Anatomical Variations Vs Splits Part 2- Acetabular Depth

Your anatomy isn’t what’s stopping your flexibility progress, but it will shape your journey—part 2 Acetabular Depth.
Ashleigh Flanagan
September 15, 2021

Welcome back. Last blog in this series, we looked at the impact of hip inclination angle on split training and what to do if you have a more closed hip inclination. If you missed it, read the blog here.

To refresh on what is really limiting your progress, Read common reasons for plateaus in flexibility.

Before we start

I want to make it clear that while your anatomical structure may make training splits more challenging, your bones are NEVER what ultimately limits your range. Bones never touch. They are connected but spaced by the soft tissues of joints. As well as this physical separation, our nervous system ensures an active resting tone that minimally limits joint range. There is no accurate, viable way to know how far into a particular range you will get. From my experience, working with hundreds of people who have been concerned that they have reached an anatomical limit, everyone can improve their flexibility. This doesn’t mean that everyone can achieve an externally rotated 180 deg middle split, but it does mean that no one can tell you it’s not possible, other than yourself.

Part 2 Acetabulum depth

The acetabulum is the socket of the ball and socket of our hip joint. There is a lot of normal variation in acetabulum depth. In straightforward terms, the acetabulum can be deeper because it recesses further into the pelvis or because it lips further around the top of the femoral head. Either way, this will limit the range available. The acetabulum can also be flatter and more shallow. When significant, this pathology is known as dysplasia. A shallow acetabulum results in more range available in the hip joint in all directions.

You can’t necessarily tell if you have a deeper or more shallow acetabulum, but there can be clues. Individuals with deeper acetabulum are more likely to experience symptoms of femoral impingement, typically pain and restriction on internally rotating then bending forward. They can also experience more pain and limitation into abduction. Individuals with a more shallow acetabulum may have been diagnosed with hip dysplasia as a baby, have difficulty stabilising their hips, and have had previous labral injuries or hip subluxations. 

Acetabulum depth and splits

As you may have guessed, those with a flatter acetabulum will have to work harder to build strength and stability. They have an increased risk of labral tears as the labrum is required to provide relatively more structural stability. Individuals may actually feel stiff in their hips in certain directions because their muscles are limiting range to increase stability. Strengthening through range is essential for both injury prevention and to access more range. 

Individuals with a deeper acetabulum will usually find middle splits training more challenging because there is less range available before their femur approaches the acetabular rim from below. If an acetabulum is deeper because it sits further into the pelvis, it can also influence range in front splits. If an individual feels pinching and restriction in the front of their forward leg, it may be due to increased opposition of a bony protuberance (femoral notch) and their acetabular rim. Taking their leg just out to the side a little and externally rotating it will take pressure off this area.  Stability and strength through range training is less urgent for those with deeper acetabulum as their joint provides a lot of passive support. 

Tips for splits training

1. Focus on strength and stability. If your hips are mobile in all directions, you need to work on being strong in all directions, through all ranges.

2. Find your own path. If you are struggling with locking and pinching in splits, spend time finding what orientation feels most comfortable and natural to you. Everyone has different hips, so we will all have different splits. If you are getting stuck, try rotating or changing the alignment a little. It’s better to wiggle around an area of resistance than it is to try to bust straight through.

3. Improve joint rotation. By improving hip rotation in both directions, you end up with a happier, more balanced hip that will allow more stretching load before resisting.

Remember, all progress is good progress, however long it takes. You will always get further if you persevere than if you stop.

Want more support in your flexibility journey? Book an assessment with a physio now

Continue Reading

pushpress gym management software for boutique gyms and fitness studios