7 - Myology

Myology Overview

• Course Title: KINS 1120

• Instructor: Raelene Lang

• Institution: Langara College of Higher Learning

Learning Objectives

• Discuss muscle naming conventions with examples.

• Describe muscle contraction through sliding filament theory.

• Explain the impact of pennation on muscle contraction.

• Define general muscle categories (e.g., agonist, synergist).

• Understand the length-tension relationship of muscle.

• Compare and contrast muscle fiber types.

• Discuss how fiber distribution influences athletic performance.

• Explain motor unit activation principles (all-or-none, size, gradation of force).

• Compare relative force, velocity, and power during muscle contractions.

Importance of Understanding Anatomy

• Essential for efficient training.

• Aids comprehension of human movement.

• Helps identify which muscles produce specific movements.

• Assists in recognizing faulty movement patterns for safer program development.

  • Example: Knee pain or lack of range of motion.

• SAID Principle: Specific Adaptations to Imposed Demands; specific adaptations require corresponding stressors.

Muscle Nomenclature

Based on Shape

• Common muscle names based on shape include:

  • Deltoideus

  • Rectus Abdominis

  • Rhomboideus Major

  • Trapezius

  • Latissimus Dorsi

Based on Size

• Size nomenclature examples:

  • Gluteus Maximus

  • Pectoralis Major

  • Peroneus Brevis

  • Gluteus Minimus

  • Longissimus Thoracics

  • Vastus Lateralis

Based on Number of Attachments

• Examples:

  • Biceps Femoris (two attachments)

  • Triceps Brachii (three attachments)

  • Quadriceps (four attachments)

Based on Depth

• Examples:

  • Flexor Digitorum Superficialis (superficial attachment)

  • Obliquus Internus Abdominis

Based on Position

• Position nomenclature includes:

  • Tibialis Anterior

  • Infraspinatus

  • Vastus Medialis

Based on Function

• Examples of function types:

  • Flexor Carpi Radialis

  • Pronator Teres

  • Supinator

  • Adductor Magnus

Muscle Microstructure

• Skeletal Muscle Structure

  • Composed of muscle tissue, connective tissue, nerves, and blood vessels.

  • Epimysium: Outer fibrous connective tissue layer contiguous with tendons.

  • Muscle fibers grouped into bundles (fasciculi) surrounded by Perimysium (CT surrounding fasciculi).

  • Endomysium: CT surrounding individual muscle fibers.

  • Sarcoplasm: Contains proteins, glycogen, fats, enzymes, and organelles.

Neuromuscular Junction (NMJ)

• Connection between motor neuron and muscle fiber;

  • Each muscle fiber innervated by a single NMJ.

  • Motor unit consists of one motor neuron and all muscle fibers it innervates.

• Muscle fibers contract together under stimulation from the motor unit.

• Motor units can be either fast-twitch or slow-twitch depending on the muscle fiber type stirred.

Crossbridge Cycling

1. Resting Phase: Low calcium in myofibril.

2. Excitation-Contraction Coupling: Calcium release triggers actin binding sites.

3. Contraction Phase (Power Stroke): Myosin heads contract and release ADP and Pi.

4. Relaxation Phase: Calcium pumped back, ceasing actin-myosin interactions.

Muscle Mechanics

• Definition of Flex: Decrease angle at a joint.

• Forces produced by muscle contractions enable movement across joints.

• **Agonist vs. Antagonist: **

  • Agonist muscles perform the action while antagonists oppose it.

• Additional roles include synergists and stabilizers for joint stability.

Length-Tension Relationship

• Refers to how the tension produced during a muscle twitch is influenced by the sarcomere length before contraction.

• Optimal length improves force production; deviations (too short/too long) can reduce effectiveness.

Muscle Fiber Types

• Type I: Slow-twitch (oxidative), fatigue-resistant, darker due to myoglobin.

• Type IIa: Fast-twitch (oxidative-glycolytic).

• Type IIx: Fast-twitch (glycolytic), contract rapidly but fatigue quickly.

Fiber Type Characteristics

Fiber Type Distribution

• Influences physical capacity and athletic performance. For example:

  • Soleus: High Type I composition, crucial for endurance.

  • Triceps Brachii: Higher Type II composition, transmits larger forces.

Motor Units and Principles of Activation

Principles:

1. All-or-None: All fibers in a motor unit activate together.

2. Size Principle: Small motor units (Type I) activated first.

3. Gradation of Force: Achieved through frequency of activation and number of recruited units.

Force, Velocity, and Power

• The force and velocity of contraction are inversely related.

• Power Definition: Power is the product of force and velocity.