Two-leg knee dominant exercises in-depth

Introduction

The squat strengthens the knee and hip extensor muscles, which are the prime movers of sprinting and jumping and nearly every other type of athletic movement, as well as the muscles of the low back to stabilize the torso.Because of the sport-specific character, the squat has an excellent transfer to athletic performance.

All these exercises are closed kinetic chain exercises (exercises where the foot is the base of support). Like athletic movement, the force with these exercises is applied into the ground, which makes them functional.

Movement compensations due to improper flexibility

The squat should be incorporated in every beginning strength program. Start performing the squat with a broomstick or empty bar to establish proper technique. If the athlete has proper flexibility at the ankle, hip and low back, he should be able to perform a full squat. However, in case of muscle tightness abnormal movements should be seen. Feet that roll in or heel elevation when squatting demonstrate tightness in the calf muscles. External rotation of the feet during the descent of the squat can be caused by tightness of the short head of the biceps femoris muscle (muscle of the hamstring group). If both piriformi (internal hip muscle) are shortened forward flexion at the hip is restricted.

Full squat versus partial squats

In a full squat the body is lowered till the tops of the thighs are parallel to the floor. If the athlete is not able to perform a full squat due to limited flexibility, focus the first weeks just on flexibility. Poor flexibility, limiting squatting performance, restricts athletic movements and makes the athlete more prone to injury. Especially flexibility imbalances have a clear influence on sport injuries. Partial squats should not be used. In partial squats excessive weight has to be lifted to provide a training stimulus, which can lead to low back injuries. Partial squats lead to over-development of the knee extensors at the expense of the assistant muscle groups. Activation of the Gluteus maximus increases with the angle of hip flexion. Hamstring activity is greatest during the descending phase of the squat when the thighs are about parallel to the floor. The hamstring muscles, the low back extensors and hip extensor muscles are involved more during the squat with increased forward lean of the trunk. The forward trunk lean increases with squat depth. However, avoid excessive forward lean of the trunk. Shear forces on the intervertebral discs increase with the angle of forward inclination of the trunk. Excessive forward lean of the trunk is a common error for novice lifters performing the squat.

Back squat versus front squat

The position of the bar and feet affects muscle involvement. The back squat emphasises the hip extensors more than the front squat. The front squat is performed with a more erect trunk position, placing more stress on the knee extensors. Less weight can be lifted with the front squat. Due to the reduced training weight in combination with a more erect trunk position, the front squat places less stress on the spine compared to the back squat.

Jump, athletic and power-lifting stance

The front squat is performed in a jump stance (feet between hip- and shoulder-width apart and toes pointing forward). When doing a back squat the athlete can choose between a jump stance, an athletic stance (feet slightly wider than shoulder-width and toes pointing forward) and a power-lifting stance (feet wider than shoulder-width apart and toes pointing outward). Squatting with a power-lifting stance is less specific to sports, but assures a more upright trunk position and requires less mobility at the ankle joint. The wider stance enhances adductor activity. The athletic stance favours more activity from the hip extensors and adductors while the jump stance places slightly more stress on the knee extensors.

The eccentric contraction

Descend in a controlled manner when squatting, with a descending speed of 45 °/second or less, to ensure a strong eccentric contraction. This prevents bouncing out of the bottom position, which can cause knee injury, and prepares the lower body to decelerate movements. Good eccentric strength improves performance and is injury-preventive.