Wallsit + alternating leg extension

Stand with your back against a wall with your feet about hip-width apart out in front of you.
Bending your knees, slide your back down the wall until your knees are at 90-degree angles and your shins are vertical, so you may need to inch your feet farther from the wall to create proper alignment. You can place hands on your waist, extend them in front of you, or rest them on your thighs.

Brace your core, shift your weight on 1 leg and lift and extend the other one.

Bring the extended leg back down and perform with the opposite leg.
It’s important to push hard through the leg that’s on the ground to prevent your hips from dropping and keep your body aligned, so contract your glutes and leg muscles.
Perform for the recommended number of repetitions.