biomechanics Flashcards
biomechanical analysis
conducted both qualitatively and quantitatively.
qualitative
non-numeric evaluation of motion based on direct observation.
quantitative
numeric evaluation of motion based on data collected during the movement.
kinematic of motion
description of motion from a spatial and temporal perspective,
linear or angular motion paths
linear motion paths
movement occurs along a straight or curved pathway in which all points on a body or object move the same distance in the same amount of time.
angular motion paths
motion around an axis so that different regions of the same object do not move through the same distance in a given amount of time.
force
Forces cannot be seen, but effects of forces can be observed e.g. produce or stop motion; accelerate or change direction of an object/body.
internal forces
Produced from structures located within the body.
active- generated by muscle contraction
passive- generated by tension in stretched tissue- ligamens stretch tendon stretch
external force
Produced by forces acting from outside the body.
Gravity acting on mass of a body segment and its attachments, e.g. splints, casts,
External load acting on mass of a body segment, e.g. hand weight, manual resistance, weight bar or back pack
Friction which can provide stability if optimum, retard motion if excessive, or lead to instability if inadequate
forces are characterised by
magnitude - weight on the limb
direction - which way muscles are pulling
point of application - where the weight is actually acting on
what can forces do
translate a body segment
produce rotation- torque = when a segment is fixed or anchored at one or more points.
torque and moment
dynamic rotatory effect of a force while moment is the static rotatory effect
measure torque
Torque (T) = Force (F) x Moment arm (MA)
composition
process of combining or adding two or more vector quantities (forces) together.
if 2 in the same direction will increase the magnitude
if in opposite direction will decrease the magnitude
2 different muscle vectors result in
resultant force
resolution of forces
perpendicular- force of the muscle
parallel- distraction of the elbow
parallel component will move- causing rotation
distraction
pull apart a joint
newton laws
1 Newton (N) is equal to the force needed to accelerate 1kg of mass at the rate of 1m/s² in the direction of the applied force.
newtons first law
For a body to maintain a state of rest or static equilibrium there can be no unbalanced external forces acting on it. Therefore, the sum of all forces acting on a body must add to zero. ∑ F = 0
newtons second law ( accel)
“A force applied to a body causes an acceleration of that body of a magnitude proportional to the force, in the direction of the force, and inversely proportional to the body’s mass.”
greater force applied to a ball- greater acceleration it will have
newtons third law
“For every action, there is an equal and opposite reaction.”
Every time the foot impacts the ground during gait it produces a force against the ground. This results in the ground generating a force of equal magnitude back in the opposite direction.
with a smaller moment arm we need to use
more force to produce same torque if we had a larger moment arm
torque and lever system
bone acts a lever
weight of limb is resistance
joint acts as a fulcrum
muscle applies force
mechanical advantage
force moment arm/ resistance moment arm
a greater mechanical advantage the less work is required
ratio less then 1
momement arm of force is less then the resistance
then bicep will need to work harder to overcome resistance
ratio greater then 1
moment arm is greater then the resistance so bicep will work less to overcome the force
first class lever
force on one side
lever in the middle
resistance on the other
second class lever
lever is on one side
resistance is in the middle
force is on the other in opposite direction to resistance
ankle usually
third class lever
lever on one side
force in the middle
resistance on the other side agaianst the force
direction
compression
e.g the effect of gravity
tension
e.g stretch or pull// due to muscle contraction placing force on bones
shear-
act parallel to the surface usually during squats
bending-
when asymetrical force is applied- compression on one side/ tension on other side reduces injury potential
torsion when a structure twist on longnitudal axis
distribution
stress- force per unit of area it acts on
magnitude and duration
acute load- single force of surficent magnitude to cause injury
macrotruama
repetitive load- repteated application/ use causing microtrauma
magnitude stress vs strain
strain= deformation
change in shape due to force applied
load/ stress- structure goes back to original shape but if it goes beyond yeild point if load is removed it may not go back to original shape and deformation occurs
bone components
spongy- trabeculae
compact- osteons
osteocytes- type 1 collagen fibre
bone isn’t hardest thing in the body that is dentin
brittle and weak
deformation curve
elastic region- tempoary deformation due to increased load and stress
yield point- defromation becomes permenant
ultimate failure
plastic region= yield point/ ultimate failure
youngs modules- higher elastic region= stiff lower= flexible
