The semitendinosus is one of the three muscles in the hamstring muscle group. The other two are the semimembranosus and the biceps femoris. The semitendinosus is the longest of these three muscles, and it runs along the back of the thigh. It helps you extend your thigh, rotate your tibia — the main bone in your lower leg, and flex your knee.
Weak or tight hamstring muscles can result in muscle strain. In fact, hamstring muscle injuries are the most common sports injury.
An imbalance between the quadriceps and hamstrings can also cause poor posture and lower back pain, so regular stretching and working to strengthen hamstring muscles can relieve leg pain as well as back pain, and it might even help you walk taller and stand straighter, too.
Exercises to Help Strengthen and Stretch the Semitendinosus
The goal of these exercises is to loosen and strengthen the semitendinosus in order to prevent injury and improve range of motion and posture. These simple stretching exercises are easy to do at home, and they require only a few typical household items you probably already have lying around.
Knee flexion is just the process of bending your knee. Doing so engages your hamstring muscles, particularly your semitendinosus.
Step 1: Stand behind a chair, using the chair back to balance as you put your weight onto one foot.
Step 2: Keeping the other foot flexed as you lift it up into the air behind you, bend your knee as you bring your foot toward your butt. The front of your leg should remain steady and straight. Don’t lean to one side or let your knees or hips fall out of alignment.
Step 3: Still maintaining the flexed foot, lower your foot back to the ground.
Repeat 8 to 10 times. Try to perform three sets of this exercise on each side.
Modifications: You can also perform the exercise lying prone on your stomach and raising one flexed foot toward your butt. This may help if you struggle to keep your leg in proper alignment while standing.
In order to increase the level of difficulty, you can add ankle weights or pull against a resistance band anchored directly in front of you.
Nordic Hamstring Curl
The Nordic hamstring curl is another strength-training exercise that particularly targets your semitendinosus. It uses your legs to control your body weight as you lean forward and straighten back up.
Step 1: Kneel on the floor, putting a pad or towel beneath your knees for comfort.
Step 2: Raise your butt off of your feet, creating a straight line from the top of your head to your knees. Hook your heels underneath something like the bottom edge of a sofa or a bar between chair legs, or have a friend hold them to the ground.
Step 3: Lean forward slowly, hinging at the knees rather than the hips and keeping the straight line from head to knee.
Step 4: Slowly return to your starting position.
Try to do two sets of 8 to 10 repetitions to start.
Modifications: In order to increase the level of difficulty, instead of relying on your body weight only, you can hold an extra weight to your chest while you perform the curl.
Supine Hamstring Stretch
Maintaining flexibility and range of motion is also important. Hamstring stretches are a vital part of injury prevention and rehabilitation.
Step 1: Lie on your back with your legs straight in front of you, toes pointing up.
Step 2: Using a towel or strap, pull one foot back toward your head, keeping your leg straight and your foot flexed. Do not allow your hip to rotate outward, but be sure your leg is straight in front of you and your hip is aligned with your shoulder.
Step 3: Hold for thirty seconds before lowering.
Step 4: Repeat the stretch on the other side.
This stretch can be done safely several times a day.
Modifications: A slightly easier variation is to lie on your back with your body perpendicular to a wall. Raise one or both legs, keeping your knees straight and resting your feet against the wall. The eventual goal should be to bring your butt to the wall, lifting your feet directly above your hips, but don't stretch more than is comfortable.
Go slow. When you’re doing strength exercises, the idea is to build strength over time — that’s how you know the exercise is working! So start with lower weights or repetitions and gradually increase them.
Any time you stretch or strength train, you should perform a short warm-up to loosen your muscles and get your body moving. If you feel stiff in the mornings, try a little walking around or a warm shower before you begin exercises. When stretching, only stretch until you notice a gentle pressure. To avoid the risk of injury, do not push the muscles past this point, but keep at it regularly, and you should be able to go further or do more before you feel the stretch. With time and practice, you should begin to see improvements in strength, flexibility, posture and more.