What movements do running, hiking and classic cross-country skiing have in common?
Very simply, the legs move from in front of the body to behind the body in the sagittal plane. The sagittal plane divides the body into left and right sides: see the Wikipedia image to the right.
While performing these alternating front and back leg movements, the hip, pelvis and thigh are in motion to propel the athlete forward. Since the hamstrings attach to the bottom portion of the pelvis, I will focus this discussion on the actions and positions of the pelvis. For anatomical clarification, the pelvis is composed of three bones - the right and left ilium into which the hip (the ball on top of the thigh bone) inserts and the sacrum at the base of the spine.
According to gait analysis studies, the pelvis rotates forward when the leg swings in front of the body and rotates backward when the leg swings behind the body. These movements are happening in the transverse plane, shown in the image above. If you stand with your feet together and take a step forward with your right foot, notice how the right side of the pelvis rotates forward while the left side of the pelvis rotates backwards.
An Asymmetrical Pelvis
The Postural Restoration Institute identifies a pattern of the body in which the pelvis becomes oriented to the right during development and stays there. The growing body is searching for stability and finds it in this distorted pelvic position. When the pelvis is turned toward the right side of the body, the center of gravity also shifts to the right and you tend to stand more balanced over the right leg. This postural deviation is believed to be the result of internal anatomical asymmetries such as one liver on the right, one heart on the left and an unbalanced diaphragm. So, according to this pattern, the pelvis is already facing right, not straight ahead and neutral.
This right pelvic orientation predisposes athletes to left hamstring injuries, which is what I see in the majority of my clients. If the athlete is in this pattern, known as the left AIC (Anterior Interior Chain), her pelvis is twisted to the right and her left hamstring is in an overly lengthened position. Attempting to turn her pelvis more to the right while running, hiking or classic skiing will further increase the tension in these muscles and can lead to muscle or tendon damage and recurring pain with the activity.
Although left hamstring injuries seem to be more common, the right hamstrings are not immune. Some clients are so strongly held in the left AIC pattern with a right oriented pelvis that they can’t efficiently transfer weight onto their left side. The athlete is stuck on her right side and can’t move off of it! The overly dominant right side is working too hard and the muscles can’t manage the additional load and break down. This can be seen with the hamstrings and many other muscles of the right side, not limited to the lower body. Often lower body muscle development imbalances are seen in these athletes, with the right leg being noticeably larger than the left.
When the pelvis tilts forward in the sagittal plane, this is referred to as an anterior tilt. In the image to the left, notice how a pelvis with an anterior tilt also lengthens the hamstrings shown in red. During the gait cycle the pelvis goes into more anterior tilt when the leg swings behind the body.
Tight hip flexors contribute to anterior pelvic tilt. These muscles shorten and pull the pelvis down and forward, shown in blue on the image. Due to repetitive hip flexion during running, hiking and classic skiing, many of these athletes have an anteriorly tilted pelvis as their starting position.
Anterior pelvic tilt + left AIC pattern + sports = hamstring pain
Images borrowed from maximum training solutions.
In addition to being in a poor position, the hamstrings may be injured due to increased functional demand. The hamstring muscles assist with the extension phase of the sports movement and work synergistically with the gluteal muscles to move the leg backwards. You may recall from a previous blog that the gluteal muscles are prone to dysfunction; anterior tilt is one of the causes. If the gluteal muscles aren’t doing their job, then the hamstrings may have to step in to provide additional power. Being in a compromised position themselves, these muscles are often injured when their demand goes up, such as when under the stress of running, hiking or classic skiing.
Relieving the Pain
As discussed in the last section, re-establishing proper hip extension mechanics is an important piece of rehabilitation. Prior to this step, however, the pelvis needs to be repositioned to neutral. Below is an exercise to get you started. Please contact me with questions and to learn more.