to move the stress load from the gluteals and hips to the quadriceps and primarily the vastus lateralis in the quadriceps group.

Similar variations are performed with similar results in the leg press, dead lift, hack squat, etc…

In the leg extension machine, you can also change the stress on different  muscles of the quadriceps by rotating the position of the feet:

1. internally rotating (pointing the toes-in) increases the stress

    on vastus lateralis.

2. externally rotating (point the toes-out) increases the stress

    on the vastus medialis.

To increase the stress of the rectus femoris is the leg extension machine, extend the upper body by posteriorly tilting the pelvis (this is the opposite of the anterior pelvic tilt in the “weight-lifters-arch”. Remember from your IFPA Personal Training Course/Manual/Workshop anterior pelvic tilt, you pour water out of the front of your pelvis (bucket), posterior pelvic tilt, you pour water out of the back of your pelvis (bucket). The posterior pelvic tilt stretches the rectus femoris more and therefore places more stress on this muscle while performing leg extensions.

Warning: Leg extensions are OPEN CHAIN EXERCISES and not recommended for injured knees. Most Critically: NOT recommended for ACL injuries (Anterior Cruciate Ligament). Remember what you learned in previous IFPA courses, leg extensions contract the quadriceps and pull the tibia anteriorly. This puts high levels of stress directly on the ACL and could cause an injury or re-injury to occur. Instead use CLOSED CHAIN EXERCISES such as the squat or leg presses. These exercises causes a co-contraction of the quadriceps and hamstrings, this axial load reduces anterior tension on the tibia and allows the ACL to heal properly.

One great benefit to performing compound exercises with high intensity loads is that high stress stimulates the endocrine system to produce anabolic hormones (HGH – Human Growth Hormone, IGF-I - Insulin like Growth Factors, testosterone, ect…), at least in males, there is limited evidence that heavy compound movements (i.e.: squat) stimulate testosterone production in females. Though I suspect that this may have more to do with what the test subjects defined as “high intensity”. Females are obviously limited in the amount of testosterone their bodies can produce, males can produce 10 – 30 times the amount of testosterone which is what makes us bigger, stronger, faster, meaner and dumber than females. Females should still do compound movements at high intensity (8 RM or heavier) for the other benefits.

James T. Bell, PhD.c. is the founder and president of the International Fitness Professionals Association, IFPA.

More Books from Jim Bell, PhD.c.

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