Hip Flexors: strength & flexibility

It’s the middle of winter and the perfect time to make an effort to improve on strength and flexibility. In the last Sports Medicine Corner, the hamstrings were discussed. Hopefully, you have been working on the Romanian Deadlifts and improving with that exercise. It’s time to move to the front of the body and address the hip flexors.

The hip flexors are a group of muscles in the front of the hip that act to lift the knee and bring the thigh towards the abdomen. The major muscles making up the hip flexors that we will focus on are the iliacus and the psoas, or the iliopsoas and the rectus femoris. The rectus femoris  is a “two joint muscle” because it crosses both the hip and knee joints. As a group, the hip flexors have attachments on the lumbar spine, the pelvis, and the femur. In addition to their major function of flexing the hip, their attachment on the spine makes them an important part of the core muscles and spinal stabilizers.

The hip flexors are prone to becoming tight and shortened. They are active with each step that we take, especially while running. A major contributing factor to their tightness is that based on their location and anatomical attachments, when we sit, we are putting the hip flexors in a shortened position. Unfortunately, many of us spend a good part of our day sitting. The combination of sitting and heavy use of the muscle during activity causes it to become shortened. A shortened muscle does not generate as much power as a normal length muscle is capable of. The shortening and weakening of the hip flexors creates a muscle imbalance in the hip, which can cause problems in other parts of the body.

The spine has a natural curvature in it in order to function correctly. With their attachment on the spine and pelvis, tight hip flexors can cause an unnatural curve of the spine called hyperlordosis. Hyperlordosis affects the way forces are distributed in the spine and can cause pain and soreness in the lower back. Other common problems that are associated with hyperlordosis are weak abdominal muscles, weak hamstrings, tight low back muscles, as well as tight hip flexors. This can lead to hip flexor and groin strains and hamstring strains…..an all around mess!

Dynamic stretching (stretching while in motion), is the most efficient way to lengthen and strengthen the hip flexor muscles. An exercise that you can do that will engage the core and all of the lower extremity muscles while focusing on the hip flexors is called the Single Leg Split Squat. Remember that the rectus femoris crosses the hip and knee joint. This exercise involves both the hip and knee joint, making it an appropriate exercise to train the rectus femoris as well as the iliacus.

To begin, place the top of one foot on a weight bench (or a chair) and step forward with the other foot out in front of you, similar to a lunge position. Make sure that the front foot is positioned at least at shoulder width and it is far enough away from your body that your knee will not come over your toes when you perform the squat. Put your hands in front of your body (or overhead to make it harder). Perform a “single leg squat” by bending the front leg. The knee of the leg that is up on the bench will go towards the floor. Get it as close to the floor as you can. Do not let the heel of the front foot come up off of the floor. Keeping your heel down will ensure that you engage your glutes and hamstrings in this exercise. You should feel the tension in the hip flexor of the leg that is on the bench when you perform this exercise (you will also feel the muscles of the front leg working). It is important to keep your torso upright throughout the full range of motion. As you go down into the squat, the hip of the back leg is going into extension, which will stretch the hip flexor as well as strengthen it as it stabilizes the hip throughout the range of motion.

This exercise is challenging and will certainly be beneficial even without weights. If you can execute perfect form with your body weight, you can make the exercise harder by adding weights to your hands, by stepping on an unstable surface with your front foot (balance disc, foam pad), or you can place your rear leg on an unstable surface such as a physioball. You should be able to comfortably perform 2-3 sets of 10 reps on each leg before advancing this exercise.

Making the Single Leg Split Squat part of your cross training routine will increase flexibility and strength of the hip flexors and help to counteract muscle imbalances in the hip. Keep in mind that the hip flexors are shortened in the sitting position, just one more reason to get up from your desk periodically throughout the day and move around!

To read a comprehensive review of the scientific research into dynamic and static stretching, click here.