What is a Force? KINESIOLOGICAL PRINCIPLES EXTERNAL INTERNAL PART 1: CLASSIFYING FORCE 1 A force is a push or a pull 2 Forces come in pairs: action and reaction 3 Causes change in movement LEE WALLACE PhD LEE WALLACE PhD Measuring Force Forces Effecting Movement • Force (F) is measured in Newtons (N) LEE WALLACE PhD Gravity Friction Drag Between body and other.. LEE WALLACE PhD Forces Effecting Movement LEE WALLACE PhD LEE WALLACE PhD LEE WALLACE PhD LEE WALLACE PhD Non-Contact Force Weight Force (FWT) • The only non contact force in EXTERNAL NON-CONTACT FORCE CONTACT FORCE GRAVITY (WEIGHT FORCE) 1. NORMAL CONTACT 2. FLUID CONTACT 3. FRICTION sport/exercise is the force of gravity • Acts through Centre of Gravity (COG) LEE WALLACE PhD LEE WALLACE PhD 1 Classifying Force Contact Force • Contact forces are the forces that occur between objects in contact with each other NORMAL CONTACT Or Ground Reaction Force FLUID CONTACT FRICTION EXTERNAL Parallel to normal contact LEE WALLACE PhD NON-CONTACT FORCE CONTACT FORCE GRAVITY (WEIGHT FORCE) 1. NORMAL CONTACT 2. FLUID CONTACT 3. FRICTION TENSILE FORCE COMPRESSIVE FORCE SHEAR FORCE LEE WALLACE PhD LEE WALLACE PhD Internal Force INTERNAL LEE WALLACE PhD Tensile Force Mechanical loads of the human body • Muscle forces, gravitational forces and bone breaking forces have differing effects on the human body. These generate internal forces LEE WALLACE PhD • A pulling force which acts on the ends of an internal structure – e.g. Ligaments and tendons LEE WALLACE PhD LEE WALLACE PhD Tensile Force LEE WALLACE PhD Compressive Force • A pushing force which acts on the ends of an internal structure – e.g. Bones and joints LEE WALLACE PhD LEE WALLACE PhD LEE WALLACE PhD LEE WALLACE PhD 2 Compressive Force Shear Force • A transverse force that acts in parallel to the analysis plane • A pushing force which acts on the ends of an internal structure – e.g. Bones and joints LEE WALLACE PhD LEE WALLACE PhD LEE WALLACE PhD Shear Force • A transverse force that acts in parallel to the analysis plane Too much tensile/compressive/shear force will cause the structure to deform/break LEE WALLACE PhD LEE WALLACE PhD Torque and Moment Vectors KINESIOLOGICAL PRINCIPLES • Torque: The turning effect produced by force – Often referred to as a moment • (𝑟) represents moment arm • ↑ 𝑟 = ↑ mechanical advantage PART 2: LEVER SYSTEMS LEE WALLACE PhD LEE WALLACE PhD 3 Muscular Torque Muscular Torque Muscles create torque that turns limbs • eg. The Biceps Brachii exerts a torque around the axis of the elbow LEE WALLACE PhD Components of a Lever System Components of a Lever System Within the lever system there are 3 parts FULCRUM ORpivot PIVOT Fulcrum or THE LOAD LEE WALLACE PhD Within the lever system there are 3 parts THE EFFORT Load Effort Fulcrum LEE WALLACE PhD 1st Class Lever LEE WALLACE PhD Components of a Lever System Load Effort The fulcrum lies between the load and the effort Load - Fulcrum - Effort Fulcrum Trade-off between Distance and Force LEE WALLACE PhD LEE WALLACE PhD 4 Components of a Lever System Components of a Lever System Greater effort to lift load but moves a greater distance Less effort to lift load but does not move as great a distance Load Effort Load Fulcrum Effort Fulcrum LEE WALLACE PhD LEE WALLACE PhD 1st Class Lever LEE WALLACE PhD 2nd Class Lever The load lies between the fulcrum and the effort Fulcrum - Load - Effort Force Multipliers LEE WALLACE PhD 2nd Class Lever LEE WALLACE PhD 3rd Class Lever The effort lies between the load and the fulcrum Load - Effort - Fulcrum Distance Multipliers LEE WALLACE PhD LEE WALLACE PhD 5 3rd Class Lever LEE WALLACE PhD LEE WALLACE PhD LEE WALLACE PhD LEE WALLACE PhD 6 LEE LEEWALLACE WALLACEPhD PhD LEE WALLACE PhD KINESIOLOGICAL PRINCIPLES 1st Class 2nd Class 3rd Class The fulcrum lies between the load and the effort The load lies between the fulcrum and the effort The effort lies between the load and the fulcrum Load - Fulcrum - Effort Fulcrum - Load - Effort Load - Effort - Fulcrum Distance and Force Force PART 3: JOINT ACTIONS, MUSCLE CONTRACTIONS Distance LEE LEEWALLACE WALLACEPhD PhD LEE WALLACE PhD LEE WALLACE PhD 7 Muscle Actions Muscle Actions What is the action of the shoulder during the up phase? • What type of contraction occurs in the latissimus dorsi? • Concentric Eccentric Isometric LEE WALLACE PhD LEE WALLACE PhD LEE WALLACE PhD Muscle Actions LEE WALLACE PhD Muscle Actions What is the action of the shoulder during the down phase? • What type of contraction occurs in the latissimus dorsi? What is the action of the shoulder during the down phase? • What type of contraction occurs in the deltoid? • • LEE WALLACE PhD Muscle Actions LEE WALLACE PhD Muscle Actions What is the action of the knee during the down phase? • What type of contraction occurs in the quadriceps? What is the action of the hip during the down phase? • What type of contraction occurs in the glutes? • • LEE WALLACE PhD LEE WALLACE PhD 8 Readings Muscle Actions • Nordin and Frankel (2012): Chapter 1 What is the action of the shoulder during the return phase? • What type of contraction occurs in the horizontal adductors? • Images in this presentation were used with permission: Nordin, M. & Frankel, V. H, (2012), Basic Biomechanics of the Musculoskeletal System (4th ed), Lippincott Williams & Wilkins, Baltimore. LEE WALLACE PhD LEE WALLACE PhD LEE WALLACE PhD 9
