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Muscle Action Spectrum
Introduction
 The characteristics of muscle and how they produce
movement is important for your understanding.
 We will cover muscle the following topics in this lecture:
– Muscle action spectrum (isotonic, concentric, eccentric,
isometric, and isokinetic muscles contractions.
– Functional anatomy of muscles
– Muscular Force
– Length-Tension Relationships
– Force-Velocity Curve
– Force-Couple Relationships
Muscle Action Spectrum
 Isotonic = same tension (load)
– Eccentric = moving in the same direction as resistance
– Concentric = moving in the opposite direction as resistance
 Isometric
= same length
 Isokinetic = same speed
Muscular Actions
 Concentric contraction
– Muscle acts as the motive force and shortens as it creates tension.
– Motion is created by the muscle contraction.
 Eccentric contraction
– Muscle acts as the resistive force and lengthens as it creates tension.
– External force exceeds the contractive force generated by the muscle.
– Motion is controlled (slowed) by the muscle contraction.
 Isometric contraction
– Muscle tension is created, but there is no apparent change in length.
– Resistance can come from opposing muscle groups, gravity, an
immovable object, or weight training.
– Motion is prevented by the muscle contraction (equal opposing forces).
Gravity and Muscular Actions
 The primary muscles must contract concentrically to lift
an object or create movement.
– The direction opposite to the pull of gravity
 The primary muscles must contract eccentrically to lower
an object or control movement.
– The same direction as the pull of gravity
 If gravity is eliminated [e.g., in movements being
performed perpendicular to the pull of gravity (parallel to
the floor)], each muscle group acts concentrically to
produce the movement.
Functional Training
 Train the movement, not the muscle.
– Benefits:
• Strengthens bone and connective tissues in multiple
directions.
• Promotes muscle balance (prevents muscle
imbalances)
• Promotes the development of healthy movement
patterns.
• Improves function in ADL’s (activities of daily living)
Principles of Functional Training
 Train throughout the muscle action spectrum (i.e.
concentric, eccentric, and isometric predominantly).
 Train in multiple planes to develop muscles and
movement patterns in a variety of directions.
 Focus on multi-joint versus single joint exercises.
 Train the primal movement patterns:
– Squat
-Pull
– Lunge
-Push
– Bend
-Twist
– Gait
Muscular Force
 Force = An influence applied
by one object to another, which
results in an acceleration or
deceleration of the second
object.
 The muscle can produce a
force which is used to either
hold (isometric), lift
(concentric), or lower
(eccentric) a resistance (i.e.
weight).
Forces
 Force is a push or pull exerted by one object on another.
– External force
– Muscular contractions
 Human movement is often
described in terms of
motive and resistive forces.
– Motive force causes an
increase in speed or a
change in direction.
– Resistive force resists
the motion of another
external force.
Muscle Length - Tension Relationship
 Length-Tension Relationship = The resting
length of a muscle and the tension the muscle can
produce at this resting length.
Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-10
Muscle Length - Tension Relationship
 If length is too short (tight) or too long (weak),
muscles will not be able to perform optimally.
 Postural distortions commonly cause inferior
movement efficiency.
 Muscle imbalances in one area affect other
areas in the kinetic chain (thus the saying, you
are only as strong as your weakest link).
Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-11
Muscle Force – Velocity Relationship
 When a muscle is lengthening
eccentrically, the force generated
increases with speed. This is
thought to be due to the elastic
nature of the connective tissue.
 When a muscle is shortening,
there is an inverse relationship
between force generated by the
muscle and velocity. The faster
one contracts, the less
resistance the muscle can exert
(which is why you want to lighten
a load when focusing on speed
or power).
Force-Couple Relationships
 Force Couple = Muscle
groups moving together
to produce movement
around a joint.
 The synergistic action of
muscles work together to
initiate movement.
Common Force-Couples
Summary
 Characteristics of muscle contractions and how the
muscle responds in different situations will help the
Fitness Trainer and Group Fitness Instructor better plan
safe and effective workouts for their clients or students.