Chapter 7 Basic Concepts of Kinematics and Kinetics

High Speed Video (Measurement Tool)

* Illustrates velocity and Joint angles/movement * Used for sports performance / injuries ( speed analysis) can access the problem with the resistance of movement and can be helped

Examples of Vectors

* The position, velocity , and acceleration of a point on a body ( e.g. COM) * A muscle force * The moment of force of a muscle about a joint * Forces arising from contact of body parts with the environment (e.g forces exerted by the ground on the feet during walking and running) * Forces acting between bones that meet at a joint (i.e. Joint-contact forces)

Knee Replacement

*Based on the properties (strength, elasticity, etc. of the ligaments in the knee) of the ligaments, biomechanists have discovered the best materials to be used to replace knee ligaments. *One of the best materials to use is a graft of the tendon of the hamstrings muscle that is braided to make it stronge

Electroconiometer (Measurement Tool)

*Measures Joint angles and joint angle change *Can be used to determine injuries and where the injury is in recovery process

Ligaments in the Knee

*There are several ligaments in the knee which are susceptible to injury in many sports. *After serious injury, the ligaments in the knee sometimes need to be replaced.

Law of Motion: Law of Inertia (Definition)

A body at rest or in motion will remain in that state unless acted upon by a force.

Force

A measure of the amount of effort applied *Vector quantity ( requires both the magnitude and direction of the force to be specified) *The SI unit of force is Newtons (N). F (N) = Mass (kg) X Acceleration (m/s/s) Split into ... * Push or Pull * Internal or External

Vector

A physical quantity that is described by both

Scalar

Any physical quantity that is fully described by a number

Sport Biomechanics

Biomechanics of athletic performance * Can be used as feedback to athletes to facilitate learning *Analysis of movement can help in the development of proper techniques and optimal equipment

Valve Replacement

Biomechanists have also helped to discover the properties of valves of the heart. They have helped in development of replacement valves with the appropriate materials.

Kinematics

Concerned with the description of movement *Measures of displacement, time, velocity and/or acceleration

Kinetics

Concerned with the forces that cause or tend to cause motion

Muscle & Tissue Mechanics: Ligaments

Connect Bone to Bone

Muscle & Tissue Mechanics: Tendons

Connect Bone to Muscle

Pressure Mats (Measurement Tool)

Determines where the center of pressure (COP) lies. [COP is the point where the pressures under the foot are centered]

Acceleration

Ex. of Vector. The rate of change in the body's velocity over time. a = Change in v / Change in t

Speed

Ex. of a Scalar. v [speed] = d [distance travelled] / t [time taken]

Velocity

Ex. of a Vector. The rate of change in the body's displacement over time; v = X - Xo ( Displacement) / Change in time

Law of Motion: Law of Reaction (Definition)

For every action, there is an equal and opposite reaction.

Electroconiometer: Kinematic or Kinetic? Why?

Kinematic ( Because it has to do with movement) ; Has two arms that attach to a motor in the middle. Motor is aligned with a joint and the arms attach to the limb on either side of the joint. The motor in the middle measures changes in the joint angle based on the distance between the arms

High Speed Video: Kinematic or Kinetic? Why?

Kinematic analysis; Ball-like markers are placed at various points on the body. Location of markers recorded with high-speed infrared cameras. Movement of the markers is tracked to indicate movements of the person

X-Ray Cinematography : Kinematic or Kinetic? Why?

Kinematic analysis; Instead of a still picture, it provides a video.

Force Platform : Kinematic or Kinetic? Why?

Kinetic (because it has to do with forces causing motion and force analysis) ; Can be used during tasks such as running, walking, swinging a golf club, etc.

Pressure Mats : Kinematic or Kinetic? Why?

Kinetics (Forces) ; Color-coded: Warmer colors (red) indicate areas of high pressure; cooler colors (blue) indicate areas of lower pressure

Examples of Scalar

Length, Mass, and moment of inertia

Force Platform (Measurement Tool)

Measures forces in three directions: forward-back (Fy), side-side (Fx), and up-down (Fz).

SI Unit of Position and Displacement

Meters ; this means velocity and acceleration are given in meters per second (m/s) and meters per second squared (m/s^2)

Law of Motion: Law of Acceleration (Definition)

Objects accelerate in relation to force and mass (Force=Mass x Acceleration, more commonly, F=MA).

Motion

Term used to describe the displacement, velocity , and acceleration of a body in space.

Line of action of the force

The direction of a force

Importance of Center of Mass

The location of the center of mass of the body has important implications in sport biomechanics. It always moves toward the side with more "stuff". * It could help with technique and performance in sports such as ski high jumpers.

Biomechanics

The study of physical principles applied to biological systems

X-Ray Cinematography (Measurement Tool)

Uses X-ray technology to examine the motion of bones within a joint during movement.

Displacement vs Distance

a.Displacement just concerned with start and finish (difference between start and finish) b.Distance is the actual length traveled

Center of Mass

the point on any body where the mass is balanced. *For a very symmetrical object, like a ruler, for example, the center of mass will be directly in the center. *For a less symmetrical object, like the human body, it will not be directly in the center, and will change with body position.