Biomechanics webinar 1

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Webinar 1 Biomechanics:

Webinar 1 Biomechanics Gabriel Somarriba , PT, DPT, BMO, LMT

Course Overview:

Course Overview On-line lecture 12 units spread out over 14 weeks 3 Written exams (multiple choice) Average is 80%= 80x 0.6 Bulletin Board assignments, Group assignments All BB assignments are due at 11.55 pm EST on the given day. Don’t forget to include your name, BB assignment number and start with stating the question and then post your answer . Check your syllabus for deadlines. As for the length of your answer this may vary with the topic at hand. Most of the time it will take not more than 1 word document page to satisfy the criteria. Remember content is more important than the length of your paper Late assignments are subject to a grading scale point deduction, unless permission has been granted by the online instructor. In certain cases BB due dates have been moved to Sunday nights. For specific check your syllabus

Written Exams:

Written Exams All three written exams will be proctored and will take place on Thursday evenings at 7.00pm EST June 11 th July 9 th August 6 th Exam offered through ProctorU or your approved local proctor Everyone will need to email Joanna Carter for DPT or MOT administrator

Biomechanics Lab:

Biomechanics Lab 7 weekends of gross anatomy labs 3 Lab exams. Average is 90%= 90x 0.4 Prosection and dissection Imaging Lab attire and requirements will be discussed first weekend

Grading Rubric:

Grading Rubric Written exams make up 60% of students base score Lab exams make up 40% of students base score Each BB assignment is worth 20 points each at the end the total score will be converted into a percentage. >90%= 5 points, 89-80%= 4 points, 79-70%= 3 points, 69-60%= 2 points, 59-50%= 1 point.

Unit 1-Motion:

Unit 1-Motion

Newton’s Law of Motion:

Newton’s Law of Motion Newton’s first law An object stays in rest or motion unless it is acted upon by a force that changes that motion If the shoulder flexors initiate flexion at the GH joint this motion will continue until for instance the deltoid activates and abducts the arm at the GH joint .

Newton’s Law of Motion:

Newton’s Law of Motion Newton’s second law Acceleration of a body or object is proportional to the magnitude of the resultant forces acting on it and inversely proportional to the mass of the object. If during an activity you want to increase the speed of elbow flexion than greater force will be needed. If a weight is added to the hand, the mass increases and this will decelerate the motion unless more force is added.

Newton’s Law of Motion:

Newton’s Law of Motion Newton’s third law For every action there is an equal and opposite reaction between the contacting objects . If you grasp a glass of water your finger flexors will overcome the resistance to extend so they move in flexion until they reach the glass surface. The finger flexors are still applying a flexion force to hold on to the object. If the flexor forces increases the glass could break.


Force Force = mass x acceleration What is the difference between total force or unit force ? Total force = the total amount of force being applied to a surface while unit force is the force being applied per unit area on the surface. If there is a total force of 100 N on a surface of 100 mm2 then the unit force would be 100N/100mm2 = 1N/mm2 .

Loads and Stresses:

Loads and Stresses What is the difference between loads and stresses ? Loads are external forces applied to a structure while stresses are forces that occur within an object against which a load is applied . A load force (external) is transmitted into a structure producing stresses within that structure (internal) Examples of loads : your fingers apply a load on a book to hold it; a tendon applies a load to a bone to move it; your feet apply a load to the floor when standing or walking


Strain What is a strain ? Strain is the deformation of the structure due to the stress placed upon it When there is a high load(external) and the stresses (internal) are beyond the limits of a tissue for example, you will have a change in the structure called a strain. Another example: If you get rubber band (structure) and stretch it, your hand is placing a load (external) and there will be a stress (tensile) placed internally on the rubber band. If you keep stretching it to the point where the rubber band begins to fail then you will have a strain to the rubber band (structure)

Loads, Stresses, Strains :

Loads, Stresses, Strains Loads: Tension, compression, shear and others Stresses: Tension, compression, shear Strains: Tension (elongation), compression (pressure), shear ( stress in opposite direction, cutting , tearing), bending ( elongation on one side, compression on the other), torsion ( twisting, rotational shear)


What strains occur at a tendon when a tensile load is applied? When a tensile load is applied to a tendon, the tensile stresses produce tensile strain (elongation) of the tendon. At the same time, the resisting compressive stresses in the tendon produce compressive strain (contraction, squeezing) in the tendon and these two stresses produce shear stresses which produce shear strain (cutting, tearing) in the tendon. If the tensile stresses > than the compressive stresses elongation of the structure will occur.


What strains occur when a long bone is bending? The concave side of the bend shows compressive stress and strain and the convex side shows tension stress and strain. Both forces are the greatest at the periphery. Think about a green stick fracture or when you bend a relative fresh branch to breaking point. The convex side will fail before the concave side will.

What is the difference between work and power? :

What is the difference between work and power? Work= the amount of force x the distance over which that force is applied. Work has no time component! W= FxL Power= work/time P= FxL / Time

Mechanical Advantage- Pulleys:

Mechanical Advantage- Pulleys Fixed pulleys: Changes direction of the force but not the magnitude. Force is equal in each strand. Force is each strand is equal to the force of resistance Many fixed pulleys in the body. Movable pulleys: Changes the direction and magnitude of the force . Forces on the supporting strands are less than the resistive force . Can be used in combination with fixed pulleys.

Mechanical Advantage-Levers:

Mechanical Advantage-Levers Three types of levers All levers have 5 parts 1. A fulcrum, 2. weight/resistance, 3. force, 4 . weight arm, 5. force arm.


Levers Class 1 lever (see-saw): Triceps acting on elbow, erector spinae acting on the spine. Class 2 lever (wheelbarrow): Toe raises with axis at metatarsophalengeal joints


Levers Class 3 lever (most joints in the body): biceps acting on the elbow, quadriceps acting on the knee

Joint Movement:

Joint Movement Osteokinematic Visible movement of a bone as it moves about The axis of a joint in the x, y and z planes Movement of a bone as described with muscle actions and ranges of motion Examples : flexion, extension, abduction, adduction, supination, pronation Arthrokinematic Movement occurring at the articular surface of a bone as it moves about the axis of a joint Depending on the structure of the joint, arthrokinematic movement may occur in the same or opposite direction of osteokinematic movement Examples : translation (glide, slide), rotation, rotation coupled with translation (curvilinear)

Athrokinematic Motion:

Athrokinematic Motion Types Rotation Angular motion: spin, rotation along a stationary axis as in a spinning top. Curvilinear motion: rotation coupled with translation as in a rolling tire

Concave/Convex Rule :

Concave/Convex Rule CONVEX surface moving on a fixed CONCAVE surface arthrokinematic joint glide opposite osteokinematic movement example :  glenohumeral joint

Concave/Convex Rule :

Concave/Convex Rule CONCAVE surface moving on fixed CONVEX surface arthrokinematic joint glide is in the same direction as osteokinematic movement example : metacarpophalangeal joint


Questions? We will have another webinar next Wednesday I will upload these slides and send you a link to view it if you like As you read your units, if having difficulty with any topic please email me and I can incorporate into the next chat Please reach out from early on. Don ’ t fall behind THANK YOU!!!