3-1 kinesiology for manual therapies chapter 3 basic biomechanical factors and concepts mcgraw-hill...

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Kinesiology for Manual Therapies

Chapter 3

Basic Biomechanical Factors and Concepts

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Learning Outcomes

o 3-1 Differentiate between the levers and explain how they apply to physical performance.

o 3-2 Discuss how the musculoskeletal system functions as a series of simple machines.

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Learning Outcomes

3-3 Describe how knowledge of torque and lever arm lengths can help improve physical performance.

3-4 Recall Newton’s laws of motion and cite examples of how the laws can apply to improving physical performance.

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Learning Outcomes

3-5 Compare balance, equilbrium, and stability and discuss how they can each help improve physical performance.

3-6 Define force and momentum and describe how they can help improve physical performance.

3-7 Analyze the basic effects of mechanical loading on the tissues of the body.

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Introduction

Motion cannot occur unless there is force behind it.Motion includes many levers, torque, and pulleys that all exist as force is applied.The study of physical action of forces is called mechanics.

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Introduction (cont.)

The study of mechanics as it relates to the functional and anatomical analysis of biological systems is known as biomechanics.

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Introduction (cont.)

Kinematics is concerned with the description of motion. Kinetics is the study of forces associated with the motion of the body.

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Types of Machines Found in the Body

Mechanical advantage – the ability to apply a relatively small force to move a greater resistance.

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Types of Machines Found in the Body (cont.)

Machines function in four ways: To balance multiple forcesTo enhance forceTo enhance range of motionTo alter the resulting direction of the applied force

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Types of Machines Found in the Body (cont.)

Three machines in the body produce movement:Levers, wheels and axles, and pulleys

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Levers

A lever is defined as a rigid bar that turns around an axis of rotation. An axis is the point of rotation around which the lever moves. The lever rotates around the axis as a result of the force.

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Levers (cont.)

Bones are the lever bars, the joints are the axes, and the muscles produce the force. First-class lever Second-class lever Third-class lever

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Levers (cont.)

First-class lever is designed for balance movements.

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Levers (cont.)

Second-class lever is designed to produce force movements.

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Levers (cont.)

Third-class levers are designed to produce speed and range-of-motion movements. The force is applied between the axis and the resistance.

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Levers (cont.)

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Levers (cont.)

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Factors in the Use of Anatomical Levers

Torque – moment of force Eccentric force Force arm Resistance arm

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Factors in the Use of Anatomical Levers (cont.)

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Factors in the Use of Anatomical Levers (cont.)

Human levers are built for speed and range of motion at the expense of force. The longer the lever, the more effective it is in imparting velocity.

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Factors in the Use of Anatomical Levers (cont.)

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Factors in the Use of Anatomical Levers (cont.)

Wheels and axles are used to enhance range of motion and speed of movement in the musculoskeletal system.

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Factors in the Use of Anatomical Levers (cont.)

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Factors in the Use of Anatomical Levers (cont.)

The lateral malleolus acts as a pulley around which the tendon of the peroneus longus runs. The pulley directs the force to the plantar aspect of the foot.

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Factors in the Use of Anatomical Levers (cont.)

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Laws of Motion and Physical Activities

Linear motion – motion along a line Angular motion – rotation around an axis Displacement – change in the position or location of an object from its original point of reference

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Laws of Motion and Physical Activities (cont.)

Distance – sum length of measurement traveled Speed – how fast an object is moving Velocity – direction and describes rate of displacement

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Laws of Motion and Physical Activities (cont.)

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Laws of Motion and Physical Activities (cont.)

Inertia – resistance to action or change Law of inertia – a body in motion tends to remain in motion at the same speed in a straight line unless acted on by a force; a body at rest tends to remain at rest unless acted on by a force.

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Laws of Motion and Physical Activities (cont.)

Acceleration – rate of change in velocity Mass – amount of matter

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Laws of Motion and Physical Activities (cont.)

Law of acceleration - A change in the acceleration of a body occurs in the same direction as the force that caused it. The change in acceleration is directly proportional to the force causing it and inversely proportional to the mass of the body.

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Laws of Motion and Physical Activities (cont.)

Law of reaction - For every action there is an opposite and equal reaction.

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Laws of Motion and Physical Activities (cont.)

Sherrington’s law – is the law of reciprocal innervation. For every neural activation of a muscle, there is a corresponding inhibition of the opposing muscle.

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Friction

Friction is the force that results from the resistance between the surfaces of two objects moving against one another.

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Balance, Equilibrium, and Stability

Balance is the ability to control equilibrium.

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Balance, Equilibrium, and Stability (cont.)

Factors enhancing equilibrium, stability, and balance include: Center of gravity falls within the base of support. Size of the base.

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Balance, Equilibrium, and Stability (cont.)

Balances depends on weight or mass. Balance depends on the height of the center of gravity. Balance depends on where the center of gravity is in relation to the base.

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Balance, Equilibrium, and Stability (cont.)

Stability is increased by enlarging the size of the base. Equilibrium can be enhanced by increasing friction. Rotation around an axis aids balance.

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Balance, Equilibrium, and Stability (cont.)

Kinesthetic physiologic functions contribute to balance. Principles of balance, stability, and center of gravity can be applied to sports, preventing injuries, and achieving good body mechanics for the manual therapist.

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Force

Force is the product of mass times acceleration.

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Mechanical-Loading Basics

Only muscles can actively generate internal force, but tension in tendons, connective tissues, ligaments, and joint capsules may generate passive internal forces.

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Mechanical-Loading Basics (cont.)

External force are produced outside the body from gravity, inertia, or direct contact.

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Mechanical-Loading Basics (cont.)

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Functional Application of Throwing

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Functional Application of Throwing (cont.)

Newton’s laws of motion apply in throwing: Law of inertia Law of acceleration Law of reaction

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Functional Application of Throwing (cont.)

Leverage factor Balance, equilibrium, stability

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Chapter Summary

Types of machines found in the body, levers, and factors in the use of anatomical levers provides a foundation for understanding how movement occurs from a mechanical perspective.

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Chapter Summary (cont.)

The laws of motion and physical activities give fundamental explanations for movement. Friction, balance, equilibrium and stability, force, and mechanical-loading basics are included in the topic of how the body moves.

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Chapter Summary (cont.)

The example of throwing utilizes the laws of motion, leverage, and balance to perform the sport.

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Chapter Review

The Chapter Review is divided into true and false, short answers, and multiple choice questions.

The questions are designed for the students to test their knowledge.

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Explore and Practice

Students should utilize the questions and charts at the end of the chapter to help focus on the content of the chapter.

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