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TEN IMPORTANT FACTS ABOUT
CORE TRAINING
by Cauê V. La Scala Teixeira, M.Sc.; Alexandre L. Evangelista, Ph.D.; Marta Santos Silva;
Danilo Sales Bocalini, Ph.D.; Marzo E. Da Silva-Grigoletto, Ph.D.; and David G. Behm, Ph.D.
Apply It!
Isometric exercises performed
with the spine in the neutral
zone should precede (anticipa-
tory activation) the dynamic ex-
ercises in a training program,
because one of the functions
of core training is to improve
stability for subsequent move-
ments to be more efficient.
Training programs should use all
movement dimensions (isolated
or combined), including exercises
that emphasize the serape (mus-
cles involved with shoulder and
trunk rotation) effect to enhance
rotational movements.
The use of unstable bases and
loads in the exercises can be
an effective strategy to increase
the level of neuromuscular acti-
vation of trunk-stabilizing muscles.
The implementation of multijoint
exercises such as Olympic lifts
or kettlebells can integrate core
recruitment with the entire pos-
terior chain.
Key words: Functional Training, Core
Stability, Strength Training, Resistance
Training, Spine
BACKGROUND
The word “core”means the central region or the most important part of a
component. In the human body, the core is the central region of the body,
comprising the pelvic girdle, trunk, and scapular region. This region has
dozens of muscle groups with functions, such as ensuring the integrity of
the spine and vital organs during postural maintenance and body move-
ments, maintaining body balance during static and dynamic tasks, and transferring forces
between lower and upper limbs (1–3). The core works as an integrated functional unit,
whereby the entire kinetic system —asystemofactive(e.g., muscles) and passive tissues
(e.g., tendons, fascias) that act simultaneously producing and transferring forces during mo-
tor tasks —workssynergistically to dynamically produce force and stabilize the body. This
integrated and interdependent system needs to be properly trained to allow its function in
day-to-day as well as athletic activities (4,5).
Although training the muscles of the central region of the body has been a recommen-
dation in the classic sports training literature for many decades (6,7), the increase in prac-
tical and scientific core training is more recent (8). Currently, core training, as well as
functional training, has been used in exercise programs aimed at quality of life, health,
and the improvement of back pain (9,10).
The recent increase in the quantity and quality of scientific publications about core
training involving different approaches, exercises, implements, and populations has pro-
vided an amplification of the specific knowledge about this type of intervention. Thus,
our objective is to highlight 10 theoretical-scientific points about core training in a practi-
cal language to avoid the dichotomy between theory and practice.
1. Local and global muscles: The core region has 29 pairs of muscles classified according
to their location, architecture, the proportion of muscle fiber types, and function.
The classification most commonly used in the literature groups the core muscles
into two classes (Table 1): local and global muscles (11,12). The local muscles are
16 ACSM’sHealth & Fitness Journal
®
January/February 2019
Copyright © 2018 American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
deep, adjacent to the spine (i.e., erector spinae), mostly
aponeurotic —non-fusiform muscle, whose connection
to the bone (origin, insertion) has no tendon but connec-
tive tissue in a flat shape —with a greater proportion of
type 1 (slow twitch) muscle fibers playing a stabilizing
role. On the other hand, the global muscles are the
superficial muscles (i.e., latissimus dorsi and others) that
are generally fusiform, have more type 2 fibers (fast
twitch), and act, mainly, to generate torque and joint
movement (13). These muscles create the foundation
of the kinetic chain/system responsible for managing
the transfer of torque and dynamics between the lower
and upper limbs of the body, whether for the tasks of
daily living, exercise, or sport. Because the stability of
the spine depends on the synergistic and integrated ac-
tion of local and global muscles (functional muscle unit),
the core training program should contain exercises with
co-contraction, as well as different characteristics (e.g.,
statics and dynamics, strength and muscle endurance).
A good example is the “bracing”—activate the abdom-
inal muscles as you would if you were about to be
punched in the stomach, keeping your breath free —
exercise that stimulates integrated and synergic action
of all abdominal muscles (full abdominal muscle cocon-
traction) (14). Another technique that will produce a nat-
ural bracing action is to get into a push-up position from
the feet or a forearm plank keeping spine neutral and
supported.
2. Neutral zone of the spine: The spine presents a small degree
of freedom of three-dimensional movements in which
the tension on passive (noncontractile) structures is minimal
or practically nonexistent (Figure). This degree of
freedom in which movements are performed without
generating tension on noncontractile structures is known
as the neutral zone, and it has a three-dimensional
amplitude of approximately 2 degrees (15,16). One of
the goals of core training is to improve the ability of
the stabilizing muscles to keep the spine within the
TABLE 1: Local and Global Muscles (Systems)
Local Muscles Global Muscles
Multifidi Rectus abdominis
Transversus abdominis Lateral fibers of external
oblique
Internal oblique Psoas major
Medial fibers of external
oblique
Erector spinae
Quadratus lumborum Iliocostalis (thoracic portion)
Diaphragm Gluteus
Pelvic floor muscles
Iliocostalis and lognissimus
(lumbar portions)
Figure Neutral zone of the spine and its three-dimensional degrees of freedom.
Volume 23 | Number 1 www.acsm-healthfitness.org 17
Copyright © 2018 American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
neutral zone, even when facing the incidence of external
forces in the region, for example, by sitting for long
periods (maintaining the naturalanatomicalcurvatures
of the spine under exposure to force of gravity) or by
performing exercises with longitudinal and transverse
loads on the spine (e.g., squat, stiff-leg deadlift).
3. Anticipatory activation: In an individual who has a nor-
mal neuromuscular function, the local muscles are
activated before performing limb movements (17).
For example, when standing on a chair, the nervous
system recruits the transverse abdominus before
recruiting the quadriceps. The idea is to keep the
spine rigid (stable) so limbs move efficiently (high speed,
high accuracy, and low-energy use). However, in people
with low back pain (LBP), this pattern of anticipatory
activation of the core muscles is impaired; that is, the
muscles have their activation delayed or inhibited (18).
In this case, late activation, especially of local muscles,
will predispose the person to pain, because movement will
occur without stabilization. One of the functions of
core training is to re-educate (in people with LBP)
and improve (in people without LBP) this pattern of
anticipatory activation of the local muscles. Re-education
exercises can involve a variety of activities. Anticipatory
strength can be enhanced by implementing unilateral
resistance exercises (i.e., unilateral shoulder presses,
bicep curls, calf raises, and squats) that force the system
to anticipate the resistive torques applied to the core
(trunk) muscles (19–21). Further anticipatory strength
adjustments can be improved by using unstable bases
to disrupt balance and ensure the system applies
compensatory contractions (20–24). These balance
and stability challenges can be amplified with eyes closed
to place more emphasis on the proprioceptive system or
with greater resistances (i.e., dumbbells, barbells, elastic
bands) to magnify the resistive torques (20,21). Finally,
greater progressions can be achieved by making the
exercises more dynamic with higher velocities by
adding hopping, bouncing, jumping, bounding, and
other similar activities on both stable (i.e., floor, ground)
and unstable surfaces (i.e., sand or undulating surfaces) (25–27).
4. Stabilize and then move: Although the dynamic exercises
for the core are the most popular, they have little trans-
fer capacity; that is, they contribute little to improve the
stability of the trunk in everyday situations or sports.
Considering that in most of the movements of daily
activities and sports the spine remains erect, even when
limbs move, isometric exercises seem to be more pro-
ductive to improve trunk stiffness and postural func-
tion (28). Thus, isometric exercises performed with the
spine in the neutral zone should precede the dynamic
exercises in a training program, because one of the
functions of core training is to improve stability for
subsequent movements to be more efficient.
5. Three-dimensional stability: During most daily tasks, labor,
or sports, the human body undergoes balance distur-
bances coming from the external and internal forces
that affect it. As the forces acting on the body come
from different factors (i.e., gravity, movement of the body
or part of it, lifting or support of external loads, muscular
contractions), they destabilize the body in the three di-
mensions (sagittal, frontal, and transverse) (29). Thus, a
training program should explore exercises in all move-
ment dimensions, isolated or combined, because one
of the functions of core training is to improve the tri-
dimensional stabilization capacity of the trunk (30).
6. The powerhouse has a floor, walls, and a ceiling: Although the
core comprises the whole trunk region, the most fre-
quent approaches in the literature highlight the lower
trunk, mainly due to the high incidence of LBP in the
world population and the strong association between
LBP and lack of conditioning of the musculature ad-
jacent to the lumbar spine (31,32). Thus, it should
be understood that the core, also known as the
“powerhouse,”has muscles forming its structure of
floor, walls, and ceiling. In this context, special at-
tention should be given to the training of all core
muscles, including those that tend to receive less at-
tention in traditional training programs such as the
pelvic floor, the transverse abdominus muscles, and
the diaphragm, these being among the challenges of
core training programs (33).
7. Instability: Disturbance of the body’scenterofgravity
leads to sudden changes in the position and length of
muscles, which stimulates proprioceptors, generating
reflexive muscular activation. Confirming this idea,
the use of unstable bases (i.e., Swiss ball, BOSU, foam
pads, wobble boards) in the exercises has been shown to
be an effective strategy to increase the level of neuromuscular
activation of trunk-stabilizing muscles (34). In addition to
CORE TRAINING
18 ACSM’sHealth & Fitness Journal
®
January/February 2019
Copyright © 2018 American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
unstable bases, the use of unstable loads (i.e.,elastic,
kettlebells) also increases the activation of stabilizer
muscles of the trunk, the scapular, and pelvic girdles.
Activating stabilizing muscles is one of the functions
of core training and therefore instability can be an in-
teresting tool for this purpose. Reassurances should be
made when the primary goal of training is to improve
strength, power, and speed. In such cases, instability
should not be the primary resource; alternative strate-
gies can be seen in point 8.
8. Basic and Olympic lifting/swings: In sports that necessitate
training for high performance as well as advanced
training, core stability should be developed together
with other physical abilities considered determinants
of performance, such as strength and power (35). For
this, isolated training of the different components of
physical fitness may be an option, but in general, it
is less effective than the integrated and synergistic
training of physical abilities. In this way, well-trained
athletes and individuals benefit from the practice of
integrated exercises that, because they present char-
acteristics that include high movement complexity,
high loads, high execution velocity, acceleration, and de-
celeration, also present great potential to synergistically
improve strength, power, and core stability. The main
examples of exercises with these characteristics are the
basic lifting (squat, deadlift) and mainly Olympic lifting
(snatch, clean, and jerk) exercises. In addition, there are
global exercises using a kettlebell, where it is possible to
perform several exercises such as swing and snatch. These
exercises provide a moderate-to-high activation of the
core muscles, especially when performed unilaterally,
in which approximately 70% to 80% of the maximum
voluntary isometric contraction of the gluteus medius
muscles (ipsilateral) and the obliquus internal muscles
(contralateral) are required (36). As in sporting situations,
high levels of core stability are required in situations ne-
cessitating high strength and power, the core training
can and should contemplate multijoint exercises with
the use of bars or kettlebells to integrate core recruitment
withtheentireposteriorchain(whichincludestheham-
strings, gluteals, erector spinae, among other muscles).
However, it should be noted that these exercises
should be part of a more advanced progression of
core training; that is, the subject must previously be
able to consciously activate the stabilizing muscles that
will protect his or her spine from the compression and
shear forces caused by these exercises.
TABLE 2: Example of Exercises in Specific Categories
Specific Categories Exercises
Coactivation exercises (points 1 and 6) Exercises that stimulate simultaneous contractions of several core muscles (e.g., bracing, pelvic
floor exercises)
Isometric exercises (points 2 and 4) Exercises that require maintenance of static postures for a fixed time (e.g., plank, hip bridge,
side plank, opposite arm, and leg lift)
Dynamic exercises (point 4) Exercises that require movement of the spine, pelvis, and hips (e.g., crunch, curl-up, back
extension, lateral flexion, trunk rotation)
Three-dimensional stability exercises
(point 5)
Exercises that stimulate core stability in the three planes of movement (sagittal, frontal, and
transverse ) in an isolated or integrated approach (e.g., several types of plank, unstable exercises)
Instability exercises (points 2, 3, and 7) Exercises that challenge the maintenance of body balance (e.g., exercises in a standing position,
with feet movement [e.g., forward and reverse lunges], over unstable surfaces [Swiss ball,
BOSU], with unstable loads [kettlebell], unilateral or alternating [unilateral shoulder press, unilateral
alternating bench press], with occluded vision)
Weightlifting exercises (points 2, 3,
8, and 9)
Exercises involving the lifting of high loads (resistance) at high intentional speed of movement
(e.g., clean and jerk, snatch, deadlift, squat, swing)
“Serape”exercises (point 10) Exercises that involve oblique movements away or approaching the opposite hip and shoulder
(e.g., crunch with rotation, wood chop, lift and chop)
Volume 23 | Number 1 www.acsm-healthfitness.org 19
Copyright © 2018 American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
9. Unilateral and/or alternating exercises: Just as traditional
weightlifting exercises are good options for developing
core stability in situations in which power and force in-
crease are desired, another viable strategy is the unilat-
eral execution of resistance exercises in the frontal (e.g.,
shoulder press) and transverse (e.g., bench press). The
unilateral execution leads to the projection of the cen-
ter of gravity to the side on which the external load is
mobilized, contributing to the increase of contralateral
core musculature activation (37,38). Similarly, the exe-
cution of unilateral exercises alternately between the limbs
also can be applied for this purpose because of the greater
changes generated in the position of the body's center of
gravity in the bilateral/simultaneous execution.
10. Serape effect: The rhomboid, anterior serratus, and outer
and inner oblique muscles together form a belt-like
structure, similar to a Mexican garment called a “serape.”
By rotating the shoulders (upper trunk) and pelvis (lower
trunk) in opposite directions, these associated muscles
are prestretched diagonally. This prestretch, known as
the “serape effect”in the literature, provides the benefits
of the stretch-shortening cycle, which potentiates maxi-
mum power/force output (39). From a practical point
of view, the “serape effect”occurs in ballistic movements
and activities such as kicking and throwing. Thus, exer-
cises based on this type of movement can be explored
when improving performance for sports activities that
require rotational movements (fights, swimming, shoot-
ing, tennis, etc.) (Table 2).
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Disclosure: The authors declare no conflict of interest and do not have any
financial disclosures.
Cauê La Scala Teixeira, M.Sc., isaprofessorinthe
Faculty of Physical Education at Praia Grande College
and a Ph.D. student at Federal University of São Paulo,
São Paulo, Brazil.
Alexandre Evangelista, Ph.D., is a professor in the
Department of Education at Nove de Julho University,
São Paulo, Brazil.
Marta Silva, is an M.Sc. student at Federal University
of Sergipe, Aracaju, Brazil, Brazil/Scientific Sport,
Brazil.
Danilo Bocalini, Ph.D., is a professor in the Post
Graduate Program at São Judas Tadeu University,
São Paulo, Brazil.
Marzo da Silva-Grigoletto, Ph.D., is a professor in
the Post Graduate Program at Federal University of
Sergipe, Aracaju, Brazil/Scientific Sport, Brazil.
David Behm, Ph.D., is a university research professor
at Memorial University of Newfoundland in St.
John's, Newfoundland, Canada.
BRIDGING THE GAP
Core training is an essential component of resistance
training and has received much greater emphasis lately.
The core contributes to a kinetic chain transferring
forces, torques, and power between the lower and upper
limbs. Among the goals of core training are toimprove the
stabilization of the spine through greater strength,
endurance, and the anticipation of body movement.
Enhanced strength can be attained with combinations of
isometric contractions, three-dimensional movements,
unstable loads, Olympic-type lifts, the use of kettlebells
in swinging and lifting actions, and unilateral resistance
exercises.
Volume 23 | Number 1 www.acsm-healthfitness.org 21
Copyright © 2018 American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
