Internal Forces In The Human Body

Question 1

Classification of forces

Answer 1

External Forces

Internal Force

Question 2

External Force Defintion

Answer 2

Can change the state of a system (gravity, grf, air resistance)

Question 3

Internal Force Defintion

Answer 3

Are generated within the system (musculoskeletal forces)

Question 4

Internal Force Considerations

Answer 4

Joint Contact Forces
Ligament Forces and other soft tissue forces
Muscle/ tendon forces

Question 5

Clinical Measurements of Internal Forces - Direct Measures

Answer 5

Buckle transducers
Optic Fibres

Limitations
Invasive
Unethical
Calibration

Question 6

Optic fibre

Answer 6

Measures changes in light as tendon moves

Question 7

Indirect measures of muscle force

Answer 7

EMG

Inverse Dynamics

Question 8

Torque

Answer 8

= f x d

Question 9

Calculating segmental inertial properties limitations

Answer 9

Moment of inertia

Each segment is uniform in density and rigid - muscle is not contracted in cadavers

The segmental mass can be considers as a single point as the segments centre of mass

the segmental moment of inertia remains constant throughout the movement

Question 10

Limitations to inverse dynamics

Answer 10

The articulating surfaces in the joints are smooth and do not create frictional force

The forces act through the centre of the joingt

The foot segment is assumed to be one rigid segment

Question 11

Muscle power defintion

Answer 11

muscle moment multiplies by angular velocity

Question 12

Implications for training and testing

Answer 12

Training moments require

• High force generated by knee extensors eccentric to concentric
• High force generated by ankle extensors eccentric to concentric
• The hip acts passively