How to Enhance Your Clam Shells (Part 1)

Introduction:

Not all clam shells are created equal. Yet, many physical therapists randomly prescribe them to everyone with low back pain or "weak" hips. But, in this article, I want to challenge your current thinking and create a paradigm shift toward your clamshell prescription. In this first part of a two-part series, we will break down the "why" and the biomechanics. We'll examine the "how" related to proper execution in part two.

Main topics in this article:

• Body Type
• Orientation

If you're a visual learner, click the video below to watch the same topics discussed in the article.

Body Type

When you think about different cars, it creates certain beliefs and expectations. For example, a truck is expected to be worse on gas than a sedan. Conversely, a truck is expected to be better at carrying heavy loads than a sedan. Similarly, the human body can be represented with expectations based on the pelvis and rib cage. It has two different archetypes that create expectations and movement patterns. Understanding these archetypes are critical to comprehending the why and how of proper clamshell prescription.

Wide ISA:

• Infrasternal angle > 90°
• Bias of Nutation, Internal Rotation, Adduction, Extension
• Eccentric Bias of Posterior Lower Pelvis

Narrow ISA:

•  Infrasternal angle < 90°
• Bias of Counternutation, External Rotation, Abduction, Flexion
• Concentric Bias of Posterior Lower Pelvis

If you're interested in learning more about these two archetypes, I encourage you to join our next Performance Redefined Course.  

Orientation

Now that you know the two archetypes, let's discuss the created orientation. Besides the more straightforward bullet point of narrow ISA being better at abduction movements (which is what a clamshell is), I want you to focus on the last bullet point — the concentric and eccentric bias. These biases are going to create the following expectations to consider for your hip clam prescription:

Wide ISA: Eccentric Bias of Posterior Lower Pelvis

• Nutation of the sacrum creates an eccentric orientation (lengthened positioned) of the posterior pelvis 
• Creates a positionally "weaker" glute
• More prone to "not feel" the glutes
• Eccentric starting position usually makes it hard to feel the glutes during a clam

Narrow ISA: Concentric Bias of Posterior Lower Pelvis

•  Counternutation of the sacrum creates a concentric orientation (shortened positioned) of the posterior pelvis
• Creates a positionally "stronger" glute
• More prone to posterior pelvic impingement
• Concentric starting position make it easy and sometimes creates hyper-sensitivity from excessive compression.

That's all for part 1! If you're feeling slightly confused, you're in the right spot — we're only halfway done! Learn these principles as we head into part 2 so you genuinely understand the "why" behind the specific setup and modifications we choose with the clamshells.