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:  m

Active Component

Passive component

Total Force

Single Joint Muscles 60% % 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 (°) Torque (Nm) Joint Angle

Brachioradialis Strength Joint Angle (°) Torque (Nm) 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

0  indicates anatomical position Varies according to force-length & MIA (moment arm) changes for all muscles in FMG

0  indicates anatomical position Resistance Muscle

0  indicates anatomical position Resistance Muscle

0  indicates anatomical position Resistance Muscle

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.