Chapter 2 Flashcards
Biomechanics
The mechanisms through which components interact to create movement
Origin and insertion
Origin is proximal (more stable)
Insertion is distal
Describe agonist
The prime mover
Describe antagonist
The muscle that works against the prime mover. Slows down and stops the movement
Describe synergist
The muscle that assist indirectly with the movement. Acts as a stabilizer
What is a lever?
A rigid or semirigid body that, when subjected to force, exerts force on any object
First class lever
The applied force and resistive force sit on opposite sides of the fulcrum
(i.e. tricep extensions)
Type 2 lever
The resistive and muscle force act on the same side of the fulcrum. With the muscle force having a longer moment arm, thus creating a mechanical advantage
(i.e. calf raises)
Type 3 lever
When the resistive force and muscle force act on the same side of the fulcrum with the MA of the resistive force being longer. Thus creating a mechanical disadvantage
(i.e. bicep curl)
Mechanical Advantage definition
The ratio of the moment arm of the applied force and resistive force
Mechanical advantage ratio
Greater than 1.0. The muscle force can apply less force than the resistive force to produce an equal amount of torque
Mechanical disadvantage ratio
Less that 1.0. The muscle force has to apply greater force than the resistive force to produce an equal amount of torque.
How does the patella affect mechanical advantage?
Mechanical advantage can vary through ROM motion. During knee extension the patella maintains the distance of the quadriceps tendon from the axis of rotation thus increasing the mechanical advantage
How does mechanical advantage vary during a bicep curl?
The elbow does not have a “patella” the distance from the joint to the tendon vary throughout moving. Changing the mechanical advantage.
Additionally, as the weight is lifted the MA of the resistive force changes, affecting the mechanical advantage
Tendon insertion and Mechanical advantage
The point where the tendon attaches to the bone can vary
-further from joint = greater mechanical advantage but loss of maximum speed
(able to lift heavier weights but not as fast)
This arrangement also reduces force capabilities during faster movements
What are the 3 planes of motion?
Sagittal, frontal, and transverse
Define Force and its SI units
F= M * A
(Newtons)
Define strength
The capacity to exert force at any given speed
Define acceleration
The change in velocity per unit of time
Define Power and its SI units
P= W/T
or
P = F* Velocity
(Watts)
Define work and its SI units
W = F * Displacement
(Joules)
What is negative work?
Work performed on, rather than by, the muscle
(occurs during eccentric movements)
Describe Angular displacement
The angle through which an object rotates
Rotational work
Rotational work = Torque X angular displacement
List the biomechanical factors of 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 ratio
-body mass
Neural control and strength
Rate coding: the rate at which MU fire
Recruitment: which and how many MUs fired
Arrangement of muscle fibers and strength
Angle of pennation: the angle between the muscle fibers and an imaginary line between the muscle origin and insertion
The more pennation = more cross sectional area and greater force production
Muscle length and strength
Resting vs contraction vs stretched
The amount of cross bridge site available determine the muscle ability to generate force.
Resting is optimal
The 3 types of muscle actions
Concentric
Eccentric
Isometric
Body size and strength
Body size incerases faster that muscle strength. Smaller athletes tend to have greater strength to mass ratio
Sources of resistance
-gravity
- inertia
-friction
- fluid resistance
-elasticity
Back injury
back should be moderately arched. Vulnerable due to compression and large MA in some movements
Intra-abdominal pressure and lifting belts
the “fluid ball” aids in supporting the vertebral column
Shoulder injury
Prone to injury of stabilizing muscles and tendons because of the shallow joint.
Knee injury
Prone to injury because of its location between two levers
Elbows and wrists
Primary concerns involves overhead lifts
