Biomechanics 1 PDF

**[TABLE OF CONTENTS]** - Kinetics - Kinematics - Static positions - Applied biomechanics **[WHAT IS BIOMECHANINCS]** Application of mechanical laws to living structures Study of forces acting on or produced by human bodies (external or internal forces) Biomechanics applies to the te...

**[TABLE OF CONTENTS]** - Kinetics - Kinematics - Static positions - Applied biomechanics **[WHAT IS BIOMECHANINCS]** Application of mechanical laws to living structures Study of forces acting on or produced by human bodies (external or internal forces) Biomechanics applies to the technique realm KINETICS -- is the study of the relationship between the force system acting on a body and the changes it produces in a body motion KINEMATICS -- is a branch of mechanics that deals with the geometry of the motion of objects, including displacement, velocity and acceleration without taking into account the forces that produce the motion **[APPLICATION: USES OF BIOMECHANICS KNOWLEDGE ]** - Understanding gymnastics skills - Analysing and teaching skills - Identifying causes of errors - Correcting errors - Applications to changes in apparatus/rules - Innovate(or evaluate new innovations) **[EXAMPLE 1 OLD VAULT TABLE ]** The old vaulting horses had significant safety and mechanical disadvantages **[NEW VAULT TABLE]** ADVANTAGES - Increased approach velocity - Shorter pre-flight times FIG re-evaluated and changed the \'\'Vaulting Horse\'\' by the \'\'Vaulting Table\'\', citing both safety reasons and the desire to facilitate more impressive acrobatics. The 2001 World Artistic Gymnastics Championships were the first international competition to make use of the \"vaulting table\". It features a flat, larger, and more cushioned surface almost parallel to the floor, which slopes downward at the end closest to the springboard; it appears to be somewhat safer than the old apparatus. New vault table = more effective force application New table - safer and more comfortable wrist position - advantage for applying vertical forces - increased friction (safety and force application) **[TYPES OF BIOMECHANICAL ANALYSIS]** 2 different prospective analyses - quantitative biomechanical analysis - qualitative biomechanical analysis **[QUANTITATIVE BIOMECHANICAL ANALYSIS]**  It is generally used for scientific studies since it requires more preparation time, more technological resources for data collection and often laborious statistical analysis **[\ ]** **[QUALITATIVE BIOMECHANICAL ANALYSIS]** Useful and easy to - identify movement parameters and deviations - describe positions and phases, actions - explain causes, mechanisms, principles - Predict effects, techniques, methodologies - Recommend physical or technical corrections **[KINETICS]** Force -- can be considered as the pushing or pulling action that one object exerts on another A force is any cause that changes or tends to change the velocity or shape of an object The international system of units (SI) unit of force is the newton (N) and the symbol for a force vector is (F) Gymnasts experience forces both internal to and external to the body Internal forces are generated by the muscles and transmitted by tendons, bones, ligaments and cartilage The main external forces are - Weight - Reaction forces - Friction Their combined effect determines the overall motion if the body  **[EXTERNAL FORCES\ ]** - Force of gravity (weight) - Centripetal force - Ground reaction force - Frictional force - Impulse force - Torque **[RESULTANT FORCE]** If a number of forces act simultaneously their combined effect can be represented by a single force known as the resultant force In gymnastics more than one force usually acts on the performer and the effect produced by the combination of these forces will depend on their magnitudes and relative directions = resultant forces **[NEWTONS LAW OF MOTION]** **[FIRST LAW OF MOTION -- LAW OF IINERTIA]** A body at rest will remain at rest and body of motion will remain in motion unless it is acted upon by an external force The fact that massive bodies resist changes in their motion is sometimes called inertia A body will remain at rest or in uniform motion in a straight line unless it is acted upon by an external force The greater the resistance to change (inertia) the greater the force needed to change the motion of an object (accelerate or decelerate it) The greater the momentum (mass x velocity) the greater the force needed to change the velocity of the object **[INERTIA AND LINEAR MOMENTUM ]** INERTIA - the reluctance of a body to alter its state of rest of motion - it is the related to the mass of the body LINEAR MOMENTUM - a measure of the total 'quantity' of motion that a body has - it is related to the mass and the velocity of the body - linear momentum = MASS X VELOCITY the linear measure of inertia is mass and has units of kg in the international system if units (SI) In angular kinetics, inertia is measured by the moment if inertia The formula of a rigid body moment of inertia about an axis (A) is IA=m - r2  **[SECOND LAW OF MOTION (LAW OF ACCELERATION)\ ]** The force action on an object is equal to the mass of the object times its acceleration. This is written in mathematical form as F=m.a where F is force, M is mass and A is acceleration **[THIRD LAW OF MOTION (LAW OF ACTION)]** For every action force there is a reaction force that is - equal in magnitude - opposite in direction - simultaneous Force always acts in pairs  **[PRINCIPLE OF ACTION -- REACTION IN THE AIR\ ]** It is not possible to move body part A towards body part B without simultaneously moving body part B towards body part A This is the basis for generating 'indirect' ground reaction forces when in contact with the floor or apparatus When a body part is extended upward, the body must move downward and vice versa When a body part is extended sideways the body must tilt in the opposite direction When the legs are extended forwards the trunk must come forwards and vice versa When the upper body is twisted to the right the lower body must twisted to the left and vice versa **[KINEMATICS]** **[VELOCITY]** Measure of how far the body has moved a specific period of time (average velocity) or of how fast it is moving (instantaneous velocity) It is usually measured in meters per seconds (m/s) **[ACCELERATION]** Acceleration is a measure of how much a body's velocity changes over time  An increase in velocity is acceleration and a decrease is negative acceleration or deceleration A change in direction is an acceleration. It is measured in meters per second per second (m/s2) A change of velocity requires the application of a force Therefore acceleration is a measure of the force applied (F= m x a) If a body slows down, speeds up or changes direction, a force must be the cause In the air the only force acting is the force of gravity Vertical force = gravity (g=9.81 m/s2) which causes acceleration downward Horizontal force = 0 there is no horizontal acceleration **[BIOMECHANICS GYMNASTICS REASEARCH EXAMPLE ]** In the example below, we see a biomechanical study that investigates the relationship between running speed and jump quality (verified by the final grade). Among the conclusions of the study, the authors highlight:\ \"\[\...\], this study confirmed that a high run-up speed is one of the most important determining factors to succeed on vault in women's and men's artistic gymnastics competition.\" A diagram of a graph showing different types of people doing gymnastics Description automatically generated with medium confidence **[STATIC POSITIONS]** **[WEIGHT AND MASS DEFINITION]** MASS - quantity of matter that an object contains - it is always the same everywhere in the universe - measure of an objects inertia or reluctance to change its state of rest or motion - mass is a measure of quantity (Kg) WEIGHT - the gravitational attraction between 2 objects - larger mass -- larger gravitational attraction (therefore it can vary with location) - Weight is a measure of force (Newton N) **[FORCE OF GRAVITY]** The force of attraction between any 2 masses On earth it is experienced as a force acting vertically downwards through the centre of mass The downward force is approximately 10m/s2 (9.81m/s2) The force measured as weight (N) The force of 1 body weight is often referred to as 1g (3g's=3 x body weight) **[CENTER OF MASS / CENTER OF GRAVITY (COM)]** Is the point about which a body is equally balanced in all directions The point of intersection of the 3 principal axes - Longitudinal - Transverse - Anterior / posterior The point at which the body's total mass is considered to be concentrated Therefore it is a point as which the force of gravity is considered to act  Important -- the centre of mass can be out side the body In the anatomical position - COM is at 57% standing height of males - COM is at 55% standing height of females The location of COM changes when we move. The COM is calculated to investigate mechanics of bodies in motion or in stable positions **[PRINCIPLES OF STABILITY -- STABILITY AND BALANCE]** STABILITY -- the resistance to linear and angular motion BALANCE -- the ability to maintain a stable position **[PRINCIPLES OF STABILITY]** the lower the COM to the base of support, the greater the stability. The larger the base of support, the greater the stability.  The nearer the COM is over the centre of the base of support, the greater the stability.  In a segmented body, the better the vertical alignment of the COM's of the individual segments, the greater the stability. 1. THE LOWER THE COM TO THE BASE OF SUPPORT THE GREATER THE STABILITY  2. THE LARGER THE BASE OF SUPPORT THE GREATER THE STABILITY 3. THE NEARER THE COM IS OVER THE CENTER OF THE BASE OF SUPPORT THR GREATER THE STABILITY 4. IN A SEGMENTED BODY THE. BETTER THE VERTICAL ALIGNMENT OF THE COMS OF THE INDIVIVDUAL SEGMENTS THE GREATER THE STABILITY **[APPLIED BIOMECHANICS\ ]** See some practical examples of the use of the principles of biomechanics to better understand gymnastics -- indirect ground reaction forces The reaction to a 'direct action' force applied by the gymnast is called a 'direct ground reaction force' The reaction to a 'reaction action' applied by the gymnast is called an 'indirect ground reaction force' 1. Jumping -- downwards pushing the legs results (F ACTION) in an upwards direct (GROUND) reaction force (F REACTION) 2. Swinging arms up (DIRECT ACTION) body wants to go down (DIRECT REACTION) and increases reaction force upward (INDIRECT REACTION FORCE)  **[MECHANICS OF SPRING]** An action force must be applied that generates a reaction force large enough to overcome the force of gravity Can be from internal forces (muscular contractions) Can be from external forces (mini tramp, bar, springboard ect) #### **Effective force application is related to** - #### **Magnitude** **- strength in all active muscles** - #### **Point of application** **- (off centre = rotation)** - #### **Direction** **- always opposite to application** - #### **Duration** **- range of motion/flexibility** - #### **Timing** **-- coordination** - #### **Rigidity of the body** **- body tension & shape** #### **[MAGNITUDE OF FORCE ]** - #### **Must be sufficient for the desired outcome (optimal vs maximal).** - #### **Strength & power in all active muscles.** #### **[DIRECTION OF FORCE ]** - #### **Must be in the desired direction.** - #### **Remember "action force \> reaction force".** #### **[DURATION OF FORCE]** - #### **Must be over the longest time and distance possible.** - #### r**ange of motion/flexibility in all active joints.** #### **[TIME OF FORCE]** - #### **Sequential summation of forces** - #### **Largest to smallest** - #### **Proximal to distal** - #### **Coordination** #### **[FORCE APPLIED TO RIGID BODY]** - #### **Otherwise forces will be used or "wasted" to change the shape of the body.** - #### **Body tension & shape.** #### #### #### at the instant of take off these are determined - #### **Angle (º) of take-off and landing (COM)** - #### **Vertical velocity up (Vz) (reduced to zero by gravity)** - #### **Vertical velocity (Vz) on landing = Initial vertical velocity (V0z).** - #### **Horizontal velocity (Vx)** - #### **Height (= Time)** - #### **Distance** - #### **Direction** #### **Time in the air (= Height)** #### #### **[ROTATIONAL MOMENTUM]** - #### **Body shape (= potential to change speed of rotation)** #### #### **[TOTAL MECHANINCAL ENERGY]** - #### **Total Mechanical Energy (= Potential Energy + Kinetic Energy)**