The squat is widely regarded as the 'king' of the lower body strength exercises. There is no other equivalent in the gym that can develop flexibility, strength, activation of muscle tissue and hormonal response as well as the squat, or its derivatives. As with any advanced exercise, the correct technique is vital to getting the most out of the exercise and minimizing the risk of injury. But again, with most advanced exercises, there are as many interpretations of correct technique as there are trainers who are instructing the exercises. With that in mind, here is how I would teach a full squat and the reasons why I teach this way, and not the way you would perhaps commonly see it performed in your local gym.
Set up:
1. Set a barbell on the upper portion of the trapezius (for the back squat) or in the clean position with the bar on the clavicles and the elbows up and in (for a front squat);
2. Grip the barbell as close as possible to the outside of the shoulders and tuck the elbows in and under the bar. Maintain this position throughout the movement, as it keeps the load as close as possible the centre of mass.
3. Elevate the chin slightly.
4. Set the feet hips width apart and turn the toes out 15 degrees.
Descent:
1. The knees move directly forward as far as possible. As the knees travel forward, the hips lower down as low as flexibility allows, breaking at the knee and hip simultaneously;
2. Keep the back as erect as possible with the chest up;
3. The body is lowered under control until the hamstrings make contact with the calves;
4. The knees should travel forward over the toes;
5. The heel should remain flat on the floor.
Ascent:
1. The hips and knees extend together to bring the body back to the starting position.
2. Keep the torso as upright as possible throughout the ascent.
As you can see, I am advocating that the squat be performed through a full range of motion at the knees which allows the knees to translate forward of the toes. Although common place in strength and weightlifting settings, this is not the norm (putting it mildly!) in the fitness industry.
When I think of reasons why partial range squatting to 90 degrees (with restricted knee movement) has become the accepted way to squat in the fitness industry, two primary explanations come to mind: The first is that most people do not possess the requisite flexibility and strength to be able to perform the exercise through the full range of motion, so perhaps rather than developing the appropriate abilities, they have little option than to resort to the half squat instead. The second reason is because most trainers are taught that you should never squat deeper than thighs parallel to the floor or to let the knee travel past the toes because it damanges the knee.
The concept of restricting the knees while squatting is so commonly known and accepted, but I am still yet to see any convincing scientific evidence that provides definitive proof that performing the squat (or it’s derivatives) through a full range of motion with correct technique (assuming a trainee possesses the required strength and flexibility) is dangerous to the knees. The evidence simply does not support such a viewpoint. The most noted squat researcher of our time, Rafael Escamilla, has recently said:
Clinicians and trainers often believe that anterior translation of the lead knee beyond the toes during squatting type exercises increases patellofemoral force and stress, but currently there is no evidence to support this belief (Escamilla, et al. 2009).
At any rate, we would know if full squatting was dangerous to the knees well before the scientific community told us because every athlete that trains for the sport of weightlifting – which involves ballistic deep squatting with very heavy loads – would be in continual rehab for their knees! Additionally every Asian or baby who sits for prolonged periods in a deep squat position would be lining up for knee replacements! And if the knee shouldn’t travel forward of the toes, then walking up stairs would be extremely difficult!
One of the most commonly cited reasons for restricted the knees and depth while squatting is due to the proposed increase in patellofemoral stress and force. Yet a close review of the extant literature does not support this belief. Escamilla et al. (1998) reported that during a back barbell squat, patellofemoral forces increases until 75-80 degrees knee flexion and then began to plateau and actually decreased as the depth of the squat increased.
A study by Salem & Powers (2001) looked at patellofemoral joint kinetics at three different depths of knee flexion: 70 degrees (above parallel), 90 degrees (at parallel), and 110 degrees (below parallel). The researchers discovered that ‘peak knee extensor moment, patellofemoral joint reaction force and patellofemoral joint stress did not vary significantly between the three squatting trials’. This study did not find any evidence that squatting through full range of motion increased stress on the patellofemoral joint. A review on squat technique in the Strength & Conditioning Journal by Comfort & Kasim (2007) had the exact same conclusions.
After analyzing the patellofemoral force and stress data during squatting published by Escamilla et al. (1998) and Salem & Powers (2001), the world’s foremost squat researcher, Rafael Escamilla, has concluded that risk to the patellofemoral joint may not increase with knee angles between 75 and 110 degrees due to the similar magnitude in patellofemoral stress during these knee angles, with the added benefit of increased quadriceps, hamstring and gastrocnemius with training the squat through full range of motion compared to partial range squatting.
Indeed, the range of motion of a squat makes a considerable difference as to which muscles are needed to contribute to joint movement. Caterisano et al. (2002) found that for the hamstring and gluteaus maximus muscle to be sufficiently recruited during a squat, a full squat depth was needed. Performing the squat to parallel, or above, recruited those muscles significantly less. As explained below, this uneven recruitment of leg muscles, in part, explains why partial range and restricted knee movement squatting is inferior to knee health than full range, unrestricted knee movement squatting.
Despite these studies, I am always intrigued that common place viewpoint can be so vigorously defended and taught to personal trainers despite there being no evidence on knee kinematics while squatting lower than 90 degrees to validate the veracity of the belief.
Of great interest is a recent study by Escamilla’s group (2009) which compared patellofemoral stress and force during the wall squat with the feet forward - so the knees are over the toes in the deepest position, a wall squat with the feet back - so the knees are forward of the toes at the lowest position but the trunk is kept upright, and a single-leg squat (where the knee travels forward of the toes but the torso is allowed to tilt forward to maintain balance).
Despite the knee translating forward of the toes during the single-leg squat, between 60 to 90 degrees knee flexion, both wall squat exercises produced significantly greater patellofemoral compressive force and stress compared with the single-leg squat.
The reason for these results is found in the relative contribution of quadriceps and hamstrings to joint movement. The wall squat variations keep the torso upright creating a relatively small hip extensor arm and large knee extensor force. So despite the knees travelling forward of the toes or not, the quadriceps are recruited significantly more than the hamstrings. EMG data showed 30-40% greater quadriceps activity during the wall squat compared to the single-leg squat. During the single-leg squat, the torso tilts forward 30-40 degrees resulting in a relatively large hip extensor activity and smaller knee extensor activity. This caused the hamstring forces to be 60-70% greater compared with the wall squat.
I agree with strength expert Charles Poliquin when he says that if a trainee cannot perform a squat through a full range of motion, they are considered to be in the rehabilitative stage of training. This is because a full squat that is performed correctly indicates structural muscular balance in the lower limbs and sufficient flexibility of the ankles, knees and hips. If a trainee cannot perform a full squat with correct technique, specific flexibility and special exercises, such as split squats and step up variations, will be recommended to address the imbalances that prevent the client from full squatting.
The correct way to perform any squatting variation (back, front, dumbbell, or overhead) is to take the three working joints – the hip, knee & ankle – through their fullest range of motion. The lowest position is where the hamstrings make full contact with calves. This keeps the knee joint healthy and lubricated, improves knee stability, mobilizes the soft tissue and activates the available musculature fully. In the terminal range, the knee will be brought forward past the toes and full contact is made between the hamstrings and calves. This complete range of motion refreshes the joint with synovial fluid (via synovial flushing), recruits the available musculature and aids flexibility development.
Stopping the squat prematurely, for example, parallel or higher, or restricting the knees from traveling forward, causes a change in motion half way through an eccentric loading cycle and creates uneven distribution of muscle and joint forces. The position of most instability for the knee joint is 90 degrees. This is why trained sports physicians assess knee stability using the Drawer Test at 90 degrees knee flexion, and not in the deep squat position. The knee is highly stable at full extension and full flexion. Despite what is commonly thought in gyms, it is more dangerous and contributes to destabilized knees, poor VMO development, over-developed vastus intermedius, inadequately recruited hamstring and gluteaus maximus, and incorrect joint tracking over the long term when one performs partial range squats.
Joints are designed to load and de-load, and for optimal lumbopelvic mechanics, the sacroiliac joint must tilt back and forth in a process called nutation and counternutation. Lack of mobility at the SI joint has been linked to low back pain. The deep squat position allows the SI joint to nutate and counternutate, keeping the SI mobile and healthy and activates the deep hip stabilizers, such as the piriformis, gemelii, obturators and the quadratus. All this is precisely what happens when the hamstrings make contact with the calves in the lowest position. This creates longevity in the joints, despite what is commonly taught to personal trainers.
There is much scientific support for the superiority of the full squat over a partial-range squat. For example, data from Sweden which has shown that the best predictor of knee injury is inadequate ankle flexibility. Put another way, athletes who could not perform a full squat had the highest incidence of knee injury. Swiss research has demonstrated that those athletes who could perform a full-range overhead squat suffered the least amount of knee injuries, groin strains and hamstring pulls. A study by Wilson et al. (1989) found that weightlifters had the best knee stability of athletes and non-athletes tested. The common feature of the three investigations was full squatting.
The obvious considerations to this ROM are injury history, painful knees (due to a variety of reasons from structural damage and knee pathology to tightness) and severe lack of mobility from the cervical spine down to the ankles. The primary point is this: if you cannot perform a full squat, you should not perform a squatting exercise at all. Split squatting and step up variations must be used until a full squat can be performed correctly with no pain. Again, despite what personal trainers have been taught by well-intentioned educators and physiotherapists, a half squat should never be used and the trainee should always be advised to take the knee forward during the movement rather than attempting to sit back and restrict forward knee movement. Research from Andrew Fry’s group showed that not allowing the knee to travel forward during squatting actually increased low back joint loading by over ten-fold! (Fry et al. 2003).
Conclusions
Once a trainee has developed the requisite flexibility and strength and is pain free, I can see no reason why squatting through a full range with unrestricted knee movement should be feared because of potential injury to the knee. So enjoy the multiple benefits that only the king of strength exercises can bring.
