Sport Science Muscles and bones

Unit Overview

• Date: Aug 23-24

• Focus: Types of Muscles and Muscle Functions

Types of Muscles

1. Skeletal Muscles

   • Characteristics: Voluntary, striated

   • Attachment: Tendons attach to bones

   • Function: Main function is moving the skeleton

2. Cardiac Muscle

   • Characteristics: Striated, involuntary

   • Location: Found in the heart

3. Smooth Muscle

   • Characteristics: Not striated, involuntary

   • Location: Lines walls of hollow organs and blood vessels

Functions of Muscles

1. Movement

   • Interaction of bones, skeletal muscles, and joints

   • Muscles contract, pull tendons, which pull bones

2. Transportation of Substances

3. Stabilization of Body Positions

   • Postural Muscles

4. Generation of Body Heat

Properties of Muscle Tissue

• Contractility: Ability to contract and generate force when stimulated by nerves

• Extensibility: Ability to stretch beyond normal length

• Elasticity: Ability to return to original length

Neuromuscular Function

• Central Nervous System (CNS): Brain and spinal cord

• Peripheral Nervous System (PNS): Nerves from spinal cord to limbs

• Motor Neurons: Carry signals from CNS to muscles for contraction/relaxation

• Count: Approx. 200,000 motor neurons in human body

Muscle Energy Source

• ATP (Adenosine Triphosphate): Main energy source for muscle contractions

Motor Neuron Structure

• Neuron Components:

  • Axon

  • Soma/Nucleus

  • Dendrites

  • Myelinated Axon

Motor Units

• A motor unit consists of a single motor neuron and the muscle fibers it innervates.

• Examples:

  • Gluteus Maximus: 2000 muscle fibers per neuron

  • Eyes: 10 muscle fibers per neuron

• Innervation Ratio: Number of muscle fibers per motor neuron

Types of Motor Units

1. Type I

   • Characteristics: Slow, low force, high endurance (Aerobic), used in endurance activities

   • Example: Marathon runners

2. Type IIa

   • Characteristics: Fast, moderate force, resistant to fatigue

   • Example: Basketball, rugby

3. Type IIx

   • Characteristics: Fastest, highest force, fatigue quickly (Anaerobic)

   • Example: Weightlifting

Fiber Composition in Muscles

• Average Composition: 50% Type I, 25% Type IIa, 25% Type IIx

• Type I Muscle Fibers:

  • High aerobic endurance, efficient ATP production

  • Involved in oxidation of carbohydrate and fat

• Type II Muscle Fibers:

  • Poor aerobic endurance, better suited for anaerobic activities

  • Generate more force than Type I

Principle of Orderly Recruitment

• Motor units recruited based on the required force; smaller units recruited first.

Muscle Hypertrophy and Atrophy

• Hypertrophy: Increase in muscle size or mass

  • Transient: Temporary size increase

  • Chronic: Long-term increase in muscle size

• Atrophy: Loss of muscle size/mass due to disuse

Sliding Filament Theory

• Muscles contain myofibrils made of actin (thin) and myosin (thick) filaments

• Sarcomere: Functional unit of muscle fiber

• Contraction Process:

  • Structural changes caused by calcium ion release, allowing myosin heads to attach to actin

Types of Muscle Contractions

1. Isometric: No motion during contraction

2. Isotonic: Motion during contraction

   • Concentric: Muscle shortens

   • Eccentric: Muscle lengthens

3. Isokinetic: Constant rate of speed during contraction

Delayed Onset Muscle Soreness (DOMS)

• Related to eccentric muscle contractions and lactic acid build-up

Roles of Muscles in Joint Movement

• Depend on type and position of muscles, type of contraction

• Agonist: Prime mover contracting concentrically

• Antagonist: Muscle relaxing during an action

• Synergists: Assist with motion, control unwanted motion

• Fixators: Stabilize the area

Connective Tissue and Joints

• Connective tissue provides support, structure, energy storage, and immune responses

• Bones: Four main types (long, short, flat, irregular)

  • Functions: Protect organs, support tissues, assist movement, and store minerals

Bone Structure

• Diaphysis: Midsection of long bones

• Epiphysis: Ends of long bones, contains cancellous bone

• Articular Cartilage: Reduces friction and absorbs shock in joints

Synovial Joints

• Structure: Articular cartilage, synovial membrane, contains bursae for cushioning

• Types: Gliding, Hinge, Pivot, Condyloid, Saddle, Ball and Socket

• Each type provides different ranges of movement and stability.