14. The Mechanics of movement Flashcards
Defining normal MOVEMENTS of the Joint
- the TYPE of motion
- translation
- rotation (e.g. hip)
- compound (e.g. knee)
- the PLANE of motion
- frontal
- saggital
- transverse
- compound (e.g. subtalar)
- the RANGE of motion
Application to gait:
* hip
* knee
* ankle and foot
Newton’s 1st Law:
Every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force.
INERTIA
Newton’s 2nd Law:
There is a force equal to change in momentum (mass x velocity) per change in time
F = M x A
force= mass x acceleration
Newton’s 3rd Law:
For every action (force) there is an EQUAL and OPPOSITE REACTION (by different bodies)
there are 2 types of MOTIONS:
- LINEAR (TRANSLATIONS)
- ANGULAR (ROTATIONS)
difference between LINEAR (translations) and ANGULAR (Rotations)
LINEAR: FORCE
needed to overcome mass (m)
ANGULAR: MOMENT
needed to overcome Moment of Inertia (I)
(moment of inertia depends on distance from centre of rotation)
what is a MOMENT
the TURNING EFFECT of a FORCE
Moments act about a point in a clockwise or anticlockwise direction.
The point chosen could be any point on the object, but the pivot - also known as the fulcrum - is usually chosen
an object is in EQUILIBRIUM when there is no..
NO ACCELERATION
NO FORCE about the body
Newton’s 1st Law applies
NON-EQUILIBRIUM when..
ACCELERATION
RESULTANT force about the body
Newton’s 2nd law applies
in rigid segments identify 3 PROPERTIES:
(modelling a body)
- MASS
- CENTRE of MASS LOCATION
- ROTATIONAL INERTIA (I)
in rigid segments identify 3 FORCES:
(modelling a body)
- GRAVITY
- EXTERNAL FORCES
- INTERNAL FORCES (muscles & ligaments)
what is TORQUE
the measure of the force that can cause an object to rotate about an axis
MOMENTS are generated by a..
TORQUE MOTOR
are MUSCLES torque motors
no they are LINEAR ACTUATORS
what type of FORCES do MUSCLES produce
additional COMPRESSIVE and SHEAR FORCES across the JOINT SURFACES
what are JOINT REACTION FORCES
force generated within a joint in response to forces acting on the joint
in Joint Reaction Forces, At extreme ends of the Range of Motion, we also need to include anatomical constraints such as:
Ligaments,
Bony blockage
how do humans walk (like an…)
INVERTED PENDULUM
(foot on ground and pivoting above)
starting point: ‘compass gait’
how are the energy levels in the INVERTED PENDULUM mechanism
POTENTIAL and KINETIC ENERGIES FLUCTUATE (makes walk more efficient)
- EXCHANGE
steps of human GAIT - INVERTED PENDULUM
Starting point: compass gait
- PELVIC ROTATION
- Centre of MASS path FLATTENS - PELVIC TILT
- centre of mass further flattens - KNEE FLEXION during STANCE
4&5. FOOT and KNEE MECHANISMS
- help smoothen the path of the centre of mass
- REDUCED LATERAL DISPLACEMENT of the PELVIS
- Otherwise would be moving right/left
- avoided by means of tibiofemoral angle and hip adduction
INVERTED PENDULUM GAIT gives ENERGY SAVING of … in humans
70% in humans
- very efficient walkers
(35-50% in most animals/quadrupeds)
RUNNING gives how much ENERGY SAVING in humans
50%
what causes FORCES in humans
COORDINATED MUSCLE ACTION
what are CENTRAL PATTERN GENERATORS for
key for a lot of daily activities like walking
- so don’t need a brain
in SPINE
in the GAIT CYCLE when is the 1ST DOUBLE LIMB SUPPORT
INITIAL CONTACT
in the GAIT CYCLE when is the 2nd DOUBLE LIMB SUPPORT
PRESWING
what are the 2 PHASES of the GAIT CYCLE
STANCE PHASE
SWING PHASE
stages in STANCE PHASE of GAIT CYCLE
- Initial Contact
- Loading Response
- Mid Stance
- Terminal Stance
- Preswing
stages in the SWING PHASE of the GAIT CYCLE
- Initial Swing
- Mid Swing
- Terminal swing
in GAIT CYCLE, what is happening in MID STANCE
one leg lifted
middle of stance phase
