Muscles worked
The Cossack squat is a deep squat to the side. The leg you bend does the work: your quads and glutes lift you, with help from the inner thigh. The straight leg gets a stretch along the inside of the thigh at the same time, so the exercise trains strength and mobility together. Your hips and ankles need plenty of mobility, and your balance is tested as your weight shifts from side to side. For the first few weeks, hip mobility usually decides how deep you get.
Common mistakes
- Going deeper than your mobility allows. Forcing your hips down rounds your back and costs you control at the bottom. Go as deep as you can with a straight back and let depth come with time.
- Your chest drops towards the floor. As your hips move to the side, your upper body tends to tip forward. Hold a light dumbbell or kettlebell at your chest, which acts as a counterweight and makes sitting upright easier.
- Throwing yourself side to side. With momentum you fly through the bottom without control. Rise all the way to the middle, pause briefly, then move across to the other side.
Variations and alternatives
- The lateral lunge is a shallower version where you step out to the side, useful before you have the mobility for full depth.
- The sumo squat trains the inner thighs with both legs bent at once and can be loaded with a dumbbell.
- The machine hip adduction strengthens the inner thighs on a machine and complements the stretch you get here.
Sets and reps
Two to three sets of 5 to 8 reps per side is a sensible start, and depth matters more than numbers. The exercise also fits into a warm-up before leg day, with a few easy reps each way. The guide to sets and reps shows how to set up your sets for your goal.
Increase depth first, then reps, and finally hold a weight at your chest. Progressive overload applies even in an exercise that is largely about mobility. If it feels like pain rather than a stretch, stop the exercise and have it looked at by a doctor or physiotherapist.