Medicine Ball Curl

• Hamstring curl exercises can be done with machines, resistance cables and also medicine balls. Lie on your stomach and bend your knees. Hold a medicine ball between your ankles. Squeeze your glutes. Put your legs straight on the ground and then bend your knees to your buttocks curling the medicine ball with you.
  Do three sets of eight reps to build strength with a medium- to heavy-weight ball and do two sets of 20 reps with a light-weight ball for toning and endurance.
  
  

Stability Ball Hamstring Curl

• The ball hamstring curl is an advanced core exercise that will tone your hamstrings, glutes and abs. Lie on your back with your arms to your sides at 45-degree angles. Extend your legs straight and put your heels on the top of a stability ball. Make sure your heels are in the center of the ball. Push into the ball and lift your hips into the air. This is your starting position. Bend your knees and curl the ball toward you as you continue to lift your hips into the air. Roll the ball until it is under your hips and knees. Press your feet flat on the ball. Roll the ball back out until your legs are straight and your hips are in the air in your starting position.
  Start with two sets of 10 reps and work up to two sets of 20. To make this exercise more challenging, hold one leg in the air and do a single-leg hamstring curl. Do 10 reps on each leg.
  
  

Frequency

• The hamstring muscles should be worked three days a week to increase strength and see results. Once you get your hamstrings as toned or strong as you want, you can drop down to two hamstring workouts a week to maintain what you have.
  
  

Warm Up and Cool Down

• You should always warm up before a workout and cool down afterward. Jogging in place for five minutes before you exercise the hamstrings will heat them up and reduce the chances of injury from the ball exercises. After you exercise, cool down for five minutes by marching in place to cool your muscles and safely bring your heart rate down. The cool down should be followed by stretching.
  
  

Stretching

• The hamstring muscles can also be stretched with a stability ball. A good stretching exercise for the hamstrings can be done by sitting up straight on a ball. Extend your legs out diagonally in front of you and open them to greater than shoulder-width apart. Lock your knees. Bend forward at the waist with a flat back and reach toward your toes. Pull your toes back. Hold the stretch for 30 seconds. Stretch daily if you have tight hamstrings, or just stretch after every hamstring workout.