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Terms in this set (53)
Biomechanics: bio means "life"
Study of the actions of forces
Term first used 1970's
Includes both internal forces produced by muscles and external forces that act on the body
Biomechanics human movement is one sub discipline of exercise science
Examines the internal and external forces acting on the human body and the effects produced by these forces.
Aids in technique analysis and the development of innovative equipment designs.
Draws on knowledge from sports medicine, physical therapy, kinesiology, and biomechanical engineering.
Involves measurement of variables that are thought to optimize
or maximize performance (the use of #)
Involves obtaining visual or aural information to asses performance (nonnumeric description of quality)
Pattern of forces using a force platform
Sequence of muscle activity using electromyography (EMG)
Three-dimensional (3D) movements of each body segment using high speed cinematography
PT - range of motion (recovery
A framework within which skilled performance can be observed
A checklist to use when identifying errors
Description of squat
The form, pattern, or sequencing of movement with respect to time
Study of actions of forces
temporal characteristics of a performance, either of the total skill or its phases
length and direction of the path an athlete takes from start to finish
displacement per unit of time
rate of change of velocity
distance, displacement, speed, velocity, acceleration
Vector quantities have both size and direction
These variables are used to describe both linear and angular motion
Change in linear position
Change in the angular position or orientation of a line segment
rate of change in linear position
angular displacement per unit of time
Skilled performers move body segments at high rate of angular velocity
angular velocity per unit of time
Biomechanics use quantitative kinematics to research differences between skilled performers and non-athletes. Examples:
Runners stride length & frequency
Swimmer's stroke rate & length
Track events velocity of takeoff
High jumpers vertical displacement
Basketball angle of projection, angle of release
Throwing events aerodynamics of flight path
Swinging (bat, racquet) timing, project speed and angle
Most biomechanical studies of human kinematics involve non-athletes:
Infant through maternity developmental stages
Adapted P.E. kinematic patterns with motor disorders
Therapeutic uses to aid in recovery of injuries/surgeries
Is any action, a push or pull, which tends to cause an object to change its state of motion by experiencing an acceleration
Generated by muscles pulling via their tendons on bones, and to bone-on-bone forces exerted across joint surfaces
Acting from without, such as the force of gravity or the force from any body contact with the ground, environment, sport equipment, or opponent
Preliminary Steps for Analyzing Human Motion
Identify the system to be studied, which is to separate the object of interest from its surroundings.
Identify the frame of reference in which the movement takes place.
Identify the type of motion that is occurring, the body planes in which movement takes place (sagittal, frontal, or transverse).
Identify the axes of rotation about which rotational motion occurs (sagittal, frontal, or vertical).
is caused by forces which act through a body's center of mass
is caused by forces that do not go through the center of mass
Force rarely acts in isolation
Overall effect of many forces acting on a body
Vector sum of all the acting forces
Net force zero = acting forces balanced in magnitude and direction
Net force present = body moves in the direction of the net force with acceleration
is the measure of how much matter an object has
is the reluctance of an object to change its state of motion from rest to moving, to moving faster, or to slowing down back to rest
Movement of inertia
is a function of the mass of a rotating object and how its mass is distributed about its axis of rotation
Center of mass
Located at the balance point of a body; a point found in or about a body where the mass could be concentrated
Generally, 15 cm above the crotch, or approximately 55% of standing height in females and 57% in males
Describe the relationship between all the external forces acting on the human body at any time and the resulting motion of the total body.
Sir Isaac Newton developed these laws to explain why things move the way they do.
An object will not change its state of motion (it will continue to be at rest or moving with constant velocity), unless acted upon by a net, external force.
For example: because of their large mass, football linemen are difficult to move out of the way
A force applied to a body causes an acceleration of that body of a magnitude proportional to the force, in the direction of the force, and inversely proportional to the body's mass
The greater the amount of force applied, the greater the speed
For every action, there is an equal and opposite reaction
In terms of forces:
When one body exerts a force on a second, the second body exerts a reaction force that is equal in magnitude and opposite in direction on the first body
Friction is a force that acts at the interface of surfaces in contact in the direction opposite the direction of motion or impending motion
Factors influencing the value of friction µ
Relative roughness and hardness of the surfaces
Type of molecular interaction between surfaces
Gloves, wax, etc...
the motion of the fluid flowing past an object or the motion of the object through the fluid.
All athletic events take place in a fluid environment, whether in water (swimming), in air (cycling), or in a combination of both (water polo).
The magnitude of the buoyant force is equal to the weight of the fluid displaced by the body
If magnitude of weight is greater than buoyant force, the body sinks, moving downward in the direction of the net force
Buoyancy is studied in relation to floatation of human body in water
Difference in floatability is function of body density
Density of bone and muscle is greater than the density of fat
What changes with floatation when a person holds inspired air in the lungs?
Orientation of the body as it floats in water is determined by the relative position of the totally body center of gravity relative to the total body center of volume
Generally, a resistance force:
A force that slows the motion of a body moving through a fluid
Theoretical square law
The magnitude of the drag force increases approx with the square of velocity
Effect seen with high velocity sports: cycling, speed skating, downhill skiing, bobsled, luge
3 types of drag
Skin friction/surface drag
Form drag/profile drag
resistance derived from friction btw adjacent layers of fluid near body moving through a fluid. (tight fitting clothing for athletes)
resistance created by a pressure differential btw the lead & rear ends of a body moving through a fluid
resistance created by the generation of waves at the interface btw two fluids, such as air & water
Balance is a very important factor in athletic performance
Generally depends upon the location of the center of mass and how stable that center of mass is
The stick figure model is useful
Process whereby the body's state of equilibrium is controlled for a given purpose.
The base of support and location of the center of mass is manipulated.
If the line of gravity passes through some part of the body's base of support, the body will be balanced.
The state of a system that is not experiencing any change in its direction or speed
System is moving with constant velocity
System is at rest
A measure of the difficulty with which equilibrium can be disturbed.
A net external force is required to overcome the static equilibrium of a sprint start.
There is a trade-off between maximizing stability and acquiring speed off a mark.
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