Biomechanics Part 1 - Chapter 4

Question 1

What is stiffness?

Answer 1

the ratio of stress to strain in a loaded material - that is stress divided by the relative amount of a change in a structures shape

Question 2

What is strain?

Answer 2

Strain is the amount of deformation divided by the original length of the structure

Question 3

What mechanical stress or loads are bones more resistant to?

Answer 3

Bones are more resistant to pushing forces, that are created in supporting the body and maintaining alignment

Question 4

What components of bone contribute to stiffness?

Answer 4

Minerals in the bone - Calcium Carbonate and Calcium Phosphate

Question 5

What component of bone contributes to the amount of strain it can withstand

Answer 5

the spongy, more porous nature of the trabecular bone

Question 6

What is the cortical bone?

Answer 6

A bone that is compact, high mineral content, stiff, and can resist stress

Question 7

What is the trabecular bone?

Answer 7

A bone that is less compact, lower mineral content, more porous/spongier, and can resist strain

Question 8

Why are the cortical bone and trabecular bone important in regard to stiffness and strain?

Answer 8

The outer part of the bone (cortical) is resistant to stress, and the interior part is resistant to strain (trabecular)

Question 9

What is stress?

Answer 9

Defined as the distribution of force (mechanical loading) within a body when an external force acts on it

Question 10

What is Wolf’s Law?

Answer 10

A bone adapts to the magnitude and direction of the stress it receives over a period of time

Question 11

How is stress related to Wolf’s Law?

Answer 11

When stress is increased, more bone tissue is added. When stress is decreased, the amount of bone tissue is decreased.

Question 12

Is bone density related to an individual’s weight?

Answer 12

Yes, Bone density IS related to an individual’s body weight.

Question 13

Why is bone density related to an individual’s weight?

Answer 13

Bones follow Wolf’s law which means bone will grow and subside as needed. A person with a lower body mass index will not need as much bone to uphold the structure of their body. A person with a higher body mass will require much more bone and more strength to carry a heavier load. Thus, bone density is relative to body weight.

Question 14

Weightlifting does what to the bone density?

Answer 14

It increases the most - weight bearing, requiring you to work against gravity, sometimes using extremely heavy weights, which increases bone density.

Question 15

Tennis does what to the bone density?

Answer 15

weight bearing, tennis players often suffer from bone hypertrophy in their “swing side.” It’s an overgrowth of bone density that causes a build-up of bone tissue that can need surgery.

Question 16

Running does what to the bone density?

Answer 16

weight bearing, on the bones of the legs, pelvis, and spine. But running can also reduce bone density if the runner lacks the proper minerals. Running is not as effective as tennis, which is higher impact, multi-directional stresses which are more effective in building bone density.

Question 17

Cycling does what to the bone density?

Answer 17

Not weight bearing, as less stress is put on bones in this sport, particularly in the spine and hips, resulting in lower bone density.

Question 18

Swimming does what to the bone density?

Answer 18

It increases the least bone density.

Not weight bearing, collegiate swimmers have the lowest bone density compared to all other sports. They are at an increased risk for osteoporosis. Swimming does not require the body to work against gravity.

Question 19

Overall what is the best exercise for your bones?

Answer 19

The best exercise for your bones is the weight-bearing kind, which forces you to work against gravity.

Question 20

Explain why bones are more resistant to pushing forces?

Answer 20

The reason bones are more resistant to compressive forces because calcium carbonate and calcium phosphate make up 60-70% of bone weight and make these bones stiff and resistant to compressive loading or stress.