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Biomechanics - lecture notes .docx

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Department
Kinesiology
Course
Kinesiology 2241A/B
Professor
Prof
Semester
Fall

Description
Biomechanics- Lecture Notes Lecture 1- September 9 ** not on the midterm - Kinematics: is it changing speeds, getting faster or slower- describing motion - Kinetics: forces that cause movement - Dynamics: kinetics and kinematics - Biomechanics: mechanics of structure and function - Forces o Buoyancy o Centripetal o Elasticity o Fluid drag o Fluid lift o Friction o Gravity o Muscle o Pressure o Reaction - Kinematics o Velocity- m/sec, degrees or rads/sec o Acceleration – change the velocity of change the direction o Displacement- in meters or degrees/radians o Momentum (M= mv (linear) OR (L= lw (rotary) - Efficient movement o Minimal energy expenditure o Necessary for endurance sports and repetitive tsk in labor o Allows performer to endure longer o Allows performer to preform faster with less energy expenditure - Effective movement o Not concerns with efficiency o Most appropriate movement to achieve mechanical purpose (MP) aka overall performance objective (OPO) o Appropriate sequence of movement – large muscle to small muscles Lecture 2 – September 11 - Muscles and bones can act as levers, and also the wheel axel – DO NOT NEED TO KNOW THE NAMES OF MUSLCES AND BONES The Axial Skeleton - Skull: has 29 bones - Thorax – 12 x 2 ribs + sternum - Vertebral Column: cervical – 7 bones, thoracic – 12 bones, lumbar – 5 bones - Coccyx – 4 bones Appendicular Skeleton - Upper extremities: shoulders to carpals – 32 x 2 right and left - Lower extremities – pelvis to tarsals – 31 x 2 right and left Functions of the skeleton - Protect the vital organs - Support the soft tissues - Manufacture red blood cells - Reservoir for minerals- calcium and phosphate - Attachment for muscles - Levers and pulleys for muscle torque – foul shot, classic lever system- flexion in the foot, shoulder and slightly in the hips (flexion and extension motions are lever type motions) - Throwing a ball- pulley system, as your arm rotates and snaps the bone (humerus) is rotating along its lateral axis and the arm is the wheel - Wheel axel kick (come around the planted leg) will get much more velocity than a lever system straight flexion in the hip and extension in the knee Physical Stress on Bones - Compression – pressing together (can lead to stress fractures) - Tension- pulling apart - Torsion – twisting - Shear- tearing across - If the stress is concentrated in one area, more likely to get injury Forces acting on players - 1. Racket weight - 2. Air resistance - 3. Ball impact - 4. Stoke type o Flat stoke and top spin stroke - When the ball is hit with top spin, the ball will drop because of the direction of the spin – greater serve (harder and faster) Harnesses, Ropes, Pads - Ligaments: act like a harness o Provide control guide path of motion - Tendons act like a rope being pulled o Transmit the load - Cartilages: act like pads o Absorb impact, restrict friction Properties of tendons and ligaments - Elasticity – tissues ability to stretch and return to its original length - Elastic limit- point of no return to original length - Plasticity- tissues stretched beyond the elastic limit (stays lengthened) - Ligaments keep are joint stable, if they are compromised, other systems need to stabilize the joints (extra strain on the muscle) It’s been a long time Baby - Injury to ligament or tendon takes a long time to heal - Limited vascularization In ligaments and tendons - Ligament is comprised of 70% water - Ligaments don’t have the greatest blood supply, this is why they take so long to heal Factors – Stability of articulation - Bone Arrangement o Strong = one fits into other (knee elbow joints) - Ligament arrangement- quality and quantity - Muscle arrangement – stabilizing lines of force - Laxity in a joint allows for mobility lateral motions a buffer zone to handle large stress ROM Factors - Shape of Articulation- elbow versus shoulder - Tightness of Muscles and Ligaments - Size od adjacent tissue- muscle, adipose - Restrictive clothing/equipment/devices Lecture 3 and 4 – September 13/16 Spatial frame of reference - X o Parallel to the ground o Defines main motion (tossing a ball) o Forward (+) and backward (-) directions o Perpendicular to Y direction - Y o Parallel to the ground o Left (+) and right (-) directions o Perpendicular to X direction - Z o Perpendicular to the ground o Upward (+) and downward (-) directions o If you threw a ball with a high arch, it would be travelling primarily in the X and Z axis (negative/ positive/ upward/ downward) Linear and Rotary Motion - Linear o Motion in the line of a path o 1. Rectilinear (straight line path, dropped ball) o 2. Curvilinear (curved line path, discus flight) – direction is constantly changing - Rotary Motion o Motion rotates due to a fixed point o 1. Fixed point (axis of rotation) – could be attached to an axel o 2. Radius of Rotation (distance from any point to axis) Planes and Axes - Plane o A flat surface that divides body or segment - Axis o A pin or axle about which a body or segment rotates - Movement occurs in a plane about an AXIS that is perpendicular to that plane - Motion of the human body can be described using three planes (talking about the body you can say (in the anatomical position), you can describe it using these three planes o 1. Sagittal: left and right o Frontal: front and back o Transverse: top and bottom - Each panes has an associated axis Sagittal Plane - Divides the left and the right - Perpendicular axis: o Mediolateral o Medio-lateral o M-L o IT WILL ALWAYS BE THE SAME AXIS (FOLLOW SAGITTAL WITH M-L) Sagittal Plane Movement about M-L axis - Dorsiflexion - lifting foot’s upper surface toward shin bone - Plantar Flexion - depressing foot, pointing toes/foot away from shin - Flexion - a bending, decreases angle between adjacent bones - Extension - a straightening, increases angle between adjacent bones - Hyperextension - bending joint beyond straight anatomical position (just like hyperextension of elbow) - Transverse Flexion ** can happen at the shoulder and the hip because they have multiple axis o Abduct shoulder/hip to parallel then move arm/leg medially (inward) – hold arm out move toward the front of your body - Transverse Extension ** can happen at the shoulder and the hip because they have multiple axis o From a position of Transverse Flexion, move arm/leg laterally (outward) – hold arm out and move toward the outside of the body - Any of these motions occur in rotation of the M-L axis - ** Called transverse in the sagittal because the bone is still in the sagittal plane, but then move the transverse plane Frontal Plane - Divides the front and back - Perpendicular axis o Anteriorposterior o A-P Front Plane Movements about A-P axis - Abduction – moving limb away from the mid-line of the body - Adduction – moving limb toward the mid-line of the body - Depression – moving shoulder/jaw downward from an elevated position - Elevation – moving shoulder/ jaw upward (shrug shoulders) - Lateral Flexion – bending the trunk laterally away from the mid-line - Radial flexion – moving hand laterally outward toward radius - Ulnar Flex – moving the hand medially toward ulnar bone - Transverse abduction – flex shoulder/hip until arm/leg reaches parallel to ground then move arm leg laterally outward (up out in front then move toward the back) - Transverse adduction – from transverse abduction position move segment medially inward (move from the back to the front) Transverse Plane - Divides the top and bottom - Perpendicular axis o Longitudinal Transverse Plane movements: longitudinal - Eversion - moving foot so that sole is turned laterally outward ** only in the foot - Inversion - moving foot so that sole is turned medially inward ** only in the foot - Lateral Rotation – turning bone outward about its long axis - Medial Rotation – turning inward of bone about its long axis - Transverse Rotation - rotate trunk to left or right - Pronation - rotating hand medially so palm faces posterior - Supination - rotating hand laterally so palm faces anterior – making a soup bowl ** only in the radial ulnar joint - Protraction - moving either shoulder or chin forward (reach) ** only in the radial ulnar joint - Retraction - moving either shoulder or chin back (“square” your shoulders) ** Throwing motion is a medial rotation of the shoulder joint Anthropometrics - Size, shape, proportions - Stoutness – Ponderal index, BMI - ECTO- thin - ENDO- fat - MESO – thick/muscular You can’t Judge a Book by its Cover - Average NBA player height 6’7” *2m01+ - Since 1970 in NBA: Muggsy Bogues 5’3 1m60 1987-2001 Earl Boykins 5’5 1m65 1998-2006 - Spud Webb 5’7 1m70 1985-1998 Greg Grant 5’7 1m70 1989-1996 Keith Jennings 5’7 1m70 1992-1995 Monte Tower 5’7 1m70 1977 Charlie Criss 5’8 1m73 1978-1985 Calvin Murphy 5’9 1m75 1970-1983 Yuta Tabuse 5’9 1m75 2005 Nate Robinson 5’9 1m75 2006 Lecture 5 – September 18 Muscle Properties - Muscle are force producers - Irritability - stimulation - Conductivity – wave - Contractility – tension - Dispensability – stretching - Elasticity – recoil ability Quality of muscles - Flexibility - ROM - Strength - Tension - Power – Fv = (force/linear velocity) (change direction quickly, throw hard, jump high) - Endurance - Repeated/sustained = ability of muscle to sustain movements - Just because someone is strong, doesn’t meant that they are powerful’ - It depends on the composition of your muscles – how powerful you are depends on how many fast twitch muscles you have Skeletal Muscle Anatomy - Two attachment points o Origin o Insertion Fiber Arrangements - Fusiform – longitudinal - Pennate – oblique angle Muscle and Articulation - Uniarticulate - Biarticulate – i.e. knee and hip joints (hams and quads) - Multiarticulate – i.e. Elbow/radioulnar/wrist/hand joints (flexor digatorum profundus) - Active insufficiency – contracting limitation – when you ask two joints to contract at the same time (knee and the hip) **BOOK PAGE 57 - Passive insufficiency – is a stretching limitation Reciprocal innervation - Agonist - Antagonist Muscular Tension Types - Static – isometric (same length) - There is a lot of tension in the muscle, but there is no movement - Dynamic o Concentric – used when standing up? ** o Eccentric - used to control motion (want to sit down slowly, lowering a weight when doing a bicep curl, you don’t just let it drop) Question page 60 FIGURE ON PAGE 61  Articulation/joint - knee  Motion name – extension and flexion  Motive Force – lifting weight –muscle, lowering it - weight  Resistive Force – the weight and gravity, when lowering it – muscle  Contraction Type – lifting - concentric, lowering – eccentric  Stabilized Area – we stabilize our trunk and thigh Lecture 6 – September 20 Factors affecting Muscle force - Fiber type –fg, fog, so - # Of units stimulated - Frequency of frings - Temperature - Elasticity - Length/tension - Force/velocity - Power (P=Fv) - Angle of pull Muscle Fiber Types # 1 - FG - Fast Glycolytic - High force, low aerobic - FOG -fast oxidative glycolytic - People that are stronger and are more powerful tend to have more of these - High force, medium aerobic SO - slow oxidative - Low force, high aerobic Number of units stimulated #2 - Force increased as the number of motor units being stimulated increases - Sstndard ndder or recruitment of fibers - 1 SO, 2 FOG, last recruitment are FG Frequency of firing #3 - Generally as the frequency of nerve stimuli increases in the motor units, the force increases - Highest level of force achieved in long length muscles at lower levels of firing frequency Muscle Temperature #4 - Warmth deep in the muscle allows for faster contraction we as well as faster relaxation - Warm muscles has less resistance to quick changes in length Elasticity #5 - 1 : tension developed in muscle - 2 : muscle is quickly stretched then shortened - Net result = INCREASED force - Examples: o Windup, impact on landing before takeoff - Elastic energy is best used in power activities - When we want to increase power in an activity, we recruit more elastic fibers - When you jump into a jump  when you land you flex both your knees and your hips, so your hip and knee extensors are flexed Length/tension #6 - Direct relationship - Resting length or slightly stretched = increased forced - Shortened state = decreased force (less F generated) - Muscle at its resting length can generate more force than when it is stretched - It is not completely direct Force/velocity #7 - Indirect relationship - As speed of contraction increases - Force of contraction decreases - Example heavy loads – wont be able to move it fast because you will not generate enough force Power #8 - P = Fv - Trade off between F and V - Approx. 30% of max. Contraction speed results in most power - Power = is strength (force) times the speed (linear velocity) - **Difference between force and power Angle of Pull #9 - 90 degree angle = 100% rotary - Less than 90 degree angle = more stabilizing - More than 90 degrees angle = more dislocating - When a muscle is pulling on a bone at 90 degrees – 100% rotary (more force) - But as stated before, when the muscle is shortening, you lose force, but gain angle of pull - There are certain angles where you are stronger - Changes throughout a motion - Understand frequency of fire, elastic properties of muscles, understand length tension relationship, know the force velocity relationship, understand the difference between strength and power Proprioceptors - Internal receptors - In and around joints - Near skin - Inner ear - Perceive body’s movements and positions - When the body is moving or even still – proprioceptors tell us what is going on - Example – standing on one foot with your eyes closed, you still know what is going on Golgi tendon organs - Located in the tendon area - Stretch activates two things: o 1. Inhibits contraction of agonist o 2. Facilities contraction of antagonist - PNF (proprioceptive neuromuscular facilitation) have them stretch, then so an isometric contraction (they push against you as you push against them) = increase the stretch Muscle Spindles - Located throughout the entire muscle (belly of the muscle) - They detect stretch - Stretch = promotes contraction of agonist o Inhibits antagonist contraction o E.g. knee jerk, windup in throwing/striking Lecture 7 – September 23 Force Define - Push or pull - Rub - Blow or impact - G - Causes change in motion or shape of a body o Not all the time – when you are standing sill, apply force to the ground, but not changing shape Kinetics – Forces - Buoyancy o Some times this is sufficient to keep you a float – depending on your body composition - Centripetal o Force that we need to keep a body traveling in a circular force - Elastic o Certain objects are more elastic than others - Fluid Drag - Fluid Lift - Friction o If you do not have sufficient friction you will fall - Gravity - Muscle o Force producers - Pressure - Reaction Properties of a force - 1. Magnitude o Summation of all the forces applied on an object (example a foul shot you use wrist flexion, elbow flexion etc.) - 2. Direction - 3. Point of Application o Where your hand is applying force to the ball - 4. Line of Action o Could be through the center of gravity of the ball – could be eccentric to the ball (outside the ball) Mass - Scalar Quantity - Common to solids, liquids, gases - Measure of inertia - Direct relationship between mass and inertia - Mass and size NOT always direct - Mass is NOT a force (measure in weight) Weight - Vector o Means that it has a direction - Weigh is a force - Measure of force of g pulling down - Direct relationship between weight and mass Volume - Space that na object occupies - Length, width, height - No relationship with mass - Objects of similar volume but different mass Density - Compactness of a body or object - Mass per unit of volume - Example o Water = 9.90 newton’s per liter o Air = 0.01 newton’s per liter Center of Gravity - Center of mass of an object or body - Point where mass is concentrated - Balance point - See figure C.2 on page 82 - Tooth pick on the rim of the glass Vectors - This could be when you are going for a spike in volleyball  - Just a symbol - example in the first just draw the two together, white it the result Vector Composition - Identify resultant magnitude and direction - You know the horizontal and vertical but not the resultant - E.g. net force, velocity, acceleration etc. - Using trigonometry - E.g. Pythagorean theorem Vector Resolution - Resultant is KNOWN - Find the 2 components that comprise R - Steps: o 1. Draw given vector to a selected scale o 2. From vector tail, draw horizontal like and perpendicular line o 3. From head, connect lines to form a rectangle Lecture 8 – September 25 Action/Reaction Forces - Body segments exert a force - Environment delivers reaction force - Newton’s third law - For every force applied on a body - That body applies an equal and opposite force - Example if you are hitting a tennis ball with a racket – the racket has a certain velocity, coming toward the ball, and the ball has a reactive force coming against the racket - T= F x FA - F is a board reaction - FA is d  (force arm) - T is board recoil time - In the example above with the diving board – there is an elastic force coming from the board - In this case gravity is a resistance force - Another force is obviously your muscle – cant do the motion with out flexing your hip, knee and plantar flexing your foot Internal Forces - Within defined body - Body free of support - Muscle contractions change bod shape - C of g position NOT changed External forces - Outside body defined - Body contact - Muscle contractions change body composition - C of g position CHAGNED Motive forces - Cause motion - Muscle pull of gravity buoyancy - Concentric contraction - Friction - Fluid lift Resistive forces - Opposite/resist motion - Muscle, connective tissue - Eccentric contraction - Friction - Fluid drag Force and pressure - Force – push, pull, blow, rub that changes a body’s motion or shape - Pressure – amount of force acting over area - P and F direct relationship, p and A indirect - F is the given force - A = as the are increases, P will go down - A = as this decreases P will go up Friction force - Force created between 2 contracting surfaces - Can be a motive or a resistive force - Texture of surfaces (rough = more friction) - Force pressing together the 2 surfaces - Size of surface are not a factor - High coefficient of friction = low slippage Centripetal Force - Center seeking - Forces rotating body to stay on a circular path - If Fc is insufficient, body will leave path on a tangent - The top has a direct relationship with Fc, the bottom has an indirect relationship - You will not run as fast on a curve – some of this fore is used to keep you on the curve (outward force) - You will run faster on a wider radius track, because when you have a tight curve, you have to expend energy to stay on the curve - When you run a curve, you are no longer on a perpendicular line with the ground, muscle expel energy to stay on the curve - You are pushing outward to get a reaction force inward - inward seeking force Elastic Force - Recoil ability - Measure of how quickly reformation follows deformation - Coefficient of elasticity = square root of rebound ht/dropped ht - High e = faster reforming - Example .83 of coefficient of elasticity (dropped from one meter) - it will rebound to 83 percent of its original height – example with a tennis ball Buoyancy force  Figure E.21 page 127 - Upward life force on a body immersed in a fluid - Archimedes principle - Reason why people will not always float, it because the center of gravity and are center of buoyancy is not in line with one another, one is above the other – you need to move your center of gravity up, to be inline with your center of buoyancy then you will float - Upward buoyant F = wt volume of water displaced - Negative buoyancy – body wt. greater than the wt. of the volume of water displaced Power - P = Force x Velocity - Power movements – change directions quickly (apply huge force to over come the inertia of their body, force needs to be large, and it needs to be done quickly) - Force by itself will cause linear motion - Torque – force that causes something to rotate - P = Force x Distance/time Energy: the ability to do work - Kinds of energy o 1. Chemical o 2. Electrical o 3. Heat o 4. Mechanical - 3 types of mechanical E o 1. Elastic o 2. Gravity – potential: when you hold a tennis ball higher, it has more potential energy then if you were to hold it closer to the ground – you are giving it more acceleration o 3. Kinetic – forces that are applied to an object Lecture 9 – September 27 Torque defined - A force applied to a system restricted to moving in a circular path - Causes a system/body to rotate - The point of application is eccentric - T = F x FA - Torque is more than just a force – it has a force arm and will cause rotation - The strength of the contraction is the force - Force arm is the perpendicular distance from the axis of rotation to the action line of the force - Example – holding a weight – need to produce greater force in the muscle than the resistive force (the weight) – concentric movement - When can the muscle be a resistive torque? When the movement is eccentric (control the motion going down) - Torque doesn’t stay constant when you are contracting he perpendicular line of the force arm is constantly changing Muscle Torques - 1. Magnitude – product of F X FA o How strong is that contraction o The length of a vector symbolizes the magnitude - 2. Direction – angle of pull on bone o Angle at which the muscle is pulling on the bone o Independent of a joint angle o End of thee vector (the arrow head) - 3. Line of action – vector direction o Vector is a straight line that symbolizes something - 4. Point of application – attachment to bone o Where the muscle is pulling on the bone FA: Force Arm - Shortest distance from axis of rotation to the line of action of the applied force - () Perpendicular to line of action Teeter – totter - Axis of rotation - 2 forces - 2 force arms - Example two people with different weights, the smaller person must have a much larger force arm in order to balance the weight See FIG 9-30 page 296 - The axis of rotation Is in the lumbar area - From each spot on the body – resistive torques that you have to overcome to lift the object (head, trunk object all have their own resistive properties that you must overcome with a small force arm) - If you bring the object closer you minimize the amount of resistive forces – better for your back Calculating torque - Force measured in newton’s - Force arm measured in meters - Torque measured in meters (Nm) Figure E.11 page 118 - Sum up all torques on each side of the axis - Side of axis with the lager sum of T determines direction of movement - T= F x FA - F is board reaction - FA is D Perpendicular - T is board recoil time Angular Motion Vectors - There are both kinetic and kinematic vectors - A vector is represented by a straight line arrow symbol - The length of the arrows is the magnitude - The orientation of the arrow is the direction - To get a straight line vector for angular motion, the right hand thumb rule is used - How do you draw a vector and know is angular velocity (how fast is it rotating?) Right hand thumb rule - Method of determining vector direction for angular motion - Curve fingers of right hand in the direction of the torque - Right thumb points in vector direction of the motion, perpendicular to the actual direction of the spin Center of Buoyancy - C of B (center of buoyancy) is the location of the C of G (center of gravity) of the volume of water displaced by an immersed body - There is no T (Torque) when the persons CB is aligned with her/his CG - When CB is co-linear with CG, the body will float and not rotate - EXAMPLES ARE ON PAGE 127 Lecture 10 – September 30 Equilibrium - A state - All forces/torques in all direction cancel oΣF = 0 / ΣT = 0 - A body/system that is not accelerating - When you walk – your arms are not in equilibrium, they are in rotary motion, it is constantly changing velocities - Static equilibrium o Not moving - Dynamic equilibrium o Moving o No change in velocity o No change in direction - Acceleration – not constant, the velocity is getting faster - Deceleration (negative velocity) it is getting slower - The greatest velocity will be just after propulsion, because after that the only thing acting on the object is resistive forces - once it changes direction and starts to fall it will accelerate again due to gravity Balance - A process – a number of sensory devices to help with balance - Control/maintain equilibrium - Use of inner ear and proprioceptors Stability - A state (either stable or not) - Resistance of a body/system to disruption of equilibrium - Linear o Resistance to acceleration o Directly related to Ft required to upset equilibrium o Depends on  Mass and friction o Pirouette – because they are decelerating and acceleration staying in a straight line - Rotary o Resistance to tipping o Resistance to a change in angular momentum o Depends on  Size of the B.O.S  Action line of gravity  Height of the c of g  Direction of tip force o Somersaulting diver – because they are constantly accelerating (c of g is travelling in a linear motion) - Do not want stability when you are sprinting 3 states of rotary equilibrium - Stable – c of g well inside B.O.S - Unstable – c of g close to edge of the B.O.S - Neutral – spherical object on a level surface B.O.S – Base of support - Outermost limits of contracting surfaces - Region bounded by a body part in contact with a surface - The applied force of the body/part receives a reaction force from the surface of contact - Width of your feet (athletic stance) Balance factors - Mass/weight of body part (the more massive the harder to move) - Height of c of g of body or part (lower the c of g – more stable) - Size of B.O.S of body or part (larger – stable) - Magnitude of friction that determines “sticking to form axis of rotation - Net Tt applied to body or part Standing on a slope - As slope angle increases: 1. Perpendicular F normal pressing bod to hill decreases 2. Parallel component of F weight in the direction of slope increases Common “athletic stance” - Feet spread apart – lateral stability - Feet staggered – forward/backward stability - Lower body of c of g – rotary stability - If you do not stagger you are unstable from forces coming at you from the front or back Pushing/pulling loads - Pulling with some upward life reduced load friction and increases feet friction - High friction load = pull with short rope - Low friction load = pull with long rope - Is it better to push or pull a load when your center of gravity is higher than the load? o Better to Pull o Pulling - you are pulling on a slight angle, so it has both a vertical and horizontal component. The vertical component un weights the load (reducing friction) making it easier to move o Pushing – pushing the load down into the ground increasing friction making it harder Safe lifting - Can I do it? - B.O.S as close as possible to load - Stabilize vertebral column in upright position with a natural curve - Lower body to load using hip/knee flexion - Raise load using hip/knee extension Starting and stopping - Starting o
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