Biomechanics Flashcards
what does “bio” refer to?
life/living organisms
what does “mechanics” refer to?
study of physical actions of forces
define statics
the study of systems in a constant state of motion
define dynamics
the study of systems in motion with acceleration
define kinematics
description of a systems motion
define kinetics
study of forces associated with a body’s motion
what are the key functions of machines?
- increase mechanical advantage
- balances multiple forces
- enhances forces to decrease the total force required to overcome resistance
- enhance ROM and speed of movement to move resistance further or faster than the applied force
- alter the resulting direction of the applied force
what are the different kinds of machines?
- levers
- wheel and axle
- pulleys
describe what a lever machine is
most common type of machine that allows the body to move and apply force.
- 1st, 2nd, and 3rd classes
define 1st class levers
effort and load are on opposite sides of the fulcrum - ex: triceps extension
define 2nd class levers
effort and load are on the same side of the fulcrum; effort is farther from fulcrum and load is closer
- ex: calf raise
define 3rd class levers
effort and load are on the same side of the fulcrum; effort is closer to the fulcrum and load is farther
- ex: elbow flexion
define torque
an eccentric force that causes rotation
- Eccentric force: muscle contraction pulling on bones at attachment sites causing bones to rotate at joint axis
describe what a wheel and axle machine is
- Purpose: enhance ROM and speed
- Function: 1st class lever; wheel and axle complete turn at the same time
- Mechanical advantage: determined by the radius of the wheel compared to the radius of the axle
describe what a pulley machine is
- Purpose: change effective direction of force application
- Function: single, compound
what is an example of a wheel and axle machine in the body?
axle = humerus
Outside of wheel = hand/wrist
Movement = internal rotation
Results = increased speed to throw objects
what is an example of a pulley machine in the body?
Pulley = lateral malleolus
Tendon = peroneus longus
Movement = ankle PF, eversion
describe Newton’s 1st law of motion: Inertia
an object at rest remains at rest and an object in motion remains in motion at a constant speed and in a straight line unless acted on by an unbalanced force
describe Newton’s 2nd law of motion: Force
acceleration of an object depends on its mass and the amount of force applied; F=MA
describe Newton’s 3rd law of motion: Action/reaction
for every action, there is an equal and opposite reaction
define static friction
resultant force from resistance between 2 object surfaces coming into contact AT REST
define kinetic friction
resultant force from resistance between 2 object surfaces coming into contact
SLIDING against each other
define rolling friction
resultant force from resistance between 2 object surfaces coming into contact
ROLLING across a surface
define balance
ability to control equilibrium
- Equilibrium: state of 0 acceleration
- Stability: needed to control equilibrium and achieve balance
how is stability achieved?
- enhanced by altering COG as needed
- COG: the point at which all of the body’s mass and weight are equally distributed
- Response to perturbation: lower COG, COG within BOS, and enlarged BOS
what is the number 1 source of force?
- Muscle contraction is the number 1 source of force
- Without forces there is no movement
- F=MA (force = mass times acceleration)
what is the momentum equation?
M=MV (momentum = mass times velocity)
- Impulse = force x time (can alter momentum)
describe what a mechanical load is
physical stress on a mechanical system or component
what are some internal and external forces effecting mechanical load?
Internal forces:
- Active: muscle contraction
- Passive: tension in tendons,
connective tissues,
ligaments, and joint
capsules
External forces:
- Gravity
- Inertia
- Direct contact
what are the different types of mechanical load?
- Tension (stretch/strain)
- Compression
- Shear
- Bending
- Torsion (twist)
- Combined (compression + rotation)
describe some injuries and prevention associated with mechanical loads
injury/damage:
- Fracture bones
- Dislocate joints
- Disrupt muscles and
connective tissues
Injury prevention
- The body can absorb
energy from internal and
external forces
- Absorb force over larger
aspects
- Spread absorption rate over
a greater time period
- Stronger and healthier
tissue can withstand greater
mechanical loading
