Introduction to Program Evaluation

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Transcript Introduction to Program Evaluation

Musculoskeletal Review
2 types of functions of bone
mechanical, physiological
 1° difference in bone structures
 Movement planes
Transverse, Sagittal, Frontal
 Muscle-tendon unit
 Motor unit
Motor neuron and all muscle fibers it innervates
5 main properties of muscle
– Excitability
– Contractility
– Conductivity
– Extensibility
– Elasticity
Types of muscular contractions
– Concentric (shortening)
– Eccentric (lengthening)
– Isometric (same length)
– Isokinetic (same speed)
– Isotonic (same tension)
– Contributing to desired motion, often by
– Opposing desired motion
Components of muscular fitness
– Strength
– Power
– Muscular endurance
– Power endurance
– Reaction time
– Quickness
– Speed
Energetic Concepts
Dr. Suzan Ayers
Western Michigan University
(thanks to Amy Gyrkos)
Terms (Carr)
Mass: matter, remains constant
Weight: gravitational pull, varies with location
– You weigh < @ equator, > toward poles
2 characteristics of inertia (resistance to change) :
-to resist motion
-to persist in motion (in a straight line)
In linear movement, mass=inertia (> mass=> inertia)
Rotary inertia involves how mass is distributed
relative to axis of rotation
Factors influencing inertia: friction, air resistance
(e.g., base runner sliding, ski jumping)
More massive athletes resist change more
Newton’s First Law
I. Law of Inertia
– Every object in a state of uniform motion tends to
remain in that state of motion unless an external
force is applied to it
Speed: how fast an object moves
Acceleration: an object’s rate of speed change
Velocity: how fast & in what direction an object
Momentum (Abernathy et al.)
– Product of mass (matter) & velocity (directed speed)
– Changes as a function of mass or velocity Δs
Velocity Δ: shot putter who spins faster one time vs
 Mass Δ: swinging a heavier bat
– Short stopping time requires ↑ force to Δ
momentum velocity
i.e., ‘giving’ when catching a ball or landing
 Key to injury prevention
Conservation of momentum and energy:
Gravity’s effect on athletic performance
“Thin” air @ altitude: same proportion of gases,
but as altitude ↑, standard volume of air has <
of each gas (have to work harder to get same O2)
Acceleration of gravity
Uniform velocity of 32ft/sec: due to constant ↑
in velocity, increasingly large distance is
covered each sec. an athlete falls (Fig 2.1, p. 17)
Newton’s Second Law
II. Law of Acceleration
– Change of motion is proportionate to the force
impressed and is made in the direction of the
straight line in which that force is impressed
Objects accelerate in the direction pushed
Formula: F = ma
Applied force F, Mass m, acceleration a
Directly proportional (push 3x harder=3x> acceleration)
Inversely proportional to mass (object that is 3x heavier
moves 1/3 slower; bowling ball vs. volleyball)
If force or time ↑, so does velocity (i.e., keeping contact w/
ball longer = > time)
M = mv
Momentum=mass x velocity
*no movement=no M
Center of gravity
Dead center (evenly distributed mass
(p. 21))
Gravity’s effect on flight
Vertical & horizontal forces applied: flight path
cannot be changed once athlete is in flight
Ground reaction force: Earth’s push up on body
(Fig 2.7, p. 23)
Newton’s Third Law
III. Law of Action-Reaction
– Every action has an = and opposite reaction
Force: push/pull that changes shape or state of
motion of athlete or object
Vector: a quantity (of force) with direction
Force vector: when direction & amount of applied
force are known
Relevance? Vector analysis is learned by athletes
practicing various combinations of horizontal
and vertical pathways (lead passing routes, etc.)
Linear motion: straight line movement
(100m dash)
Angular motion: body moves through an angle or
number of degrees around an axis (360° dunk)
General motion: combination of linear/angular
Projectiles (people/objects)
Trajectory: flight path, influenced by gravity and
air resistance; influenced by 3 factors:
Angle of release: influences shape of flight path;
1) straight up=vertical flight path
2) closer to vertical (>45°)=height > distance
3) closer to horizontal (<45°)=distance > height
Speed of release: apex of flight path ↑ as speed ↑
Height of release: relative to landing surface;
velocity (speed and direction), height and angle of
takeoff/release combine to determine flight
Terms (Abernathy et al. ch.6)
Energetics: energy and its transformations
Centripetal: toward the center/axis
Centrifugal: away from the center/axis
Moment of force: measure of the force needed
to rotate a body around a point
Equilibrium: all points of body have = velocity
– Static equilibrium: all points’ velocity/acceleration=0
Kinetic energy: body’s mechanical energy due
to its motion
Potential energy: mechanical energy by virtue
of height above ground (gravitational in nature)
Elastic strain energy: stored energy in elastic
tissues of muscles and tendons (elastic potential
Power: rate of doing work
(aka, strength x speed)
– Positive: concentric contractions produce energy
– Negative: eccentric contractions absorb energy
Momentum & kinetic energy: an athlete on the
move has both momentum and kinetic energy
Law of conservation of energy: one form of
energy is exchanged for another; energy is
conserved, not gained/lost
Friction: when an object moves while in contact
w/ another object
– Static: contacting surfaces of resting objects > resistance than sliding
– Sliding: between two sliding objects > resistance than rolling
– Rolling: between a rolling object and a supporting/contacting surface
*It is easier to keep an object moving than to start it moving
Points of Application
1) Which muscles most important in the vertical
jump? (A, p. 89)
Quadriceps and gluteals
How & what muscles you train to improve VJ
should dictate training programs when VJ
matters to performance
2) Relative to metabolic energy consumption…
The cost associated with quiet standing is
~30% higher than resting (sitting/lying down)
After contests, have your athletes cool ↓ slowly
vs drop to the ground suddenly
3) Walking saves met energy by converting
gravitational potential energy into forward
kinetic energy. Running stores/re-uses elastic
strain energy, but less efficiently than
pendulum-like walking mechanism.
Running less efficient than walking, ergo >
caloric cost