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ch. 2 biomechanics

Terms in this set (44)

muscle origin
proximal attachment
muscle insertion
distal attachment
fleshy attachments often found
at proximal end of muscle
fibrous attachments (tendons)
blend into and are continuous with both the muscle sheaths and the connective tissue surrounding the bone
agonist
prime mover of a joint
antagonist
opposing muscle of the prime mover of the joint
Antagonist protect
ligamenetous and cartilaginous joint structures towards the end of a fast movement.
EX: during throwing, the triceps are the agonist and the biceps acts as an antagonist to low down elbow extension and bring it to a stop protecting the elbow from internal impact.
synergist
when a muscle assists indirectly in a movement.
EX: the muscles that stabilize the scapula act as synergism during upper arm movement.
first class lever
muscle force and resistive force act on opposite sides of the fulcrum
fulcrum
the pivot point of a lever
mechanical advantage
the ratio of the moment arm through which an applied force acts to that through which a resistive force acts
moment arm
The perpendicular distance from a reference point to the line of action of the force.
muscle force
force generated by biochemical activity, or the stretching of noncontractile tissue, that tends to draw the opposite ends of a muscle toward each other
resistive force
force generated by a 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

ex: calve muscles = generate the most force
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

most common in the body
torque
(moment) degree to which a force tends to rotate an object about a specified fulcrum
variation in tendon insertion
a person whose tendons are inserted on the bone farther from the joint center should be able to lift heavier weight because muscle force acts through a longer moment arm and thus can produce greater torque around the joint.

- loss of max speed
anatomical postition
hands at sides, palms forward
sagittal plane
divides body into left and right
transverse plan
divides the body into upper and lower portions
frontal plane
Divides the body into front and back portions.
strength
ability to exert force
acceleration
change in velocity over time
power
the time rate of doing work
work
product of the force exerted on an object and the distance the object moves in the direction
work equation
work = force x distance
power equation
power = work/time
*postive and negative work calculations* pg. 28
...
biomechanical factors in human strength
Neural Control
Muscle Cross-Sectional Area
Arrangement of Muscle Fibers
Muscle Length
Joint Angle
Muscle Contraction Velocity
Joint Angular Velocity
Strength-to-Mass Ration
Body Size
Nerual control
affects the maximal force output of a muscle by determining which and how many motor units are involved in a muscle contraction ( recruitment) and the rate at which the motor units are fired (rate coding)
Generally, muscle force is greater when:
-more motor units are involved
-the motor units are greater in size
-rate of firing is faster
first few weeks of resistance training is attributable to
neural adaptations as the brain learns how to generate more force from a given amount of contractile tissue.
muscle cross sectional area **
The force a muscle can exert is related to its cross-sectional area rather than to its volume.

EX: two athletes with similar BF % and same bicep circumference, their upper arm muscle cross-sectional areas are about the same. Although the taller athletes longer muscle makes for greater muscle volume, the strength of two athlete biceps should be about the same.
arrangement of muscle fibers
wide range due to variation in arrangement and alignment of sacromeres in relation to the long axis of the muscle
pennate muscle
has fibers that align obliquely with the tendon, creating a featherlike arrangement
the angle of pennation
the angle between the muscle fibers and an imaginary line between the muscle's origin and insertion
muscle length
the muscle can generate the greatest force at its resting length , when it is stretched beyond resting length , a smaller proportion of the actin and myosin lie next to each other. Because there are fewer potential crosssbridge sites the muscle cannot generate as much force as it can at its resting length.
joint angle
Amount of torque depends on force versus muscle length, leverage, type of exercise, the body joint in question, the muscles used at that joint, and the speed of contraction.
muscle contraction velocity
the force capability of muscle declines as the velocity of contraction increases
joint angular velocity
concentric, eccentric, isometric
strength to mass ratio
directly reflects an athlete's ability to accelerate his or her body.
When body size increases, muscle volume increases proportionally more than does muscle cross-sectional area.

-trial and error can help athletes find their most competitive weight class
body size ***
everything else equal- smaller athletes are stronger pound for pound than larger athletes. Because muscle maximal contractile force is family proportional to the cross-sectional area, which is related to the square of linear body dimensions, where a muscle mass is proportional to the volume.
sources of resistance to muscle contraction
gravity
inertia
friction
fluid resistance
elasticity
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