Chapter 4 Flashcards
Functional anatomy
study of how body systems cooperate to perform certain tasks
Biomechanics
mechanical principles to understand the function of living organisms and systems
*note: in biomechanics, body can refer to the human body or a collection of matter
linear motion
a body moves in a straight line (rectilinear motion)
or along a curved path (curvilinear motion)
Angular motion
rotational motion: body rotates about a fixed line known as axis of rotation
Axis of rotation
aka: Fulcrum or pivot
a fixed line that body rotates about
General Motion
a combination of linear and angular motion
Frontal plane
shoulder to shoulder
Sagittal
back to chest
Transverse
across the waist
kinematics
study of movement from a descriptive perspective without regard to the underlying forces
Five primary variables:
1) timing, or temporal measures
2) position or location
3) displacement
4) velocity
5) acceleration (change in velocity per unit of time)
Kinetics
movement assessment with respect to the forces involved
Force
mechanical action or effect applied to a body that tends to produce acceleration
Internal forces
muscle, tendon, ligament
external forces
gravity, friction, air resistance
Magnitude
how much force is applied or produced
Location
where on a body or structure force is applied
Direction
where the force is directed
Duration
how long the force is applied
frequency
how many times the force is applied in a given time period
Variability
if the magnitude of the force is constant or changing over the application period
rate
how quickly the force is produced or applied
Newton’s first law of motion
a body at rest or in motion tends to remain in that state unless acted upon by an outisde force
Second law of motion
force equals mass times acceleration
Third law of motion
for every action there is an equal and opposite reaction
Momentum
a body’s quantity of motion
Linear momentum
product of mass and velocity
angular momentum
product of moment of inertia and angular velocity
Transfer of momentum
the mechanism by which momentum is transferred from one body to another
impulse
the product of force multiplied by the time.
torque/moment of force
M-the effect of a force that tends to cause rotation or twisting about an axis
moment: rotational or bending action of a force
torque: refers to the twisitng action of a force
two terms are used interchangably
- Torque creates an angular acceleration similar to the way force creates a linear acceleration
- increase torque by increasing force and/or moment arm
moment arm
the perpendicular distance from the fulcrum to the line of force action
Unit of torque
Newton-meter
Net torque/net moment
usually, more than one torque is being applied.
level
a rigid structure fixed at a fulcrum (axis) to which two forces are applied
ie: bone moving about its axis of rotation
First class lever
fulcrum is located between two forces
ie: elbow or knee
* force with longer moment arm with have the mechanical advantage
Second class lever
Fr is located between the fulcrum and Fa
ie: foot during plantar flexion against resistance
* applied force always has the mechanical advantage
Third class lever
Fa is between the fulcrum and Fr.
most joints are third class levers, the first, and with few second class
ie: forearm
* the resistance force always has the mechanical advantage
Mechanical advantage
Fr:Fa
Fa
applied force
produced by active muscle
Fr
resistance force, load
produced by weight being lifted or another external force being applied
Work (mechanical definition)
how much force is applied an dhow far an object moves
W=F x d
joule=N x M
Power
Rate of work
P= W/t
*standar unit is watt 1 W=1 J/s
1 horsepower=550ft
Mechanical Energy
the ability or capacity to perform mechanical work
:kinetic (energy of motion)
potential (energy of position or deformation)
Kinetic Energy
LKE (linear)=1/2 x m x v^2
m=mass
AKE (angular)= 1/2 x I x w^2
I=moment of inertia
w= angular velocity
Small increase in v and w = more kinetic energy
Potential Energy
gravitational p.e.=potential energy of position, measures the potential to perform mechanical work as a function of a body’s height above a reference level
PE=m x g x h
m=mass
g=gravitational acceleration
h=height in meters above the reference level
Deformational energy: energy stored within a body when it is deformed (stretched, compressed, bent, twisted)
ie: pole vaulters pole
Efficiency
how much mechanical output (work) can be prduced with use of a given amount of metabolic input (energy).
human skeletal muscle is 25% efficient
muscular coactiviation
antagonist muscle action that works against agonist muscle action on the opposite side of a joint
Muscle
40-45% of body weight
excitability (ability to respond to a stimulus)
contractility (ability to generate a pulling force aka tension)
extensibility (ability to lengthen or stretch)
elasticity (ability to return to its original length and shape)
contractile produces force, noncontractile doesn’t
unipennate, single set of fibers, bipennate two sets of fibers with different angles, multipennate muscles…etc.
fusiform
muscles fibers that run parallel to a line between the muscle’s origin and insertion
Pennation angle
fibers are arranged at an angle (usually <30 degrees)
allows more muscle fibers to be packed into a given volume with increases force production potential
Muscle action
concentric: if torque is greater than that created by the external force (shortening)
positive: if muscular force and the displacement are in the same direction
negative: muscular force and displacement are in opposite directions (eccentric)
length-tension
the force produced by the musculotendinous unit is determined, in part, by the muscle’s length.
Force-velocity
muscle’s ability to generate force depends on its velocity, or speed, of contraction
specific tension
force of contraction per unit
fast twitch have higher specific tension than slow twitch (they are larger)
recruitment
most strength gain at first is neural because it exceeds increase in muscle fiber size
(clients will see a lot of progress at first and then plateau because of this)
*slower gains due to hypertrophy will result in enhanced strength and improved physical appearance
RFD
rate of force development
*maximal muscle force can take up to 0.5 seconds to develop. any less, it won’t happen
*the ratio of change in force over the change in time
SSC
Stretch Shortening Cycle
*requires an eccentric muscle action immediately followed by a concentric muscle action
Pre-forcing the muscle
muscles are tensed prior to lifting the bar
*during eccentric muscle action, the muscle is developing force, so the muscle does not commence concentric action with zero force
Moment arms
a person with larger moment arm can produce more torque for the same level of muscular force
*moment arm change as a function of joint angle
Strength
the maximal force that a muscle or muscle group can generate at a specified velocity
Sticking point
weakest point in the range of motion
*occurs where the external resistance has the greatest mechanical advantage compared to the muscle
Kinematic chain
a series of linkages
two ends fixed, linkage is closed (the movement of one joint will cause every other joint to move in a predictable fashion)
ex: bench press, squat
not fixed, linkage is open (not necessarily cause movement at another joint)
ex: arm curl, leg curl
Muscle Control Formula:
1) Identify the join movement
2) Identify the effect of external force on the joint movement
3) Identify the type of muscle action
4) Identify the plane of movement
5) Determine which side of the joint axis the muscles are lengthening and which side they are shortening
6) Combine info from 3 and 5 to determine which muscles must be producing or controlling movement
Resistance types
constant, variable, or accommodating
free weights
ex: dumbbells, medicine balls, a person’t body
fixed mass and no constraints on motion
resistance to movement depends on direction of movement
Fr=ma + W
