Think about this Case study:
Three groups of 15 year old male and female athletes were put on a leg strength program consisting of just squats during the summer for 10 weeks.
Group One - Did Full Squats (full squat to floor)
Group Two - Did 1/2 Squats (squat to 90 degrees)
Group Three - Did No Squats. (No squats at all)
Results: The group that did the ½ squats was found to be the most often injured! In group one (the full squat group) no knee injuries over the next one year were reported. In group two (the 1/2 squat group) 3 of the five athletes reported some kind of knee pain or injury. One ACL tear in a female, patella tendonitis in a second female, and an MCL sprain in the third athlete a male! The other two reported no incidence. In group three (the no squat group) 2 of the five reported knee injuries, an ACL rupture in a female and quadriceps tendonitis in a male athlete the other three reported no incidence.
Conclusion: This research study is one of many that bear out the fact which is common knowledge in strength training research. Females are more susceptible to ACL injuries due to hormonal levels and quadriceps angle or Q-Angle (increased angle of the femurs). Doing half squats can cause flexibility deficits and muscle imbalances to the quadriceps. EMG (electromyography) studies show the ½ squat under recruits the VMO or Vastus Medialis oblique (the teardrop or inner portion of the knee), hamstrings and gluteals forcing the lateral quadriceps to do most of the work. Omitting squats completely will deprive the athlete of knee and hip stabilization that may help prevent or reduce knee injuries. Half squatting disallows the knee to travel across the toes and move through a full range of motion again facilitating quadriceps/muscle imbalance by under recruiting the VMO muscle which is the pillar of knee joint stability.
OK so who cares about research studies, VMO's and squats? If you want a good insurance policy for your knees and low back incorporate squatting into your strength program! Squat variations are a staple in all of my athletes programs but prescribing correct squat technique, progression and exercise sequence can be the difference in effective and non effective outcomes in your program.
As much as the squat can be beneficial it can also be disastrous if misused or prescribed haphazardly. One of the worst and most dangerous variations of the squat I have seen is the Smith machine Squat or lunge. The Smith Machine is basically a plate loaded barbell affixed to metal bars or tracks. Quite frequently the Smith machine is prescribed by inexperienced coaches to young trainees who lack the overall body strength to balance a barbell on their shoulders. The idea is that because the barbell is fixed to a stationary track it will keep the trainee from losing balance or getting stuck in the bottom position. While the idea may seem logical it is extremely dangerous and can cause significant injury to the knee and patella femoral joints.
In a poor attempt to mimic the barbell squat or barbell lunge and the idea that it will take stress off the low back the Smith Machine allows you to lean back against the machine pushing your weight up against the bar. This causes the hamstrings to become deactivated and uninvolved in the movement. The problem with this is that the hamstrings dynamically stabilize the Anterior Cruciate Ligament (ACL) and Patella (kneecap). When the hamstrings shutdown, the knee joint will encounter extreme shearing or shear forces. Shear forces are high levels of friction or force in the knee joint that are attempting to pull the knee apart. This puts a considerable amount of stress on the ACL and back of the kneecap because the lower portion of the leg (tibia) is fixated to the ground and the upper portion of the leg (femur) is forcing itself forward.
