biomechanical principles Flashcards
biomechanics definition
=A field that combines the disciplines of biology and engineering mechanics and utilizes the tools of physics, mathematics, and engineering to quantitatively describe the properties of biological materials
kinesiology
=The scientific study of human movement. Kinesiology addresses physiological, biomechanical, and psychological dynamic principles and mechanisms of movement.
arthrokinetics
=A field that combines the disciplines of biology and engineering mechanics and utilizes the tools of physics, mathematics, and engineering to quantitatively describe the properties of movement of the joints
what’s involved in biomechanics
static structures–> e.g. bones & ligs dynamic structures–> e.g. muscles & proprioceptors
neurological mechanisms–> central & local control, corrective measures. fedback & forward loops
physiological mechanisms–> vascularity, energy systems
time–> age, timelines, degeneration
external influencing factors–> gravity, inertia, ground reaction forces
biomechanical principles–> center of gravity, levers, torque, power, force, force coupling, form & force closure, roll, slide & spin
pathological processes–> degeneration, developmental issues, trauma, malnutrition
forces
=push or a pull with an unequal force allowing an object/ limb to move as a result
6 types:
-tension
-compression
-bending
-shearing
-torsion
-combined loading
newtons laws of physics
1st law of motion= 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 (e.g. football)
2nd law of acceleration= the acceleration of an object is dependent upon two variables - the net force acting upon the object and the mass of the object (e.g. heavier someone is= more energy needed to jump)
3rd law= for every action (force) in nature there is an equal and opposite reaction (e.g. jumping into ground- ground reaction in opposite direction)
fulcrum
bone= lever & fulcrum= joint where bone moves around pivot point
effort force= from muscles–> applied to lever system at the point where tendons attach to bone serving as the lever
1st, 2nd & 3rd class levers= in OA, elbow & foot/ ankle joints
torque
=a force that acts on a body through a lever arm–> the ability of a force to cause rotation on a lever
e.g.= the weight of the ball is causing a torque on the forearm with the elbow joint as the . The size of a torque depends on several things, including the distance from the pivot point to the force that is causing the torque.
levers
made up of 3 parts: effort, load and fulcrum
effort= muscle
load= weight of body and resistance
fulcrum= joint
type 1–> extension/ flexion of skull on atlas (fulcrum in middle)
type 2–> plantar flexion of foot/ ankle on ball of foot (fulcrum, resistance, effort)
type 3–> elbow flexion (fulcrum, effort, resistance)
concave, convex roll and slide principles
convex-concave surface movement= the convex surface rolls and slides in opposite directions. EG. GH
concave-convex surface movement= the concave surface rolls and slides in the same direction. EG; Elbow
function: Helps to maintain articular surface contact
Helps to maintain joint congruity through range of movement
convex- concave examples
=the convex surface rolls and slides in opposite directions
Atlantooccipital; flexion/extension
Glenohumeral; abduction
Sternoclavicular; elevation
Wrist carpals on radial/ulnar deviation
Knee, flexion into extension (Getting up from sitting)
Knee extension into flexion (Sitting down)
Talocrural Dorsi/plantar flexion
concave- convex examples
=the concave surface rolls and slides in the same direction. EG; Elbow
Elbow, ulnar humeral joint; flexion/extension
spin examples
Glenohumeral flexion/extension
Screw home mechanism of knee on full extension.
Occipitoatlanto Joint into flexion/extension
concave= atlas, convex= occiput rolls posteriorly & slides anteriorly
occiput is active. c1 is passive
Glenohumeral joint into abduction
concave= Glenoid fossa of scapular, convex=Head of humerus, both rolls superiorly and slides inferiorly simultaneously.
The humerus spins during flexion/extension.
Scapular is fixed. Active movement is driven by humerus
Sternoclavicular Joint into abduction
concave= menubrium, convex= Proximal clavicle
Both clavicle and manubrium are passive, active movement is driven by humerus and scapular
Carpals into radial deviation
concave= radius, convex= proximal carpals
Movement driven actively by carpals, and passively allowed by distal radius and ulnar.
Elbow into flexion/extension
concave= ulnar, convex= humerus
The humerus is passive in both flexion and extension, which is driven by active movement of the ulnar and radius
knee flexion into extension (getting up from sitting)
Tibia is fixed and quadricep’s brings femur into extension.
The femur rolls anteriorly whilst sliding posteriorly.
The healthy force transmission through the patella and gradual relaxation of hamstrings to allow controlled elevation.
It is the cruciate ligaments that control the anterior/posterior slide of the tibia.
knee extension to flexion (sitting down)
First for a knee to flex it must ‘unlock’ this is done by Politeus which medially rotates knee.
It is the Tibia that is fixed and the femur that is moving.
The femur is rolling posteriorly whilst sliding anteriorly.
There is an interplay between gradual contraction of hamstrings to flex knee and gradual controlled relaxation of quadriceps group to allowed controlled descent.
It is the cruciate ligaments that control the anterior/posterior slide of the tibia.
Talocrural into plantar and dorsi flexion
concave= tibia, convex= talus
During dorsi flexion, the talus rolls anteriorly whilst it slides posteriorly on the calcaneum.
During plantar flexion, the talus rolls posteriorly and simultaneously slides anteriorly on calcaneum
Screw-Home mechanism of Knee
Stabilising mechanism for tibiofemoral joint during extension.
Requires 10 degrees of external rotation during the last 30 degrees of extension.
It is mechanically linked to extension and flexion of knee and cannot be performed independently.
It maximizes overall contact area of adult knee.
Thus, favouring joint congruence and stability.
Remember Popliteus is the muscles that ‘unlocks’ the knee, prior to locomotion
movement of a a joint perspectives
- Proximal on distal eg: femur on tibia during flexion produced by a squat exercise
- Distal on proximal eg tibia on femur during extension during a kick in football
form and force closure
=uses the shape of one bone in relation to bones to provide stability to the surrounding joints
For mobility to occur further joint compression and stabilisation is required to withstand a vertical load.
Force closure is the term used to describe the other forces such as the ligaments and muscles acting across the joint to create stability.
Examples of this mechanism are the SIJ, talus and cuboid of the ankle and foot.
types of movements
Concentric= the muscle tension rises to meet the resistance then remains stable as the muscle shortens
Eccentric= slow, lengthening muscle contractions
Isometric= tightening (contractions) of a specific muscle or group of muscles
Movers are large muscles such as deltoid and will be able to move a whole limb
Stabilisers are small muscles that control the range of movement and accessory movements.
Open Chain exercises–> End of the chain is unattached, EG, bicep curl, dumbbell press
Closed chain exercise–> Both ends of the chain are fixed, EG: Squats
force coupling around a pivot point
=2 opposing forces rotating around a pivot point.
There are multiple forces at any given moment. These can be equal or unequal, depending on the function required and balance of moving elements such as muscles and balance of stabilising elements such as ligaments.
An example of force coupling around a pivot point is the balance of position of the pelvis around S2 and the hip joint. Excessive contraction of Psoas muscle will lead to an anterior rotation of pelvis, excessive contraction of the hamstring group will lead to a posterior rotation of the pelvis.
Another example of Force coupling is the scapula-humeral rhythm.
