Chapter 2 Flashcards
biomechanics
focuses on the mechanics through which the musculoskeletal components interact to create movement
fleshy attachment
muscle to bone attachment often found at the proximal end of a muscle where the muscle fibers are directly fixated to the bone
fibrous attachment (tendons)
muscle to bone attachment that is blends into and is continuous with both the muscle sheaths and the connective tissue surrounding the bone, very strong union
agonist (prime mover)
the muscle most directly involved in bringing about a movement
antagonist
a muscle that can slow down or stop the movement that is happening, assists in joint stabilization
synergist
a muscle that assists indirectly in a movement or controls body motion when the agonist is a muscle fiber that crosses two joints
first class lever
a lever for which the muscle force and resistive force act on OPPOSITE sides of the fulcrum
fulcrum
the pivot point of a lever
lever
a rigid or semirigid body that exerts force on any object impeding its tendency to rotate when subjected to a force whose line of action does not pass through its pivot point
mechanical advantage
the ratio of the moment arm through which an applied force acts to that through which a resistive force acts
mechanical advantage ratio greater than 1
mechanical advantage ratio that allows the applied muscle force to be less than the resistive force to produce an equal amount of torque
mechanical advantage ratio less than 1
mechanical advantage ratio that indicates that one must apply a greater muscle force than the amount of resistive force present, creating an obvious disadvantage for the muscle
moment arm (force arm, lever arm, torque arm)
the perpendicular distance from the line of action of the force to the fulcrum
muscle force
force generated by biochemical activity, or the stretching of non-contractile tissue, that tends to draw the opposite end of a muscle toward each other
resistive force
torce generated by source external to the body that acts contrary to muscle force
second class lever
a lever for which the muscle force and resistive force act on the SAME side of the fulcrum with the muscle force, acting through a moment arm LONGER than that through which the resistive force acts
third class lever
a lever for which the muscle force and resistive force act on the SAME side of the fulcrum, with the muscle force acting through a moment arm SHORTER than that through which the resistive force acts (mechanical advantage is thus < 1)
torque (moment)
the degree to which a force tends to rotate an object about a specified fulcrum, defined quantitively as the magnitude of a force times the length of its moment arm
smaller
due to the mechanical advantage of a second class lever, the required muscle force is smaller or larger than the resistive force?
greater
due to the mechanical advantage of a third class lever being less than 1, the muscle force has to be smaller or greater than the resistive force to produce a torque equal to that produced by the resistive force?
strength
the ability to exert force at any given speed
acceleration
change in velocity per unit of time
power
time rate of doing work, “explosive strength”
work
product of the force exerted on an object and the distance the object moves in the direction in which the force is exerted
newtons (N)
SI unit for force
meters (m)
SI unit for distance
joules (J)
SI unit for work
seconds (s)
SI unit for time
watts (W)
SI unit for power
disadvantage (requires MORE force)
do most muscles work at a mechanical advantage or disadvantage?
torque x displacement
rotational work =
angular displacement
the angle through which an object rotates
tricep extension
prime example of a first class lever arm?
standing heel raise
prime example of second class lever arm?
bicep curl
prime example of a third class lever arm?
patella
increases the mechanical advantage of the quadriceps muscle group by maintaining the quad tendon’s distance from the knee’s axis of rotation
less
muscle moment arm is shorter = more or less mechanical advantage?
true
true or false: tendon insertion farther from the joint center results in the ability to lift heavier weights
muscle force acts through a greater moment arm which creates greater torque around the joint
why does tendon insertion farther away from the joint center allow you to lift heavier weights?
mass x acceleration
force =
work / time
power =
force x displacement
work =
eccentric
“negative” work and power occur during what types of muscle actions?
true
true or false: the term negative work really refers to work performed on, rather than by, a muscle
radians (rad)
SI unit for angular displacement
angular velocity
object’s rotational speed
radians/second (rad/s)
SI unit for angular velocity
torque (moment)
the degree to which a force tends to rotate an object about a specified fulcrum
torque x angular displacement
rotational work =
force and velocity
power is a direct mathematical function of what two things?
pennate muscle
a muscle with fibers that align obliquely with the tendon, creating a featherlike arrangement
angle of pennation
the angle between the muscle fibers and an imaginary line between the muscle’s origin and insertion
resisting length
muscle length when actin and myosin filaments lie next to each other, maximal number of potential crossbridge sites are available, and the muscle can generate the greatest force
stretched length
muscle length when a smaller proportion of the actin and myosin filaments lie next to each other, fewer potential cross bridge sites are available, the muscle cannot generate as much force
contracted length
muscle length when the actin filaments overlap, the number of crossbridge sites is reduced, and there is decreased force generation capability
resting length
what muscle length is muscle force capability greatest due to the increased opportunity from actin-myosin cross bridges?
concentric muscle action
a muscle action in which the muscle shortens because the contractile force is greater than the resistive force
eccentric muscle action
a muscle action in which the muscle lengthens because the contractile force is less than the resistive force
isometric muscle action
a muscle action in which the muscle length does not change because the contractile force is equal to the resistive force
strength to mass ratio
the ratio that directly reflects an athlete’s ability to accelerate his or her body
true
true or false: given constant body proportions, the smaller athlete has a higher strength to mass ratio than does the larger athlete
friction
the resistive force encountered when one attempts to move an object while it is pressed against another object
fluid resistance
the resistive force encountered by an object moving through a fluid (liquid or gas), or by a fluid moving past or around an object or through a hole
valsalva maneuver
the glottis is closed to keep the air from escaping the lungs + the muscles of the abdomen and rib cage contract creating rigid compartments of liquid in the lower torso and air in the upper torso which makes it easier to support heavy loads
fluid ball
created when the diaphragm and the abdominal muscles contract without the glottis closing to avoid pressurizing the chest compartment
pressure in the chest puts pressure on the heart, making it more difficult for blood to return to the heart
undesirable side effect of the valsalva maneuver
it is between the two long levels of the femur and tibia
why is the knee prone to injury?
epiphyseal growth plate damage or overuse
what is one of the primary concerns in the elbow and wrist either in the posterior aspect the elbow or in the distal radius in young athletes?
inertial force
force exerted on the athlete when the barbell is accelerated in addition to the gravitational force
classic formula
formula to compare loads lifted, where the load lift is divided by body weight to the two-thirds power
motor recruitment
how many motor units are involved in a muscle contraction
rate coding
the rate at which the motor units are fired
bracketing technique
form of acceleration training where the athlete performs the sport movement with less than normal and greater than normal resistance
surface drag
results from the friction of a fluid passing along the surface of an object
form drag
results from the way in which a fluid presses against the front or back of an object passing through it
cross sectional area
has a major effect on form drag
