PT on the Net Research

Bracing vs Drawing In


Question:

I recently stumbled across this statement from an article on your site: “Clients should be educated in the 'drawing in' process to activate the core.” Biomechanically, this is unsound advice. Dr. Stuart McGill has clearly demonstrated that drawing in the core actually destabilizes the lower back by not allowing for proper activation of the obliques. What’s your opinion?

Answer:

This is an on-going question that has unfortunately evolved into a segregated and often opinionated debate within the health and fitness industry. The intent of this response is to show the “other side” of this issue, using another opinion and other aspects of the research. It will be suggested that drawing in is not biomechanically unsound advice and that perhaps research exists to show the contrary.

It may be best in this case for us to start by defining some terms and then move into a brief and non-comprehensive review of some of the literature to better establish an opinion.

Definition of Terms

Two of the terms that are at the forefront of this debate are “core” and “stability.” The term “core” has been defined as the cervical, thoracic and lumbar spine, the rib cage, pelvis and hips. The term “stability” is defined as a dynamic process that includes both static positions and controlled movement and the ability of a loaded structure to maintain static equilibrium after perturbation around the equilibrium position.

It seems basic, but it’s important in that the core may be more of a multi-layered structure with myofascial support both superficially and intrinsically. As such, “core stability” may be derived from multiple aspects (or layers) and require spinal stabilization (stability of each segment within the spine – intervertebral segmental stabilization) and trunk stabilization (stabilization of the spine, rib cage, pelvis and hips collectively). They are independent operations that work in synergy during function.

This concept can actually be demonstrated from research by Dr. Stuart McGill. In a study looking at the spines of powerlifters during competition, one participant was injured. The injury was sustained as L2-3 when this segment moved out of sequence or differently than the other spinal segments. There was a lack of segmental control at L2-3 (lack of segmental stabilization) and thus the whole spine buckled (lack of trunk stabilization). Arguably, it may be that intervertebral segmental stabilization is the first line of defense and perhaps most important. It is also the deepest layer, closest to tie spinal cord and perhaps more hierarchically important.

So perhaps true stability comes from control of motion or, maybe better stated, as the proper sequencing of motion at each spinal segment and the trunk, pelvis and hips collectively. The unit is only as strong as the weakest link, and any lack of control in a segment of the spine can disrupt the “stability” of the entire unit.

Another vital issue that needs to be resolved is that stability is probably achieved through motion, not through the elimination of motion. In other words, stability is accomplished when motion can be properly sequenced and controlled, not when it is eliminated from occurring. Perhaps similar to earth, a baseball or even a Frisbee is more “stable” in its path of motion when spinning compared to a non-spinning state.

Literature Review

The premise behind bracing is to increase stiffness of the muscles surrounding the trunk/low back through concurrent activation and thus increase the “stability.” This is achieved by isometrically co-activation of the abdominal and erector muscles (superficial myofascial tissue attaching to trunk and pelvis). Stability, as it relates to bracing, is thus derived by research from Bergmark in which he stated that, ”stable equilibrium prevails when the potential energy of the system is minimum.” Or in essence, stability is achieved when the potential for motion is minimized.

The premise behind drawing in is to heighten or regain the control of the segments through proper timing of activation to increase stability of the vertebrae, sacroiliac joint (SI joint) and lumbopelvic region. This is achieved by drawing in the lower abdomen below the navel, which activates the transverse abdominis, internal oblique and multifidus muscles (deep myofascial tissue attaching to each vertebrae). So actually, the drawing in maneuver increases activation of portions of the internal obliques. Stability, as it relates to drawing in, is again derived from research by Bergmark to an extent but also from Panjabi. Panjabi theorized that there is a “neutral zone” in the spine (a range of motion in mid-range) in which the myofascial system was much more responsible to provide support and control motion.

Bracing is centered on mechanical principles of reducing the potential for motion and providing as much stiffness as possible through superficial myofascial tissue of the trunk/pelvis. Drawing in is centered on increasing the activation and timing of deeper segmental/intervertebral myofascial tissue to control movement. So we are dealing with a mechanical model (bracing) and a neuromuscular control model (drawing in).

This idea is supported in the methodologies of many of these studies. Many studies looking at bracing define stability as “the ability of the spinal column to survive an applied perturbation.” This is known as Euler column stability and uses a system of modeling the spine based upon Euler mechanics. Some important issues with Euler mechanics are as follows:

Relative to stabilizing the low back (though the definition of “stabilizing” must always be evaluated), research has shown that both bracing and drawing in techniques provide a significant effect at the SI joint, with the drawing in maneuver having a greater effect than bracing. A recent systematic review of the literature has demonstrated that specific exercises such as drawing in have a significant impact on the reduction of low back pain.

Research has also shown that using the drawing in maneuver in a one-time intervention and, over a four week period, increases the timing and activity of the deep abdominal muscles during arm and leg motion as well as during gait. When a bracing (or co-contraction) technique was used, there was no change in timing and activation of deep abdominal stabilizing muscles of the spine. Research has further shown that using motor control strategies that begin with teaching drawing in techniques in isolation and progress to functional tasks also increase muscle function and decrease LBP in highly athletic individuals.

In lieu of this notion, it appears that with injury/pain, the nervous system gets de-programmed much like how a virus affects a computer. Thus, drawing in may be a technique that helps to re-set the programming to allow timing and activation to regain better and even proper function.

With respect to bracing, both Dr. McGill and other researchers have noted that it is difficult to activate the muscles collectively at high enough level of co-contraction. Furthermore, based upon the research findings for drawing in, the concept of bracing must be evaluated for functional purpose and/or significance. During function, stabilization is achieved by timing, activity and sequencing muscles that change throughout the motion. Bracing requires that all available muscles be activated to help minimize motion. This could and may limit proper motion of the spine, trunk, pelvis and/or hips. Any of which may be detrimental to performance.

Research has shown that drawing in focuses on muscles that activate bilaterally, regardless of direction and/or speed of motion. This is important for functional performance because activation of these muscles occurs anyway regardless of the movement. During asymmetrical tasks, movement-dominant muscles are recruited based upon direction of resistance and force requirements. However, the deep stabilizing muscles of the spine are activated regardless of the movement requirements. If a bracing technique that promotes activation of all muscles of the trunk symmetrically is used during a functional asymmetrical task, it may limit asymmetrical movement, which must take place between the hips/pelvis, spine and rib cage.

Lastly, it is important to emphasize that drawing in has been shown to have a very efficacious effect on LBP. However, it is not well known or researched as to whether this matters or if this technique has any bearing on persons without LBP. It can be argued that between 60 to 90 percent of the world’s population will at some point in life have LBP, and therefore this technique may have benefit for anyone but remains to be studied.

Conclusion

Bracing and drawing in are two different techniques used to artificially enhance the stabilization capability of the body. Each has a different focus: bracing on mechanical parameters, drawing in on neuromuscular control parameters. Drawing in has been shown to increase activation and timing of muscles used for stabilization during functional activities (gait) while bracing has not. Drawing in does not interfere with muscle recruitment of movement-based or direction specific muscles. Bracing suggests that all muscles should be activated. And lastly, the question must be asked as to why someone may need to brace or draw in at all?

References:

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