Muscles worked
The sissy squat is one of the few bodyweight exercises that isolates the quads. Your hips stay extended while your knees travel far forward, so straightening the knee does nearly all the work, rather like a leg extension without the machine. The rectus femoris, the part of the quads that also crosses the hip, works in a stretched position as you lean back. Your abs and glutes hold the line from knees to shoulders, and your calves keep your heels up. Leaning further back and going deeper both make it harder.
Common mistakes
- Going too deep too soon. Full depth with your knees far forward is a lot if you are not used to it. Start with about a third of the range and go deeper over a few weeks. If your knee hurts, rather than your thigh just burning, stop the exercise and have it looked at by a doctor or physiotherapist.
- Your arm does the work. The support is there for balance. Pulling yourself up with your arm takes load off your legs, so keep a light hand.
- Dropping into the bottom. The last part of the descent is hard to control, and many simply fall through it. Take two to three seconds on the way down and reverse while you still have control.
Variations and alternatives
- The leg extension trains the same knee straightening on a machine, with a weight you can adjust.
- The Spanish squat gives your quads plenty of work with a resistance band and is easier to dose.
- The bodyweight squat is the foundation to master first if squatting still feels unfamiliar.
Sets and reps
Two to three sets of 6 to 12 reps is a good start, working up towards 15 once the movement feels solid. Put it late in your leg session or use it as a quad finisher. Begin with a proper warm-up so your knees and thighs are warm before you go deep. The guide to sets and reps links set numbers to your goal.
Progress in this order: more depth, a slower descent, then more reps. Once you can go all the way down with control, hold a weight plate against your chest. That is what progressive overload looks like without a machine.