Stability ball hamstring curl
The stability ball hamstring curl targets your hammies without using a typical machine. Plus, it requires greater engagement of your core, glutes, and hips to maintain your balance.
Lie on the ground and place your lower calves and heels on top of a stability ball, your legs fully extended. Place your arms along your sides, palms down, to help with balance. Engage your core and press your hips up so your body forms a straight line from your heels to your shoulder blades.
Pressing your heels into the ball, bend your knees, rolling the ball toward your torso, all the while keeping your hips up, maintaining a straight line between your knees and shoulders. When you've drawn the ball as close to your body as you can, reverse the movement and extend your legs, pressing the ball away from you. That's one repetition. Perform two sets of 10 to 12 repetitions.