This content is for participants of Exercise Selection: Single Leg, Volume One. Please visit the programs page to register.

FBB Exercise Selection: Knee Flexion

General Notes on Single Leg Knee Flexion Training

Developing Hip Balance from Side to Side – In far too many training programs, there is a predominance of double leg squatting over single leg knee flexion. We aim to bring more balance to this discrepancy by providing you with a toolbox of movements and progressions to use.

When we squat on both legs, our hips are able to support one another, and if there are unilateral discrepancies in motor control or strength abilities they can be masked. Therefore, by training single leg knee flexion we can work towards bringing balance to each hip’s unique stability, motor control, and strength. By challenging your legs independently you have the ability to create balance.


Challenging the hips and legs with more degrees of movement stability – The hips are designed anatomically to work in a wide range of motion. There are 360 degrees of movement that you can apply force to with the hip, and training single leg knee flexion forces the brain and muscles to work in all of these ranges. Unlike double leg squatting, single leg squatting will build a more well rounded strength that can handle different angles. The resultant strength will make you more capable of double leg squatting.


A defense against common low back and knee pain – Unilateral stability of the hips, when underdeveloped, can be a root cause for knee and lower back dysfunction. These two areas that get a lot of attention due to common pain points for people are both supported well by single leg training.

Balance and body weight distribution in your foot – In the education of athletes on squatting a lot of emphasis gets place on where body weight is distributed in the foot. It is no different for single leg squatting movements like the ones that follow. Special care should be taken to learn where load needs to be distributed on the foot.

Points of Performance

Flat Foot – In the identified “Working Leg” for each of the movements that follow, the foot should always remain flat against the floor or box surface through the range of motion.

  • Watch for heels lifting and pressing off the toe only
  • Watch for ankles rolling in or out and thereby lifting the outer or inner edge of the foot off the floor
  • Watch for an overemphasis of weight in the heel and the resulting toes lifting off the ground or box

Weight Distribution – After you ensure that the foot is staying level and the entire sole of the foot is in contact with the floor or box surface, we want to have a discussion about where the weight is distributed in the foot.

  • The great benefit of single leg squatting exercises is that they allow athletes to engage the hips, glutes, and many of the muscles of the posterior leg to enhance motor control and strength. Therefore, we want to create connection through those muscles by emphasizing the weight distribution through the back of the foot.
  • With a flat foot you will want to perceive that more of the force being applied in the exercise is moving through the back of the foot as opposed to the ball of the foot.
  • Driving force through the heel, whether performing a split squat, step up, or any other exercise in this series, is ideal and will allow for better connection to the posterior leg muscles.
  • 70/30 Rule – There should be about 70% of the force and load through the back (heel) of the foot and 30% of the load through the front (ball) of the foot.