Biomechanics Concept.pdf

Biomechanics Concept  Definition of biomechanics The term biomechanics combines the prefix bio with the meaning of life with the field of mechanics that studies the actions of forces. Biomechanics (70s): science that studies the mechanical aspects of...

Biomechanics Concept  Definition of biomechanics The term biomechanics combines the prefix bio with the meaning of life with the field of mechanics that studies the actions of forces. Biomechanics (70s): science that studies the mechanical aspects of living organisms. For kinesiology and sports science, the living organism that arouses the most interest is the human body. The forces studied include both those generated internally by the muscles and the external forces that affect the human body. (eg gravity) 2  Definition of biomechanics Biomechanics use the tools of mechanics (the branch of physics responsible for analyzing the actions of forces) to study the anatomy and functional aspects of living organisms.. Mechanics Dynamic Static Kinematics Kinetics Balance Tomada de A. Navandar 3  Kinematics Is a branch of mechanics that describes the motion of a body (And/or any of its parts and segments), without regard to the forces or torques that may produce the motion. Analysis of the trajectory of a body that is in motion over time. Concepts – Body position at a given time – The displacement that was made. – The time it takes to do it. – The speed – Acceleration 4  Linear motion Linear motion is motion in which all parts of the body travel the same distance and in the same direction. – Center of mass movement (CoM) – Ignore the rotation – Rectilinear (1D) or curvilinear (2D or 3D) movement Pure linear motion implies uniform motion of the system of interest, with all parts of the system moving in the same direction at the same speed. Linear motion is also known as translational or translational motion. 5  Linear motion Displacement Measure the change of position of an object in space Displacement (𝑆𝑆) = final position - Initial position Angular Displacement: The change in orientation of a line segment. Two-Dimensional Motion: The angle between the initial and final orientations regardless of the path taken. 6  Speed Measures the rate of change of displacement in a given time. The same direction as the displacement. Units: meters/second (linear) or degrees/second (angular) Average speed= total displacement/total time Instant speed (𝑣𝑣) = 𝑑𝑑𝑆𝑆/𝑑𝑑𝑡𝑡 omada de A. Navandar 10  Acceleration Indicates the direction and rate of change of speed. Units: m/s2 or °/s2 average acceleration instant acceleration 8  Angular movement Angular motion is rotation about a central imaginary line known as the axis of rotation, which is oriented perpendicular to the plane in which the rotation occurs. Almost all voluntary human movement involves the rotation of a segment of the body about an imaginary axis of rotation that passes through the center of the joint to which the segment is attached. When angular motion or rotation occurs, moving body parts are constantly moving relative to other body parts. 9 Relationship between angular and linear displacement Considering that the movement time is the same: – Which point, A or B, has the greater linear velocity? – Which point, A or B, has the greater angular velocity? Position Speed Acceleration 10  Kinetics study of the forces associated with movement Newton's laws of motion First law, "law of inertia“ A body at rest remains at rest, or, if in motion, remains in motion at a constant velocity unless acted on by a net external force Second Law: Law of momentum The rate of change of linear impulse of an object is proportional to the force causing it and occurs in the direction in which the force acts. Third Law: Law of action-reaction every action (force) in nature there is an equal and opposite reaction. If object A exerts a force on object B, object B also exerts an equal and opposite force on object A. In other words, forces result from interactions. 11  General motion When translation and rotation are combined, the resulting motion is a general motion. A soccer ball kicked from field to field moves through the air while rotating simultaneously around a central axis. A runner translates along the angular movements of the body segments in the hip, knee and ankle. Human movement usually consists in a general movement instead of a move pure linear or angular. 12  Quantitative versus qualitative The analysis of human movement can be qualitative or quantitative. Qualitative: refers more to the description of quality without the use of numbers. – A qualitative description does not mean that it is general, it can be general or very precise. – Physicians, trainers, and fitness instructors regularly use qualitative observations of their patients, athletes, or students to formulate opinions or give advice. Observations of videos or patrons through the analysis of graphs Differentiate between individuals and teams Improve performance and technique perfection Give qualitative feedback for the patient. Tomada de A. Navandar 13  Quantitative versus qualitative Quantitative: use of numbers. Biomechanical researchers rely heavily on quantitative techniques to try to answer specific questions related to the mechanics of living organisms. Measurement of different mechanical parameters applying physics laws Better comparisons Assess risk of injury Improve performance Give feedback to the patient Tomada de A. Navandar 17  Quantitative versus qualitative Analyzing human movement, whether to identify a gait abnormality or improve technique, is essentially a problem-solving process. Whether the analysis is qualitative or quantitative, it involves identifying, then analyzing, and finally answering problem of interest. 1. Is the movement being performed with the proper (or optimal) force? 2. Is the movement being performed through an appropriate range of motion? 3. Is the sequence of body movements appropriate (or optimal) for the execution of the skill? 4. Why does this old lady have a tendency to fall? 5. Why doesn't this shot putter get more distance? More specific questions may include these: 1. Does excessive pronation occur during the stance phase of gait? 2. 2. Is the ball being released at the instant of full elbow extension? 3. 3Does selective strengthening of the vastus medialis obliquus relieve patellar deviation? 18