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Fundamentals of Biomechanics (KP 251)

Biomechanics Final Exam Key Terms and Concepts

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-The essential feature of a FBD is the isolation of the system or body or the body under
consideration and the inclusion of all forces which act ON the body
Development of a FBD
- The FBD is achieved bu a specific order of steps:
-Step 1: place “cuts at the region of interest to separate from the rest of the body /
system
-Step 2: define a reference system
-Step 3: Put on weight forces
-Step 4: include all external forces acting on the segment – including unknown forces and
moments
-Step 5: check if all forces that are acting on the object are shown on the FBD and that
the segment is really isolated and free
-Step 6: If step 5 is satisfactory, apply equilibrium equations and solve for unknown
forces and moments
-
Σ F=ma
OR
Σ M =Ia
-
if static a=α=0
Steps for solving a FBD
- assumptions
a) static (no movement)
b) all forces are acting in the same 2D plane (x, y)
c) joints are considered hinge joints
d) muscles under consideration are represented as single muscle equivalent
e) unknown forces are acting in the positive direction
- Define equations
1.
Σ M =0
2.
Σ Fx=0
3.
ΣFy=0
- Sub in what is known and solve for unknowns

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Biomechanics Final Exam Terms

Kinematics In sport - Glow puck in hockey o Was introduced so people could follow the hockey puck  Didn’t last long because Canadians hated it

Video: The math behind basketball’s wildest moves - Sports carry the most data about movements - Teach the machine to see with the eyes of a coach - Spatiotemporal pattern recognition: figuring out all relationships with relative and absolute location, distance, timing, and velocities o Take a shot and turn it into quality of shot and quality of shooter

Kinematics - Kinematics: Description of motion of a body in terms of displacement, velocity, and acceleration – without reference to force causing motion - Anatomic Position: standing upright on a horizontal surface with arms hanging down at the sides of the body, palms turned forward and head erect - Any plane dividing a human body into left and right is called a sagittal plane o Sagittal plane is positioned in anteroposterior direction - If a plane divides the body into two symmetrical halves, it is called the cardinal, or principal sagittal plane - For bodies in an upright posture, the horizontal plane passing through the body is called the transverse plane - Frontal or coronal plane divides the body into anterior and posterior sections - Coordinates are a set of numbers that locate a point in a reference system - Cartesian reference systems are the preferred choice and have been used more commonly

The Coordinate Method - The description is performed in three steps: o A global reference system of coordinates is defined; o Any one-point P on the body Is specified; and o The location of this point, in the global reference system, is determined

Data Collection: - Need a camera (high speed) - Markers – must be on boney markings - Define global reference system to something relevant within your study

Linear kinematics - Position o The position of a n object refers to its location in space relative to some reference o Units of length are used to measure the position of an object from a reference axis - Motion occurs when an object or body changes position – is sometimes thought of progressive change of position over a period of time - Displacement is measured in a straight line from one point to the successive position. The distance an object travels may or may not be a straight line

Velocity - When the concepts of displacement and time are combined, velocity is concerned - velocity is a vector quantity defined as the rate of change in position - Slope of a line indicates the relationship between two parameters, in this case, displacement and time, which results in velocity - Calculating velocity from displacement - -

First Central Difference Method

Instantaneous Velocity

Visual Estimation of Velocity

Visual estimation of acceleration

Angular Kinematics

Angular motion - All parts of a body move through the same angle but do not undergo the same linear displacement - Angular motion will occur about an axis of rotation

Relative joint Angles - Relative joint angle is the angle between two longitudinal axes of two segments - This will not describe the position of the segment in space - Three points of interest needed – proximal, vertex, and distal points o Always needed in order to calculate a relative joint angle

Calculating Relative joint - Relative angles are calculated using cosine law - In order to calculate this angle you will also need the length of each segment o C squared = a squared plus b squared

Absolute Angles - Absolute angles: the angle of inclination of. A body segment relative to some fixed reference in the environment - Two points of interest needed – proximal and distal points - The angle calculated relative to right horizontal is called the segment angle

Calculating Absolute Angles

Ankle Angular Motion - Knee, ankle, toe - Formula: o Angle= 90- relative angle of ankle

Rearfoot Angles

Gait Cycle Timing - Demonstrates gait disorders o Asymmetry  Spend more support time on one leg than the other o Abnormal cadence  How many steps per minute o Improper time in double or single stance - Risk of falling (trip or skid) – stability o Elderly population

Foot Contact Kinematics

Gait parameters - Stride length – distance between successive points of initial contact of the same foot - Step length – distance between the point of initial contact of one foot and the point of initial contact of the opposite foot o 2 steps in stride, right and left step length – distance covered - Step Width – lateral distance between successive points of opposite feet - Foot angle – describes an angle between the line of progression and a line drawn between the midpoints of the calcaneus and the second metatarsal head

o Pigeon toed (toes pointing inward), pointing out?

Walking vs. running - To increase velocity we can either o Increase stride length o Increase cadence

Centre of Mass Anthropometrics

Centre of Mass: considered the point about which the body I evenly distributed - Individuals body wight is product of their mass and the acceleration due to gravity

Center of gravity - Body weight vector originates at point referred to as the centre of gravity o The point about which all particles of the body are evenly distributed

The moments about point A and are equal about point C, therefore C can be considered the COM

Calculate COM location: - You can calculate the location without coordinates - EG. If you know the length of the led segment is 0 a) COM/segment length ratio is 0 from the proximal end b) Location of COM = (0)(0) = 0

Calculate Segment Mass: - EG. If you know the mass of the individual is 60kg a) Segment weight/Total body weight for the leg is 0. b) 60kg x 0 = 2 kg

Free Body Diagrams - Free Body diagrams is the link between the complexity of the human situation and the application of the limited, although powerful, techniques of mechanics - The essential feature of a FBD is the isolation of the system or body or the body under consideration and the inclusion of all forces which act ON the body

Development of a FBD - The FBD is achieved bu a specific order of steps: - Step 1: place “cuts at the region of interest to separate from the rest of the body / system - Step 2: define a reference system - Step 3: Put on weight forces - Step 4: include all external forces acting on the segment – including unknown forces and moments - Step 5: check if all forces that are acting on the object are shown on the FBD and that the segment is really isolated and free - Step 6: If step 5 is satisfactory, apply equilibrium equations and solve for unknown forces and moments - OR - Steps for solving a FBD

  • assumptions a) static (no movement) b) all forces are acting in the same 2D plane (x, y) c) joints are considered hinge joints d) muscles under consideration are represented as single muscle equivalent e) unknown forces are acting in the positive direction
  • Define equations 1. 2. 3.
  • Sub in what is known and solve for unknowns