S and C quiz 1

Origin

Muscles proximal attachment (towards center of body)

Insertion

Muscles distal attachment (away from center of body)

Agonist

Most directly involved muscle for bringing about a movement (prime mover)

Antagonist

Muscle that can slow down or stop a movement (opposes the agonist)

Synergist

Muscle that assist the agonist (either indirectly through stabilization, or to increase force production)

Fulcrum

Axis of rotation.

Resistive force

Location of the external force (dumbbell or other weight)

Applied force

The working muscle (bicep)

Moment arm of resistive force

perpendicular distance between the fulcrum and resistive force.

Moment arm of applied force

Perpendicular distance between the fulcrum and applied force.

1st class lever

The applied force and resistive force act on opposite sides of the fulcrum.

High/low force and speed/ROM. Depends on moment arm.

2nd class lever

The applied force and resistive force act on the same of the fulcrum. (ball of foot).

The applied force acts on a longer moment arm than the resistive force making it always advantageous.

Greater force but lower speed/ROM.

3rd class lever

The applied force and resistive force act on the same side of the fulcrum. (elbow flexion).

The resistive force acts on a longer moment arm than the applied force making it always disadvantageous.

Greater speed/ROM and lower force.

Mechanical advantage

Ratio of the moment arm of applied force to the moment arm of resistive force (Maf/Mrf).

>1 allows applied force to be less than the resistive force. 2nd class lever.

Mechanical disadvantage

<1 indicates applied force must be greater than the resistive force to create movement. Ex: tricep muscle group must produce 8x the force in order to lift dumbbell.

Sagital plane movements

Flexion/extension, planter flexion, dorsiflexion.

Frontal plane movements

Abduction/adduction, lateral flexion, elevation/depression.

Transverse plane movement

Rotation, horizontal abduction/adduction, pronation/supination.

Strength

Capacity to exert force (at any given speed of movement)

Power

The time rate of doing work

Work

The product of force exerted on an object and the distance an object moves in the direction of the force is exerted.

Muscle cross sectional area

Cross sectional area (rather than muscle volume) is related to muscle force (all things equal, bigger muscle is stronger muscle)

Angle of pennation

Angle of the muscle fiber and an imaginary line between muscle origin and insertion

Greater pennation

Allows for more muscle fibers side-by-side (parallel) for greater force production.

Less pennation

Allows more muscles fibers in a row (series) greater shortening velocity

Neural control

Which/how many motor units are involved (recruitment)

Rate at which motor units fire (rate coding)

Joint angle

Muscle insertion, lever type, moment arms, and muscle length.

Length-tension relationship

Maximal force production is achieved at a particular point in the ROM.

This point is associated with optimal actin and myosin cross bridging (as well as optimal Maf/Mrf).

Eccentric muscle action

Muscle lengthens because contractile force is less than the resistive force.

Concentric muscle action

Muscle shortens due to contractile force is greater than the resistive force.

Isometric muscle action

Muscle length does not change because the contractile force is equal to the resistive force.

Angular velocity

Speed of a movement through a joints ROM. Measured in degrees per second.

Torque

Rotational force

Isokinetic

Constant speed.

Force-velocity relationship (concentric contraction)

As concentric angular velocity increases, the ability to produce force decreases.

Inverse relationship. Greater force, Lower velocity.

Force-velocity relationship (eccentric contraction)

As force production increases, velocity also increases. Proportional relationship.