Q. Within
health, fitness, and exercise, we constantly here the term "core",
"core strength", and "core stability". However, what is Core? What does
it mean and how can personal trainers and fitness professionals better
inform clients regarding overall core training?
A. It is critically important to discuss differences between core strength and core stability.
Interestingly enough, individuals use them interchangeably. However, in
reality, they are different. In addition, it is imperative to converse
on the application of core training and current research involved with
this phenomenon. It is fascinating that trainers and coaches implement
these modalities into their program without knowing either historical
significance or current research and application initiatives.
The "core musculature" consists of the 29 pairs of muscles that support the lumbo-pelvic-hip complex
in order to stabile the spine, pelvis, and kinetic chain during
functional movement (1). Stability is the ability of the body to
control the whole range of motion of a joint thereby not creating
deformity, neurological deficits, or incapacitating pain (2,3). In the
proceeding paragraphs, there is evidence to support that endurance is
the better training variable when training core musculature (4,5).
To differentiate between terms, the article from Faries (6) notes core 'stability' is being made to the stability of the spine,
not the stability of the muscle themselves. The authors also mention
there has been no reference to enhancing the stability of a muscle, but
rather the ability of the muscle to contract. Specifically, the muscles
are contracting in order to control that functional movement.
Core "strength" is used and reference is made to the ability of the musculature to stabilize the spine through contractile forces and intra-abdominal pressure
(6). However, confusion exits on labeling an exercise core strength or
stability. According to Faries (6), core exercises do not aim to
increase the stability of the musculature, but enhance the muscles
ability to stabilize the spine, specifically, the lumbar spine.
Recent research has promoted the Transverse Abdominis (TrA) and Multifidis
or Multifidi as the primary stabilizers of the spine (1,2,7), and thus
when contracted they are able to increase tension of the thora-columbar
fascia and increase intra-abdominal pressure, increasing spinal
stiffness in order to resist forces acting on the lumbar spine. So, in
other words, this lends the fact that core stability is essential for resisting forces on the spine such as in squatting, deadlifting, and overhead pressing.
It is also useful for upper body movements, and can aid in single arm
or leg exercises. In addition, since these muscles do not create
movement of the spine, the internal oblique, the medial fibers of the
external oblique, and the quadratus lumborum also assist in stabilizing
the spine, but also FUNCTION, secondarily to MOVE the spine (2).
Faries
(2007) stresses the importance of both local (i.e. TrA, Multifidis) and
global (rectus abdominus, erector spinae) musculature in terms of
incorporating both into a training program, although overall the whole 'application' to core training from a 'research view' is limited.
Since those global muscles have long levers and force arms, they are
able to produce high outputs of torque with emphasis on speed, power,
and a large arc of multiplanar movements, while counteracting the
external loads for transfer to local systems (1,8). In regards to fiber
typing, the local system consists of mainly type 1 and global is mainly
type II (8,9).
It has been suggested that focus should move
past the strength alone to understand the speed with which the muscles
contract in reaction to a force (2). Also, some individuals might do
well on a strength test of force but do poor on a performance test of
endurance (10). History and specificity of training are major
influences. As with assessment, measures of the core should include various performance measures of force, endurance, and power (6).
There is also the possibility of too much stability
as well as too little stability and what the optimum dosage response
should represent. "Sufficient stability" would be the minimal level to
assure spinal stability without imposing unnecessary loads on the
muscles and tissues (11). However, an ideal set of exercises for all
individuals currently does not exist, but general suggestions for
exercises that emphasize trunk stabilization in a neutral spine, while
emphasizing mobility of the hip and knees (12, 13, 5). For a further
discussion in this area, please refer to McGill in the reference
section.
In regards to performance enhancement, limited
research has been conducted. However, Hagins (14) showed that a 4 weeks
lumbar stabilization exercise program improved the ability to perform
progressively difficult lumbar stabilization exercises. Six weeks of
swiss ball training specifically designed for core activation improved
ability of core musculature to stabilize the spine significantly, while
also improving core endurance (15).
Functional progression is the important aspect of core strengthening,
which includes performance goals, history of functional activities,
variety of assessment, and training in all 3 planes of motion (16,10).
Interestingly, a brief statement made of the possibility of
overtraining the global system such as rectus abdominus, which seems to
be the most utilized part of core training. Consequently, the local
system must compensate
Many coaches are big advocates
of the whole 'functional' aspect because it works for them and their
athletes and clients, while others are not as convinced.
Notwithstanding, personal trainers, fitness professionals and coaches
will continue to use what has worked and what they are successfully
with, despite what 'research' says. This can be a good thing (used
cautiously) as it opens more doors for new types of training,
philosophies and principles.
1). Fredericson, M., and T. Moore. Core stabilization training for middle and
long-distance runners. New Stud. Athletics. 20:25-37. 2005
2). NORRIS, C.M. Functional load abdominal training: Part 1. J. Body Work
Mov. Ther. 3:150-158. 1999.
3).
Panjabi, M.M. The stabilizing system of the spine. PartI. Function,
dysfunction adaptation and enhancement. J. Spinal Disord. 5:383-389.
1992.
4). McGill, S.M. Low back exercises: Evidence for improving exercise regimens.
Phys. Ther. 78:754-765. 1998.47.
5). McGill, S.M. Stability: From biomechanical concept to chiropractic practice.
J. Can. Chiropractic Assoc.43:75-88. 1999.
6). Faries, M, and Greenwood, M. Core Training: Stabilizing the Confusion. Strength and Conditioning Journal. 29 (2). 2007
7).
Moseley, G.L., P.W. Hodges, and S.C. Gandevia. Deep and superficial
fibers of the lumbar multifidus muscle are differentially active during
voluntary arm movements. Spine. 27:E29-
E36. 2002.
8). Standford, M.E. Effectiveness of specific lumbar stabilization exercises: A
single case study. J. Man. Manipulative Ther. 10:40-46. 2002.
9).
Richardson, C., G. Jull, R. Toppenburg, and M. Comeford. Techniques for
active lumbar stabilization for spinal protection: A pilot study. Aust.
J. Physiother. 38:105-112. 1992.
10). Kroll, P.G., L. Machado, C. Happy,
S.
Leong, and B. Chen. The relationship between five measures of trunk
strength. J. Back Musculoskeletal Rehabil. 14:89-97. 2000.
11).
Vera-Garcia, F.J., S.H.M. Brown, J.R. Brown, and S.M. McGill. Effects
of different levels of torso coactivation on trunk muscular and
kinematic responses to posteriorly applied sudden loads. Clin. Biomech.
21:443- 455. 2006.
12). Axler CT, McGill SM. Low back loads
over a variety of abdominal exercises: searching for the safest
abdominal challenge. Med Sci Sports Exerc. 1997 Jun;29(6):804-11.
13).
Barr KP, Griggs M, Cadby T. Lumbar stabilization: core concepts and
current literature, Part 1. Am J Phys Med Rehabil. 2005
Jun;84(6):473-80. Review.
14). Hagins, M., K. Adler, M. Cash,
J. Daughtery, and G. Mitrani. Effects of practice on the ability to
perform lumbar stabilization exercises. Orthop. Sports Phys. Ther.
29:546-555. 1999.
15). Stanton, R., P.R. Reaburn, and B. Humphries. The effect of short-term
Swiss ball training on core stability and running economy. J. Strength Cond.Res. 18:522-528. 2004.
16). Akuthota, V. Core strengthening. Arch. Phys. Med. Rehab. 85(3 Suppl.1):S86-S92. 2004
.
~Jonathan Mike, CSCS,
Doctoral Student, Assistant Editor
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