Unit 3

Introduction to Resistance Training

• The objectives are to define and list types of muscle performance and adaptation, describe the difference between resistance exercise and training, and describe the benefits of resistance training.

Overview

• Muscle performance refers to a muscle's capacity to do work
• This is calculated as force multiplied by distance (W = F x d).
• Muscle performance is complex, essential for movement, and influenced by body systems.
• Neurological, biochemical, metabolic, cardiovascular, respiratory, cognitive, and emotional factors are all critical to muscle performance.
• Muscle morphology and physiology impacts performance
• A healthy muscle system is vital for daily activities

Trainable Characteristics of Muscle

• Strength includes strength, local muscular endurance, and power.
• Muscle adaptation includes hypertrophy and muscle length (flexibility).

Resistance Training

• Resistance exercise is physical activity where dynamic/static muscle contraction is resisted by an outside force that is manually/mechanically applied
• Resistance training is a systematic exercise program designed to increase an exertion or resisting force.
• Resistance training should:
  • address specific goals like impairments
  • improve activity performance; provide general conditioning; and prevent injuries.
  • be tailored to individual goals.
  • consider individual personal and environmental contextual factors.

Benefits of Resistance Training

• Enhanced muscle performance is achieved through restoration, improvement, or maintenance of muscle strength, power, and endurance.
• Increased strength of connective tissues including tendons, ligaments, and intramuscular connective tissue.
• Positive changes in body with increased lean muscle mass (or decreased body fat), enhances physical well-being, and creates positive perceptions of disability as well as quality of life.
• Improvements include:
  • bone mineral density
  • decreased joint stress and risk of soft tissue injury during physical activity.
  • capacity for repair and healing of damaged soft tissues and tissue remodeling.
  • balance
  • physical performance during daily, occupational, and recreational activities

Resistance Training Adaptations

• Increased strength and muscle endurance which affects performance
• Increased power that affects performance
• Increased muscle size and length which has effects on flexibility.

Factors Affecting Muscle Performance

• Define key terms related to muscle performance, including muscle tension, load, contraction types, and motor units.
• Objectives of subject include:
  • Identifying the structural components of skeletal muscles.
  • Identifying the process of muscle contraction.
  • Describing the different types of muscle fibers.
  • Identifying and explaining biomechanical, motor Performance and psychological factors that influence muscle performance.

Definitions: Tension vs. Load

• Muscle tension is the force produced when a contracting muscle acts on an object and is an internal force.
• Load is the force exerted on the muscle by the object, which is an external force.
• Contraction as the tension-producing process of contractile elements within the muscle.

Structure of Skeletal Muscles

• Sarcomere Structure contains the myofibrils which are systems of proteins called sarcomeres.
• Sarcomeres are the contractile units of muscles
• Myosin (thick) and Actin (thin) are major filament proteins and are connected by cross-bridges which facilitate muscle contraction.

Muscle Contraction Mechanism

• Acetylcholine released from a somatic motor neuron triggers an electrical signal in the muscle fiber at the neuromuscular junction.
• Excitation-Contraction (E-C) Coupling: Translates muscle action potentials into calcium signals, which initiate contraction-relaxation cycles.
• Sliding Filament Theory explains how muscle contraction occurs at the molecular level:
  • interaction of myosin and actin filaments leads to muscle contraction

Motor Units: One Neuron and Its Fibers

• A motor unit comprises a group of muscle fibers innervated by one somatic motor neuron.
• Fibers unit contracts each the motor neuron fires
• Functions of motor units differ based on number of fibers, a few fiber give more control while many fibers results lower control.
• A motor unit has only one type of fiber

Process of Muscle Contraction

• Calcium binds to troponin, altering tropomyosin's position, which enables actin-myosin interaction for contraction.
• Calcium removal via the sarcoplasmic reticulum leads to relaxation.
• Myosin heads bind to actin to form cross-bridges
• ATP binds to myosin, providing the energy needed for myosin heads to attach, pivot, detach from actin filaments, and facilitate muscle contraction and relaxation cycles.

Fiber Types: Fast Twitch and Slow Twitch Fibers

• Slow-twitch fibers known as ST/Type I are smaller diameter, darker color due to myoglobin, and resist fatigue.
• Fast-twitch includes:
  • oxidative-glycolytic FOG or Туре IIA, and
  • glycolytic fibers (FG or Type IIX)

Muscle Fiber Type Characteristics

• Type I (Slow Oxidative) muscles based on metabolic properties:
• slow contraction time
• has high triglyceride and oxidative enzyme.
• is small with slow conduction
• has low recruitment threshold, which make it highly resistant to fatigue with low production of force and slow relaxation time.
• Type IIa with Fast Oxidative Glycolytic (FOG):
  • moderately fast, intermediate in respect to metabolic activity and size of motor neuron.
  • has fast conduction with high recruitment threshold.
• Type IIx is in Fast Glycolytic (FG):
  • fastest with high PCr and glycogen
  • large with fast conduction and high resistance to fatigue, resulting high production of force with fast relaxation time.

Many Factors Influence Muscle Performance

• Influencing parameters:
  • Cross-section size and muscle fiber number/size - the larger the diameter, the greater the tension-producing capacity
  • Muscle fiber arrangement and length - Short fibers design with pennate and multipennate design is typical in high force-producingLong fibers with parallel design are typical in fast shortening rates but lower force production
• Contraction relations depend on muscle and fiber-type distribution, where: -High percentage of type I supports resistance to fatigue
• High percentage of type IIA and IIX favors rapid high force production and rapid fatigue
• Tension is highest near (or at) the physiological resting length at the time of contraction.
• Force depends on:
  • muscle force vector
  • joint movement - greater tension is produced with longer moment arm
  • motor units recruitement
    • higher firing frequency result greater the tension
    • muscle contraction from greatest to least is eccentric, isometric, concentric. -Contraction Speed
    • speed effects on eccentric (speed increases tension), Concentric (speed decreases tension)

Factors Influencing Muscle Performance

• Key aspects associated with muscle's performance depends on mecanical factors,muscle Activation,Recruitment and Biomechanical Factors, muscle Size/architecture, Muscle Fibre types,Rate coding etc.

Mechanical Factors Influencing Muscle Contraction

• Contraction depends on: -Length-Tension-Angle-relation, Force-Velocity relation -Muscle: elasticity and passive tension, physical attributes, cross-sectional area and morphology and architecture

The Total Length-Tension Curve

• Length and Forces are key
• Active forces are from myofilaments
• Passive forces are from components- Titin, fascia, tendon. -Absloute length depends on- sarcomeres, Tendon flexibility and Length.
• Angle movement depends on joints action

Torque/Joint Angle Relationship

• Relation between muscle length (relaxed), tenson angle application.

Force-Velocity Relationship

• Force has an indirect effect in the velocity ( eccentric ,shortening,concentric,isometric).

Elasticity in Muscle Force Development

• elastic properties are crucial for storing and releasing energy.
• Enhanced contraction:
  • muscles being pre-stretched (eccentric action) before contraction action, which enhances force.

Physiological Cross-sectional Area of a Muscle (PCSA)

• PCSA describes the direction of contractile force

Muscle Morphology and Architecture

• Fiber is a muscle cell
• Bundle/fascicles of Fiber are surrounded by connective tissue Fascicular arrangements: longitudinal, Fusiform, Radiate, Unipennate, Bipennate and Circular"

Muscle architecture

• affects force generation for fiber
• there is vector parallel that can affect angle

Anthropometry

• Length affects action

Muscle architecture

• Force is used to balance the applied pressure at an angle
• the moment arm depends on length

So Does Muscle Size Matter?

• increased muscle size is generally measured through anatomical CSA
• positive correlations exists muscle force.
• Mathematical modeling supports such actions

Activating Muscle via the Nervous System

• Smallest MUs are recruited first during a given task- successively larger MUs engaged as force production requirements increase. Sufficient time + effort are needed to get maximal recruitment/efforts

Neural Drive

• Humans are at greater muscle activation during high intensity exercise. trained athletes than non-athletes.
• Neural drive occurs for the brains incapacity to voluntarily produce maximal muscle force.

Fatigue

• fatigued muscle is no longer able to generate or sustain the expected power output.
• fatigue is classified by the central mechanism (CNS effect), Protective reflexes, and peripheral fatigue Excitation contraction coupling, with muscle fatigue causes
• This due too:
• the contraction activity intensity and duration
• whether it uses areobic or anaerobic metabolism
• muscle compostiton

Motor Performance

• Technique: skill and strategy, technique applied - Motor learning is feedback and cueing

Phsycological Factors

• Phsycological Factors-arousal and motivation

So Does Muscle Size Matter

• Larger muscles often translates as a greater ability to demonstrate strength, but strength still depends on task factors

Key TakeAways

• The muscle tensiton must exceed the load to allow movement and is measured by fornce .
• size effect maximal form, is by the architecture.
• motor Unit action recruitment and the contraction impact perform. psychological motivation and stress

Resistance Training Principles

• Stress is used to achieve adaptions, such as - periodization, specificity/SIAD

Progressive Overload

• Gradual stress improves body during exercise-continuous stress or adaptive response.

Training variables

• Load, intensity, volume, stability and duration.

Practical application

• effective traning = appropriate levels w effort vs high intensity
• Common issues = mistaking in weight increase, or misguided increases
• Adjust based on performance and individual levls

Training Status

• novice, intermediate, to advanced

UnTrained Novice

• motor control vs intensity

Untrained expectations

• linear progressions of volume

Untrained Reality

• slow then rapid-communicaiton etc

Rate of adaptation

training complexity requires goals

Periodization

• systematic. involves progression-training model