Restricted versus Non-Restricted squat. Not all squats are created equal.
The squat is a common exercise that can improve lower body strength, mobility and balance. However, there is some controversy about the optimal technique for performing the squat, especially regarding the position of the knees relative to the toes. Some people believe that allowing the knees to go past the toes during the squat can increase the risk of knee injury, while others argue that restricting the knee movement can impair the natural biomechanics of the squat and lead to other problems. This blog will review some of the scientific studies that have compared the effects of restricted and unrestricted squats on various kinematic and kinetic parameters.
A restricted squat is defined as a squat where the knees do not go past the toes, while an unrestricted squat is defined as a squat where the knees are free to go beyond the toes.
Video: This person is performing a restricted squat. The left leg is more restricted by a stiff ankle.
According to Fry et al. (2003), who measured the joint angles and moments of 15 experienced weightlifters during both types of squats, unrestricted squats resulted in:
1. greater ankle dorsiflexion
2. lower tibial translation
3. lower knee joint compression (not to be confused with shear force below)
4. lower patellofemoral joint stress
than restricted squats.
They concluded that unrestricted squats are more natural and safer for the knee joint than restricted squats.
=> Suggesting that unrestricted squats might be better for people with a history of knee pain and degenerative changes, common in younger populations and older populations, respectively.
Other studies have found different results. For example, Escamilla et al. (2001) compared the biomechanics of 12 elite powerlifters during restricted and unrestricted squats with different stance widths and foot placements. Keep this in mind, because stance width and foot placement can change the squat quest technique and the muscles and joints involved completely!
They found that unrestricted squats produced:
1. higher knee joint shear forces (not to be confused with compression above)
2. higher quadriceps muscle activity than restricted squats, regardless of the stance width or foot placement.
They suggested that unrestricted squats may increase the risk of anterior cruciate ligament (ACL) injury and patellofemoral pain syndrome.
=> Such claims have led to some over-exaggerated caution by fitness instructors that the knees should never go beyond the toes, and over time this has become somewhat of a myth in the fitness industry.
Another factor that may influence the comparison between restricted and unrestricted squats is the load used.
=> This is especially important for training novices who tend to have poor lumbopelvic control, and especially people recovering from back pain.
Hartmann et al. (2013) investigated the effects of increasing load on the spinal kinematics of 10 male athletes during both types of squats. They found that unrestricted squats resulted in:
1. less lumbar flexion
2. less thoracic flexion
3. more pelvic tilt
than restricted squats, indicating a more stable spine posture.
Hartmann also observed that increasing load led to more lumbar flexion and more thoracic flexion in both types of squats, suggesting a higher risk of spinal injury.
=> Recovery from injury and novice training should be progressive, with strict attention to technique. People with poor lumbopelvic control should initially avoid restricted squats and start with unrestricted squats. To do so, they must have adequate ankle dorsiflexion.
In conclusion, there is no clear consensus on whether restricted or unrestricted squats are better for performance or injury prevention. The effects of different squat techniques may depend on various factors such as individual anatomy, skill level, stance width, foot placement, and load. Therefore, it is important to perform squats with proper form and technique and to adjust them according to one's goals and preferences. This may not be an either/or scenario – both techniques can be useful. As usual, individualised exercise prescription is the best way to improve performance and avoid injury.
References:
Fry AC, Smith JC, Schilling BK (2003). Effect of knee position on hip and knee torques during the barbell squat. Journal of Strength and Conditioning Research 17(4):629-633.
Escamilla RF, Fleisig GS, Zheng N, Barrentine SW, Wilk KE, Andrews JR (2001). Effects of technique variations on knee biomechanics during the squat and leg press. Medicine & Science in Sports & Exercise 33(9):1552-1566.
Hartmann H, Wirth K, Klusemann M (2013). Analysis of the load on the knee joint and vertebral column with changes in squatting depth and weight load. Sports Medicine 43(10):993-1008.