Biomechanics: Kinetics and Muscle Contraction

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Questions and Answers

What is the term for a muscle group that is most directly related to the execution of a particular movement?

Agonist (correct)

Synergist

Antagonist

Protagonist

What type of lever system is most common in the musculoskeletal system?

First class

Second class

Third class (correct)

Fourth class

What is the term for the muscle that opposes the action of a particular agonist?

Protagonist

Agonist

Synergist

Antagonist (correct)

How do muscle torques occur in the musculoskeletal system?

Through a system of bony levers Signup and view all the answers

What type of contraction would the quadriceps muscle undergo during a CKC movement?

Eccentric Signup and view all the answers

What is the term for a muscle that cooperates during the execution of a particular movement?

Synergist Signup and view all the answers

What type of instrument is used to measure an applied force by the amount of strain of a deformable material?

Instrumento mecánico Signup and view all the answers

What is a characteristic of a first-class lever system in the musculoskeletal system?

The axis of rotation is located between the opposing forces Signup and view all the answers

What is the primary mechanism of a manual dinamometer?

Mechanical movement of a dial caused by material strain Signup and view all the answers

What is the purpose of calibration in transducer output?

To convert measured voltage to meaningful measures Signup and view all the answers

Which device is commonly used for dynamic strength assessment?

Isokinetic dynamometer Signup and view all the answers

What is the primary function of an encoder in kinetic analysis?

To combine force, distance, and time data Signup and view all the answers

What is the scope of electromyography (EMG)?

To record and interpret muscle electrical activity Signup and view all the answers

What type of muscle activation can be measured using an isokinetic dynamometer?

Concentric, isometric, and eccentric muscle activation Signup and view all the answers

What is the branch of mechanics that describes the effect of forces on the body?

Kinetics Signup and view all the answers

What type of force is generated by stimulated muscle?

Active force Signup and view all the answers

What is the product of a force and its moment arm?

Torque Signup and view all the answers

What type of muscle contraction occurs when the muscle is producing a pulling force while maintaining a constant length?

Isometric muscle contraction Signup and view all the answers

What is the direction of a force depicted by an arrow?

Direction Signup and view all the answers

What type of forces are produced by forces acting from outside the body?

External forces Signup and view all the answers

What occurs when a muscle is stimulated by the nervous system?

Muscle activation Signup and view all the answers

What type of muscle contraction occurs when the muscle produces a pulling force as it is being elongated by another more dominant force?

Eccentric muscle contraction Signup and view all the answers

Study Notes

Kinetic Principles of Muscle Contraction

Kinetics is a branch of mechanics that describes the effect of forces on the body, including forces that move, fixate, or stabilize the body, which can also deform and injure the body.

Internal and External Forces

Internal forces are generated by structures within the body, including:
- Active forces: generated by stimulated muscle, not necessarily under volitional control
- Passive forces: generated by tension in stretched periarticular connective tissues
External forces are produced by forces acting from outside the body, including gravity and external loads.

Forces and Vectors

A force is represented by an arrow, which is a vector with magnitude, spatial orientation, direction, and point of application.

Torque

Forces exerted on the body can translate a body segment (linear) or apply a rotational force (torque) at a distance from the axis of rotation.
Torque is the product of a force and its moment arm (distance from the axis of rotation).

Muscle Activation

Muscle activation occurs when a muscle is stimulated by the nervous system.
Types of muscle activation:
- Isometric: muscle produces a pulling force while maintaining a constant length
- Concentric: muscle produces a pulling force as it contracts (shortens)
- Eccentric: muscle produces a pulling force as it is being elongated by another force

Muscle Terminology

Agonist: muscle group that is most directly related to the execution of a particular movement
Antagonist: muscle that has the opposite action of a particular agonist
Synergist: muscle that cooperates during the execution of a particular movement

Musculoskeletal Levers

Muscle torques occur through a system of bony levers, including:
- First class: axis of rotation between the opposing forces
- Second class: axis of rotation at one end of a bone and the muscle
- Third class: axis of rotation at one end of a bone and the muscle possesses lower leverage than the external force

Kinetic Analysis

Instruments used in kinetic analysis:
- Mechanical instruments (e.g. manual dinamometer, pressure dinamometer)
- Transducers: measure applied force by deforming a material, resulting in a change in voltage
- Electromechanical instruments (e.g. isokinetic dynamometer): measure kinetic data produced by concentric, isometric, and eccentric muscle activation
- Electromyography (EMG): records and interprets electrical activity of activated skeletal muscle
- Encoder: records force parameters based on a dynamometer, mixed with data of distance and time

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Description

Understand the principles of kinetics and muscle contraction, including internal and external forces that affect the body. Learn how forces can deform and injure the body.