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Muscle PerformancePTA 130 – Fundamentals of Treatment I
Introduction to muscle performance Discuss anatomical considerations of muscle Describe various types of resistance training Describe muscle adaptation to resistance training
Lesson Objectives
The capacity of a muscle to do work W = force x distance A complex component of functional movement and
is influenced by all of the body systems Key elements of muscle performance include: ◦ Strength◦ Power◦ Endurance
Muscle Performance
Muscle tissue is made up of contractile and noncontractile tissues
Connective tissue structures are: ◦ Endomysium (innermost layer)◦ Perimysium ◦ Epimysium (envelops the entire muscle)
Muscle Structure (Figure 4.2)
Individual muscles are composed of muscle fibers A single muscle fiber is made up of many myofibrils Each myofibril is composed of the smallest
contractile units known as sarcomeres Sarcomeres are composed of overlapping
myofilaments of actin (thin) and myosin (thick) What happens to the actin-myosin filaments when a
muscle actively shortens?
Muscle Structure – cont’d
Structure of Skeletal Muscle
Sarcomere = from Z-disc to Z-disc Contraction is triggered by a stimulatory
nerve impulse that causes an action potential to spread across the sarcomere
The action potential stimulates the sliding of filaments to occur
A change in muscle length results
Sliding Filament Theory
Structure of a Sarcomere
A functional structure consisting of a motor neuron and the muscle fibers it innervates
Larger muscles are made up of more muscle fibers◦ Produce less specific movements
Smaller muscles are made up of fewer muscle fibers◦ Produce very specific movements
Examples:◦ A motor unit inside the eye will usually contain two to three fibers, with
only three to five motor units residing in the entire eye. ◦ The calf muscle can have between 1,000 and 2,000 motor fibers per
motor unit.
Motor Unit
Dependent upon many factors: ◦ Biological ◦ Neurological ◦Metabolic◦ Biomechanical factors◦ Energy stores available to muscle◦ Influence of fatigue and recovery from exercise◦ Age◦ Gender
Tension Generation in Normal Skeletal Muscle
The diminished response of muscle to a repeated stimulus
Occurs during exercise when a muscle repeatedly contracts statically or dynamically against an imposed load
Muscle fatigue is normal and reversible The rate at which muscle fatigue occurs is also
dependent upon the type of muscle fibers involved
Muscle (local) fatigue
Affects how resistant the muscle is to fatigue Two broad categories: ◦ Type I
Slow-Twitch◦ Type II
Fast-Twitch
Fiber-Type Distribution of Muscle
Type I fibers Tonic, slow-twitch Generate low level of muscle tension Can sustain the contraction for a long period of time More resistant to fatigue For prolonged, sustained aerobic activity What muscle(s) are composed primarily of Type I
fibers?
Slow-Twitch Muscle Fibers
Type II fibers Generate a great amount of tension within a short
period of time For brief, intense anaerobic activity More force production possible because of greater
muscle fiber numbers in motor unit What muscle(s) are composed primarily of Type II
fibers?
Fast-Twitch Muscle Fibers
Type I vs. Type II Muscle Fiber Contraction Rates
Muscles are composed of both slow- and fast-twitch fibers
Ratios of each type vary from muscle to muscle and from person to person
Fast and Slow Twitch
Irritability: ◦ Stimulation is required to produce a response. ◦ Threshold = minimum stimulation required for a response
Contractility: ◦ Ability to contract = twitch. ◦One contraction occurs with each stimulus ◦ Sustained contractions: require repeated stimuli
Physiological Properties of Skeletal Muscle
Excitability◦ Capacity of muscle to respond when stimulated by nerve
impulse Extensibility (stretchability)◦ Capacity of muscle to stretch beyond its relaxed length
Elasticity◦ Ability to return to original length after contraction or
stretching
Terminology
Extensibility and Elasticity: ◦ As muscle is stretched, it becomes more extensible◦ Inactivity produces stiffness◦ Stiffness can be overcome with active exercise (which
increases temperature, decreases viscosity, and improves extensibility)
Physiological Properties of Skeletal Muscle
Muscle Contracture: ◦ The failure of a muscle to relax; it is normal for muscle to relax
after contraction ◦ Fatigue reduces the ability to produce maximum contraction
and to completely relax◦ It is important to stretch after activity since fibers do not
resume normal length with fatigue◦Muscle contracture is not the same as orthopedic contracture
(connective tissue shortening) or muscle spasm
Physiological Properties of Skeletal Muscle
Fatigue: ◦ Related to contracture ◦ From exhaustion of muscle with activity or from inadequate
circulation to provide nutrients needed for continued activity◦ Lactic acid: builds up with inadequate amount of oxygen to
metabolize it◦ Endurance proportional to tolerance of pain produced by
lactic acid buildup: tolerance endurance
Physiological Properties of Skeletal Muscle Fatigue
Fatigue:◦ Lactic acid production varies:
Untrained muscles produce more lactic acid than trained muscles Type II muscle produce more than type I muscle High intensity exercises produce more than low
◦ Sustained isometric exercises: block blood flow to increase lactic acid buildup fatigue (e.g., carrying suitcase: grip)
Physiological Properties of Skeletal Muscle Fatigue
The type of resistance training selected for a therapeutic exercise program are dependent on many factors: ◦ Cause and extent of impairments◦ Stage of tissue healing◦ Condition of joints◦ General abilities of the patient◦ Patient’s goals and intended functional outcomes
Types of Resistance Training
Static◦ Isometric
Dynamic ◦ Isotonic◦ Isokinetic
Types of Muscle Activity
◦ Force produced in muscle without a change in the muscle’s length; no visible joint motion
◦ Advantages: Strengthen muscle without undue stress (no change in position) Can start early (e.g., surgery, fracture) Appropriate when muscle is too weak for active range of motion
against gravity, isotonic, or isokinetic exercises
Isometric Exercise (Static)
Muscle – setting exercises◦Quad sets◦ Glut sets◦ Hamstring sets
Stabilization exercises◦ Core stabilization◦ Rhythmic stabilization
Types of Isometric Exercise
Intensity of muscle contraction◦ Exercise intensity load of 60-80% of a muscle’s force
Duration of muscle activation◦ 6-10 second hold during contraction
Repetitions performed depends upon◦Muscle’s condition◦ Ability of part to move◦ Healing phase of tissue
Characteristics of Isometric Exercise
Precaution - Valsalva maneuver:◦ Breath – holding commonly occurs during isometric exercise◦ Causes a rapid increase in blood pressure◦ It is important to emphasize exhalation during the contraction
Isometric Exercise
Causes joint movement and a change in length of muscle tissue
Concentric Contraction – ◦Muscle contracts and shortens
Eccentric Contraction – ◦Muscle lengthens under tension
Concentric and eccentric contractions are involved in most activities
Dynamic Exercise
A form of dynamic muscle loading where tension in a muscle develops and physical shortening of the muscle occurs as an external force (resistance) is overcome
Example?
Concentric Exercise
Involves dynamic loading of a muscle beyond its force-producing capacity, causing physical lengthening of the muscle as it attempts to control the load
Example?
Eccentric Exercise
Both types of exercise have value in rehabilitation programs
A combination of both concentric and eccentric activities occur in our daily life
Are concentric or eccentric exercises more difficult to perform?
Why?
Concentric vs. Eccentric
Type of dynamic activity Velocity of muscle shortening or lengthening is
maintained, but force varies through range of motion The term isokinetic refers to movement that occurs
at an equal velocity Also known as accommodating resistance exercise Offers reciprocal training of agonist and antagonist
Isokinetic Activity
QUESTIONS?