Understanding the Mythical Core: A Deep Dive into Strength, Posture, and Movement
- John Wilson
- Jan 7
- 5 min read
When you hear the phrase "strengthen your core," what comes to mind? Most people think about abdominal muscles or maybe the six-pack everyone wants. But is that really what the core means? The term "core" is used so often in fitness, therapy, and movement practices that it has become standard. Yet, few stop to ask what it truly refers to, why it matters, and how different approaches understand and work with it.
This post explores some of the concepts of core, from common fitness ideas to deeper anatomical and functional perspectives. We will look at how physical therapy, Pilates, Feldenkrais, and Rolfing each interpret the core and what that means for posture, movement, and strength.
What Does "Core" Really Mean?
The word "core" is often used loosely. In fitness, it usually means the abdominal muscles—the rectus abdominis, obliques, and transverse abdominis. These muscles help with trunk stability and movement a little, but not as much as people think.
Anatomically, if there is any anatomical definition of core, it can include the deeper muscles such as the psoas, quadratus lumborum, pelvic floor muscles, and multifidus. These muscles can work together to maintain posture, and coordinate movement. They are less visible but crucial for what we call postural control and fine motor coordination.
The confusion arises because different disciplines focus on different layers or functions of the core:
Physical therapists often see core weakness as a root cause of pain or dysfunction. Their solution is usually to strengthen these muscles with targeted exercises, weights, or resistance bands.
Pilates emphasizes control and activation of the deeper core muscles, aiming to improve coordination and stability through mindful movement.
Feldenkrais focuses less on strength and more on improving sensory-motor skills through gentle, mindful movement patterns.
Rolfing uses the terms "core" and "sleeve" to describe two distinct but interconnected systems in the body.
The Core and Sleeve According to Ida Rolf
Ida Rolf, the founder of Rolfing Structural Integration, introduced a useful way to think about the core. She described the body as having two main components:
The Core: Like the inside of a motor, it is the network of inner muscles responsible for relaxed posture and fine movement. These muscles work quietly and continuously to keep the body balanced and aligned.
The Sleeve: The outer casing of the motor, made up of larger, more visible muscles that produce movement and action. These muscles protect and organize the core but need to work independently and the core needs to be able to spin independently inside the sleeve.
This analogy highlights the importance of differentiation between the core and sleeve. If the sleeve muscles are too tight or overactive, they can restrict the core’s ability to function properly. This leads to inefficient movement, poor posture, and sometimes pain.
In Rolfing sessions, work usually begins with the sleeve muscles to release tension and improve their ability to move independently from the core. Strengthening happens naturally as these muscles are used more effectively.
Illustration showing the outer sleeve muscles in the human body.
Why Is the Core Considered Weak?
Many people are told their core is weak, but what does that mean? Weakness can mean different things depending on the context:
Muscle strength: The ability of muscles to generate force.
Muscle endurance: The ability to sustain activity over time.
Neuromuscular control: The ability to activate and coordinate muscles effectively.
Postural stability: The ability to maintain balance and alignment with minimal effort.
Physical therapists often focus on strength and endurance because weakness in these areas can contribute to pain or injury. For example, weak deep stabilizers of the spine may lead to poor posture and back pain.
Pilates and Feldenkrais practitioners emphasize neuromuscular control and sensory awareness. They argue that many problems come from poor coordination rather than just weakness. Learning to activate the right muscles at the right time can improve function without necessarily increasing muscle size or strength.
Rolfers focus on the relationship between the core and sleeve, aiming to restore balance and ease of movement. They see weakness as a symptom of poor differentiation and tension patterns rather than a simple lack of muscle power.
How to Approach Core Strengthening and Posture
Understanding the core as a complex system helps us approach it more effectively. Here are some practical ideas:
1. Differentiate Between Core and Sleeve
Learn to feel the difference between deep inner muscles and outer muscles.
Practice movements that isolate the core without overusing the sleeve.
Use myofascial release to relax tight sleeve muscles (See a Rolfer).
2. Focus on Control and Coordination
Try exercises that emphasize slow, mindful activation of deep muscles.
Use gentle breathing techniques to engage the diaphragm and pelvic floor.
Incorporate balance and stability through mindfulness to improve embodiment.
3. Build Strength Through Use, Not Just Exercise
Relax the sleeve muscles by using them in natural, functional ways.
Avoid overloading muscles by using too much strength to do ordinary things.
Remember that strength comes from purposeful movement.
4. Include Sensory-Motor Training
Explore Feldenkrais, Tai Chi, or similar methods to improve body awareness.
Use gentle, varied movements to retrain the nervous system.
Focus on the quality of movement.
Why Strengthening the Core Alone Is Not Enough
Strengthening core muscles is helpful, but it is not a cure-all. Without proper coordination and differentiation, stronger muscles can still lead to poor posture and inefficient movement.
For example, if the outer muscles (sleeve) are tight and overactive, they may restrict the core’s ability to stabilize the spine. This can cause compensations and discomfort. Strengthening the core without addressing these patterns may reinforce bad habits.
True improvement comes from a balanced approach that includes:
Releasing tension in the sleeve
Activating and coordinating the core
Using the body in functional, natural ways
Final Thoughts
The instructors a the Dr. Ida Rolf Institute eventually got together to decide on how to used the term "core" in our training. Unfortunately they chose the one definition that no one else uses, visceral space. Visceral manipulation, a system of addressing the organs and the systems they govern became a popular study among Rolfers in the 1980's, along with cranialsacral work. This newer definition does not reflect any use that Ida Rolf was teaching, i.e. a motor functioning independently of its outer encasement, and it does not help us communicate with other disciplines either. I find it nearly useless at this point and prefer to use other terms. If however you find yourself pondering how to strengthen or engage your core, you might also ask yourself "what do I mean by Core?"
Very useful explanation.