Torque
- Torque = The turning effect of an _________ force.
- Equals the product of the force magnitude and the length of the moment arm.
- Moment arm is the ___________ distance from the line of force to the axis of rotation.
- Torque may be modified by changing either force or moment arm.
eccentric
perpendicular
THE LEVER
*A rigid bar that can rotate about a fixed point when a _____ is applied to overcome a ________.
- They are used to:
- Balance 2 or more forces.
- Favor _____ production.
- Favor ______ and ______ of motion.
- Change the direction of the applied force
force, resistance
force
speed, range
Anatomical Levers
- Nearly every _____ is a lever.
- This is especially evident when we recognize that bone is a rigid bar that turns about a _______ when a force is applied to it.
1) If bone is the rigid bar, what acts as the fulcrum in the body?
2) What is the supplying force?
bone, fulcrum
1) Joint
2) Contracting Muscles
True or False:
-All bones in the body resemble bars and/or are considered levers.
-False
-Some bones do not necessarily resemble bars.
Ex. skull, scapula, vertebrae
Lever Arms
*Lever Arm = Portion of lever between ______ and ______ application (synonymous with that of a moment arm).
- Effort arm (EA):
- Perpendicular distance between fulcrum and ____ of _____ of effort.
- Resistance arm (RA):
- Perpendicular distance between fulcrum and ____ of _________ force.
fulcrum, force
line, force
line, resistance
Classification of Levers
- Three points on the lever have been identified
1. _______ (the point at which it turns)
2. ______ force application
3. _________ force application - There are three possible arrangements of these points.
- Any 1 of the 3 may be situated between the other 2.
*This arrangement is the basis for the classification of levers.
1) Fulcrum
2) Effort
3) Resistance
First-Class Lever
- The effort force and the resistance (load) force are located on ________ sides of the axis of rotation.
- First class levers can be used to magnify the effects of the effort or to increase the [force production/speed and range of motion].
- This is accomplished on the basis of:
- The relative lengths of the effort moment arm (EA) and the resistance moment arm (RA).
- First class levers [are/are not] very common in the human body.
- Example: the joint between the skull and the atlas vertebrae of the spine.
- -The spine is the fulcrum across which the muscles lift the head (up and down).
- Exercise example: tricep extension: tricep pushdowns, tricep db extensions, dips
opposite
speed and range of motion
are not
Second-Class Lever
- The resistance (load) force and the effort force are on the _____ side of the axis of rotation (fulcrum), where the_________ force is in the MIDDLE.
- Primary function is to magnify the effect of [force production/speed and range of motion].
- The _______ arm is always longer than the __________ arm.
- The main disadvantage is that range of motion is sacrificed.
- Second class levers [are/are not] very common in the human body.
- Exercise example: is ankle extension: calf raises, pushups
same, resistance
force production
effort arm > resistance arm
are not
Third-Class Levers
- Primary function is to magnify [force production/speed and range of motion].
- _________ arm is longer than _______ arm – so even though the entire lever will move through the same angular distance, the _________ moves a small linear distance, while the __________ moves through a larger linear distance.
*The advantage of the third-class lever is [force production/speed and range of motion] at the expense of [force production/speed and range of motion].
- Third-class levers are the MOST COMMON LEVERS in the body.
- Examples include: bicep curl, hamstring curls, leg extensions, dumbbell flies, shoulder press, lateral raises
speed and range of motion
Resistance, effort
effort, resistance
speed and range of motion, force
The Principle of Levers
*Principle of levers = Any lever will _______ when the product of the effort and the effort arm equals the product of the resistance and the resistance arm
Equilibrium = Effort x ______ Arm = Resistance x ________ Arm
balance
Effort, Resistance
Equilibrium = E x EA = R x RA
The heel joint is an example of a _____-class lever.
Second-class lever.
The joint between the skull and the first vertebrae is an example of a _____-class lever.
First-class lever
The elbow joint is an example of a _____-class lever.
Third-class lever
Doing a push-up is an example of a _____-class lever.
Second-class lever
Performing tricep extensions is an exmaple of a _____-class lever.
First-class lever
Performing hamstring curls is an example of a _____-class lever.
Third-class lever.
