Lecture 2 - Biological Materials

Question 1

What are typical Achilles characterises of athletes such as basketballers and high jumpers?

Answer 1

• Short powerful calf muscles with long Achilles tendons resulting in a more efficient SSC and energy return.

Question 2

What is the ultimate failure strain, viscoelastic behaviour and resultant energy effects from this?

Answer 2

• Ultimate failure strain is between 8-10%.
• Their viscoelastic is limited and only have a 2.5-20% hysteresis.
• As a result they have high levels of energy return during elastic recoil in the MTU.

Question 3

What are the biomechanical properties of cartilage?

Answer 3

• Rapid initial deformation followed by more gradual
  increase
• Returns to initial shape on load removal (hysteresis)

Question 4

What are the five types of bone fractures?

Answer 4

• Diaphyseal impaction
• Transverse
• Spiral
• Oblique transverse
• Oblique

Question 5

What are the factors that determine ligament failure

Answer 5

• Ligament failure is due to bending and torsional loads applied to the limb and is dependant of the load generation rate.

Question 6

How far can muscle stretch before rupture and what is the maximal stiffness that they can reach and during what contraction ?

Answer 6

• Can stretch up to 160% of resting length before rupture.
• Maximal stiffness is encountered during eccentric exercise and can be up to 200x the level found in concentric exercise.

Question 7

What can lead to injury of the articular cartilage?

Answer 7

• Overuse injuries resulting in degeneration and subsequent osteoarthritis.
• High impact loads causing swelling to cartilage.

Question 8

What are some examples of deep connective tissue ?

Answer 8

• Tendons
• Aponeurosis
• Fascia
• Ligaments
• Joint capsules

Question 9

Why do transverse fractures occur in bones?

Answer 9

• Bones are weaker to tension than compression so side of bone away from force breaks first.

Question 10

What is the composition of bone?

Answer 10

• 25-30% water
• 30% Collagen, provides flexibility, resistance to tensile loading and toughness( resistance to shock loading).
• 70% minerals, Mainly
  calcium phosphate/carbonate. These resist compression, and provide rigidity.

Question 11

What do ligament contain that can have resultant effect upon muscles?

Answer 11

• Mechanoreceptor which can initiate tension in nearby muscle to assist with maintaining joint stability.
• E.g. the hamstring during rapid knee extension.