How do the muscles and joints function during a simple soccer ball kick?
The relationship of the muscle groups to the kicking event depends a great deal on the contraction through the phases of the kick from pull-back, swing, and contact. Agonists contract to initiate movement at the hip, knee, ankle, and toe joints through the phases. The hip flexor muscles will dominate during the majority of the swing to the ball as they contract eccentrically to slow the leg's backswing and become concentric as the kick approaches the ball. Just before contact the extensor muscles will dictate the influence of the kick causing the hip and knee joint to slow or stop. The knee flexors become dominant just prior to contact, reducing the rate of knee extension. This interplay of extension and flexion which seems antagonistic serves to protect the knee joint from reaching its maximum range of motion and beyond, which can cause severe knee damage. The posterior femoral muscles act on the anterior cruciate ligament to keep the tibia in contact with the femoral condyles. They will pull back on the tibia maintaining proper alignment toward the ball. After contact the leg is mostly a flexor concentric contraction followed very quickly by the eccentric contraction (or brakes), while the hip flexor and knee extensors shorten. It is often suggested that after a kick the contact leg should be a landing leg to minimize the interrelational strain on the knee.
During the actual kicking phase the quadricep muscle group consisting of the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius will flex to extend the leg at the knee joint for kicking and standing. The rectus femoris pulls the leg up at the hip and will be primarily responsible for the kicking and lifting of the knee. These muscles are attached lateral to the pelvis below the iliac crest at the top two thirds of the femur and distal to the patella and upper tibia.
The muscle of the lower leg, especially the calve region, will be responsible for pointing the toes in the following manner. The gastrocnemius, proximally attached to the posterior of the lower femur and distally posterior of the heel via the Achilles tendon will allow much of the running and lifting of the heel for one leg while helping to steady the other (standing) leg. The soleus muscle, proximally attached to the posterior of the upper fibula/tibia and distally attached to heal via the Achilles (deeper to the bone than the gastrocnemius) will point the toes and lift the heels. The plantaris muscle, proximally attached to the posterior lower lateral femur and distally to heal via Achilles, will somewhat assist in pointing toes and flexing knees. The popliteus muscle, proximally attached to the lower lateral femur and distally to the posterior superior tibia will unlock and flex the knee. The flexor hallucis longus, proximally attached to the posterior fibula and distal to the underside of primary toe digit (big toe), it will flex the digit and support the arch of the foot. The flexor digitorum longus, proximally attached to the posterior tibia/fibula and distally to the four secondary toe digits, also support the arch of the foot and flex the four small toes. The tibialis posterior, proximally attached to posterior tibia/fibula and distally to the underside of the foot, will invert the foot for an inside step kick tipping the pinky toe down and the big toe up.
The hip joint, knee joint, ankle joint, and the joints of the toes in reference to the afore mentioned muscle groups attached at their respective bones. It will be necessary given the information presented to now associate which muscle will influence the hip, knee, ankle, and toe respectively. Essentially, quadriceps influence the hip and knee, the calve muscles the knee, ankle and foot. It may be pertinent to note that the central nervous system will control the motor units through the cerebellar processes in a learned manner for experienced kickers much like one walks without thinking. While more conscious learning in process kickers will be much more focused and have a greater variability in motor unit control. The muscles as described of course will influence the three primary associated joints of the lower extremeties. Make sure to point out that the muscles will be in antagonism at certain stages of the kick to allow momentum to be slowed and then reversed. Usually, this is a complex muscle unit integration but if you put it simply as pulling the leg back and swinging it forward you can perceive which muscles are exercising the most contractile influence.
1: Med Sci Sports Exerc. 2004 Jun;36(6):1017-28.