Squat Physiology - A Brief Discussion

Abstract:

This report will attempt to define the sports skill �the squat’ by describing the associated physiology in its performance. Topics of discussion will include: Mobility and Stability; Development of Force; Coordination of movement; Delivery of Energy; Maintenance of Working Muscles; Integration of Systems and Functions.

Introduction:

Often named “The King of all Exercises”, the squat is a complex movement which targets the Quadriceps, Hamstrings and the Gluteus Maximus muscles, amongst others. It is an exercise which Physiologists, Sports Scientists and Personal Trainers will all agree is a necessary component of any weight lifting or rehabilitation program. "[the squat] is capable of inducing more and faster muscle growth than any other exercise" (Dr. Fred Hatfield).

Advantages of the squat encompass more than muscle growth in the target muscles. Due to the nature of the squat, i.e. the intensity of the movement, it increases testosterone in the body by 1000% in some cases . This testosterone increase benefits all parts of the body when other excercises are performed. Similarly, this increase will help in the building of other muscels in the body.

Discussion:

There are some criticisms regarding the squat, which a minority of physiologists and doctors make. The argument against the squat is that the huge force on the knee joint and associated ligaments is dangerous. The people who believe this are often those associated with the treatment of squat injuries, so they have a rather narrow view of the exercise.

However, studies on the squat and the associated forces on the knee show that it is indeed safe. The strengthening of the muscles around the knee helps to stabilise it in everyday activity and sport alike. Similarly, if overtraining isnt present, it will also have advantages on the ligaments of the knee. In particular, when proper form is used, the stress on the knee tendons is lessened since the hamstrings assist the patellar tendon in stabilization of the knee . If the hamstring isn’t properly utilised, such is in a partial squat the amount of shearing force on the patellar tendon increases rapidly. Therefore, with proper form, this is why the squat is a reccomended exercise for rehabilitation of knee injuries. It must be said that form is more important than the weight itself. Too many things can go wrong with disregard of proper form.

Mobilitiy and Stability:

The squat is performed by the subject flexing the knee and hips joints, as if sitting down on an imaginary chair, followed by the execution of pushing back up to the starting position. For this assignment, it will be assumed that a weight is situated across the subject’s back.

The target muscle and agonist in the squat is the quadricep. Different positions of the body will produce different stresses in the quadricep. For instance, leaning forward further (greater hip flexion) in the execution of a squat will shift the subject’s centre of gravity forward, resulting in the quadricep having to take over a larger amount of weight. However, this change in COG will result in a loss of stability, as in many cases. The same will result from raising the heels and adducting the legs, i.e. greater concentration on the quadriceps with reduced stability.

The primary antagonist in the squat is the hamstring. During the first phase of the squat, where the subject is lower themself, the hamstring is shortening and taking load. However, it is in the extension phase that the hamstring antagonises the quadricep.

The synergists which help in the squat are the gluteus maximus, adductor magnus and the soleus. Again, a different positioning of the body will alter the mobility and stability of the subject executing a squat with an emphasis on different muscles. Abduction of the legs, for instance, will target the synergists more, especially the gluteus maximus. The position also allows a wider base which increases stability during execution, as the centre of gravity is lower.

The dynamic stabalisers are the hamstrings and gastocnemius. Notice here that the hamstring is also the antagonist. Therefore there is a change of length in the hamstring, which is obvious because there is flexion and extension of the knee joint. How, then, can the hamstring also be a stabiliser? We must remember that because of the complex nature of the squat, some muscles will take on more roles than simply pushing or pulling. In this case, the hamstring will stabalise the whole knee joint, counteracting the anterior forces generated by the quadriceps.

Finally, the rectus abdominus and obliques in the midsection with the erector spinae in the lower back also stabilise the subject.

Development of Force:

In the squat there are many forces applied on the subject. These include internal and external forces. The external forces include: acceleration due to gravity, the mass of the weight across the subjects back, the resultant force from the ground and friction between the feet and floor. Internal forces include those between joints, tendons, ligaments and finally muscles. Also, there is an intertial force on the whole body between the flexion and extension phases of the squat.

See mobility and stability for forces around knee.

Forces required to execute the squat are given by

muscles described above.

Coordination of Movement:

During different phases of the squat, muscles are doing different tasks in moving and stabilising the body. Similarly, there is an order to which muscles move first.

Before the downward movement begins, the erector spinae, rectus abdominus and obliques are tight, stabilising the body in all three planes of movement. Also, the hamstrings are isometrically contracted to stabilise the legs. The first movement is flexion at the hips. Secondly, the knee joint flexes. During this phase, the quadriceps are not exerting maximally. It is mostly the antagonist and synergists, i.e. hamstring and gluteus maximus. Once the thigh is parallel to the floor (or lower), the upward phase can begin. Firstly, the hips extend and the pelvis is subsequently pushed forward. Secondly, the gluteus maximus contracts which provides the first upward thrust. Finally, the quadriceps provides the final necessary force to drive the subject to the starting position. Throughout the whole exercise, the core and