The squat is a type of resistance training that strengthens the lower body as well as the core muscles. This exercise has been widely used in training programs with the two main types being weighted squats and bodyweight squats. While the weighted squat is often seen as the more superior type, the bodyweight squat also proves to have its own benefits.
Studies have proved that bodyweight squats enhance the strength, power, and endurance of lower body muscles. Additionally, this exercise strengthens the core, reduces the risk of injury, and helps improve mobility. There is also the added benefit of being able to perform the exercise anywhere because no equipment is needed.
Understanding the biomechanics, proper form, and benefits of bodyweight squats is important in attaining fitness goals as well as progressing to weighted squats.
Also known as air squats, the bodyweight squat is a type of squat that does not make use of external weight or equipment. Although it only uses the individual’s body weight in performing the exercise, the bodyweight squat is considered ideal in strengthening the lower limbs for sporting activities and activities of daily living.
The two main phases of the bodyweight squat, or squats in general, are the descending (lowering) phase and the ascending (standing) phase. The descending phase requires moving the body from a standing position into a squat while the ascending phase involves movement from a squatting position to an upright position.
During the descending phase, there is hip flexion, knee flexion, and ankle dorsiflexion. As the hip joint flexes, the trunk bends toward the legs producing eccentric contraction of the hip extensors. This involves the controlled lengthening of the gluteus maximus, semimembranosus, semitendinosus, and biceps femoris muscles.
The knee extensors (rectus femoris, vastus medialis, vastus intermedius, and vastus lateralis) also undergo eccentric contraction as the knee flexes. For ankle dorsiflexion, the gastrocnemius and soleus counteract the pull of gravity as the body is lowered into a squat.
As the individual moves to the ascending phase, concentric contraction occurs in order to produce hip extension, knee extension, and ankle plantarflexion. The same muscles are activated during the descending and ascending phases. The difference between the two is the type of contraction occurring in the muscles.
Eccentric contraction occurring in the descending phase is essentially the lengthening of the muscle as it contracts. Concentric contraction during the ascending phase, on the other hand, is the shortening of the muscle as it contracts.
Throughout all phases of the squat, spinal extensors contract isometrically to maintain a neutrally extended spine. The core muscles such as the abdominals and obliques work to stabilize the trunk all throughout the activity.
Although there are variations to the bodyweight squat, the typical starting position consists of a shoulder width stance with toes pointing straight ahead. As the individual enters the descending phase, the hip is translated backward while the knees and ankles are bent. It is ideal to keep the chest up, shoulders back, and the neck at a neutral position.
The squat should be lowered to a depth that avoids movement compensations such as knee valgus, rounding of the lower back, and external foot rotation. During the ascending phase, gluteal contraction should be done to bring the hips back to a standing position while placing pressure through the heels. Full contraction of the gluteal muscles is necessary at the end of the ascending phase for maximal muscle recruitment.
Benefits of bodyweight squats include muscle hypertrophy, increase in lower body strength, and improved mobility. It is an ideal exercise to strengthen the entire lower limb for both sporting and daily living applications.
Increase in muscle size and strength is possible even with body weight training only. Bodyweight squats can induce muscle hypertrophy with progressive overload. Progressive overload is the gradual increase in weight, frequency, or number of repetitions in a strengthening routine.
In the context of bodyweight squats, progressive overload may be achieved through an increase in training frequency, increase in number of repetitions, or applying technique variations to make the activity more difficult. This challenges the muscles in play, allowing for an increase in strength.
Core muscles are responsible for keeping the trunk upright and stable at all times. A study published in 2018 concluded that “squatting resulted in greater erector spinae activation, but similar rectus abdominis and oblique external activation as the prone bridge.” These findings suggest the use of squats to target back extensors and core muscles for avoiding injury risk and boosting athletic performance.
Since squats are both hip and knee-dominant activities, the exercise builds and maintains mobility in the aforementioned joints. Due to its ability to imitate various functional activities of daily living, squats are ideal for general health and fitness training programs.
Aside from the muscles primarily working to complete the activity, other structures such as ligaments, connective tissues and stabilizer muscles contribute to the integrity of a squat. With the right technique, squats help strengthen these supporting tissues, thus helping in injury prevention.
Having an adequate available range of motion is required to be able to do proper bodyweight squats. Limitation of motion is the most common restriction for individuals in their squat performance.
The ankle joint is capable of moving in all three planes of motion, namely sagittal, frontal, and transverse planes. Because of this, the ankle joint can perform dorsiflexion, plantarflexion, inversion, eversion, and axial rotation.
Ankle mobility contributes to a balanced and controlled motion in performing a squat. Good ankle dorsiflexion, in particular, allows an individual to maintain a flat and stable foot position during the descending phase of the squat when the knee is flexed. The presence of stiffness in the ankle joint results in poor dorsiflexion, possibly causing movement compensation in the foot and the knee joints.
One movement compensation in individuals with ankle stiffness is heel raising. During the ascending phase of the squat, the center of pressure in the foot moves toward the heel. If the heels are allowed to rise off the ground during a squat, the center of pressure becomes restricted affecting squat technique. Additionally, the force created by raised heels is greater than when the heels are flat on the ground which may lead to unnecessary wear on the joints.
The knee joint is a modified hinge joint allowing flexion and extension movements. This joint is considered a stability joint due to its structure and limited movement ability. Because the knee joint functions for stability, the ideal position for the knees during a squat is one where they are aligned with the hips and feet. In the event that knee alignment is not maintained, the stabilizing ligaments and tendons of the knee are compromised.
Misalignment of the knee with the hips and feet has been said to occur due to weakness in the joints and muscles directly above and below the knee. The most commonly reported movement pattern contributing to knee dysfunction is excessive anterior motion.
Excessive anterior motion is the movement of the knees past the toes during the descending phase of the squat. This should be avoided as it creates increased shear and compressive forces on the knees. However, an increase in forward lean is observed when the knees are restricted behind the toes which results in an increase in force on the lumbar spine. Thus, slight movement of the knees past the toes is still considered necessary for a proper squat.
The hip joint is a ball and socket joint which allows for movement in all three anatomical planes. This degree of motion available in the hip joint makes it a mobility joint.
The main function of the hip joint is to transmit loads from the pelvis to the lower extremity such as in squatting. When there is limitation in the range of motion of the hip, this may hinder the individual from reaching appropriate squat depth.
In order to increase hip range of motion, the body compensates through posterior rotation of the pelvis during the descending phase and lumbar flexion at the squat's lowest point. This strategy should be avoided as it puts greater stress on the lumbar spine.
When doing squats, the position of the trunk in relation to the ground must remain constant with the thoracic spine placed in neutral extension all throughout the activity. This would indicate trunk stability and control. Inability to stabilize the lumbar spine and maintain slight extension of the thoracic spine places excessive compressive and shear forces on the lumbar spine.
Available literature discussing the effects of head position to the squat kinematics have described a significant increase in trunk and hip flexion when head position and gaze were directed downward. Because excessive hip and trunk flexion cause excessive compressive and shear forces on the spine, these movements are contraindicated in the squat.
To decrease the amount of lumbar and thoracic flexion, holding a proper gaze direction, head position and minimizing head movements must be maintained.
Doing bodyweight squats come with an array of benefits such as increased core strength, improved balance and posture, and better mobility which help with activities of daily living. Working this functional exercise helps develop strength and power which are essential in athletic performance as well. With proper form and technique, bodyweight squats also help prevent the risk of injuries.