1/4 Heure LabO #73: "Does Doing Crunches Strengthen Core Stability?"

What is Core Stability Beyond Crunches?

Core stability is often misunderstood, reduced to the mere execution of crunches. However, there is a fundamental difference between targeted strengthening of certain trunk muscles and functional core stability.

According to Emmanuel Lehjeart's definition, core stability is not achieved through sets of crunches, but by learning to activate the various descending motor pathways in the correct order. These pathways activate motor patterns that interlock like nesting circuits. It is about skillfully leveraging physiological synergies, recruiting the right muscles in the right order, unconsciously and reflexively.

Thus, trying to force the contraction of the body's deep muscles does not guarantee a fundamental improvement in core stability. Core stability is more about the transmission of force and collaboration among various factors, within a logic of resilience and the capacity to remain unyielding in motion.

The Central Role of the Brainstem and Postural Alignment

Core stability is intrinsically linked to postural alignment. Observing posture, that is to say, static alignment, is a key indicator. These alignments are managed unconsciously, mainly by the brainstem.

The brainstem, rich in cranial nerves and reflex pathways, plays a crucial role in managing tone and stabilizing the body's center during movements of the extremities. Understanding that core stability is unconscious and depends on the quality of sensory information relayed to the brain highlights that purely voluntary approaches are often ineffective.

This reveals a methodological bias similar to thinking one can work on proprioception by simply standing on a BOSU. It is essential to distinguish between moments when muscular strengthening is relevant and those when core stability is developed through reflex pathways.

Functional Core Stability and Neuro-Athletic Approach

A "functional" approach to core stability, advocated by some physical trainers, promotes diverse and varied movements in all three planes. This approach aligns more closely with Emmanuel Lehjeart's definition than analytical work, although the latter can sometimes have its place.

The idea is that core stability should be transferable to each individual's sports activities. Reflexive stability precedes voluntary movement. Each specific task, whether it involves throwing a javelin or shooting a basketball, requires efficient movement dynamics made possible by good stability. The neuro-athletic approach aims to work on the person behind the athlete by stabilizing unconscious and involuntary processes.

It is not about choosing between a classic approach (more stability training in various forms) and a neuro approach (more vestibular), but rather about combining both. One must identify the problematic reflex pathways in the athlete, work on them specifically, and add progressive stress to strengthen the system. This progressive overload enables reflex pathways to become more efficient, thereby optimizing stabilization strategies for the practiced sport.

The Importance of Breathing in Core Stability

A often overlooked but fundamental element of core stability is breathing. During intense athletic movement, such as a squat, stabilizing the body's center is impossible without proper management of abdominal pressure through breathing.

Breathing is central: the rib cage is rich in mechanoreceptors, and the fluidity of breathing across the widest possible continuum is essential. Being capable of complete inhalation and exhalation, stretching the diaphragm, allows for maximal loads while maintaining variability.

If breathing is not optimal, with reduced amplitudes, it can create issues with core stability. Working on the coordination between the head, pelvis, and rib cage during inhalation and exhalation is a major prerequisite. Breathing is not just a matter of gas exchanges; its mechanics and coordination are vital for core stability. This coordination involves numerous muscles and joints, influencing proprioception managed by the vermis, a central part of the cerebellum. Thus, reorganizing respiratory work can significantly enhance core stability.

Core Stability: A Complex Body Mechanic

In summary, core stability is not simply a matter of static strength but rather an adaptability for better force transmission. This involves good respiratory mechanics, head-diaphragm-pelvis coordination, and reflexive stabilization involving the brainstem and primitive reflexes.

It is only after laying these foundations that one can work on the more familiar forms of core stability (anti-flexion, anti-rotation, etc.). All these aspects constitute a continuum. It is crucial to adapt exercises according to the sport and individual needs. Core stability is also linked to specific postural strategies, such as head inclination or pelvic positioning, which can be observed through the infrasternum angle and correlated with the autonomic nervous system.

Ultimately, understanding the "why" behind each exercise is fundamental for an effective approach to core stability, tailored to the individual and the desired effects.