Core training has become an increasingly popular fitness trend as people strive to tone their waist-line and achieve that six-pack look. Workouts such as Yoga and Pilates are gaining popularity and have proven to be excellent exercises to build core endurance.
The goal of achieving a toned and slim physique may be a motivating factor to workout but more importantly is the vital internal functional role of the core musculature on spine mechanics.
The core musculature is essential to human movement as it stabilizes the lumbar spine in order to allow for fluidity in our daily motions. Considerable emphasis on core strength and stability has been purposed in spinal health and rehabilitation as these primary muscles act like a corset to brace and coordinate torso and limb movements; it is the center of power generation and energy transfer.
The core is a functional group of muscles that act on the spine and pelvis; it is more than just the 'abs'. The major muscle groups and adjoining connective tissues that are emphasized when enhancing core function include: the rectus abdominis, transverse abdominis, internal and external obliques, erector spinae, multifidus, pelvic floor musculature, the diaphragm, and thoracolumbar fascia. These groups are coupled with muscle actions of the hip including both flexors and extensors. When stability, range of motion, and/or balance in one of these subsystems becomes compromised, an individual may have reduced ability to efficiently transfer force through the trunk to the upper or lower extremities. This leads to poor joint mechanics, energy leaks, and an increased risk of injury.
Stability of the lumbar spine requires both passive and active components. The passive component is made up of the osseous (bone) and ligamentous structures whereas the active component is achieved through muscles. Spinal instability occurs when either of these components is disturbed.
In large, in the absence of trauma, spinal instability is usually the result of imbalances in muscular systems; either inhibited or overactive muscles. A bare spine, without muscles attached, is unable to bear much of a compressive load. This translates into disproportionate pressure(s) loaded onto vertebral discs and facet joints in the lumbar spine. Ongoing stress to the disc and joints can eventually lead to disc herniation(s), degenerative joint disease, arthritic changes, pain, and inflammation. Proper neural feedback between the brain and muscles is vital to an optimally functioning spine.
Muscles act like guy-wires to leverage, support, and disperse forces throughout the body. When certain muscles are not coordinating or contracting properly, spinal support becomes hindered. This is where the importance of a healthy nervous system, precise muscle coordination, core strength and endurance come into play.
Traditionally, core workouts have been based around isolation exercises such as abdominal crunches, planks, and back extensions. These exercises are basic and tend to only focus on singular plane motions. This is a downfall because real human movement never really occurs in a single plane thus these exercises are not reflective of natural human motions. Introductory core stability training can initially focus on isometric planks and bridges to develop baseline endurance, but logically it makes sense that subsequent training techniques should have a dynamic component to it for best possible applicability to human movement.
Recent literature shows that stability activities such as the side planks or superman exercises fail to exert the same core activation as compound lifts such as the dead-lift and back squat exercises. The compound lifts actually allow for greater activation of the core musculature than isolated static movements. Compound lifts require more global muscles to be recruited thus increased core stabilization must be attained in order to support the distal contractions.
Imagine contracting your quadriceps to produce leg extension without central support from your torso; the result would be an unsupported contraction leading to give-way weakness. This occurs from the lack of proximal leverage and tendon anchoring. The same theory can be visualized with a door. Similar to a muscle, the hinge of a door has two attachment sites, one on the door and one to a supported frame or wall. If the connection to the wall (core) was weak or absent, there would be no anchoring point to leverage a door swing (muscle contraction). The door (muscle) would have no foundation (torso) or fulcrum to support its movements. This illustrates the biomechanical importance of central torso stabilization on limb kinetics.
The activation of the core musculature is further challenged when the lifts combined ground reaction force with asymmetrical loading as seen in the single arm dead-lift and sandbag squats (single shoulder loaded). Likewise it appears greater trunk activity is encouraged from side loading and rotational exercises rooted in the ground such as the diagonal low to high cable chop. Asymmetric loading increases transitional and moment arm forces in the body which in turn increases the propensity of muscle recruitment as a reaction force. Some asymmetric exercises you can add to your next workout include, single-arm snatches, single-arm kettleball swing, rotational ball throw against a wall, single-legged squat, and single-arm weighted side bends.
So what does this tell us about core stabilization in relation to exercise?
Simple isolation exercises such as abdominal crunches are good, compound exercises such as squats and lunges are better, and asymmetric loading exercises like single-arm snatches are best when inspiring to challenge and strengthen core musculature.
Exercise should be performed in progression and adapted to each individual's fitness level. Yoga and Pilates are great workouts as they integrate whole body movements in different planes of the body. Resistance training is excellent for spine loading and the development of strength. A mix routine encompassing dynamic movements, asymmetric loading, and diverse compound exercises in different planes is optimal for enhancing proprioceptive feedback and improving human kinetics.
By: Albert Huang, DC
Akuthota V, Nadler SF. Core strengthening. Arch Phys Med Rehabil 2004;85(3 Suppl 1):S86-92.
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