The squat exercise in sports biomechanics is classified as a Closed Kinetic Chain (CKC) movement where the distal end is fixed to one position. In comparison the Open Chain (OKC) movement where the distal end moves freely like a seated knee extension. CKC movement uses the quadrecips comparable to OKC movements but is far superior at recruiting and activating the hamstrings, glute maximus and gastrocnemius muscles. The squat works the entire body both with eccentric and contrentric loading to provide great strength benefits. The core is one area many people are not aware is switched on during the squat movement. The rectus abdominis and deep spine muscles activity increases with unstable squat movements and this is why you should avoid using machines. To recruit more muscle activation and neurological pathways use weight that is unguided by a machine to engage stabilisation of the deep trunk muscles and the core.
Sports athletes utilise squats within their physical rehabilitation program for muscular recovery of different injuries of the lower limb in particular the knee. Muscular atrophy resulting from injures to the lower limbs plays a major role in recovery time and return to sport. Eccentric loading of connective tissue is very effective in regaining strength especially for tendon repair. There has been much study in the rehabilitation parameters of ACL and PCL in regards to safe depth and angle of squats. Safe squatting in general continues to be a much talked about topic amongst practitioners and health professionals. In particular ACL stress at high knee flexion angles in healthy individuals. For rehabilitation purposes squats during recovery of cruciate ligament injuries should be adjusted and under supervision with a professional sports practitioner.
First we must breakdown and assess some anatomical structures and biomechanics involved in the squat exercise. We will first look at the peak stress of the cruciate ligaments in both CKC and OKC movements. A study by Medicine & Science in Sports & Exercise looked at the ‘Biomechanics of the knee during closed kinetic chain and open kinetic chain exercises’, which analysed stress on cruciate ligaments during both CKC and OKC. It gives evidence the peak of stress in the posterior cruciate ligament (PCL) is double in exercises in CKC. PCL forces rise consistently with every flexion angle beyond 30° of knee flexion peaking at about 90° and declining significantly after with minimal PCL forces past 120°. However, the peak of tension of anterior cruciate ligament (ACL) takes place in the exercise of OKC close to full extension of the knee. Peak ACL forces of CKC movements occur between 15 - 30° of flexion and decreases significantly at 60° then levelling off afterwards at further flexion angles.
So when we break this down what does all this mean? Well it means for health individuals with no injuries there is minimal evidence that deep squatting with high flexion of the knee causes stress injuries to ACL and PCL and therefore is safe to carry out. Although some authorities caution against deep squats the forces on the ACL and PCL decrease at high flexion and compressive forces on the menisci and articular cartilages in the knee peak at these same high angles. In theory there is a possibility for stress injury overtime during deep squatting of the menisci and articular cartilage. Tibiofemoral joint compressive forces have been shown to peak at 130° of knee flexion where the menisci and articular cartilage are under load. Deep squatting overtime may increase susceptibility to patellofemoral degeneration with stress between the patella and the articulating aspect of the femur. However there is not enough evidence in this area and needs further study and investigation. To be safe this means if you are aware of articular damage or meniscus injury to your knee to minimize stress small squats below 50° of knee flexion is advised to decrease compression forces.
With proper technique the health benefits of squatting far outweigh any perceived risk of injury. It is subject of considerable controversy in recent years where some allege that squats are associated with injuries to the lumbar spine and knees. It is concluded that there is minimal evidence that deep squats performed with proper technique do not lead to increased rates of degenerative knee injuries and are an effective exercise. It is possible that shallow squats may be less effective and more likely to cause injury. safe and lead to degeneration in the lumbar spine and knees in the long-term.
The squat stimulates muscle building hormones like testosterone and growth hormone. This provides a highly anabolic environment which builds muscle not just in the lower legs but throughout the entire body when trained. Other than strengthening muscles squats strengthens bones, ligaments and insertion of the tendons throughout the lower body. Squatting is good for bone density health and may help prevent osteoporosis later in life. If done properly squats strengthen the muscles and structures around the knee providing stability and preventing injury. It is well known that squats are great exercise for burning fat as it works the entire body. Balance, stability, proprioception and core activation are all functionally used everyday and also highly relevant to sports performance making it one of the most efficient exercises.
Now we now go through the proper technique, with the steps to follow and things to avoid.
- First you must warm up prior with dynamic exercise of the functional muscle groups. This may include jumps or squats without weight.
- Lower your ego and drop the weight right down whilst learning the technique of squatting. It is key to start with correct technique in mind rather than heavy amounts of weight.
- Stand with your feet a little wider than shoulder width apart.
- Have feet slightly angled outwards. The more the feet flare the more work is placed on the hamstrings and glutes. If your calves are particularly tight this can help to achieve full range of motion.
- Keep your lower back in a neutral position with core braced keeping your knees centred over your feet.
- Avoid flexing the lower back as it increases the risk of disc bulge injury.
- Make sure the chest is out keeping the head facing forward with eyes straight ahead.
- Your weight should be back on the heels rather than on your toes.
- Slowly hinge from your hips, knees and ankles down to a deep squatting position.
- Keep your knees over your toes and prevent them from tracking forward.
- A full squat terminates with hips at or below knee level.
- Drive up from your heels returning to the starting position and repeat 8 to 10 times for 3 sets two times a week.
- Breathe in as you lower and breathe out as you return to starting position.
- Be aware of muscle imbalances during movement keeping weight even on both sides. You may find one side to be stronger.
- The heels should never rise up at any stage and should be well planted throughout the movement.
- Using heavier weight will make squatting to a deeper level easier.