Muscle and Tendon

Question 1

How do muscles differ?

Answer 1

• Size
• Fibre length
• Pennation angle
• Fibre type
• Tendon length

Question 2

Give examples of different ratios of muscle fibres and how it affects joints

Answer 2

Long fibres and short tendons = large active range of motion at joints
Shorter fibres and long tendons = important for elastic

Question 3

explain how kangaroos increase speed without metabolic cost

Answer 3

springy limbs reduce metabolic cost of locomotion

Question 4

Explain the mechanism of springy limbs?

Answer 4

• KE and PE decrease in early stance
• KE and PE lower at mid stance
• -> Spring compressed
• spring recoil in late stance to return elastic energy to KE and PE of CoM
• reduces the amount of work muscles need to do to accelerate the body during each stride

Question 5

what does elastic energy stored =

Answer 5

1/2 force x linear deformation
- for a given force, the more it deforms, the more energy it will store
Tendon strain must be high

Question 6

What is the definition of stiffness?

Answer 6

• Its resistance to to deformation due to a force

Question 7

What is the formula for stiffness?

Answer 7

Force / Change in length

Question 8

What is the formula for compliance?

Answer 8

1 / stiffness

Question 9

Young’s modulus (Pa)

Answer 9

Stress / Strain

Question 10

What are the effects of a stiff tendon?

Answer 10

• the more force it can withstand/transmit
• the less it will strain for a given force
• the less energy it will store for a given force

Question 11

What amount of tendon energy is lost to heat?

Answer 11

approximately 7%

Question 12

What are the most elastic sites in the human body?

Answer 12

ankle joint and foot

Question 13

Briefly describe the achilles tendon

Answer 13

• Free tendon of gastrocnemius and soleus
• strain during running
• high injury incidence

Question 14

What are the invasive methods of measuring strain in tendons in vivo?

Answer 14

tendon buckle

fibre optics

Question 15

What are the non invasive methods of measuring strain in tendons in vivo?

Answer 15

ultrasound

Question 16

when will the opposed tendon heal

Answer 16

if it is partially ruptured

Question 17

Describe the key features of ultrasound

Answer 17

High frequency sound wave

• sound is differentially reflected or absorbed by tissues of different densities
• cheap and available
• high skill level required
• soft tissues and bone surface
• difficult to get generl picture of the area
• low risk

Question 18

Define tendinopathy

Answer 18

• tendon loaded to high strain, which is near failure limit of collagen fascicles
• this loading cycle is repeated 1000s of times

Question 19

common sites for achilles tendinopathy

Answer 19

achilles
patella
tendon of origin extensor carpi radialis brevis

Question 20

what are the risk factors for tendinopathy

Answer 20

• change in training
• high stress placed on tissue due to sub optimal technique
• inappropriate equipment
• inappropriate tendon stiffness

Question 21

How do you adapt a tendon?

Answer 21

• by overload

–> repetitive loading above normal rate initiates normal collagen and extra cellular matrix synthesis and degradation

• -> diagram = degradation + synthesis
• if the rest between loading sessions is not adequate it results in tissues degradation

Question 22

How can resistance training increase tendon stiffness?

Answer 22

• Due to an upregulation of collagen type 1 fascicles

- a stiffer tendon can resist more