Spine Stabilization and Neutral Spinal Posture
Functional movement, or the ability to move and respond without restriction, as well as to move and respond effectively and with intention, begins with an understanding of core stabilization and neutral spinal posture.
Core Stabilization and its Importance to Functional Movement
Obviously, the ability to position the spine and activate the muscles necessary to do so is a key skill as it relates to all movement. Equally important, is training the core with the understanding that it links upper and lower body movement. Putting the importance of alignment skill and integrated movement capability in perspective requires a brief discussion of 1) the “serape effect,” 2) the impact of load, 3) abdominal bracing, as well as, 4) the development of a definition for core training that aligns with functional training.
The Serape Effect
The serape effect, first described by Logan and McKinney (1970) helps one to visualize what the core musculature is anatomically suited to accomplish, especially as it relates to rotational power development. The serape is a scarf-like blanket worn by natives in some areas of Mexico and South America. It drapes around the neck and shoulders and crosses near the waist, tucking into the belt area. Visualizing how the serape is worn captures the functional design of the torso muscles' crisscrossing nature. In essence, how the serape is worn reflects fiber direction of the torso muscles, which in turn determines muscle function and movement capability. Most of the muscles of the core/ torso and their associated fiber directions are oriented in horizontal or diagonal directions. This anatomical design lends itself well to rotational force production between the hip and opposite shoulder, especially when coupled with ankle, knee and hip extension movement. The so called serape effect (Logan and McKinney, 1970) is specifically the result of interaction between the rhomboids, serratus anterior, and the external and internal obliques.
Based on this functional model, it becomes obvious that useful core/torso training must be more involved than, for example, training the rectus abdominis with isolated trunk flexion and the torso with barbell chest presses. Note that Logan and McKinney made this observation in 1970, yet integrated core and torso training has not been universally received or implemented, though understanding and use of functionalintegrated training is gaining momentum. All of the BOSU® Programs incorporate this concept of integrated movement into exercise progression and include the BOSU Integrated Balance Training, BOSU® Pro Fitness Training Series, BOSU® Sport Training Series and the BOSU® Balance Trainer Complete Workout System programs.
The serape effect and this diagonal patterning of muscle synergy can best be observed in rotational movements when the core is loaded or prestretched, and prepared to assist a throwing or other rotary motion like a golf or baseball swing. The serape effect represents the most favorable lengthtension (best prestretch) for a muscle that results in optimal, not necessarily maximal, force production.
This understanding of how the core and torso function together (the serape effect), and how the core links the upper to lower body, establishes a base of knowledge behind the belief that the body should be trained in an integrated fashion, from headtotoe. In light of this information, the importance of linked power development is evident, but does not exclude traditional approaches to training.
The Impact of Load
As is true of any form of training, sometimes good intentions can be carried too far. In an attempt to make an activity “sport specific” or “look like a sport skill,” some functional training enthusiasts train certain motions or positions without considering load application. This mistake has caused confusion in the area of functional training and has led many experts to question its relevance.
To follow are a few examples that can get a wellintentioned professional in trouble, in terms of putting an athlete or fitness enthusiast at risk for injury. Though it is necessary for a pro road cyclist to generally assume a flexed, and rounded spinal posture while riding, that does not justify doing deadlifts or bent over rowing movements with a rounded spine. The risk outweighs the benefit and is not specific to the sport. No cyclist that we know has ever ridden a bike with a weight hanging from his or her neck or arms! Baseball or softball players may field a ground ball with a flexed spine, but that does not justify training the spine in a flexed position with heavy loads. Additionally, trying to replicate a golf swing or pitcher's throwing motion against load (i.e., elastic cable) by tethering elastic resistance to a ball or part of a club handle is ludicrous, especially if the speed of these movements that occur while playing either sport are replicated.
Creating exercises that use high risk postures and/or attempt to replicate the same speed of movement against inappropriate load for a given movement found in a sport, not only can put the spine at risk for injury, but can include other joints like the shoulder and knee. Many sports and daily occupations require positions that constitute poor posture or can place a number of joints, not only the spine, in vulnerable positions that represent the end rangeofmotion of joint capsule tolerance. This reality should not justify training with heavy load in these compromised positions. In fact, the body can tolerate many of these positions without load, and a well designed training program can help to counter any negative effects by using exercises to counter any harmful consequence. In sport, it must be exact, not close, in terms of skill replication to be called sport specific.
Abdominal Bracing and Neutral Posture Application
Being able to establish a braced spine and maintain a braced core is essential to effective and safe movement. This is accomplished by maintaining a mild contraction or tension in the abdominal wall. However, abdominal bracing is very different than abdominal hollowing, which generally refers to a pulling or drawing in of the abdominal wall. When the bracing is performed correctly no change occurs in the abdominal wall. McGill (2002) refers to this as muscle stiffening and terms it “abdominal bracing.”
Much of the confusion and controversy between abdominal hollowing and bracing may stem from previous research (Richardson et al. 1999). Richardson's group observed increased muscle activation of the transversus abdominis with abdominal hollowing. In contrast, McGill has shown that an isometric abdominal brace coactivates the transversus abdominis with the external and internal obliques to ensure stability in virtually all modes of instability (Juker et al. 1998; McGill 2002, pg. 210). When the abdominal wall is braced, it is neither hollowed nor pushed out.
With this background in mind, Richardson and colleagues also observed that transversus abdominis recruitment is impaired after injury. Therefore, Richardson's group developed a reeducation program of exercise to activate this muscle group in low back patients. However, McGill (2002) points out that this is misguided because hollowing as a reeducation exercise for this particular muscle does not ensure stability. Therefore, to encourage back patients or athletes to use hollowing over abdominal bracing if the goal is to enhance stability when performing daily activities and sport is mistaken. Abdominal bracing activates three layers of the abdominal wall (transversus abdominis, internal oblique, external oblique) with no added motion of drawing in, and is much more effective at improving spinal stability (McGill 2001; McGill 2002).
Teaching Abdominal Bracing
Teaching abdominal bracing, as is true for teaching neutral posture, is challenging. An instructor is simply asking the participant to stiffen the abdominal wall with a mild isometric contraction, where no movement occurs in the spine or pelvis. If a participant can already establish neutral posture and can differentiate hip flexion from spinal flexion and extension, he/she will be ready to combine these skills with abdominal bracing. A trainer or instructor should teach that abdominal bracing occurs when the abdominal wall is neither sucked in nor pushed out.
McGill (2002) suggests communicating this idea of bracing by having the person stiffen one joint, such as the elbow, by simultaneously contracting the flexors and extensors. The person stiffens the joint without any movement occurring at the joint and palpates the joint to feel what is happening. This can be practiced at other joints like the knee. Then, the drill is moved to focus on the core/torso region and the person uses the same technique to achieve the bracing effect. Finally, an instructor can teach the participant to maintain the abdominal brace during functional movement situations that include picking up a child, moving in and out of a chair, or during an explosive athletic movement. We often refer to this involved bracing concept as “setting” the core. Realize that stiffness of the core might be sustained for a period of time or only needed on and off for
brief moments during performance. But, to set the core correctly, regardless of the situation, one must understand all of the ingredients that contribute to effectively creating optimal core stability.
Training the abdominals and back musculature has been referred to as core, trunk, torso, abdominal and back training to name a few, and in addition has been referenced as the body's power or control center. No matter what one calls this type of conditioning, the breadth of meaning with regard to a functional and complete training of the core should be reflected by what one actually does in a training program.
Bottom line requirements with regard to training the core include a need for 1) stability and 2) a strong, integrated link between the upper and lower body (the serape effect). This coupling link between the upper and lower body must be able to provide stabilization of the core and serve as a springboard for linked power development that can occur during a variety of movement situations, and can include skillful tasks like striking, throwing, lifting, bending or jumping.
Complete core training must involve all of the muscles of the midsection, and include training of these muscles simultaneously with motion that should involve the hip flexor, hip rotator, gluteal and hamstring muscle groups (refer to the BOSU® Sport Conditioning Series). Being able to create stability and motion in the core region allows for a smooth transition of power between the upper and lower body which equates to applied – or functionalpower development. This powerful link cannot be developed by only training the trunk musculature in isolation. Instead, stabilization, bracing, and rotation are key elements to train in the core region if a functional, performance oriented carryover is a desired training outcome.