Muscular Analysis of
Movement
Chapter 14, pp.260-264
Chapter 17
Simple
Joint
System
System Level Function
Force & torque production for joint
mobility and stability through rotation and
translation of bones (segments)
Muscle Actions
Muscle Coordination (Synergy)
Related Terminology
 muscle action – the development of tension
(force) by a muscle
 functional muscle group – a group of muscles
that are capable of causing a specific joint
action (e.g., wrist radial deviators)
 motive force (or torque) – force causing the
observed movement
 resistive force (or torque) – force opposing the
observed movement
Types of Muscle Actions
Concentric
Eccentric
Isometric
Concentric
Shortens to cause movement
Rotational movement
Mechanically:
Net Muscle (Motive) Torque > Net Resistive Torque
Eccentric
Lengthens to resist, control, or slow down
movement
Rotational movement
Mechanically:
Net Muscle (Resistive) Torque < Net Motive Torque
Isometric
Stays the same so that bone will stay
fixed
No movement
Mechanically:
Net Muscle Torque = Other Torque
Total Net Torque = 0
System Level:
Muscle Actions
 Resulting
motion
dependent
on all
torques
acting about
the joint
(net torque)
Conditions for concentric?
Eccentric?
Isometric?
Muscle Coordination:
Roles that Muscles Play
Agonists
Antagonists
Stabilizers
Neutralizers
Agonist (Mover)
 The role played by a muscle acting to
cause a movement
Prime movers
Assistant movers
Arbitrary distinction
 Force development during concentric action
 Relaxation during eccentric action
Antagonist
The role played by a muscle acting
to control movement of a body segment against
some other non-muscle force
to slow or stop a movement
 Force development during eccentric action
 Check ballistic movements
 Relaxation during concentric action
Stabilizer
 The role played by a muscle to stabilize
(fixate) a body part against some other
force
 rotary (joint) stabilizer
 linear (bone) stabilizer
 Isometric muscle action
Neutralizer
 The role played by a muscle to eliminate
an unwanted action produced by an
agonist
Scapular or pelvic stabilization
Multijoint muscles
Elevation of the humerus
 Muscle action varies
To perform a muscular analysis:
1. Break the skill into phases.
2. Determine the joint action?
3. Determine the motive force – muscle or
some other force?
4. Determine the resistive force – muscle
or some other force?
To perform a muscular analysis (ID
muscle actions and responsible
groups):
5. Identify whether there are joints/bones
that must be stabilized
6. Identify
 the FMG(s) that is(are) developing force
 the type of muscle action of the FMG(s)
 the roles played by the FMG(s)
7. Identify neutralization.
Example 1: Biceps Curl
Up Phase
Joint Action
Flexion
Motive Force
Muscle
Resistive
Force
FMG
Developing
Force
Muscle Action
Weight/Gravity
Elbow Flexors
Concentric
Down Phase
Example 1: Biceps Curl
Up Phase
Down Phase
Joint Action
Flexion
Extension
Motive Force
Muscle
Weight/Gravity
Resistive
Force
FMG
Developing
Force
Muscle Action
Weight/Gravity Muscle
Elbow Flexors
Elbow Flexors
Concentric
Eccentric
Agonists:
Flexors
Extensors
Example 1: Biceps Curl
Up Phase
Down Phase
Joint Action
Flexion
Extension
Motive Force
Muscle
Weight/Gravity
Resistive
Force
FMG
Developing
Force
Muscle Action
Weight/Gravity Muscle
Elbow Flexors
Elbow Flexors
Concentric
Eccentric
Antagonists:
Extensors
Flexors
Example 1: Biceps Curl
Up Phase
Down Phase
Joint Action
Flexion
Extension
Motive Force
Muscle
Weight/Gravity
Resistive
Force
FMG
Developing
Force
Muscle Action
Weight/Gravity Muscle
Elbow Flexors
Elbow Flexors
Concentric
Eccentric
Stabilization?
1. Rotary stabilization
 Wrist flexors
2. Linear stabilization
Neutralization?
1. To prevent scapular or pelvic movement
when moving humerus or femur
Shoulder girdle retractors
Shoulder girdle elevators
2. To prevent unwanted motion caused by
multijoint muscles
Shoulder extensors
Forearm pronators
Neutralization
3. To prevent scapular movement during
elevation of the humerus
4. Other?
 Biceps brachii – shoulder flexion, RU
supination
 Brachialis – none
 Brachioradialis – RU motion
 Pronator teres – RU pronation
Summary
Movement at a single joint is possible because
of the complex coordination that occurs
between numerous muscles.
Therefore, all those muscles must have
adequate strength to accomplish its task in a
given movement.
Injury to or lack of strength in any of those
muscles can result in the inability to perform the
movement.
Summary
A muscular analysis allows us to identify
the muscles that contribute to a
movement and how they contribute to the
movement.
We can then prepare conditioning &
rehabilitation programs that target utilized
muscles appropriately.