Transcript Document
Basic Biomechanics • Mechanics-study of forces and motions produced by their action. • Biomechanics-apply that to the structure and function of the human body. Basic Biomechanics • Statics deal with factors associated with nonmoving. • Dynamics deal with moving systems – Kinetics are the forces causing the motion – Kinematics are time, space and mass of the moving system. Basic Biomechanics • Kinematics– Osteokinematics bones moving in space in regard to joint surface (flexion) – Arthrokinematics are the manner in which joint surfaces move in relation to each other.(concave) Basic Biomechanics • Vector- quantity having both magnitude and direction – Force-push or pull action – You throw a ball with direction and speed Basic Biomechanics • Scalar- has only magnitude. – Length, area, volume, mass – Mass is the amount of matter a body contains. – Inertia is change in motion in either speed or direction. Basic Biomechanics • Law of Inertia- an object at rest tends to stay at rest, and an object in motion tends to stay in motion. Basic Biomechanics • Think about what happens with your head in a car. It is not in motion, so when acceleration/deceleration happen your neck is not always happy. Basic Biomechanics • Law of Acceleration-the amount of acceleration depends on the strength of the force applied to an object. Basic Biomechanics • Acceleration is inversely proportional to the mass of an object. – If you roll a soccer ball , then a bowling ball, with the same force, the heavier object will not travel as far. Basic Biomechanics • Law of action-reaction- every action there is an equal and opposite reaction. – Strength of reaction is equal to strength of action, just in the opposite direction. – Harder you jump harder you rebound. Basic Biomechanics • Go outside and create a demonstration of one of the laws of physics for us all to understand. Basic Biomechanics • Force (a vector describe magnitude and direction – Linear force- 2 forces act on the same line in the same direction or opposite direction. or Basic Biomechanics • Parallel Forces– In the same plane and in the same or opposite directions. Basic Biomechanics • Concurrent Forces- two or more forces act from the same common point but pull in different directions Basic Biomechanics • Force Couple- two forces act in an equal but opposite direction resulting in a turning effect. Torque • – Angle of Pull: angle between muscle insertion and bone on which it inserts. – Angular Force: force of a muscle contributing to bone's movement around a joint axis; greatest when muscles angle of pull is perpendicular to bone (i.e. 90 degrees). Stabilizing force: degree of parallel forces generated on the lever (bone and joint) when the muscles angle of pull is less than 90 degrees. Dislocating force: degree of parallel forces generated on the lever (bone and joint) when the muscle's angle of pull is greater than 90 degrees. Components of Force – – Basic Biomechanics • State of equilibrium- all torques actin on it are even. • Center of gravity- COG-balance point of an object at which torque on all sides are equal. Basic Biomechanics • Base of support is that part of the body that is in contact with the supporting surface. (BOS) • Line of gravity is the imaginary vertical line that passes through the COG to center of earth. (LOG) • Draw this in your notes pg 78 Basic Biomechanics • Equilibriums – Sable- to disturb you would have to raise COG – Unstable- only slight force needed to disturb – Neutral- COG is not raise or lowered to disturb. – Lower COG is more stable. Basic Biomechanics • The closer COG is to center of BOS the more stable you will be Basic Biomechanics • Lets try it together. • Stand up and stand on both legs, then balance on one standing straight up. • Then lean to the side you are standing on. What changes. Basic Biomechanics • List some ways to increase stability – Wider base of support – Greater mass (which will decrease speed) – Increase friction (carpet vs ice) – Focus on stationary Basic Biomechanics • Simple Machines – 4 types of Machines • Lever • Wheel and Axle • Inclined plane • The pulley Basic Biomechanics • Lever is a rigid bar that can rotate about a fixed point when a force is applied to overcome resistance. Basic Biomechanics • A-Axis is the fixed point around which the lever rotates. • F-Force causes the lever to move. (muscle in the body) • R-Resistance that must be overcome for motion to occur. ( can be gravity or the weight to move.) Basic Biomechanics Force Arm distance between force and axis Resistance arm is distance from axis to resistance. A F R Basic Biomechanics • First-class lever – Axis is located between the force and the resistance. – Balance Basic Biomechanics • Second Class Lever – Has the axis at one end, the resistance in the middle, and force at the other end. – power Basic Biomechanics • Third class Leaver – Has the axis at one end with the force in the middle and resistance at the opposite end. – ROM Basic Biomechanics • The body has more 3rd class levers because the body favors the advantage of ROM. • Levers can change class depending on where the resistance is, if there is resistance added vs just gravity. Or if the direction gravity comes from changes. Pg 83-84 Basic Biomechanics • Mechanical Advantage- ratio between the force arm and resistance arm. MA=FA RA Less force is needed when mechanical advantage is greater. Page 85 force arm on leg Basic Biomechanics • Pulley is a grooved wheel that turns on axle with rope or cable. – It allows for change of direction of force or to change the magnitude of a force. Basic Biomechanics • Fixed pulley is one attached to a beam. It acts like a fist class lever, it is used to change directions. • Medical malleolus Acts as a pulley for the Tendon of peroneus longus Basic Biomechanics • Movable pulley has one end of the rope attached to a beam then the rope runs through the pulley to the other end where the force is applied. • What is gained in force is lost in distance. Basic Biomechanics • Wheel and Axle- a lever in disguise. – Wheel with a crank attached. It helps increase the force exerted. – Large radius requires less force. Basic Biomechanics • Incline Plane is a flat surface that slants. – It creates more distance with less effort Simple Machines • Basic rule of simple machines: what is gained in force is lost in distance.