Loading of the Musculoskeletal System

Question 1

What is Injury

Answer 1

When the load applied to a tissue exceeds its failure tolerance

Question 2

What are the two crucial factors in Injury?

Answer 2

Load

Characteristics of Load Structures

Question 3

What are the 4 things we cannot change?

What are the 3 things we can attempt to change?

Answer 3

Age, Gender, Surfaces, Load

Fatigue, Skill, Fitness Levels

Question 4

What are the 3 types of injury?

Answer 4

1) Chronic - repeated overloads without recovery
2) Acute - single/few repeated episodes
3) Overtraining - result in injury - psychological

Question 5

What are the 4 different load characteristics?

Answer 5

Type of Load, Load Magnitude, Load Rate, Frequency

Question 6

What are the 5 types of load?

Answer 6

Tension, Compression, Torsion, Bending, Shear

Question 7

What is load magnitude?

Answer 7

how much of the load occurs

Question 8

What is load rate?

Answer 8

rate of change of force over time (f/t)

Question 9

What is load frequency?

Answer 9

How it affects overuse injury - load reps and reps

Question 10

What is the difference between stress and strain?

Answer 10

Stress - how much resists the change

Strain - amount of deformation that arises from an applied load

Question 11

What are the variables measured in the stress-strain relationship?

How much is 100N/cm2 in Megapascals?

Answer 11

Strain = % of change

Stress = load per unit of CSA - N/cm2

1 MPa

Question 12

What is Young’s Modulus of Elasticity?

Answer 12

The ratio between stress and strain - measures stiffness of the joint

Question 13

What is the difference in young’s modulus between a spanner and a Theraband?

Answer 13

Spanner has high young’s modulus = high strain

Theraband has low young’s modulus = low strain

Question 14

On the graph what define A, B and C and ER, PR and HR?

Answer 14

A = proportional limit
B = elastic limit
C = failure point
ER = elastic range (where it can go back to normal)
PR = plastic range (cannot return to normal)
HR = Hookean Region (where elastic body is deformed)

Question 15

What is the relationship between muscle stiffness and the stretch shortening cycle?

What are the stages of the SSC?

Answer 15

eccentric activity enhances force production in the proceeding activity = increases stiffness

Preload –> Elastic energy stored –> reflex potential

Question 16

What happens to muscle stiffness when you grow older?

Answer 16

Muscle stiffness increases and is therefore more resistant to change

Question 17

What is resilience?

If a tennis ball has 50% resilience, how high will it bounce back up if dropped from a metre?

Answer 17

amount of energy returned as a % of the amount of energy stored during deformation

0.5m

Question 18

What is a hysteresis loop?

Answer 18

Area within the loop is the amount of energy absorbed during one load/unload cycle

Question 19

By what percentage does Achilles tendon lose energy and how can it be improved?

Answer 19

10% - can be improved through resistance/strength training

Question 20

What does high passive stiffness in tendons infer?

Answer 20

Reduced braking phase muscle activation - get tired later on in races
Reduced tendon strain
Reduced muscle activity = improved running efficiency

Question 21

What does training aim to achieve to stiffness?

Answer 21

• Improve muscle tendon stiffness through Plyometrics
• Increase muscle strength not size
• Improve CSA of important tendons to reduce the risk of injury