Tearing an ACL is one of the most dreaded injuries an athlete can suffer. It can sideline you for months and involves a long, hard recovery process. Female athletes need to be especially careful: they’re six times more likely than males to sustain an ACL injury.
The difference between frequency of ACL injuries in females and males comes down to anatomy. Several characteristics of the female body, including knee/hip alignment, knee bone structure, ligament composition and hormones, may increase their risk of ACL injuries. Since you can’t change your anatomy, you must take proactive measures to reduce the risk.
To prevent ACL injuries—in both males and females—develop more hamstring strength. The hamstrings (the large muscle group on the back of the thighs) are often underdeveloped and relatively weak compared to the quads (the large muscle group on the front of the thighs). This, along with other risk factors, can place excessive stress on the ACL and cause it to tear. However, if your hamstrings are strong, they provide stability across the knees and help relieve your vulnerable ligaments of unwanted stress.
To strengthen your hamstrings to support your knees, perform exercises that involve flexing or curling the knee. The three exercises below—in order of increasing difficulty—develop this critical muscle group to help you prevent ACL injuries while also improving your speed and running technique.
Towel Leg Curl

• Lie with back on ground and hands out to side
• Place towel on low-friction surface and place feet on towel
• Bridge hips toward ceiling
• Flex knees and hips to slide heels toward glutes until feet are directly under knees
• With control, extend knees and hips; slowly return to start position
• Repeat for specified reps

Sets/Reps: 3×8-10
Progression: Perform with single leg on ground and opposite leg in air at a 45-degree angle to the ground

Physioball Hamstring Curl

• Lie with back on ground, hands out to side and feet on physioball
• Bridge hips toward ceiling and dig feet into physioball
• Flex knees and hips to roll ball and feet toward glutes until feet are directly under knees
• With control, extend knees and hips; slowly return to start position
• Repeat for specified reps

Sets/Reps: 3×8-10
Progression: Perform with single leg on ground and opposite leg in air at a 45-degree angle to the ground

Glute Ham Raise

• 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 with control; pause for one second and repeat

Sets/Reps: 3×10-12
Progression: Hold med ball or plate at chest

For more information on the ACL please see the STACK ACL Guide.
Photos:  bayinjury.com