(DONE) Lecture 6 - Biomechanics

Question 1

define: biomechanics

Answer 1

the application of mechanical laws to living structures, specifically to the locomotor system of the human body.

Question 2

list the 6 uses of biomechanical analyses

Answer 2

• Improvement of sports skill techniques
• Design of sports equipment
• Prevention of injuries
• Clinical analysis of movement pathologies
• Design of prostheses
• Design of rehabilitation devices

Question 3

define: qualitative analysis; who primarily conducts this analysis type?

Answer 3

• a non-numerical description of a movement based on direct observation.
• conducted primarily by teachers and coaches

Question 4

define: quantitative analysis; who primarily conducts this analysis type?

Answer 4

• a movement is analysed numerically based on measurements from data collected during the performance of the movement
• conducted usually by researchers

Question 5

define: lever

Answer 5

• rigid bar that turns about an axis

Question 6

define: force point

Answer 6

• where effort is exactly applied (muscle insertion)

Question 7

define: resistance point

Answer 7

• exact point which resistance acts (segment plus external weight)

Question 8

define: mass

Answer 8

• quantity of matter contained in a n object

Question 9

define: moment arm

Answer 9

• perpendicular distance between forces line of action and axis rotation

Question 10

define: torque

Answer 10

• the product of force and the perpendicular distance from the force’s line of action to the axis of rotation. It may be thought of as rotary force. Units = Newton-meters (N·m)

Question 11

define: volume

Answer 11

• amount of space that a body occupies

Question 12

define: pressure
- give equation
- give units

Answer 12

• force distributed over a given area
• P=FA
• N/cm^2

Question 13

define: compression

Answer 13

• pressing or squeezing force directly axially through a body

Question 14

define: tension

Answer 14

• pulling or stretching force directly axially through a body

Question 15

define: shear

Answer 15

force directed parallel to a surface

Question 16

define: mechanical stress by its equation

Answer 16

• force/ area

Question 17

List the 8 tips for lifting a heavy object off the floor

Answer 17

1. get help if its too heavy or use techniques to minimize effort
2. stand facing the object with feet flat and shoulder width apart pointing straight ahead
3. face object in direction you intend to move it; avoid twisting
4. keep close to body to minimize low back strain
5. get a good grip
6. bend at knees and hips, keeping back straight as possible while avoiding a fully flexed back
7. use knee and hip extensor muscles to lift
8. carry close to COG

Question 18

Why is a flat back lifting posture better than a rounded back?

Answer 18

• minimizes L5/S1 disc compression and ligament strain

Question 19

Why should you avoid full flexion of the trunk? (2)

Answer 19

• increases shear load on vertebrae and probability of ligament damage
• increases probability of disc herniation from repeated full flexion

Question 20

What activity/ state should you avoid doing/ being in before lifting to avoid increased chance of injury? (2)

Answer 20

• immediately after being in a stooped posture/ prolonged sitting
• immediately after rising from bed

Question 21

How does the contraction of your abdominal muscles aid your vertebral column while lifting?

Answer 21

• reduces force required by erector spinae muscles and associated disc compressive force to perform lift

Question 22

What can impact the human body’s COG? (3)

Answer 22

• body proportions
• change of body position/ limb position
• addition of external weight

Question 23

Why is it useful to determine COG?

Answer 23

• Used to describe the movement of the body through space
• Important for stability
• It is an important factor in calculation of amount of work done

Question 24

What are 2 ways you can determine COG?

Answer 24

• reaction board method for static positions

- segmental method

Question 25

define: balance

Answer 25

• the ability to control equilibrium

Question 26

define: stability

Answer 26

• firmness of balance

Question 27

fill in the blank: For balance to be maintained in any stationary position, the CG must remain ___ the base. Whenever the CG passes outside the _________, the body is ___________.

Answer 27

• over
• base of support
• off balance in that direction

Question 28

How can you increase your stability (5)?

Answer 28

• Increasing body mass
• Increasing the size of the base of support in the direction of the line of action of an external force
• Vertically positioning the CG as low as possible
• Increasing friction between the body and the surface contacted
• Horizontally positioning the CG near the edge of the base of support towards the oncoming external force

Question 29

First Law: Law of Inertia

Answer 29

“A body will maintain a state of rest or constant velocity unless acted on by an external force that changes the state.” The amount of inertia a body possesses is directly proportional to its mass.

Question 30

Second Law - Law of Acceleration

Answer 30

“force equals mass X acceleration”

Question 31

Third Law - Law of Reaction

Answer 31

“When one body exerts a force on a second body, the second body exerts a reaction force that is equal in magnitude and opposite in direction on the first body.”

Question 32

define: momentum

Answer 32

A mechanical quantity that is important in situations involving collisions. Momentum = mass X velocity

Question 33

give the equation and units for: work

Answer 33

• force x distance

- 1.0Nm; 1.0 J (joule)

Question 34

give the equation and units for: power

Answer 34

• work/ time OR (force x distance)/time OR force x velocity

- joules/sec OR watts

Question 35

Differences between walking and running (3)

Answer 35

• In running there is a period when both feet are off the ground. Consider running as a series of jumps.
• In running, there is no period when both feet are in contact with the ground at the same time
• In running, the stance phase is a much smaller portion of the total gait cycle than in walking.

Question 36

running speed equation

Answer 36

stride length X stride rate

Question 37

What is stride length and stride rate dependent on?

Answer 37

• Length of stride depends mostly on leg length and stride power.
• Stride rate is dependent on the speed of muscle contraction and neuromuscular coordination (skill) in running.

Question 38

Fill in the blank: At slower running speeds, runners tend to run ________, whereas at full speed, the typical sprinter _______________.

Answer 38

• more erectly

- leans forward at about 15 degrees from the perpendicular