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


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the muscles in relation to the resistance. The dif-
ference between the distance that the weight is from the center of the joint, and the muscle\u2019s at-
tachment and line of pull (direction through which tension is applied through the tendon) is
from the joint will determine the efficiency that the muscles manipulate the movement
(1,4,5,9). Because we cannot alter the attachment sites or the line of pull of our muscles
through the tendon, the easiest way to alter the amount of torque generated at a joint is to
move the resistance. In other words, the closer the weight is to the point of rotation (the joint),
the less torque it creates. The farther away the weight is from the point of rotation, the more
torque it creates.
For example, to hold a dumbbell straight out to the side at arm\u2019s length (shoulder ab-
duction), the weight may be approximately 24 inches from the center of the shoulder joint
(Fig. 2.13). The prime mover for shoulder abduction is the deltoid muscle. Let\u2019s say its at-
tachment is approximately two inches from the joint center. That is a disparity of 22 inches
(or roughly 12 times the difference). If the weight is moved closer to the joint center, let\u2019s say
to the elbow, the resistance is only approximately 12 inches from the joint center. Now the
difference is only 10 inches or 5 times greater. Essentially, the torque required to hold the
weight was reduced by half. Many people performing side lateral raises with dumbbells
26 CHAPTER 2
TABLE 2.4
Classes of Levers
Class Common Example Body Example
I Teeter-totter Flexion-extension of the head
II Wheelbarrow Dorsiflexion\u2014rising up on tiptoes
III Lifting a shovel Forearm flexion
A B C
FIGURE 2.12 Torque.
Rotary Motion
Movement of the bones
around the joints.
Torque
A force that produces
rotation. Common unit of torque
is the Newton-Meter or N.m.
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INTRODUCTION TO HUMAN MOVEMENT SCIENCE 27
Up
pe
r e
xt
re
m
ity
 w
ei
gh
t (w
)
Shoulder abduction angle (degrees)
0 30 60 90 120 150 180
Compression load on joint
Abductor muscle force
FIGURE 2.13 Load and Torque Relationship.
Functional Anatomy
Traditionally, anatomy has been taught in isolated and fragmented components. The traditional
approach mapped the body, provided simplistic answers about the structures, and categorized
each component. Looking at each muscle as an isolated structure fails to answer complex ques-
tions such as, \u201cHow does the human movement system function as an integrated system?\u201d Or
even more simply, \u201cWhat do our muscles do when we move during sports?\u201d The everyday func-
tioning of the human body is an integrated and multidimensional system, not a series of iso-
lated, independent pieces. Over the last 25 years, traditional sports performance training has fo-
cused on training specific body parts, often in single, fixed planes of motion. The new paradigm
is to present anatomy from a functional, integrated perspective. The Sports Performance Profes-
sional armed with a thorough understanding of functional anatomy will be better-equipped to
select exercises and design programs.
Whereas muscles have the ability to dominate a certain plane of motion, the central nervous
system optimizes the selection of muscle synergies (1,20\u201325), not simply the selection of indi-
vidual muscles. The central nervous system coordinates deceleration, stabilization, and accelera-
tion at every joint in the HMS in all three planes of motion. Muscles must also react propriocep-
tively to gravity, momentum, ground reaction forces, and forces created by other functioning
muscles. Depending on the load, the direction of resistance, body position, and the movement
(laterally raising dumbbells to the side) do this inadvertently by flexing their elbow, bring-
ing the weight closer to the shoulder joint and effectively reducing the required torque.
Sports Performance Professionals can use this principle as a regression for exercises that are
too demanding, which reduces the torque placed on the HMS, or as a progression to increase
the torque and place a greater demand on the HMS.
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being performed, muscles will participate as an agonist, antagonist, synergist, and/or a stabilizer.
Although they may have different characteristics, all muscles work in concert with one another to
produce efficient motion (1,23,24,26,27). 
28 CHAPTER 2
TIME OUT
Muscle Category
Agonists: muscles that act as prime movers. For example, the gluteus maximus is the prime
mover for hip extension.
Antagonists: muscles that act in direct opposition to prime movers. For example, the psoas is
antagonistic to the gluteus maximus.
Synergists: muscles that assist prime movers during functional movement patterns. For exam-
ple, the hamstring and the erector spinae are synergistic with the gluteus maximus during hip ex-
tension.
Stabilizers: muscles that support or stabilize the body while the prime movers and the syner-
gists perform the movement patterns. For example, the transverse abdominus, internal oblique,
multifidus, and deep erector spinae stabilize the lumbo-pelvic-hip complex (LPHC) during
functional movements while the prime movers perform functional activities.
Traditional sports performance training and conditioning has focused almost exclusively on
uniplanar, concentric force production. But this is a shortsighted approach as muscles function
synergistically in force-couples to produce force, reduce force, and dynamically stabilize the en-
tire HMS. Muscles function in integrated groups to provide control during functional movements
(5,8,9,28). Realizing this allows one to view muscles functioning in all planes of motion
throughout the full spectrum of muscle action (eccentric, concentric, and isometric). 
CURRENT CONCEPTS IN FUNCTIONAL ANATOMY
It has been proposed that there are two distinct, yet interdependent, muscular systems that en-
able our bodies to maintain proper stabilization and ensure efficient distribution of forces for the
production of movement (28,30). Muscles that are located more centrally to the spine provide
intersegmental stability (support from vertebrae to vertebrae), whereas the more lateral muscles
support the spine as a whole (30). Bergmark (28) categorized these different systems with rela-
tion to the trunk into local and global muscular systems.
JOINT SUPPORT SYSTEM
THE LOCAL MUSCULAR SYSTEM (STABILIZATION SYSTEM) 
The local muscular system consists of muscles that are predominantly involved in joint support
or stabilization (3,28,30,31). It is important to note, however, that joint support systems are not
confined to the spine and are evident in peripheral joints as well. Joint support systems consist of
muscles that are not movement specific, rather they provide stability to allow movement of a
joint. They usually are located in close proximity to the joint with a broad spectrum of attach-
ments to the joint\u2019s passive elements that make them ideal for increasing joint stiffness and sta-
bility (3,31). A common example of a peripheral joint support system is the rotator cuff that pro-
vides dynamic stabilization for the humeral head in relation to the glenoid fossa (32). Other
joint support systems include the posterior fibers of the gluteus medius and the external rotators
of the hip that provide pelvofemoral stabilization (1,36\u201339) and the oblique fibers of the vastus
medialis that provides patellar stabilization at the knee (1,40,41).
The joint support system of the core, or LPHC, includes muscles that either originate or insert
(or both) into the lumbar spine (28,31). The major muscles include the transverse abdominis
(TA), multifidus, internal oblique, diaphragm, and the muscles of the pelvic floor (13,28,30,31).
Stabilization of the