Author’s note: In parts one and two of this series, I discussed what PRI describes as the Posterior Exterior Chain (PEC) pattern and outlined two exercises that help counteract it. If you haven’t read those yet, then I recommend doing so as they’ll give you a better understanding of the concepts I discuss in this post.
I don’t know if any muscle group has been vilified more in the last few years than the hip flexors. Tight hip flexors have been accused of being the culprit of, among other things, lower back pain, weak glutes, and hamstring injuries. This seemingly ubiquitous demonization of the hip flexors may have some merit. As you can see in the picture to the right, shortened hip flexors can cause excessive anterior pelvic tilt and limit the ability to extend the hip. By altering the position of the pelvis, the hip flexors affect the lengths of other muscles, which consequently affects these muscles’ function (e.g., some become biomechanically weakened). Tight hip flexors can also contribute to excessive lordosis at the lumbar spine, as illustrated by the deep arch in the lower back in the picture. Based on the above analysis, it seems that overactive (or hypertonic) hip flexors indeed deserve their bad reputation. Moreover, many gym-goers, athletes, and everyday people tend to have tight hip flexors, so the problem merits attention.
This analysis might not be complete, however, if I didn’t I discuss how hypertonic hip flexors affect breathing. (Is anyone else excited, or am I the only one?) The psoas, which is one of the primary hip flexors, and the diaphragm, which is the main muscle of inhalation, are intimately related. In PRI lingo, the ipsilateral psoas and diaphragm are both a part of the Anterior Interior Chain, which is a polyarticular chain of muscle. (For those unfamiliar with the concept of polyarticular chains, Peter outlines the four different types of chains that PRI describes in the third installment of his “Intro to PRI” series, which you can read here.) Expressed another way, if you affect the position or function of one muscle in this chain, like the psoas, then you will affect the position and function of the other muscles in that chain, like the diaphragm.
Both the diaphragm and psoas attach to the lumbar spine. Therefore, when the psoas shortens and pulls the lumbar spine downward and forward, the ipsilateral diaphragm descends, flattens and becomes less effective as a respiratory muscle. In addition, when the diaphragm descends more air is drawn into the lungs. Having your diaphragm descended and having lots of air in the lungs are appropriate when you’re inhaling or, as dictated by the autonomic response to threat appraisal, dealing with a stressful event. Being chronically stuck in this state, however, may be undesirable for many reasons, such as decreased mobility and a decreased ability to relax and recover, a problem I discuss in more detail in this series’ first post. Ideally, the diaphragm should alternate between a dome-shape during exhalation and a flattened and descended shape during inhalation, but chronically tight hip flexors decrease the ability of the diaphragm to alternate between being ascended and descended. Taking this logic one step further, might tight hip flexors also contribute to, among other things, stiff necks, anxiety, and poor sleep via their deleterious effects on breathing and the autonomic nervous system? Maybe.
According to PRI, there are two orthopedic tests to determine the position of the pelvis in the sagittal plane and whether you might have tight hip flexors: the Thomas Test and the Adduction Drop Test. The Thomas Test is perhaps more widely-known, but may have some limitations. Hence, it is often necessary to perform both the Thomas Test and the Adduction Drop Test to determine the position of the pelvis.
The Thomas Test can tell you a few things: 1) whether the connective tissue structures of the anterior hip capsule (iliofemoral and pubofemoral ligaments specifically) are intact, and 2) whether the hemipelvis being tested is anteriorly tipped. A positive Thomas Test indicates that the anterior ligamentous structures of the hip joint are healthy and that the hemipelvis is anteriorly tilted. A positive Adduction Drop Test indicates: (1) whether the femur being tested is limited in adduction, which is secondary to (2) whether the hemipelvis being tested is anteriorly tipped. While the overlap in the purpose of the tests might make doing them both seem redundant, there actually is clinical value in performing both: it is possible that a negative Thomas Test doesn’t necessarily mean that the pelvis is neutral, the primary example being when pathology of the anterior hip ligaments that would normally check excessive hip extension yields a “false negative” test result. In this case, the individual would have a negative Thomas Test and a positive Adduction Drop Test, which indicates that their hemipelvis is indeed anteriorly tilted but compromised anterior hip ligaments are allowing them to gain extra hip extension ROM. This speaks to the fact that more mobility is not always a good thing–it’s more important to consider how a joint gets from point A to point B rather than just being concerned with total ROM.
To summarize the testing methodology, a positive Thomas Test indicates that yes, your hip is anteriorly tilted. However, a negative Thomas Test doesn’t guarantee that your hip is neutral. If the Thomas Test is negative, then you also need to perform an Adduction Drop Test to determine whether the hip extension ROM that the individual demonstrated is due to position of the innominate or laxity of connective tissue structures.
One conventional approach to treating an anteriorly tipped pelvis is to stretch the hip flexors. This approach may be helpful when a person stretches correctly, which involves a) knowing what you’re doing and why you’re doing it, and b) a high attention to detail. However, people often perform hip flexor stretches with the inaccurate belief that achieving a greater range of motion during the stretch is better. As a result, they might feel a big stretch in the front of their hip, but they might be stretching both the hip flexors and the anterior hip ligaments. Since ligaments can’t grow back, stretching ligaments can create pathology (i.e., it’s bad, no bueno, etc.). Thus, it’s important that you know how to properly treat tight hip flexors. Below is a video that explains how to safely and effectively stretch.
How to safely and effectively stretch the hip flexors.
(Kudos to Dean Somerset for making and sharing an excellent video. Here’s the link to Dean’s corresponding article.)
Another exercise that can improve pelvic position and diaphragmatic function is the Supine Hemi Extension with Alternating Respiratory Rectus Femoris and Sartorius. I like to joke that the name is as long as the exercise is awesome, but just so you’re not confused I want to make my enthusiasm for this exercise explicit: this exercise is awesome. It might be my favorite hip flexor “stretch,” though I might prefer to call it a sagittal plane repositioning exercise (that may also affect the frontal and transverse planes). Watch the video below before reading my discussion of it.
Supine Hip Extension with Alternating Respiratory Rectus Femoris and Sartorius
When I first saw this exercise I was confused, since it didn’t seem to be stretching anything, let alone the hip flexors. However, this exercise works via neurological mechanisms, such as the crossed-extensor reflex and the autonomic regulation of and response to breathing. In the crossed-extensor reflex, when flexor muscles on one side of the body contract, the ipsilateral extensor muscles relax, the contralateral extensor muscles contract and the contralateral flexors relax. For example, if the right hip flexors activate, then both the right hip extensors and left hip flexors relax, while the left hip extensors contract. Thus, if you want to relax the left hip flexors, then one way you can do so is to activate the right hip flexors.
With regards to the breathing component, you won’t achieve any meaningful acute or lasting changes in hip flexor length or tonicity if you don’t, in PRI terms, secure the pelvic inlet by creating a Zone of Apposition via facilitation of abdominal muscles such as the internal obliques and transverse abdominis. What this means is that in order to (1) put the pelvis in the proper position to enable the hip flexors to be stretched, and (2) maintain that position and avoid falling back into “bad habits” (e.g., allowing the hemipelvis to tilt anteriorly), you want to work on engaging the abs. The Supine Hemi accomplishes this by putting those muscles in a biomechanically facilitated position (via activation of the ipsilateral hip extensors and inhibition of the lumbar extensors–note the “low back flat to the table” cue) as well as actively engaging them during a full, forced exhale (note the “ribs down” cue).
In summary, using the Supine Hemi Extension with Alternating Respiratory Rectus Femoris and Sartorius, you can reposition the pelvis and “stretch” the hip flexors without the risk of stretching the anterior hip ligaments and creating pathology. (Again, is anyone else excited about that, or am I alone?)
For a PEC (aka the “Extended Bro”), you’d want to perform this exercise on both sides since both innominates are anteriorly tipped. That prescription might be confusing because the exercise involves activating the hip flexors on one side of the body to inhibit the hip flexors on the other side and thus performing it on both sides might seem to negate any changes. However, the “power” of the neurological reflexes and responses that drive inhibition are strong, so to speak, and so doing it bilaterally should inhibit the hip flexors on both sides. Anecdotally speaking, I’ve observed this improvement enough times to get over my own initial doubt.
As mentioned in the video, you want to perform this exercise with a bolster whose thickness depends on the person’s test results. If a person’s thighs are two inches off the table in their initial Thomas Test, then you want to use a bolster that’s slightly thicker (e.g., four inches thick) to ensure that they are performing the exercise in a neutral spinal alignment rather than in lumbar hyperextension. A good rule of thumb is to use a bolster that’s thick enough so that the person can feel their lower back on the table throughout the set. I alluded to this particular cue earlier but I’m going to stress it again because it’s crucial: the person’s lower back should always be in contact with the table during the set. If someone is performing the exercise with their right leg in flexion and their left leg in extension, then there is a tendency for the left lower back to come off the table. Again, I often cue people to “feel their left lower back in the table,” or alternatively I might put my hand beneath their left lower back and tell them to press their lower back into my hand.
After you perform the first set on both sides, you can perform another Thomas Test to determine if the person needs a different-sized bolster. If the person’s thighs are now only half an inch off the table, then you can decrease the thickness of the bolster. If the person has somewhat asymmetrical test results (e.g., the left thigh is four inches off the table and the right thigh is two inches off the table), then you can use different-sized bolsters for each side.
The set and rep scheme for this exercise may vary depending on your test results (e.g., people with worse results might need to perform more sets). As a rule of thumb, three sets of five breaths on each side is a good approach. Speaking to my earlier discussion of the breathing component for this exercise, the reps are prescribed in terms of breaths because, as with many of PRI’s exercises, the breathing is crucial (I wrote a more detailed discussion of the breathing in part one of this series). You can also use a balloon for this exercise to improve the exercise’s efficacy, and impress your friends.
If you’ve read all three articles in this series, then a) I’d be pleasantly surprised and b) you have learned three great exercises to prescribe for hyperextended folks: the Swiss Ball All Four Belly Lift, the 90-90 Hip Lift with Passive FA IR, and the Supine Hemi Extension with Alternating Respiratory Rectus Femoris and Sartorius; the videos of the first two exercises are below. The first exercise “turns on” the internal obliques, transverse abdominis and serratus anterior, which posteriorly tilt the pelvis, internally rotate the ribs, and flex the thoracic spine, respectively. The second exercise “turns on” the hamstrings, adductors, internal obliques, and transverse abdominis, which posteriorly tilt the pelvis, and adduct and internally rotate the femurs. The last exercise, which I discussed in great detail in this post, inhibits the hip flexors and activates the internal obliques and transverse abdominis, thereby repositioning the pelvis to a neutral position from an excessively anteriorly tilted position while also improving diaphragmatic function. Used together, these exercise can inhibit and facilitate the appropriate muscles to restore better posture for PEC’s.
Swiss Ball All Four Belly Lift
90-90 Hip Lift with Passive FA IR
Stay tuned for the next installment of this series. As always, don’t hesitate to share your questions or feedback in the comments section, or to share this post with everybody you know. I’m mostly kidding about that last part, but kind of not really.