Biomechanics Flashcards
Biomechanics definition
the science (or study) of internal and external forces acting on the human body, and the effects produced by these forces
different actions we do to produce force
Newton’s Laws of Motion
1st Law
1st Law: a body stays at rest or in motion, unless acted upon by an external force.
Inertia: The resistance an object has to change in it’s state of motion. (highert mass = more inertia)
a heavier football player would have more inertia and therefore harder to be stopped
Newton’s Laws of Motion
2nd Law
2nd Law: The change in velocity (acceleration) of an object is directly proportional to the force applied and inversely proportional to the mass of the object (F=ma)
Impulse: I=F∆t, decides how fast the ball is going to accelerate.
Impulse is a term that quantifies the overall effect of a force acting over time.
F=force, m=mass, a=acceleration, I=impulse, ∆t= change in time
Newton’s Laws of Motion
3rd Law
3rd Law: For every action(force), there is an equal and opposite reaction (force)
Friction
Friction: A force generated when one body moves across the surface of another body, in the opposite direction of the motion
momentum
momentum: the quantity of motion a body possesses; a function of the mass and velocity of the body (P = mv) the mass of the player times their velocity
P-momentum
P-before must = P after the collition
Types of motion
1-Linear motion
mov’t in a particular direction (a straight line), force acts on object through its centre of mass. Example: spriter accelerating down track
Types of motion
Rotaional motion
mov’t about an axis, force does not act on centre of mass, causing rotation.
Example: bending a soccer ball.
Lever Systems
what is a lever?
An instrument for performing work
Bones in body act alone or with others as part of a lever system that facilitates movement
all levers involve a force (effort), resistance (load), and a fulcrum (pivot point/axis)
to lift a boulder (resistance), a rock (fulcrum) and as stick is used along with our force
Classes of Levers
Class I lever
fulcrum is located b/w the force and resistance (in the middle)
ex: see-saw, neck
Classes of Levers
Class II Lever
The resistance is b/w the force and fulcrum
pivot and effort on both ends, load in the middle facing in
ex: standing on tipy toes, one wheel cart
Classes of Levers
Class III lever
The force is b/w the fulcrum and the resistance. This is the most common lever in the body
pivot and load at both ends, effort at the middle facing out
ex: flexion at the elbow
7 principles of biomechanics
1`
Lower centre of mass = larger base of support, and more stability
7 principles of biomechanics
2
To produce max force, use all possible joints in movement
7 principles of biomechanics
3
to produce max velocity, use all joints in order from largest to smallest
7 principles of biomechanics
4
the greater the applied impulse, the greater the increase in velocity
7 principles of biomechanics
5
movement occurs in direction opposite that of the applied force
7 principles of biomechanics
6
Angular motion occurs when force is applied away from axis
7 principles of biomechanics
7
Angular momentum is constant when an athlete or object is free in the air
stability
When athletes want to become stable, they should:
- lower their centre of gravity (bend knee)
- widen their base of support (spread legs
- Place their centre of gravity in the middle of the base
- Increase their mass, when possible (wear weight)
stability
When athletes want to move quickly (become less stable), they should:
- Raise their entire entre of gravity
- narrow their base of support (hug body when want to increase spinning speed)
- move their centre of gravity outside the base (point your head out when get ready to race)
- decrease their mass (when possible)
maximum effort
when athletes want to exert maximum force they should:
- use as many joints as possible
- use joints simultaneosly (at the same time)
ex. wrestling
maximum velosity
when athletes want to produce maximum velocity, they should:
- use as many joints as possible
- use joints in sequence, beginning with those associated with largemuscle mass
ex. pitching
linear motion
when athletes want to move in one direction, they should:
apply a force in the opposite direction
ex. racing
angular motion
when athletes want to spin faster, they should
movement of inertia: relative difference in how easy or difficult it will be to set any object in motion about a defined axis of rotation
when athletes want to spin faster, the should: decrease their movement of inertia
ex. figure skating
angular motion
when athletes want to spin slower
increase their moment of incertia
* the further the mass is from the rotation point, the greater the moment of inertia.
uses of biomechanics
- analyze and enhance performance
- injury prevention and rehabitation
- fitness and personal training
analysis of gait (walking)
phases of normal gait:
the gait cycle is the time interval between the exact same repetitive events of walking.
the defined cycle can start at any movement, but it is generally begun when one foot contacts the ground.
two phases of the gait cycle
stance phase: the part of the cycle when the foot is in contact with the ground (60% of cycle)
Swing phase: occurs when the foot is in the air (40% of cycle)
the cycle of walking can be divided into 6 further phases:
- heel strike (HS)
- Foot flat (FF)
- Mid-stace (MS)
- Heel off (HO) terminal stance
- Toe off (TO) preswing
- initial & Mid-swing
- Terminal swing
periods 1-3 make up the stance phase, while periods 4-6 make up the swing phase
non-pathological gait patterns in a child
- wider BOS (base of support)
- faster cadence
- shorter stride length
- initial contact with floor is flat foot
- knees remain mostly extended during stance phase
non-pathological gait patterns in elderly
- walk slower
- spend more time in stance phase
- longer periods of double support
- shorter steps
- less vertical displacement
- wider BOS
- greater horizontal displacement
why study gait?
- to see if developmental milestones are achieved or delayed.
- the ability to walk safely often determines when a patient can be discharged home
- issues involving pain in other areas of body (back, knee, hip, etc.) can originate from improper gait
non support
occurs when neither foot is in contact with the floor
does not occur during walking
running- biggest difference between runing and walking is non-support, in speed walking, there is always contact with floor.
