Try 2-3 sets of 20 for move, on each leg.
Single Leg Lifts
Lie on your left side, rest your head on your left arm, and place your right hand on the floor in front of your chest. Your legs should be straight with your right leg on top of your left leg. Without moving any other part of your body, slowly raise your right leg as high as you can. Pause, then return to the starting position.
Lie on your left side with your hips and knees bent 45 degrees. Stack your right leg on top of your left leg, heels together. Keeping your feet together and left leg on the floor, raise your right knee as high as you can without your heels coming apart. Pause, then return to the starting position.
Lie faceup on the floor with your knees bent and feet flat on the floor. Squeeze your glutes and press into your heels to raise your hips until your body forms a straight line from your shoulders to your knees. Pause, then slowly lower back to the starting position. That's one rep.
Cross Body Mountain Climbers
Start at the top of the pushup position, with your body forming a straight line from head to heels. Keeping your abs braced, pick up your right foot and slowly bring your right knee toward your left shoulder. Then return to start.