With an understanding of the anatomy of certain joints, and how they should move, any exercise can be analyzed. The purpose of this is to ensure exercises are done correctly; not only to gain maximum results from the exercise, but also to prevent any injuries. Correct execution of an exercise can only be achieved through learning, and correct instruction. Thereafter, close monitoring is needed, to ensure the learning is put to good practice. This means that the person administering the exercises needs to not only have a good understanding of the anatomy involved in the movement, but also the correct execution of the exercise, itself. Only the combination of these two aspects will result in sound analysis of the movement, and therefore correct execution of the exercise.
Conducting a Biomechanical Analysis
When instructing an exercise, or movement, each aspect of the movement needs to be monitored. For the sake of this section, we will use the squat as an example.
When squatting, we have to observe all for the joints involved in the movement, as well as other body parts that may be involved for stabilization, or balance. As with most movements, it is best to start with the base of the movement, as this is where it is most likely to start going wrong. As we work our way from the base, any corrections will have a knock-on effect. In other words, a correction of the ankles may lead to correcting any improper movements at the knees and hips.
As already mentioned, a good knowledge of how each joint should move is necessary for any analysis to be done. So, for the squat, knowledge of the feet, ankles, knees, hips and pelvis are most important, and should be observed in that order. Thereafter, attention can be moved to the lower back, neck and shoulders to ensure correct posture and balance.
Feet:
First, foot positioning is very important. The angle of the foot, relative to the mid-line, as well as the thighs, is a hot topic as there are a few differing opinions on this. Positioning needs to prevent any excessive rotation of the tibia, as this will place strain on the knees. It also needs to not cause excessive flexion in the knee. The most commonly accepted positioning is to be angled at the same angle as the femur, relative to the mid-line, and wide enough to not result in excessive flexion. Next, the shape of the foot needs to be monitored. Excessive flattening, or arching, may point to improper movement at the ankles.
Ankles:
Rotation (either internal or external) needs to be closely monitored. While a small amount is allowable, any excess will lead to strain on the knees and hips, as we look further up the chain of movement. Excessive dorsiflexion may be a result of poor foot positioning, or of falling forward due to poor balance. Both of these will result in improper movement in the knees, which could cause excessive strain on ligaments and tendons.
Knees:
Positioning relative to the feet, as well as the hips, will give an indication of balance, as well as equal force application of the involved muscle groups. Knees which remain predominantly over the feet will ensure the force is applied relatively by the calves, quadriceps and hamstrings, as well as ensure correct application from the gluteal groups. Knees which stray either outside, or inside the feet will show excessive rotation in the knee, as well as indicate an imbalance between the abductors and the adductors of the hips. If only one knee is straying, this may indicate rotation at the ankle, or at the hip, of that leg. Lastly, knees which move further forward than the toes will show potentially excessive flexion. But, more importantly, it is likely to indicate poor balance, as well as improper force couples.
Hips:
If everything below the knees is working correctly, the hips will almost always follow and automatically correct movement. This is because the hips and pelvis are where the two legs meet, and they are therefore controlled by what is happening in the legs. However, rotation, flexion and abduction/adduction still need to be monitored.
Pelvis:
Essentially the centre of this movement, the pelvis is the most likely to display any faults in the gross movement. But, while it may show that there is a problem in the overall movement, it is usually not the cause of the problem. Left and right rotation of the hips, with accompanied shift to that side, will usually show favouring of one leg. The rotation and shift will be towards the leg doing most of the work. This could be attributed to an outright strength deficit. Or, it could be favouring do to pain or instability. Rotation without the shift is more likely to show tightness in the hip musculature, or it will be a result of improper movements lower in the chain. The other movement to watch for will be pelvic tilt. Lateral tilting will be in line with rotation and shifting. But, anterior and posterior tilt will usually show lack of mobility and core strength. The lack of core strength results in the body needing to tighten the lower back and pelvic complex through adjusting the positioning of these structures. It will lead to excessive strain on muscles which are meant to be prime-movers, as opposed to stabilizers, as well as excessive strain on joints and ligaments which are not being adequately supported.
If all of these structures are positioned and moving correctly, the peripheral structures should naturally position themselves correctly. And, it is therefore reasonable to think that any malalignment in the peripheral structures can be corrected through correcting of the primary moving joints of the exercise.
These principles can be applied to all other movements of the body. First, knowing which structures are involved in the movement. Next, knowing how these structures interact with each other, in creating the movement. And finally, being able to recognize when movements are not happening the way they are meant to. With this knowledge, movements can be analyzed, and corrected where necessary.