Study Notes for Kinesiology: Scientific Basis of Human Motion

KINESIOLOGY: Scientific Basis of Human Motion

Presentation Overview

• Textbook: KINESIOLOGY: Scientific Basis of Human Motion, 12th edition

• Authors: Hamilton, Weimar & Luttgens

• Presentation Created by: TK Koesterer, Ph.D., ATC, Humboldt State University

• Revision by: Hamilton & Weimar

• Publisher: McGraw-Hill/Irwin

• Copyright: © 2012 by The McGraw-Hill Companies, Inc. All rights reserved.

Key Learning Objectives

1. Describe the structure and properties of the whole muscle, fast and slow twitch muscle fibers, and the myofibril.

2. Explain how the relationship of the muscle line of pull to the joint axis affects the movement produced by the muscle.

3. Describe the relationship between skeletal muscle fiber arrangement and function.

4. Define the roles a muscle may play and explain the cooperative action of muscles in controlling joint actions by naming and explaining the muscle roles in a specified movement.

5. Define the types of muscular contraction, name, and demonstrate each type of action.

6. Demonstrate an understanding of the influence of gravity and other external forces on muscular action.

7. Describe various methods of studying muscle action.

8. State the force-velocity and length-tension relationships and explain their significance to static and dynamic movements.

9. Identify muscle groups active in a variety of motor skills.

Muscle Properties

1. Extensibility and Elasticity

• Definition: Extensibility and elasticity enable muscles to be stretched and subsequently return to their normal length.

• Tendons: Tendons, as continuations of the muscle’s connective tissue, also possess extensibility and elasticity properties.

2. Contractility

• Definition: The ability of muscle tissue to shorten and produce tension.

Muscle Fiber Structure

1. Muscle Fiber Constituents

• Components: Muscle fibers consist of myofibrils that are held together by the sarcolemma (cell membrane), which can propagate nerve impulses.

• Muscle Layering:

  • Epimysium: Encloses a bundle of muscle fibers (fascicule).

  • Perimysium: Surrounds individual fascicles.

  • Endomysium: Encloses each muscle fiber.

• Figures: Refer to Fig 3.1 and Fig 3.2 for visual representation of muscle fiber arrangement and myofibril structure.

2. Myofibril and Banding

• Striated Appearance: Muscle fibers are arranged in parallel formation, exhibiting alternating dark (A-band) and light (I-band) bands leading to a striated appearance.

• Fibers and Myofilaments:

  • Actin: Filament that slides over myosin when stimulated.

  • Myosin: Contains cross-bridges (projections or heads) that attach to actin during contraction.

• Sarcomere:

  • Definition: The functional contractile unit of skeletal muscle, situated between two Z lines.

  • Cross-Bridges: Myosin heads interacting with actin cross-bridges, contributing to muscle contraction.

Types of Muscle Fibers

1. Fiber Distribution

• Major Categories: Fast twitch and slow twitch fibers are the two main types critical for kinesiology.

• Characteristics:

  • Fast Twitch Fibers:

  • Types: Includes IIa (fast oxidative glycolytic) and IIb (fast glycolytic) fibers.

  • Attributes: Large, pale, lesser blood supply; suited for intense responses over short periods.

  • Slow Twitch Fibers:

  • Attributes: Small, red, rich in blood supply and myoglobin; highly efficient, fatigue-resistant, suited for endurance and posture.

Muscle Attachment and Action

1. Muscle Attachment to Bone

• Mechanism: Muscles connect to bone via connective tissue which continues beyond the muscle belly to form a tendon.

• Origin vs. Insertion:

  • Origin: Typically more proximal to the body.

  • Insertion: Typically more distal.

• Reverse Muscle Action: Occurs when the distal bone is stabilized, leading to movement at the proximal bone.

Structural Classification of Muscles by Fiber Arrangement

1. Types of Muscles

1. Longitudinal: Strap-like muscle with fibers parallel to the long axis (e.g., Sartorius, Rectus femoris).

2. Quadrate: Four-sided, typically flat muscles with parallel fibers (e.g., Rhomboids).

3. Triangular: Fibers radiate from a narrow base to a broad apex (e.g., Pectoralis major).

4. Fusiform: Muscle shape that is thick in the middle, tapering at the ends (e.g., Brachioradialis).

5. Pennate: Short, parallel fibers extend diagonally from a long tendon (e.g., Tibialis posterior).

6. Bipennate: Central tendon with fibers extending in pairs on either side (e.g., Rectus femoris).

7. Multipennate: Several tendons with diagonally running fibers (e.g., Deltoid).

Muscular Force Production

1. Force Generation

• Physiological Cross Section (PCS): The amount of force a muscle can exert is proportional to its PCS; broader, thicker muscles exert more force.

• Comparative Analysis: According to the arrangement of fibers, pennate muscles can exert greater force compared to longitudinal configurations of comparable thickness due to their fiber arrangement.

2. Muscle Shortening and Length

• Contractile Ability: Muscles can shorten to approximately half their resting length. Long muscles with longitudinally arranged fibers can produce force over longer distances, while pennate muscles, despite their superior force generation, are limited to shorter ranges due to their structure.

Joint Motion and Muscle Action

1. Joint Dynamics

• Movement Produced: The movement of a contracting muscle is influenced by:

  • Type of Joint: It spans.

  • Muscle's Line of Pull: The relationship of the muscle to the joint's axis.

  • Example: Pectoralis Major (Clavicular) serves primarily as a flexor but also aids in adduction when the arm is abducted.

2. Rotational Forces

• Rotational components of muscle tension depend on the angle of the muscle's line of pull relative to the bone; maximum efficiency occurs at a 90-degree angle.

Muscle Contraction Types

1. Definitions

• Isometric Contraction: "Equal length"; muscle tension develops without significant length change. Occurs through:

  1. Muscles of equal strength contracting antagonistically.

  2. Muscle opposing a force.

• Isotonic Contraction: "Equal tension"; tension remains constant as the muscle shortens or lengthens.

• Isokinetic Contraction: "Equal or same motion"; requires maximum effort at a consistent speed.

Gravity and Movement Dynamics

1. Influence of Gravity

• Movement actions are categorized as:

  • In Direction of Gravity: Downward movements requiring concentric contraction against gravity.

  • Against Gravity: Upward movements necessitate eccentric contractions to manage resistance.

  • Horizontal Motion: Not affected by gravity.

2. Other Contraction Mechanisms

• Concentric: Agonist muscles contract when lifting against gravity.

• Eccentric: Muscles actively lengthen while controlling downward motion.

Length-Tension Relationship

1. Optimal Muscle Length

• Maximum Tension: Achieved at a length slightly greater than resting length, impacted by passive stretching and total tension developed.

• Figure Reference: Refer to Fig 3.7 for visual representation.

2. Force-Velocity Relationship

• Incudes the principle that as contraction speed increases, the force exerted decreases, eventually reaching a maximum velocity where load is zero.

• Refer to Example: Fig 3.8 illustrates this relationship.

Elastic Properties of Muscles

1. Elastic Energy Utilization

• Concentric contractions benefited by preceding active stretching utilize stored elastic energy located in tendons and muscle fibers (both series and parallel elastic components).

Cooperative Muscle Function

1. Muscle Roles

• Agonists: Directly responsible for movement.

  • Prime Movers: Muscle groups having significant impact on movement.

  • Assistant Movers: Muscle groups that assist as needed.

2. Synergists and Antagonists

• Synergists: Cooperate to stabilize and fixate muscle actions, preventing unwanted movements.

• Antagonists: Oppose the actions of agonists, relaxing to enable movement and acting as brakes upon completion.

Bi-articular Muscles and Movement

1. Action Dynamics

• Concurrent Actions: Involves simultaneous flexion or extension actions across multiple joints without net length change.

• Countercurrent Actions: One muscle shortens while its antagonist lengthens, both maintaining tension across joint movements.

Movement Initiation and Techniques

1. Types of Movements

• Passive Movement: Movement occurs without muscular effort, facilitated by external forces.

• Active Movement: Movement produced by one's own muscular effort; muscle tension can vary between slow and rapid movements.

• Vigorous Movements: Such as throwing or kicking utilize forceful contractions; emphasis on form during initial learning stages is essential.

Analysis of Muscle Actions

1. Research Methods

• Conjecture & Reasoning: Understanding muscle location, attachments, and joint structure assists in deducing possible muscle actions.

• Visual Methods: Dissection, palpation, and models aid in visualizing muscle potential movements.

• Muscle Stimulation: Observing the contraction of individual muscles in practice.

• Electromyography (EMG): Provides data on muscle electrical activity, revealing intensity and duration of contractions but not their nature.

Documentation of Joint Action

1. Analysis Charting

• Descriptions of muscular contributions should be charted alongside respective joint movements, detailing type of contraction and involved muscle groups.

2. Example Documentation

Conclusion

Summary

The study of kinesiology encompasses understanding muscle properties, contraction types, and the interrelationship of muscle actions during movement. It is critical to analyze joint actions thoroughly, documenting pertinent details to develop a comprehensive understanding of human motion.