Force and Form Closure

Has it become a lost art?

I always had an inclination that the body was an interdependent entity, long before I entered the Pilates world. I simply had to affirm this way of thinking through the literature I was reading and even more importantly, work out a way that I could pass this information to clients.

Over the last decade, huge advancements have been made in exercise science, resulting in vast amounts of information at our fingertips. However, within this timeline the art of understanding and delivering these findings have been forgotten. My affirmation came during my mat certifications around 2010, in the context of form and force closure. This terminology signifies the ability for the human body to produce biomechanical mechanisms that help support the Lumbo-pelvic hip complex during both static and dynamic posture. Essentially, both the physical and location and makeup of the [muscular] synergies involved help create a binding process, helping to prevent uncontrollable motion. 

There is (in my opinion) presently a more ‘copy me’ trainer delivery, than helping the client to create autonomous movement. Whether the trainer needs a better biomechanical understanding of human movement, or it's a little simpler to visually deliver than explain a movement, the trainer has opted for a process that could be a little more beneficial to the client if explained with some simple points.

Why is Force Closure so important?

Integrating the knowledge of force closure into regular techniques enables the clients to tap into the biomechanical mechanism designed for both stability and force transfer. In other words, it provides the client with the ability to apply methods designed to help them direct tension towards structures that help support us during both static (standing tall) and dynamic activities (walking, running, jumping and even sitting) without discomfort, or the over reliance of support aids.

The good part is that you don’t have to change the methods, or do something in addition other than have an understanding of a basic principle.

Firstly, let’s take a look at what form closure are and how this anatomy can help us understand mechanisms that provide support during movement (force closure)

Form Closure

Form closure is the reference to the sacrum sitting within the pelvic girdle (ilium) to create the sacroiliac joint (SIJ). The SIJ is similar to a keystone construction and requires little pressure (other than downward force) to provide ‘wedge-like’ stability during a standing (static) position.

Fantastic design, right? If only it was that simple. Ground reaction, directional force, contra, bilateral and unilateral movements will determine the amount of stability will be needed within the SIJ. Unlike a knee or elbow, the SIJ has very little movement to offer. By design, the SIJ needs as much ligamentous support as it can get , given that it can only offer 2-4mm of movement, dependent of course to who it belongs to.

Regardless of the force required, structures around the joint help remove the impact from the SIJ itself. Think of the impact on this joint just in a simple task like walking. It’s involvement is huge. Now add a particular issue with any structure above, below, or to the side of the side, we will experience discomfort or even pain within the SIJ.

Force Closure

During movement and in particular directional force, the SIJ requires a suitable level of support, depending on the complexity, load and intensity of the task.

Force closure is best described as a perpendicular force applied from above, below and from each side of the joint. We have a kind of ‘compass of tension’ all directed inwards at the SIJ.

Remember, the joint can barely move. Therefore, the force production, reduction and dissipation has to be delivered through ligamentous and muscular structures. Think back to your lessons in anatomy, focusing particularly on the buttocks and lower back (deep thoracolumbar junction and superficial Lat Dorsi). It provides a small insight to the crossing of both contra (opposite) lateral gluteus maximus and Lat Dorsi. This ‘strap like’ structure is known as a functional ‘sling’ or ‘train’.

Taking both this information and the aforementioned compass of directional force, let’s look at the other slings/trains that are influential over force closure. With the want to avoid over simplifying, I have included both the most influential structures and slings. However, you should incorporate the need of involving the deep and superficial structures of the torso.

It’s also worth noting that like any other format of exercise/therapy, none of these functional lines work within isolation and there are a number of exercises out there that could represent two, or all three functional lines.

Superficial Back Line / Deep Longitudinal Sling

This particular line becomes the north and south directional force compass. Ground reaction force is produced by earth’s gravitational pull and the equal force being directed back up through the body. Particular focus should be drawn to the line of pull leading up from the hamstring group through the junction around the SIJ. This is called the sacrotuberous ligament. The multifidus (pat of the core unit) creates tension within the thoracolumbar fascia (superficial tract of fibrous tissue in relation to the multifidus). Both with contraction of thoracolumbar fascia and Erector Spinae, create an inward ‘squeeze’ of the ilium (the big ears of the pelvis). This creates security for the keystone-like sacrum within this structure.

Exercise example: Lunge or split squat

Back Functional Line / Posterior Oblique Sling

By looking at this line, it begins to be evident why this would become helpful to activate. The contralateral (opposite) sides work in unison to provide stability, especially within unilateral exercises.The green dot within the middle of the lower back indicates the thoracolumbar fascia, which connects both Gluteus Maximus and contralateral Lat Dorsi.

Simultaneous tension between these structures creates force generally through activity, to trigger a stabilising mechanism. This is opposed to the nature of the functional line above, whereas the SBL/DLS can be active within a static position.

Exercise Example: Shoulder (or Glute) Bridge; Plank

Front Functional Line / Anterior Oblique Sling

This particular sling works within opposition to the former line. Again, this line is based upon contralateral lines of tension and is triggered through activity.This continuous ‘looped circuit’ provides a means of transferring force from anterior to posterior and left to right and vice versa. Without this line being included the others would not function to help create movement.

Exercise example: Wood chop

Putting it all together

The biomechanical dynamics can alter within these structural components, due to a number of reasons. This could be through altered posture, injury and or pregnancy. This can result in hip pain or specifically pain around the SIJ. There can be a journey to recovery from this ailment, with the intervention of physiotherapy and a timely regimen that enables the client to move pain free. As with many other musculoskeletal issues, prevention is far better than cure. This begins with teaching the client to produce an (eventual) autonomous movement.

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