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In the previous two articles I covered several ways in which the Extension/Compression Stabilizing Strategy (ECSS) directly causes pathology in the spine. As hyper-activity of the spinal extensors (resulting from a muscular imbalance), the ECSS also has a detrimental effect on function as well. This not only negatively impacts performance, but often causes injury - in today’s case to the intervertebral disc.
The most common way to injury a disc is exposing the the spine to repetitive, loaded, flexion. This increases the tension in the annular fibers of the disc (the cartilaginous rings that surround the jelly-like substance in the middle of the disc). Over time, this breaks down these fibers, eventually weakening them to the point where they stretch and distort. In medical speak, this is called a disc bulge or herniation.
Strength training, while it comes with many benefits, often results in injury to the lower back. This is for the simple reason that strength training often involves repetitive exposure of the lumbar spine to loaded flexion. Other than the Jefferson Curl (which I have written about previously), this loaded flexion is unintentional. One of the most common movements that puts the spine in this dangerous position is the squat, particularly the back squat. At the bottom of the squat, if the athlete lacks sufficient hip range of motion, to achieve a “full depth” or “below parallel” squat, they will have to compensate with lumbar flexion to get their hips to the desired depth. This is often called a “butt-wink”.
If you observed 100 athletes doing back squats, nearly all of them would have some degree of a butt-wink. While this may be common, it is not optimal, and only increases the athlete’s risk of injuring their lower back. The topic of how much is too much will need to be addressed at another time. The short answer is less is better. The more often the lumbar spine is exposed to loaded flexion, especially with heavy loads, the more likely they are to injure the disc.
There are many causes of the butt-wink: tight hamstrings, retroverted hips, tight glutes, limited ankle dorsi-flexion, short torso with long legs, but what is often missed is the ECSS’s roll in this movement dysfunction. Yes, there are many factors that play a roll, but the vast majority of the butt-winks out there are caused almost exclusively by the ECSS.
Mechanism of the Butt-Wink:
The buttwink happens when an athlete lacks sufficient hip range of motion to achieve the desired squat depth. If the ECSS is a spinal stabilizing strategy, the question then is how does it affect hip range of motion? It does so by altering the starting position of the pelvis for the squat.
Most humans have roughly 120˚ of hip flexion range of motion. To achieve a full depth squat, most will need 110-120˚ (depending on their morphology). This is one of the reasons squatting to full depth is so challenging, because it requires near end-range hip flexion. Because the squat uses near 100% of the athlete’s available hip flexion range of motion, the athlete really doesn’t have a lot to spare. Even the tiniest loss in range of motion may result in a butt-wink.
Remember that the ECSS is a massive muscular imbalance between the dorsal stabilizers (the posterior chain) and the ventral stabilizers (the abdominals and intra-abdominal pressure), where the dorsal stabilizers overpower the ventral stabilizers. This imbalance distorts the pelvis’ positioning, affecting the hip range of motion. The hyper-active posterior chain pulls (rotates) the pelvis forward into an anterior pelvic tilt. This anterior pelvic tilt with associated hyper-lordosis of the lumbar spine is a hallmark postural attribute of the ECSS.
If we are in a standing position, as we often are in sports, and as we are while we squat, this change in pelvis positioning affects the available hip range of motion. When the pelvis tilts forward, it does so via closed-chain hip flexion (pelvis moving on femur); it is not just through lumbar extension. Hyperactivity of the lumbar extensors may have caused the anterior tilt, but the hips had too flex to allow the motion to occur.
Before the athlete even has the bar on her back, she may have lost as much as 30˚ of hip flexion due to the anterior tilting caused by the ECSS. Put a bar on her back, and she has to tilt her torso forward to hold the bar. Where does that motion come from? You guessed it, hip flexion. Say it is only a modest tilt of 15˚. If the athlete started the motion with the pelvis tilted forward 30˚ and she then had to tilt forward another 15˚ to balance the bar on her upper traps, she haven’t even started the rep, but has gone from 120˚ to 85˚ of available hip flexion, well below the requisite hip flexion range of motion necessary for executing a proper squat without a butt-wink.
Challenges for correcting the butt-wink:
It may be hard to see, but the amount of hip flexion range of motion that can be lost with nothing more than movement of the pelvis is staggering. Correcting or at least minimizing a butt-wink is really all about changing the position of the pelvis throughout the squat. Easy as it sounds, it can be difficult for athletes to execute. For the athlete with the lumbar spine cranked into hyper-extension because of excessive posterior chain training, tilting the pelvis back toward neutral fells quite odd, assuming they are even capable of this motion.
Also adding to the challenge is the fact that many athletes “brace” for the squat by cranking on their spinal extensors intentionally. Achieving a neutral pelvis position requires the spinal extensors relaxing to allow the motion. Until they learn how to stabilize correctly, relaxing the spinal extensors will often make the athlete feel weak, not a great sensation if you’re about to attempt a heavy squat.
Another challenge is that most athletes try to keep their chest up as they descend. This feels good and stable, but is achieved, again, by cranking on the spinal extensors, which pulls the pelvis into an anterior tilt, resulting in an early butt-wink. The athlete may be able to achieve neutral’ish pelvis positioning at the start, and they may be able to maintain it for the initial movement in the descent, but once their hips start to shift back and their torso angle flattens, the spinal extensors will kick on to keep the “chest up”, pulling the spine and pelvis into the ECSS.
Finally, the ECSS is a compensatory strategy for stabilizing the spine. It activates in the absence of stability. Back squatting, especially heavy back squatting, places quite a challenge on the athletes spinal stability/stiffness. So even if the athlete can achieve a more neutral pelvis position, the moment they lift the bar off the rack, because of their lack of adequate stiffness, their lumber extensors will kick on, tilting their pelvis forward. The result is a loss of available hip flexion range of motion for the squat and increased exposure to loaded flexion in training, which often causes injury to the intervertebral disc.
Correcting this will take practice, but the benefit is a healthier spine and athlete. Lower back pain and injury is one of the most common injuries in strength training and one that often takes athletes out of practice, games, and the sport all together. There is no question that one of the major causes for such a high prevalence of lower back injury is ubiquity of the ECSS.
Next week will be the final segment on the ECSS and its contribution to spinal pathology. (Pun intended)
-Richard Ulm, DC