NASM essentials of sports performance training
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NASM essentials of sports performance training


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LPHC will be discussed in more detail in Chapter 6 on core training.
THE GLOBAL MUSCULAR SYSTEMS (MOVEMENT SYSTEMS) 
The global muscular systems are responsible predominantly for movement and consist of more
superficial musculature that originate from the pelvis to the rib cage, the lower extremities, or
both (1,23,24,28,30,31,42). Some of these major muscles include the rectus abdominis, external
obliques, erector spinae, hamstrings, gluteus maximus, latissimus dorsi, adductors, hamstrings,
quadriceps, and gastrocnemius. The movement system muscles are predominantly larger and as-
sociated with movement of the trunk and limbs that equalizes external loads placed upon the
body. These muscles are also important in transferring and absorbing forces from the upper and
lower extremities to the pelvis. The movement system muscles have been broken down and
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described as force-couples working in four distinct subsystems (1,29,43,44): the deep longitudi-
nal, posterior oblique, anterior oblique, and lateral subsystems. This distinction allows for an eas-
ier description and review of functional anatomy. It is crucial for Sports Performance Profession-
als to think of these subsystems operating as an integrated functional unit. Remember, the central
nervous system optimizes the selection of muscle synergies, not isolated muscles (23,24,45,46).
THE DEEP LONGITUDINAL SUBSYSTEM (DLS) 
The major soft tissue contributors to the DLS are the erector spinae, thoracolumbar fascia, sacro-
tuberous ligament, biceps femoris, and peroneus longus (Fig. 2.14). Some experts suggest that the
DLS provides a longitudinal means of reciprocal force transmission from the trunk to the ground
(13,23,24,43,44). As illustrated in Figure 2.14, the long head of the biceps femoris attaches in
part to the sacrotuberous ligament at the ischium. The sacrotuberous ligament in turn attaches
from the ischium to the sacrum. The erector spinae attaches from the sacrum and ilium up the
ribs to the cervical spine. Thus, activation of the biceps femoris increases tension in the sacro-
tuberous ligament, which in turn transmits force across the sacrum stabilizing the sacroiliac joint
(SIJ), then up the trunk through the erector spinae (43,44) (Fig. 2.14).
As illustrated in Figure 2.14, this transference of force is apparent during normal gait or
running. Prior to heel strike, the biceps femoris activates to eccentrically decelerate hip flexion
and knee extension. Just after heel strike, the biceps femoris is further loaded through the lower
leg via posterior movement of the fibula. This tension from the lower leg, up through the biceps
INTRODUCTION TO HUMAN MOVEMENT SCIENCE 29
Sacrotuberous
ligament
Biceps
femoris
Tibialis
anterior
Peroneus
longus
Erector
spinae
Thoracolumbar
fascia
FIGURE 2.14 Deep Longitudinal System.
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femoris, into the sacrotuberous ligament, and up the erector spinae creates a force that assists in
stabilizing the SIJ (12).
Another force-couple not often mentioned consists of the superficial erector spinae, the
psoas, and the inner unit. Although the erector spinae and psoas create lumbar extension and an
anterior shear force at L4\u2013S1, during functional movements the inner unit provides interseg-
mental stabilization and a posterior shear force (as a neutralizer) (29,31,43,44,47,48). Dysfunc-
tion in any of these structures can lead to SIJ instability and low-back pain (44).
30 CHAPTER 2
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The Inner Unit
The inner unit is the functional synergy between:
\u2022 Transverses abdominus
\u2022 Posterior fibers of the internal oblique
\u2022 Pelvic floor muscles
\u2022 Multifidus
\u2022 Lumbar portion of the longissimus and iliocostalis
Iliotibial
tract
Sacrotuberous
ligament
Sacroiliac
joint
External
oblique
Erector
spinae
Biceps
femoris
Latissimus
dorsi
Thoracolumbar
fascia
Gluteus
maximus
Gluteus
medius
FIGURE 2.15 Posterior Oblique Subsystem.
THE POSTERIOR OBLIQUE SUBSYSTEM 
The posterior oblique subsystem (POS) works synergistically with the DLS. As illustrated in Figure
2.15, both the gluteus maximus and latissimus dorsi have attachments to the thoracolumbar
fascia, which connects to the sacrum whose fibers run perpendicular to the SIJ. Thus, when the
contralateral gluteus maximus and latissimus dorsi contract, a stabilizing force is transmitted
across the SIJ (44). Just prior to heel strike, the latissimus dorsi and the contralateral gluteus
maximus are eccentrically loaded. At heel strike, each muscle accelerates their respective limb
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(through its concentric action) and creates tension across the thoracolumbar fascia. This ten-
sion also assists in stabilizing the SIJ. Thus, when an athlete sprints, the POS transfers forces
that are summated from the muscle\u2019s transverse plane orientation to propulsion in the sagittal
plane. The POS is also of prime importance for rotational activities, such as swinging a golf
club, a baseball bat, or throwing a ball (29,43,47). Dysfunction of any structure in the POS can
lead to SIJ instability and low-back pain. The weakening of the gluteus maximus, the latissimus
dorsi, or both, can lead to increased tension in the hamstring\u2014a factor in recurrent hamstring
strains (42,44,47). If performed in isolation, squats for the gluteus maximus and pull
downs/pull ups for the latissimus dorsi will not adequately prepare the POS to perform opti-
mally during athletic activities. 
THE ANTERIOR OBLIQUE SUBSYSTEM 
The anterior oblique subsystem (AOS) (Fig. 2.16) is similar to the POS in that it also functions in
a transverse plane orientation, mostly in the anterior portion of the body. The prime contributors
are the internal and external oblique muscles, the adductor complex, and the hip external rota-
tors. Electromyography of these AOS muscles show that they aid in pelvic stability and rotation
as well as contributing to leg swing (11,12,14,49). The AOS is also a factor in the stabilization
of the SIJ (48). 
When we walk, our pelvis rotates in the transverse plane in order to create a swinging mo-
tion for the legs (43,49). The POS (posteriorly) and the AOS (anteriorly) contribute to this rota-
tion. Knowing the fiber arrangements of the muscles involved (latissimus dorsi, gluteus max-
imus, internal and external obliques, adductors, and hip rotators) emphasizes this point. The
AOS is also necessary for functional activities involving the trunk and upper and lower extremi-
ties. The obliques, in concert with the adductor complex, not only produce rotational and flex-
ion movements, but are also instrumental in stabilizing the LPHC (29,48).
THE LATERAL SUBSYSTEM 
The lateral subsystem (LS) is comprised of the gluteus medius, tensor fascia latae, adductor complex,
and the quadratus lumborum, all of which participate in frontal plane (13) and pelvofemoral
INTRODUCTION TO HUMAN MOVEMENT SCIENCE 31
Hip
adductors
External
obliques
FIGURE 2.16 Anterior Oblique Subsystem.
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stability (10,50). Figure 2.17 shows how the ipsilateral gluteus medius, and adductors combine
with the contralateral quadratus lumborum to control the pelvis and femur in the frontal plane
during single-leg functional movements, such as in gait, lunges, or throwing a pitch (42). Dys-
function in the LS is evident during increased pronation (flexion, internal rotation, and adduc-
tion) of the knee, hip, feet, or all three during functional activities (10). Unwanted frontal plane
movement is characterized by decreased strength and neuromuscular control in the LS
(10,50\u201352).
The description of these four subsystems has been simplified, but realize that