If you're used to squatting with heavy loads, bodyweight squats aren't going to do much for you. In that case, the best option is to go single leg. Because regular split squats will still likely be too easy, try this hybrid move.
Split-Squat Sissy Hybrid
Essentially, the front leg is doing a short-step, very quad-dominant split squat, while the back leg almost resembles a sissy squat. You'll actively be pressing through both your front and back legs at the same time.
If you've got a little history with your knees then you might want to omit this, but otherwise it'll help hammer your quads while building knee resilience.
- Start your split squats from the floor. Use a cushion for your back knee if needed.
- Adopt a short-step position. This should be the narrowest stance you can handle while still being able to keep your heel down on the lead leg and limit "butt wink" at the bottom.
- Maintain a fully upright torso throughout.
- Stand up. Keep your feet stationary and your bodyweight evenly distributed through both your front and back legs.
- Return to the floor.
If you don't feel your knees are up to it, use a wider split squat and encourage more load through your front leg.