Flashcards in Chapter 2 Deck (42):
focuses on the mechanisms through which the musculoskeletal components interact to create movement
proximal attachment (toward center of body)
-attached to stationary structure
distal attachment (away from center of the body)
-attached to mobile structure
muscle fibers directly attached to bone over a wide area so force is distributed rather than localized.
-most often found at proximal end of a muscle
blend into and are continuous with both the muscle sheaths and the connective tissue surrounding the bone.
muscle that brings about movement
muscle that can slow down or stop movement
-assist in joint stabilization
joints connected by cartilage
a muscle that assists indirectly in a movement
-ex. muscles that stabilize scapula act as synergists during upper body arm movement
lever for which the muscle force and resistive force act on opposite sides of the fulcrum
pivot point of a lever
rigid or semirigid body that, when subjected to a force whose line of action does not pass through its pivot point, exerts force on any object impeding its tendency to roate
ratio of moment arm through which an applied force acts to that through which a resistive force acts.
perpendicular distance from the line of action of the force to the fulcrum.
-aka force arm, lever arm, or torque arm
Line of Action
infinitely long line passing through the point of application of the force, oriented in the direction in which the force is exerted.
force generated by biomechanical activity, or the stretching on non-contractile tissue, that tends to draw the opposite ends of a muscle toward each other
force generated by a source external to the body (gravity, inertia, friction) that acts contrary to muscle force
lever for which the muscle force and resistive force act on the same side of the fulcrum, which the muscle force acting through a moment arm longer than that through which the resistive force acts
-i.e. calves raising the body onto the balls of the feet
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
degree to which a force tends to rotate an object about a specified fulcrum.
-defined quantitatively bas the magnitude of force x length of its moment arm.
arms down at sides
ability to exert force
change in velocity per unit time
time rate of doing work
-Power = Work / Time
product of force exerted on an object and the distance the object moves in the direction in which the force is exerted
-Work = Force x Displacement
Weight to equal Newtons
N = pounds x 4.448
N = kg mass x 9.8 m/s2 (gravity)
N = kg force x 9.807
angle through which an object rotates
-measured by radians (rad)
object's rotational speed
-measured in rad/s
Rotational work equation
Work = torque x angular displacement
Rotational power equation
Power = Work / Time (same are power eq.)
recruiting motor units during muscle contraction
rate at which motor units are fired
Muscle force is greater when:
More motor units are involved in a contraction.
Motor units are greater in size.
Rate of firing is faster.
fibers that align obliquely with the tendon
Angle of Pennation
angle between muscle's origin and insertion
-0 degrees corresponds to no pennation
Concentric Muscle Action
muscle shortens bc contractile force is greater than the resistive force.
-forces generated within the muscle and acting to shorten it are greater than the external forces acting at its tendons to stretch it
Eccentric Muscle Action
muscle lengthens bc contractile force is less than the resistive force.
-forces generated within muscle and acting to shorten it are less than the external forces acting at its tendons to stretch it (increases risk of soreness/injury)
Isometric Muscle Action
muscle length does not change, bc contractile force is equal to resistive force.
-force generated within in the muscle and acting to shorten it are equal to the external forces acting at its tendons to stretch it