(DONE) Lecture 6 - Biomechanics Flashcards
define: biomechanics
the application of mechanical laws to living structures, specifically to the locomotor system of the human body.
list the 6 uses of biomechanical analyses
- Improvement of sports skill techniques
- Design of sports equipment
- Prevention of injuries
- Clinical analysis of movement pathologies
- Design of prostheses
- Design of rehabilitation devices
define: qualitative analysis; who primarily conducts this analysis type?
- a non-numerical description of a movement based on direct observation.
- conducted primarily by teachers and coaches
define: quantitative analysis; who primarily conducts this analysis type?
- a movement is analysed numerically based on measurements from data collected during the performance of the movement
- conducted usually by researchers
define: lever
- rigid bar that turns about an axis
define: force point
- where effort is exactly applied (muscle insertion)
define: resistance point
- exact point which resistance acts (segment plus external weight)
define: mass
- quantity of matter contained in a n object
define: moment arm
- perpendicular distance between forces line of action and axis rotation
define: torque
- 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)
define: volume
- amount of space that a body occupies
define: pressure
- give equation
- give units
- force distributed over a given area
- P=FA
- N/cm^2
define: compression
- pressing or squeezing force directly axially through a body
define: tension
- pulling or stretching force directly axially through a body
define: shear
force directed parallel to a surface
define: mechanical stress by its equation
- force/ area
List the 8 tips for lifting a heavy object off the floor
- get help if its too heavy or use techniques to minimize effort
- stand facing the object with feet flat and shoulder width apart pointing straight ahead
- face object in direction you intend to move it; avoid twisting
- keep close to body to minimize low back strain
- get a good grip
- bend at knees and hips, keeping back straight as possible while avoiding a fully flexed back
- use knee and hip extensor muscles to lift
- carry close to COG
Why is a flat back lifting posture better than a rounded back?
- minimizes L5/S1 disc compression and ligament strain
Why should you avoid full flexion of the trunk? (2)
- increases shear load on vertebrae and probability of ligament damage
- increases probability of disc herniation from repeated full flexion
What activity/ state should you avoid doing/ being in before lifting to avoid increased chance of injury? (2)
- immediately after being in a stooped posture/ prolonged sitting
- immediately after rising from bed
How does the contraction of your abdominal muscles aid your vertebral column while lifting?
- reduces force required by erector spinae muscles and associated disc compressive force to perform lift
What can impact the human body’s COG? (3)
- body proportions
- change of body position/ limb position
- addition of external weight
Why is it useful to determine COG?
- 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
What are 2 ways you can determine COG?
- reaction board method for static positions
- segmental method
define: balance
- the ability to control equilibrium
define: stability
- firmness of balance
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 ___________.
- over
- base of support
- off balance in that direction
How can you increase your stability (5)?
- 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
First Law: Law of Inertia
“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.
Second Law - Law of Acceleration
“force equals mass X acceleration”
Third Law - Law of Reaction
“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.”
define: momentum
A mechanical quantity that is important in situations involving collisions. Momentum = mass X velocity
give the equation and units for: work
- force x distance
- 1.0Nm; 1.0 J (joule)
give the equation and units for: power
- work/ time OR (force x distance)/time OR force x velocity
- joules/sec OR watts
Differences between walking and running (3)
- 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.
running speed equation
stride length X stride rate
What is stride length and stride rate dependent on?
- 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.
Fill in the blank: At slower running speeds, runners tend to run ________, whereas at full speed, the typical sprinter _______________.
- more erectly
- leans forward at about 15 degrees from the perpendicular
