As a runner, your two training goals should be to get faster and reduce the risk of injury. To accomplish both, you have to strengthen your hamstrings. (Find out more ways to increase your speed.)
The hamstrings are a group of three muscles on the back of the thigh. They are a critical part of the posterior chain (muscles in the back of the body), which are the primary power generators when you run. If you fail to strengthen these muscles, you won’t reach your speed potential. Also, untrained hamstrings won’t be strong enough to cope with the forces of sprinting, ultimately risking a pulled or torn muscle.
When most people work their hamstrings, they immediately run to the leg curl machine. This machine does strengthen the hamstrings, but it isolates the muscle, which never happens when you run. Instead you need to focus on hamstring exercises that engage the entire posterior chain to teach the hamstrings, glutes and other backside muscles to work together.
Add these three hamstring exercises to your lower-body program, and you will be on your way to reaching your speed potential.

Physioball Leg Curls

This exercise is a great way to strengthen the hamstrings and glutes while also challenging the core.

• Lie on back with feet on physioball
• Raise body into straight line so that only shoulder blades touch floor
• Keeping hips high, curl ball toward butt
• Slowly allow ball to roll back out until legs are straight

Sets/Reps: 3×10

Floor Hamstring Curls

This is an advanced exercise and must be done with a partner. It targets the eccentric (lengthening) phase of the hamstring to prevent injury.

• Kneel on Airex pad, keeping hips and upper body in straight line
• Have partner hold ankles to ground
• Slowly lean forward for five seconds to touch ground; keep body in straight line
• Catch body with hands during descent
• Push body up to starting position
• Repeat for specified reps

Sets/Reps: 3×5

Glute-Ham Raise

This is one of the best exercises for strengthening the hamstrings, glutes and lower back at the same time.

• Position yourself on glute/ham machine with legs locked in place
• Raise torso up until chest is parallel to floor
• Drive knees into foam pad until they are at 90-degree angle and body is upright
• Lower back down with control
• Pause for one second and repeat

Sets/Reps: 3×5
Photos:  bayinjury.com