The squat is a fundamental human movement observable in nearly every aspect of human life. It is also a common exercise used in rehabilitation, general fitness training, and to improve performance in elite athletes. Physiotherapists love squats for two reasons:
they are a functional movement that is transferable to many movements that occur in daily life; and
they activate almost every muscle of the lower limb as well as muscles of the trunk.
At Restore Function Physio, we frequently prescribe squat variations to clients of many backgrounds. In our neurological rehabilitation and osteoarthritis clients, we often start with the sit-to-stand to improve weight shift onto the affected side, which in turn helps to increase lower limb muscle strength and neuromuscular control. For those further along their rehabilitation journey, for example elite athletes returning to sport after lower limb injury, we use single leg variations like the Bulgarian split squat to target single leg stability, dynamic neuromuscular control, balance, strength and power. Squats are so versatile and effective because they have a direct correlation to many activities of daily life (such as getting out of a chair and lifting a package from the floor) and sport (such as jumping and landing).
Correct performance of the body weight begins with the person in an upright standing position with the knees and hips fully extended. The squat is performed by flexing at the hip, knee and ankle joints to descend to the desired squat depth. Returning to the upright position occurs by extending the hip, knee and ankle joints. The squat recruits muscles crossing the ankle, knee and hip joints, as well as abdominal and trunk muscles to facilitate postural stabilization. Squat depth is generally measured by the degree of flexion (bending) of the knee. Broadly speaking, squats are divided into 3 groups: partial/mini squats (45 degree knee angle); half squats (70 – 100 degree knee angle); and deep squats (>100 degree knee angle). Squats can be modified to increase or decrease the level of difficulty my changing variables including the number of repetitions, foot placement, speed of movement, position and amount of load.
The Ankle Joint
The gastrocnemius and the soleus are the primary muscles responsible for carrying out movement at the ankle joint during squatting. They contract eccentrically during the descent as the ankle dorsiflexes and concentrically during the ascent as the ankle plantar flexes. Other muscles of the ankle, such as the peroneus brevis and longus and the tibialis anterior and posterior, are also active during squatting to control the position of the foot.
The Knee Joint
The quadriceps femoris are active during the squat to carry out concentric knee extension during the ascent, as well as control knee flexion during the descent. The hamstrings contract at the same time as the quadriceps to help control the position of the tibia by reducing anterior shear force generated by the pull of the quadriceps.
The Hip Joint
The primary muscles working at the hip during a squat are the gluteus maximus and the hamstrings. The gluteus maximus acts eccentrically to control the descent, and concentrically during the ascent. The hamstrings function at the hip to assist the gluteus maximus during hip flexion and extension.
Proper squat technique requires a rigid/stiff spine to ensure a stable and upright posture is maintained throughout the movement. Superficial and deep muscles of the spine and trunk including the erector spinae, transversus abdominus and deep posterior group (multifidus) stabilize the spine and resist vertebral shear as the spine flexes during the descent phase. Forces on the spine increase as squat depth increases.
Squat Pearls of Wisdom
The greatest compressive force on the patella-femoral joint (knee-cap) occurs at maximal knee flexion. For those with patellofemoral pain during the squat, partial or half squats may be preferred.
Quadriceps development is maximized by squatting to parallel (half squats). Full depth squats may be more effective at increasing hip muscle recruitment.
The hip adductors and hip extensors (hamstrings and gluteus maximus) are more active in a wider stance squat. A wider stance squat may also reduce forward knee translation thereby reducing compressive forces on the patellofemoral joint.
Front squats produce lower knee compression and lumbar stress when compared to back squats and may be preferred by those with knee or back issues.
Proper spinal alignment should be maintained during squatting to minimize unwanted spinal flexion and shear stress.
Squats are great no matter what level you are at. They can be modified for people of almost every background! If you need help with exercise prescription, contact us today on (07) 3148 4417.
Schoenfield, J.B. Squatting Kinematics and Kinetics and Their Application to Exercise Performance. Journal of Strength and Conditioning 24:12, 2010.