Muscular Analysis of Movement

Chapter 14, pp.260-264Chapter 17

Simple Joint System

System Level Function

Force & torque production for joint mobility and stability through rotation and translation of bones (segments)

Muscle ActionsMuscle 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

ConcentricEccentricIsometric

Concentric

Shortens to cause movementRotational movementMechanically:

Net Muscle (Motive) Torque > Net Resistive Torque

Eccentric

Lengthens to resist, control, or slow down movement

Rotational movementMechanically:

Net Muscle (Resistive) Torque < Net Motive Torque

Isometric

Stays the same so that bone will stay fixed

No movementMechanically:

Net Muscle Torque = Other TorqueTotal Net Torque = 0

System Level: Muscle Actions

Resulting motion dependent on all torques acting about the joint (net torque)

Isometric?Eccentric?Conditions for concentric?

Muscle Coordination: Roles that Muscles Play

AgonistsAntagonistsStabilizersNeutralizers

Agonist (Mover)

The role played by a muscle acting to cause a movementPrime moversAssistant 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 actionCheck 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 CurlUp Phase Down Phase

Joint Action

Motive Force

Resistive Force

FMG Developing Force

Muscle Action

Flexion

Muscle

Weight/Gravity

Concentric

Elbow Flexors

Example 1: Biceps CurlUp Phase Down Phase

Joint Action

Motive Force

Resistive Force

FMG Developing Force

Muscle Action

Flexion

Muscle

Weight/Gravity

Concentric

Extension

Muscle

Weight/Gravity

Eccentric

Elbow FlexorsElbow Flexors

Example 1: Biceps CurlUp Phase Down Phase

Joint Action

Motive Force

Resistive Force

FMG Developing Force

Muscle Action

Flexion

Muscle

Weight/Gravity

Concentric

Extension

Muscle

Weight/Gravity

Eccentric

Elbow FlexorsElbow Flexors

Agonists: Flexors Extensors

Example 1: Biceps CurlUp Phase Down Phase

Joint Action

Motive Force

Resistive Force

FMG Developing Force

Muscle Action

Flexion

Muscle

Weight/Gravity

Concentric

Extension

Muscle

Weight/Gravity

Eccentric

Elbow FlexorsElbow Flexors

Antagonists: Extensors Flexors

Stabilization?

1. Rotary stabilization Wrist flexors

2. Linear stabilization

Neutralization?

1. To prevent scapular or pelvic movement when moving humerus or femurShoulder girdle retractorsShoulder girdle elevators

2. To prevent unwanted motion caused by multijoint musclesShoulder extensorsForearm 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.