Improving Core Timing & Hip Stability: The 90-90 Series

This week’s Pose of the Week is all about isolating the deep hip stabilizers for improving core timing and hip stability.

Spoiler Alert! This is not your typical yoga posture or your “old school” boring clamshell. This little series can help tackle a multitude of issues, but I often use it for expectant moms, new moms (hello postpartum recovery!), and anyone needing improved hip stability or strength. This series also better connects the muscles of the back and spine with the hip, core, and pelvic floor! So it’s a win-win!

Sneak Peek of the 90-90 Series

Why is Improving Core Timing & Hip Stability Important?

First, a few truths:

  • We are all athletes of various shapes and sizes, no matter what our fitness level!
  • The human body was built to move.

Why are these important?

Because in order to move, we need a certain level of joint stability. How do we achieve that? Especially – when the all important areas of the pelvic girdle and low back tend to be where injury and chronic pain show up the most.

One more truth: there is no simple single answer.

There are many variables that can contribute to back or pelvic pain. But one of the most common culprits is a lack of basic fitness.

Yep, oftentimes it’s just because we don’t get enough physical activity and movement. We sit too much, eat poorly, don’t sleep well, need better ways to manage stress (and more time to do it), and even when we do ALL of that right, the environment around us – the air we breathe, food we eat, and dirt we grow food in – can pollute us. Tackling all those is the domain of Lifestyle Medicine and holistic practice. It’s beyond the scope of this blog to address it – but it should be an important and vital part of all physical therapy care and healthcare you receive. For example, if sleep is an issue for you, here’s some simple ways you can improve your sleep tonight.

One of the chief mechanical mechanisms that can contribute back or pelvic pain is core timing and strength, as well as hip stability.

Core timing, put simply, is the ability for the abdominals, back muscles, hip, respiratory diaphragm, and pelvic floor to be able to work in synergy with one another. More specifically, it is the ability for muscles to fire in a certain pattern and with a particular timing – not too late or early, and not too much or too little – in order to make movement fluid and sustainable. When and how much are still up for debate, and the research in this area can yield controversial conversations. However, there is no doubting that without core and hip strength, we aren’t moving anywhere fast, far, or pain-free. At least not for long.

Considerations on Opposite ends of the Spectrum

Let’s consider two examples.

Pregnancy, when the abdominal muscles become so stretched they split with 100% incidence by the third trimester. The respiratory diaphragm becomes shorter because it has less room to expand. And the pelvic floor can become stretched and weak from all the downward pressure from weight gain and the growing baby. The low back becomes more swayed in absence of support from the core and expectant moms can start to leak toward the end of pregnancy, struggling with incontinence. These things are a perfect storm for back and pelvic pain; and as you may expect are a pretty universal experience for expectant moms.

Core Timing and Hip Stability
The Three diaphragms of support – vocal/laryngeal/thoracic, respiratory, and pelvic. These 3 diaphragms must be addressed when tackling core timing and hip stability.


On the other end of the spectrum, athletes can also overdevelop or use faulty training principles to try and tackle core timing and hip stability, which can end up decreasing shock absorption and increasing risk for injury, instead of decreasing it. This study illustrates how.

How the 90-90 Series Can Tackle Core Timing

Improving core timing (and therefore hip, back, and pelvic pain problems) can be more effective with this time saving series because it’s not an isolated movement. Specifically, this series requires you to integrate abdominal, pelvic floor, back, and hip strength work (see the three diaphragms diagram at right).

The 90-90 Series requires you to stabilize the spine AND the hip at the same time during dynamic, and rather challenging, movement. To get more detailed, when done correctly – this series targets integration and improved timing of the core muscles (think abs, respiratory diaphragm, and back muscles) with the deep gluteal sling (stabilizers of the hip).

Who doesn’t want better core strength AND hip control?

How the 90-90 Series Can Improve Hip Stability

This little series can lend itself to being a big time saver if you are trying to improve:

The Screw Home - Hip Hack
The muscles of the pelvic girdle that contribute to hip stability. The 90-90 series targets the majority of these muscles.

  • Strength of the gluteus medius (read: improve hip stability, the gluteus medius is the main contributor to hip joint lateral stability)
  • Strength of deep hip stabilizers (read: obturator internus is perhaps the most important hip rotator because it that has a feed forward mechanism to the pelvic floor via the arcus tendinous of the levator ani)
  • Pelvic floor recruitment and endurance
  • Strength of the low back and abdominals (sustainable participation in activity that requires the hip depends on optimizing strength in this area)
  • Strength of the respiratory diaphragm (read: more lung power! Additionally the diaphragm is the “roof of the house” or cylinder-like structure that makes up the core. This means any work on the respiratory diaphragm can improve and positively impact core stability, and indirectly, hip stability.
  • Normalizing breath patterns and getting out of a stress response that creates fight, flight, freeze, or persistent pain. Watch this video on abnormal breath patterns to learn more
  • Recruitment of secondary stabilizers like the quadratus lumborum (QL) to fatigue any muscle spasm and change output of QL activity

Ok, let’s practice!

Building Pelvic Girdle Power

Happy pelvic girdle power building!

Want more Core Stability Strength work?

Try these On-Demand Series with Dr. Ginger Garner to improve core stability and hip strength without leaving home or needing expensive equipment

Plus! Uplevel your Core Stability knowledge base for free: