Chapter 2 Flashcards
Biomechanics
focuses on the mechanisms through which the musculoskeletal components interact to create movement
Origin
proximal attachment (toward center of body) -attached to stationary structure
Insertion
distal attachment (away from center of the body) -attached to mobile structure
Fleshy attachements
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
Fibrous attachments
i.e. tendons
blend into and are continuous with both the muscle sheaths and the connective tissue surrounding the bone.
Agonist
muscle that brings about movement
Antagonist
muscle that can slow down or stop movement
-assist in joint stabilization
Cartilaginous joint
joints connected by cartilage
Synergist
a muscle that assists indirectly in a movement
-ex. muscles that stabilize scapula act as synergists during upper body arm movement
First-class lever
lever for which the muscle force and resistive force act on opposite sides of the fulcrum
Fulcrum
pivot point of a lever
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
Mechanical Advantage
ratio of moment arm through which an applied force acts to that through which a resistive force acts.
Moment arm
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.
Muscle Force
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
Resistive Force
force generated by a source external to the body (gravity, inertia, friction) that acts contrary to muscle force
Second-class lever
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
Third-class lever
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
Torque
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.
aka moment
Anatomical position
body erect
arms down at sides
palm forward
Sagital plane
left right
Frontal plane
front back
Transverse plane
top bottom
Strength
ability to exert force
Acceleration
change in velocity per unit time
Power
time rate of doing work
-Power = Work / Time
Work
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
Angular Displacement
angle through which an object rotates
-measured by radians (rad)
Angular Velocity
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.)
Recruitment
recruiting motor units during muscle contraction
Rating Coding
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.
Pennate Muscle
fibers that align obliquely with the tendon
-featherlike arrangement
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
Classic Formula
load lifted / body weight^2/3
