Sissy Squat: Knee-Flexion Quad Isolation

The sissy squat is a bodyweight quadriceps exercise in which you rise onto the balls of your feet, drive the knees forward, and lean the torso back so the body stays in a straight line from knee to head. Because the hips never bend, the quadriceps handle the entire movement through deep knee flexion, including the rectus femoris, which stays lengthened at the hip while shortening at the knee. Despite the name, it is a genuinely difficult exercise that places significant demand on the knees, so it belongs in a program only after a base of squatting strength has been built.

Muscles Targeted

• Primary: Quadriceps (especially rectus femoris and vastus muscles)
• Secondary: Hip flexors, core stabilizers
• Tertiary: Calves (for balance), gluteus maximus (isometric hip extension)

Starting Position

Stand upright with your feet hip-width apart, holding a rack upright, a doorframe, or a sturdy post with one hand for balance. Rise onto the balls of your feet with the heels lifted. Squeeze your glutes to lock the hips in extension, so your torso and thighs form one straight line. Brace your core and keep your chest open. This straight body line from knees to head is the position you will hold throughout the entire set.

Execution Steps

1. Lock the hips in extension by squeezing the glutes, so the body forms one line
2. Rise onto the balls of your feet with the heels lifted off the floor
3. Push the knees forward while leaning the torso back, keeping the hips straight
4. Descend slowly over three seconds, letting the knees travel well past the toes
5. Lower as far as your knees allow, ideally until the hamstrings approach the calves
6. Reverse the movement by pushing the knees back and contracting the quads
7. Return to the upright line without bending at the hips at any point

Form Cues

• Hips locked, glutes squeezed: The moment the hips bend, the exercise becomes a partial squat
• Knees travel forward: This exercise is defined by knee travel; the usual warning against it does not apply here
• Straight line from knee to head: Keep the torso and thighs in one plane the whole rep
• Control the descent: The lowering phase carries most of the stimulus and most of the risk
• Use support: A light hand on a rack for balance lets you focus on the quads

Common Mistakes

• Bending at the hips: Folding at the waist converts the movement into an inefficient squat and removes quad tension.
• Descending too fast: Dropping into deep knee flexion under bodyweight is how knee irritation starts.
• Going too deep too early: Depth should follow strength, not lead it.
• Training it with existing knee pain: The deep, loaded knee position aggravates most patellar issues.
• Skipping the warm-up: Cold knees in this position tolerate very little.

Variations

• Assisted sissy squat: Holding a rack with both hands and pulling to reduce the load
• Sissy squat bench: Using a dedicated sissy squat station that anchors the feet
• Partial-range sissy squat: Limiting depth while building tolerance
• Weighted sissy squat: Holding a plate to the chest once bodyweight sets are easy
• Leg extension: Machine alternative training knee extension with far less joint stress

Tips for Progression

• Start partial: Descend only as far as you can control, then extend the range over weeks
• Increase reps: Build to 12 to 15 controlled reps before adding difficulty
• Reduce assistance: Move from two hands to one hand to no support as balance improves
• Add load last: Hold a light plate against the chest once 15 bodyweight reps are comfortable

Training Notes

Program sissy squats once or twice per week for 3 sets of 8 to 15 reps, placed at the end of a leg session as a quad finisher rather than a main lift. Rest 60 seconds between sets. Introduce them gradually: start with partial range and support, and add depth only when the knees feel fine the following day. Lifters with a history of patellar tendon issues should treat this exercise carefully or use leg extensions instead.

Frequently Asked Questions

Are sissy squats good or bad for your knees?

Sissy squats are safe for healthy knees when introduced gradually, and the deep knee flexion can strengthen the quadriceps tendons over time. They are a poor choice during active knee pain, and every lifter should start with partial range, slow tempo, and hand support before going deeper.

What muscles do sissy squats work?

Sissy squats isolate the quadriceps, including the rectus femoris, which stays stretched at the hip while shortening at the knee, a combination almost no other bodyweight movement provides. The glutes and core work isometrically to hold the straight body line.

Why are they called sissy squats?

The name is usually traced to the myth of Sisyphus, condemned to push a boulder uphill forever, with the burning quads to match. Despite how the name sounds, the sissy squat is an advanced movement that challenges strong, experienced lifters.