Biomechanics Flashcards
Galileo Galilei
Interested in structure of bones
Animals’ with large mass bones increase in girth (theorized adaptation to load bearing)
Suggested that bones are hollow for this affords maximum strength with minimum weight
Giovanni Alfonso Borelli
Studied walking, running, jumping, and piston action of the heart within a mechanical framework
Determined position of the center of gravity
Calculated and measured inspired and expired air volumes
Showed that inspiration is muscle driven and expiration is due to tissue elasticity
Andrew Taylor Still
Frontier minister, Doctor, farmer, millwright
Applied principles of mechanics to human afflictions
Structure
Three-dimensional and respond to applied forces, and to motion, in each dimension
Function
Different types of structures respond to forces applied to them differently
Levers
Most common
Torque and length
1st class: head (OA joint)
2nd class: toe off
3rd class: elbow flexion (most common)
Wheel-Axles
Function essentially as a form of a lever
Pulleys
Single pulleys function to change effective direction of force application
Joint Motion
Muscle contraction
Drawing a distal segment more proximal
Distal segment will rotate about the center of the joint
Muscle contraction effectively mobilizes one segment of the involved structures while simultaneously stabilizing another
Relaxation
As the matrix of the segment reaches equilibrium or a neutral position the load necessary to maintain the length of the segment will decrease
aka flexibility
Important to balance with strength to maintain an effective, full ROM of the joint
Relative Motions of Joints Surfaces
Gliding Rolling Spin Compress Distract
Strength
Amount of force needed to contract a muscle
Dependent on degree of resistance (aka load) experienced
Produces a rotation (torque)
Center or rotation, fulcrum or axis, is created at the point of muscle insertion
The Moment
Force being applied plus the moment arm
Force x distance
Used to overcome the resistance on the distal limb
Exerts a moment into the joint
Moment Arm
The distance from the center of the joint to where the contracting muscle is attached
Joint Reaction Force
Sum of the separate moments, together with the force of the contracting muscle directed into the joint
Applies a stress to the joint during movement
Stiffness
Amount of force necessary to bend an object
Viscosity of a Tissue
Related to its’ water content
Rapid stretch: increased resistance
Slower stretch: less resistance = creep
Stress
Force acted upon a structure
- tension - acts to stretch
- compression
- shearing - acts parallel to the surface
- bending - acts to fold about an axis
- torsion - twists about an axis
Load
Sum of all stresses on an object
Tissue deformation can result from mechanical loading
Applied Force: External
Pressure applied to an object at rest (manipulative thrust)
Moving object require no force
Magnitude and combination of vectors leads to a resultant applied force
Produced from outside the body and originate from: gravity, inertia, direct contact
Applied Force: Internal
Force generated to achieve limb movement
Ex: muscle contraction
Muscular, joint, and skeletal actions of hate body during the execution of a given task
Only muscles can actively generate internal force
Tension in tendons, connective tissue, ligaments, and joint capsules may generate passive internal forces
Excessive cumulative internal forces can: fracture bones, dislocate joints, disrupted muscles and connective tissues
Ground Reaction Forces (GRF)
Force exerted by the ground on a body in contact with the ground
Vertical Load
Summarize weight transmitted through the kinetic chain to the ground
Friction
Force that results from the resistance between surfaces of two objects from moving upon one another
Strain
Magnitude of the force applied to the insertion or the muscle at the bone
Results in a compensatory change in the shape or deformation of the bone
Deformation
Lost resiliency of the structure
A recurrent or persistent load is necessary to maintain a constant deformation
Static
Study of systems that are Ina constant state of motion
Involve all forces acting on a body being in balance resulting in the body being in equilibrium
Dynamic
Study of systems in motion with acceleration
System in acceleration is unbalanced to to unequal forces acting on the body
Kinematics
Description of motion and includes consideration of time, displacement, velocity, acceleration, and space factors of a system’s motion
Kinetics
Study of forces associated with the motion of a body
Balance
Ability to control equilibrium, either static or dynamic
Equilibrium
State of zero acceleration where there is no change in the speed or direction of the body
Static equilibrium: body is at rest or completely motionless
Dynamic equilibrium: all applied and inertial forces acting on the moving body are in balance, resulting in movement with unchanged speed or direction
Stability
The resistance to a change in the body’s acceleration, disturbance of the body’s equilibrium
To control equilibrium and achieve balance stability needs t one maximized
Who defined the concept of "center of gravity"? A. Andrew Taylor Still B. Galileo Galilei C. Giovanni Alfonso Borelli D. John J. Dougherty E. Leonardo da Vinci
C. Giovanni Alfonso Borelli
Stress through the joint during movement results in a reciprocal reaction by the structures within that joint (Joint reaction force). This reaction is in direct response to which of the following contributing factors: A. Moments (length) B. Load (weight) C. Elasticity D. A & B E. A, B, & C
D. A & B
Which of the following applies a stress to the joint during movement? A. Anatomical joint lever B. Cumulative load C. Joint reaction force D. Tissue deformation
C. Joint reaction force => tissue deformation
Deformation can result in loss of: A. Range of motion B. Relaxation C. Resiliency D. Viscosity E. All of the above
E. All of the above
A slow stretch resulting in more complete expression of fluid from within the matrix is known as: A. Creep B. Force C. Friction D. Strain E. Stress
A. Creep
Tenets of Osteopathic Medicine
The body is a unit; the person is a unit of body, mind, and spirit
The body is capable of self-regulation, self-healing, and health maintenance
Structure and function are reciprocally interrelated
Rational treatment is based upon an understanding of the basic principles of body unity, self-regulation, and the interrelationship of structure and function
Primary Joint Types
Fibrous
Cartilaginous
Synovial
Cartilaginous and synovial = vast majority where motion occurs
Somatic Dysfunction
Compensatory change to maintain homeostasis => functional correction => unintentional alteration of a structural function
Hard Biomaterials
Bone
Undergo mechanical deformation
May be analyzed with the theory of linear elasticity
Can alter size, shape, and structure to withstand the stresses placed upon it
Soft Tissue Biomaterials
Usually undergo large deformations
Cartilage
Tendon
Muscle
Skin
Wolff’s Law (1870)
Bone is increased where needed and reabsorbed where it is not
Increased density/hyper trophy related to increase stresses
Decreased - condition of disuse, aging
Can lead to altered stress/strain properties of the bone
Remodeling and Adaptation: Cartilage
Trauma or abnormal wear leads to structural disruption of matrix
Loses elasticity therefore increases stiffness
Limited capacity to regenerate or repair
With repeated high stresses can lead to development of degenerative joint disease
Type I = fibrous = between bones
Type II = hyland = end of bones
Remodeling and Adaption: Ligaments and Tendons
Become stronger and stiffer with increased stress
Number and quality of collagen cross-links increase
Become weaker and less stiff with a reduction of stress
Loss of collagen
Lower deformation to fail: immobilization, aging
Remodeling and Adaption: Skeletal Muscle
Muscle fiber will have Specific Adaptation to Imposed Demands (S.A.I.D. Principle)
Remodels according to the stresses placed upon it
Hyper trophy with physical training results from increased cross section of fibers
Atrophy results from disuse or functional alteration of nerve stimulus to the muscle
Fatigue
Accumulated breakdown of the structure due to repeated application of stresses
Chronic Somatic Dysfunction Characterisics
Fibrosis (excess collagen fibers laid down)
Contracture
Skin is thin, dry, cool
Muscles may feel fibrotic
Anterior Pelvic Tilt => Lordotic Back
Pelvis tilts forward and pulls lumbar spine into lordosis
Posterior Pelvic Tilt => Flat Back
Pelvis tilts backward and pulls lumbar spine flat
Forward Shifted Pelvis => Swayback
Pelvis shifts forward and is also tilted backward
Upper trunk shifts backward to compensate
Knees are hyperextended
Osteopathic Structural Exam
Gait and station (posture)
Anterior and posterior spinal curve - scoliosis
TART findings: tenderness, asymmetry, restriction of motion, tissue texture changes
Inspection
Percussion
Palpation
Note any misalignment, asymmetry, crepitation, defects, tenderness, masses, or effusions
Range of motion: note any pain, crepitation, or contracture
Stability: note any dislocation (luxation), subluxation, or laxity
Muscle strength and tone - flaccid, cog wheel, spastic: note any atrophy, abnormal movements
A 43-year-old female presents complaining of pain on the bottom of her feet that is worse with the first few steps in the morning. The pain is at times a 7 out of 10, ibuprofen helps some as does wearing her high heels, which she reports having worn daily since she was 19. An x-ray of her feet is ordered which shows bilateral anterior calcaneal spurs. The cause is most likely from excessive altered mechanical loading from her high heels. As a result of this altered mechanical loading, which of the following changes has occurred bilaterally to her calcanei? A. Crepitance B. Deformation C. Eburnation D. Relaxation E. Viscosity
B. Deformation
Leonardo da Vinci
Recognized as the first true biomechanist
First to study anatomy in the context of mechanics
Analyzed muscle forces as acting along lines connecting origins and insertions and studied joint function
