Chapter 2 Flashcards
biomechanics
the study of how musculoskeletal systems interact to make movement
muscle origin
a muscle’s proximal attachment
muscle insertion
a muscle’s distal attachment
fleshy attachment of muscle
characteristics, location
a type of muscle attachment typically found at the proximal muscle origin.
muscle fibers are directly attached to bone over a wide area
Fibrous attachments of muscle
characteristics
type of muscle attachment.
contiguous with periosteum and epimysium.
has fibers that extend into bone
agonist
the “prime mover”
the muscle most responsible for causing movement
antagonist
the muscle that can slow down or stop a movement.
this protects the structure of joints
synergist
the muscle that assists indirectly in a movement
especially important when an agonist crosses 2 joints
first class lever
lever type in which muscle force and resistive force are on opposite sides of fulcrum
fulcrum
the pivot point of a lever
lever
a body that:
- doesn’t go through pivot point when subjected to force
- is rigid or semirigid
- exerts force on any impedance to its rotation
mechanical advantage
the muscle force moment arm > the resistive force moment arm
muscle force
the force generated by muscle tissue
resistive force
the force generated by an external source in opposition to the agonist
second class lever
a lever type in which:
- muscle force and resistive force are on same side of fulcrum
- mechanical advantage
moment arm
aka force arm, torque arm, lever arm
the perpendicular distance from a force’s line of action to the fulcrum
third class lever
a lever type in which:
- muscle force and resistive force are on same side of fulcrum
- mechanical disadvantage
torque
definition, formula, unit
the measure of how much a force rotates an object around its fulcrum
Formula: force * length of moment arm
measured in Newtons * meters
work
= (the force exerted on an object) x (the distance it moves) =
F * D =
measured in joules or Newtons * meters
power
formula(s), unit, definition
the time rate of doing work
P = W/t P = F * v
measured in Watts or Joules/seconds
angular displacement
definition, unit
the angle through which an object rotates
measured in radians
angular velocity
definition, unit/measurement
an objects rotational speed
measured in radians/sec
rotational work
formula, unit, definition
the work done in rotating an object
measured in Joules
rotational work = Torque * angular displacement
rotational power (formula)
rotational work / time
recruitment
the involvement of motor units into a contraction
rate coding
the rate motor units are fired
pennate muscle
fibers align obliquely with tendon. featherlike arrangement
angle of pennation
angle between muscle fibers and imaginary line connecting origin to insertion
(rare to see pennation greater than 15 degrees)
classic formula
used to equate loads lifted between athletes
= load/bodyweight^2/3
bracketing technique
training method in which a lighter than competition load is used to develop acceleration, and a heaver than comp load is used to develop strength/force production
friction
resistive force from one object pressed against another
fluid resistance
resistance met from an object going through a fluid, or fluid around or through an opening in an object
surface drag
1 of 2 forms of fluid resistance produced from friction of fluid on objects surface
form drag
1 of 2 forms of fluid resistance produced from fluid meeting front or rear of object.
(cross sectional area affects this)
lordotic spine position
neutral spine position in which the lumbar region is arched ventral
ventral
towards the front - anterior
dorsal
towards the back - posterior
Valsalva maneuver
closed glottis. rib + abdomen muscles are contracted to make torso rigid and support spine
Factors in muscle force
- muscle length
- arrangement of fibers
- Neural control
- Muscle cross sectional area
- strength to mass ratio
- joint angle
- joint angular velocity
- muscle contraction velocity
Loose Apples Never Can Slow JAV^2
factors of neural control component on muscle force production
more force when
- more motor units involved (recruitment)
- bigger motor units involved
- higher firing rate (rate coding)
effect of cross sectional area on muscle force
higher cross-sectional area indicates more strength
effect of fiber arrangement (pennation) on muscle force
more pennation means more force potential, but less velocity potential
effect of muscle length on muscle force
resting length = most potential crossbridge sites = most force potential
factors contributing to effect of joint angle on muscle force
dependent on
- moment arms
- type of exercise
- joint in question
effect of contraction velocity on muscle force
force capability declines as velocity increases
effect of joint angular velocity on muscle force
higher for eccentric actions vs. concentric
lower speeds = greater force capabilities
importance of strength:mass ratio
important for sports with weight classes
body size effect on strength
body mass increases faster than strength
the classic formula can equate lifts from different body sizes
sources of resistance to muscle contraction
- gravity
- inertia
- friction
- fluid resistance
- elasticity
gravity as resistance
things to know
F (weight) = mass * acceleration of gravity
gravity’s effect differs due to moment arms
inertia
inertia reduces resistance at the end of a movement
heaver weights can be used in high acceleration movements than in slow movements
back injury
location, how, avoidance
common location : L4 - S1
how: when the torso is supporting a heavy load
avoidance: neutral posture (lumbar lordotic, thoracic kyphotic), intra-abdominal pressure
kyphotic
neutral spine position in which the thoracic vertebrae are arched slightly dorsal
shoulder injury
why prone, avoidance
why: high mobility and varying tissue types makes the joint less stable
avoidance: warm up with light weights
knees
how do the get injured
injured when torque is applied not in normal plane of movement (i.e. lateral/medial rotation)
or repetitive high-forces on patellar tendon
elbows/wrists (how)
how: overhand sports and overhead lifts
effects of tendon insertion location
- moment arm
- velocity
eccentric muscle action
F(m) > F(r)
muscle shortens
concentric muscle action
F(r) > F(m)
muscle shortens
isometric muscle action
Fm = Fr
muscle length unchanged
3 ways to create intra-abdominal pressure
- valsalva maneuver
- contract diaphragm with open glottis
- weight belt
