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Biomechanics 2015 Section 1:1 An Introduction to Biomechanics Dr. Moira McPherson, School of Kinesiology
AN INTRODUCTION TO THE STUDY AND ANALYSIS OF HUMAN MOVEMENT • During the past decade the term BIOMECHANICS has emerged as an area of inquiry in the sport science domain. Biomechanics is based on NEWTON'S LAWS and involves the study of the motion of bodies and the interrelationships among the forces acting on these bodies.
INTRODUCTION TO THE STUDY AND ANALYSIS OF HUMAN MOVEMENT BIOMECHANICS: BIO = LIVING • MECHANICS = FORCES & EFFECTS • The application of mechanics to the living organism • Involves the principles of anatomy and physics in the descriptions and analysis of movement. • Has many diverse applications to all biological systems • The study of biological structures, processes and functions by applying the methods and principles of mechanics
HAY, 1995 • THE SCIENCE THAT EXAMINES THE INTERNAL AND EXTERNAL FORCES ACTING ON THE BODY AND THE EFFECTS PRODUCED BY THESE FORCES • KINEMATICS & KINETICS
AREAS OF STUDY, RESEARCH AND PRACTICE • Sport and Exercise Science • Coaching • Ergonomics • Equipment Design • Gait & Locomotion • Orthopedics - Rehabilitation -Physiotherapy, Occupational Therapy • Prosthetics and Orthotics • Motor Control • Computer Simulation
MECHANICS • Rigid body mechanics are based on the assumption that a solid body is considered to be a rigid body if the distance between the particles remains fixed when a force is applied.
SEGMENTAL ANALYSIS • We often make the assumption that the human skeleton can be represented as a series of links. Researchers have used everything from cones to spheres to form the links which best approximated the complexity of the human body. However, by far the most widely adopted and simplest link system representation is the stick man.
The stick man uses straight sticks to represent each of the links. In any case, regardless of the shapes which are used we also make the assumption that the human link system is a system of rigid bodies connected at the joints
Figure 3. Rigid Body Mechanics kinematics kinetics linear curvilinear statics dynamics angular parabolic
KINETICS • examines the causes of motion, the internal and external forces that cause motion or cause a body to remain at rest, and the interactions between these forces. There are two branches of kinetics; STATICS and DYNAMICS
KINEMATICS • Describes the motion of a body without reference to the forces causing it. Kinematics examines how, when, and where a body moves.
For example, variables such as the displacement of a ball, the velocity of a skater, and the acceleration of the free leg all describe motion, and are kinematic variables.
We classify the kinematic motion according to the pathway it takes. Movement may be LINEAR, CURVILINEAR, or a combination of the two. Curvilinear motion can be further specified as ANGULAR or PARABOLIC.
LINEAR MOTION • Linear motion is the movement of a body in a straight line or along a straight pathway. Linear motion is also produced when external forces are applied directly through the centre of mass of an body.
ANGULAR: Angular motion takes place when a body moves along a circular path about some AXIS in space. This axis is known as the axis of rotation. Angular motion is produced when forces are applied away from the axis of rotation of a body.
Our body limbs are able to rotate about the joints because all of our muscles are attached at some distance from the centre of the joints.
PARABOLIC: Bodies which are projected into the air will assume a PARABOLIC PATH and are governed by the laws of projectile motion.
STATICS: Statics refers to situations where the body or object remains at rest, or is moving at a constant speed in a state of equilibrium. Equilibrium is a balanced state in which there is no acceleration.
DYNAMICS: Dynamics deals with the changes in motion brought on by unbalanced forces.
QUANTITATIVE VS QUALITATIVE • Both kinematics and kinetics can be analyzed using a quantitative or qualitative approach • A quantitative analysis requires a numerical evaluation of an individual’s movement • Qualitative analysis involves a systematic analysis of movement based on biomechanical concepts but without actual measurement
METHODS OF ACQUIRING DATA • 1. VIDEO ACQUISITION • 2 D or 3D • Points are digitized manually or by attaching reflective markers and digi auto • 2. 3 D OPTICAL ACQUISITION • 3D in controlled environment • Marker only system that uses 2 – 12 cameras and infra red lights to collect 3D coordinates • 3. ANALOG ACQUISITON • analog sampling from force platforms, EMG or other devices. • Can be integrated with video or 3D optical
SOME QUESTIONS that may require quantitative video analysis? • 1. An objective of prescribing an orthosis is usually to improve the function of the patient. How can we determine if the use of a foot orthotic is correcting for the severe pronation exhibited by a patient? • Video tape, digi and compare joint angular displacement throughout stride
Hydro workers • Hydro workers are required to lean out of a lift to repair the lines. The action of leaning and working from a distance puts dangerous loads on the lower back – injury. • How can the lift be modified to reduce the risk of injury?
EMG • BASED ON RELATIONSHIP BETWEEN FORCE AND THE ELECTRICAL ACTIVITY ACROSS THE MUSCLE MEMBRANE • EXAMPLE: Which exercise is best for rehabilitation of a particular muscle?
ELECTROMYOGRAPHY-EMG Raw EMG Full wave Rectify Linear Envelope Integrate over contraction
FORCE ANALYSIS FX Fy Fz How much force is applied in the Horizontal direction?
QUALITATIVE ANALYSIS • Qualitative analysis involves a systematic analysis of movement based on biomechanical concepts but without actual measurement
What does the QA process include? • Is there a technique error? • What are the mechanical concepts that govern specific parts of the skill? • What the critical features of the performance? • What is the best observation strategy? • How do you detect errors in performance and remediate?
Sally, a powerful outside hitter on a high school volleyball team, has been out for two weeks with mild shoulder bursitis, but has recently received her physicians clearance to return to practice. The coach notices that Sally’s spikes are traveling at a slow speed and are being easily handled by the defensive players?????
TEXT BOOK • Page28-61