6 - Biomechanics Flashcards
def: the application of mechanical laws to living structures, specifically to the locomotor system of the human body
biomechanics
what are 4 applications of biomechanical analyses?
- improvement of sports skill techniques
- design of sports equipment
- prevention of injuries
- clinical analysis of movement pathologies
def: a non numerical description of a movement based on direct observation, conducted primarily by teachers and coaches
qualitative movement analysis
def: a movement is analyzed numerically based on measurements from data collected during the performance of the movement, usually conducted by reasearchers
quantitative movement analysis
def: pressing or squeezing force directly axially through body
compression
def: pulling or stretching force directly axially through a body
tension
def: force directed parallel to a surface
shear
def: a rigid bar that turns about an axis
lever
what do the bones represent in levers in the body?
the bars
what do the joints represent in levers in the body?
the fulcrum
def: the exact point where effort is applied(muscle insertion)
the force point
def: the exact point on which the resistance acts (segment plus external weight)
resistance point
def: the axis of motion
fulcrum
def: has its fulcrum at some location between the force point and the resistance point
a first class lever
def: has its resistance point at some location between the force point and the fulcrum
second class lever
def: has its force point at some location between the resistance point and the fulcrum
third class lever
what is an example of a second class lever
wheel barrow
what is an example of a third class lever?
elbow
what is an example of a first class lever?
seesaw
def: the ratio of force arm length to resistance arm length
mechanical advantage of a lever
def: the force arm of a lever is longer than its resistance arm, the mechanical advantage favors application of force at the sacrifice of speed
force lever
def: when the resistance arm is longer than the force arm, the lever favors the speed and range of motion at the sacrifice of force
speed lever
second class levers have a MA of…
> 1
third class levers have a MA of…
< 1
first class levers have a MA of…
1, < 1, > 1
def: the perpendicular distance between the force’s line of action and the axis of rotation
moment arm
def: the product of force and the perpendicular distance from the force’s line of action to the axis of rotation
torque
def: an imaginary point in the centre of the body where the weight of the body is balanced
centre of gravity
what are the three other definitions of centre of gravity?
- the point intersection of the three cardinal planes of the body
- the point of exact center, around which the body may rotate freely in all directions
- the point around which the weight is equal on all opposite sides
the CG is approximately ____ below the _______
6 cm below the bellybetton
the exact location of the center of gravity varies from person to person depending _____ __________
body proportions
what is CG influenced by?
- changing body position
- limb positions
why is it useful to determine CG?
- used to describe the movement of the body through space
- important for stability
- it is an important factor in calculating the amount of work done
what are two techniques for locating the center of gravity?
- reaction board method
- segmental method
how can stability increased?
- bigger body mass
- increasing the size of the base of support
- vertically positioning the CG as low as possible
- increasing friction between the body and the surface contacted
- horizontally positioning he CG near the edge og the base of support towards the oncoming external force
def: law of inertia - a body will maintain a state of rest or constant velocity unless acted on by an external force that changes that state
first law
def: law of acceleration- force equals mass X acceleration
second law
def: 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
third law
def: a mechanical quantity that is important in situations involving collisions
momentum
what are the three differences between walking and running?
- in running there is a period when both feet are off the ground
- in running there is no period when both feet are in contact with the ground at the same time
- in running, the stance face is a much smaller portion of the total gait than in walking
running speed =
stride length X stride rate
what is length of stride dependent on?
leg length and power of the stride
what is leg speed dependent on?
speed of muscle contraction and neuromuscular coordination in running
