Internal Forces In The Human Body: Direct vs Indirect

Question 1

What are External forces?

Answer 1

Forces that can change the state of a system (gravity, ground reaction or other external forces, air resistance)

Question 2

What are Internal forces?

Answer 2

Forces that are generated within the system (musculoskeletal forces)

Question 3

Three internal forces?

Answer 3

1. Joint contact forces
2. Ligament forces and other soft tissue forces
3. Muscle/Tendon forces

Question 4

Two direct ways of measuring muscle/tendon forces and the limitations?

Answer 4

1. Buckle transducers
2. Optic fibres

Limitations -
•Invasive procedure
•Ethical issues
•Tendon suitability (not all tendons are suitable for measurements)
•Calibration

Question 5

Two Indirect measurements of muscle force?

Answer 5

1. EMG -
   High correlations exist between muscle force and muscle activity in clinical isometric settings. Validity of EMG has been questioned within dynamic activities
2. Inverse Dynamics -

Calculates the internal joint forces and then subsequently the net turning torque (moment) of a joint. Torque = f * d

Question 6

Three types of Kinetic equipment used to calculate internal forces?

Answer 6

1. Force Plates
2. Linear Transducers
3. Accelerometers

Question 7

Three types of Kinematic equipment used to calculate internal forces?

Answer 7

1. High speed video cameras
2. Infrared auto tracking
3. Cineradiography

Question 8

Watch Lecture Recording

Answer 8

11: 58 - 20:39
24: 28 - 42:23

Question 9

Limitations to inverse dynamics

Answer 9

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

The forces act through the centre of the joint and the centre of the joint does not change in relation to the corresponding connecting segments

The foot segment is assumed to be one rigid segment that included the metatarsal segment and joint

Question 10

Clinical measures are what and can therefore not be used in what situations

Answer 10

Clinical measures are invasive and can not be used in dynamic situations

Question 11

Muscle Moments identify what?

Answer 11

The internal joint kinetics

Question 12

Calculating mechanical joint power and work can identify what?

Answer 12

Levels of mechanical effort