Exercise Evaluation

Exercise Evaluation

Strength curve similarity

Strength Curve (Kulig et al., 1984)

strength curve – plot of how maximum strength varies as a function of joint angle

strength - the ability of a muscle group to develop torque against an unyielding resistance in a single contraction of unrestricted duration

Mobility Determined by Torque Output

Factors that Affect Muscle Torque Output Force Moment arm

Point of force application (attachment site) Angle of force application (muscle insertion

angle)

Factors That Affect Force Output

Physiological factors Cross-sectional area Fiber type

Neurological factors Muscle fiber activation Rate of motor unit activation

Biomechanical factors Muscle architecture Force-length relationship Force-velocity relationship

Humans: 2.6-2.8 m

Active Component

Passive component

Total Force

Single Joint Muscles

60% 110-120% 160%

Multi Joint Muscles

60% >160%

Mobility Determined by Torque Output

Factors that Affect Muscle Torque Output Force Moment arm

Point of force application (attachment site) Angle of force application (muscle insertion

angle)

Muscle Attachments

1. Further from joint is better (theoretically)

2. Structural constraints negate #1

3. Cannot alter attachment sites

4. Strength differences due, in part, to attachment differences

Muscle Insertion Angle

1. 90 is better

2. MIA typically < 45

3. MIA not constant through joint ROM, affecting strength through ROM

4. Cannot alter MIA

5. Strength differences due, in part, to MIA differences

Understanding Moment Arm Changes Through ROM

JA = 150° JA = 120°MIA = 60 °

JA = 90°MIA = 90 °

JA = 45°MIA = 120 °

JA = 30°MIA = 150 °MIA = 30 °

Understanding Moment Arm Changes Through ROM

JA = 150°MIA = 30 °

JA = 120°MIA = 60 °

JA = 90°MIA = 90 °

JA = 45°MIA = 120 °

JA = 30°MIA = 150 °

Understanding Moment Arm Changes Through ROM

JA = 150°MIA = 30 °

JA = 120°MIA = 60 °

JA = 90°MIA = 90 °

JA = 45°MIA = 120 °

JA = 30°MIA = 150 °

Biceps Brachii Strength

Joint Angle (°)

Tor

que

(Nm

)

0 90 180

Joint Angle

Brachioradialis Strength

Joint Angle (°)

Tor

que

(Nm

)

0 90 180

Joint Angle

Summary of System Level Rotational Function

Torque output varies across ROM Variation depends on:

Force-length changes Moment arm changes

Variation differs across muscles & joints

Torque

Joint Angle (degrees)

0 30 60 90 120 150

Shoulder Flexors

Flexion

0 indicates anatomical position

Varies according to force-length & MIA (moment arm) changes for all muscles in FMG

Torque

Joint Angle (degrees)

0 30 60 90 120 150

Shoulder Flexors

Flexion

0 indicates anatomical position

Resistance

Muscle

Torque

Joint Angle (degrees)

0 30 60 90 120 150

Shoulder Flexors

Flexion

0 indicates anatomical position

Resistance

Muscle

Torque

Joint Angle (degrees)

0 30 60 90 120 150

Shoulder Flexors

Flexion

0 indicates anatomical position

Resistance

Muscle

Torque

Joint Angle (degrees)

0 30 60 90 120 150

Shoulder Flexors

Flexion

0 indicates anatomical position

Resistance

Muscle

Exercise Evaluation

Strength curve similarity Specificity of muscle roles Specificity of ROM Specificity of movement & contraction speed

Summary

Exercise evaluation is important to ensure appropriate physical training, whether for performance enhancement, injury prevention, or injury rehabilitation.

Exercise evaluation should focus on the progressive overload principle and the specificity principle.

The importance of each principle depends on the goal(s) of the exercise program.