Principles of Skeletal Muscle Adaptations

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Principles of Skeletal Muscle Adaptations

• Chapter 19

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Principle of Myoplasticity

• There is tremendous potential to alter the gene
  expression of skeletal muscle
• Skeletal muscle is 20 protein
• All types of protein can be regulated by
  alterations in gene expression
• Quantity or amount of protein
• Quality or type of protein
• Proteins
• Structural
• Contractile
• Metabolic

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Figure 19-2
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Microenvironment of skeletal muscle

• Signals
• Energy intake
• Hormones (insulin, thyroid, IGF-1
• Recruitment
• Load
• Results
• Protein synthesis or
• Protein degradation
• This changes the concentration/activity of
  specific proteins
• Also know as a change in phenotype

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Muscle Fiber Types in Elite (Pritshcet-like)
Athletes

• Sprinters and cats have more type II fibers
• Distance runners and dogs have more type I fibers

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Training and Fiber Types

• Training can significantly affect the
  biochemistry of a muscle fiber
• Myosin isoforms, however, are not changed with
  training (i.e. Type I to Type II)
• Possibly type IIx and IIiz

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Other Stimuli

• Chronic low frequency stimulation can increase
  Type I fibers
• Cross innervation

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Adaptations to Endurance Training

• Major adaptations
• Increase in mitochondrial number
• Increase in glycolytic enzymes
• Amount of change is dependant on
• Pre-training values
• Intensity and duration of training
• Which fiber type you look at (less change in IIb,
  for example)
• Significance
• Higher lactate threshold
• Increase fatty acid oxidation

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Adaptations to Resistance Training

• Muscle hypertrophy
• Type I and II muscle cell hypertrophy
• Fiber pinnation angle
• Shift from IIb to IIx and IIx to IIa
• Decrease in mitochondrial and capillary density
• Increase neural activity/stimulation
• Onset of training gain more than expect
• Continued training gain less than expect

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Muscle Strength, Power and Flexibility

• Chapter 20

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Milo of Crotona

• Milo of Crotona, Greek athlete, lived about the
  end of the 6th century B.C. He was six times
  crowned at the Olympic Games and six times at the
  Pythian for wrestling, and was famous throughout
  the civilized world for his feats of strength -
  such as carrying an ox on his shoulders through
  the stadium at Olympia. In his native city he was
  much honored, and he commanded the army which
  defeated the people of Sybaris in 511.
• The traditional account of his death is often
  used to point a moral he found a tree which some
  woodcutters had partially split with a wedge, and
  attempted to rend it asunder but the wedge fell
  out and the tree closed on his hand, imprisoning
  him until wolves came and devoured him. His name
  became proverbial for personal strength.
• Encyclopaedia Britannica

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Programs
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Programs

• Novice
• ACSM 1 set of 10 reps for 8-10 exercises
• Hypertrophy
• Studies show high resistance, low reps are more
  effective than low resistance high reps.
• Typical program contains more sets and reps and
  exercises compared to strength training
• Strength
• Results from studies
• 3 or more sets
• 4 to 8 reps

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Periodization Sample

• Load 2-3 months of 5-7 sets, 4-7 reps, at 80 of
  1RM with microcycles or day to day variations
• Recovery 2-3 weeks of moderate to light volume
  (reps) and moderate intensity
• Peak Low volume, high intensity (e.g. 1-3 sets,
  1-3 reps) for same length as load cycle
• Conditioning Low intensity (60-70), 4-6 sets,
  8-10 reps with weeks of higher intensity for
  maintainance

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Periodization

• Practiced for 20 years
• Little evidence of its effectiveness

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Classifications of Strength Exercises

• Isometric
• Isotonic
• Concentric
• Eccentric
• Isokinetic

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Isometric

• German researchers help to make isometrics
  popular in 1950s
• They claimed that one, 6 second contraction a day
  was enough

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Recent research

• Significant gains require maximal voluntary
  muscle action
• Contractions need to be a minimum of 3 to 5
  seconds in length
• A minimum of 15 to 20 maximal contractions are
  required
• Isometrics need to be performed on a daily basis
• Isometrics do produce hypertrophy that is not
  correlated to strength
• Strength gains are joint-angle specific 20
• Isometric training does not improve motor
  performance skills/contraction velocity

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Concerns

• Valsalva maneuver can occur
• Motivation may be a problem

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Recommendations

• Training should be done in increments of 10-20
• Contractions should be 3-5 seconds in length,
  repeated 15-20 times
• Focus could be given to sticking point angles

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Electrical Muscle Stimulation (EMS)

• Causes isometric contractions
• Developed for rehabilitation
• Small gains in strength (Transfer?)
• Able to activate muscles at supra-maximal
  intensities
• Effectiveness depends on frequency of
  stimulation and rest intervals

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Isotonic Exercise

• Constant load
• Variable load
• Plyometric
• Speed
• Isokinetic

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Constant Resistance

• Barbell or dumbbell
• Resistance constant
• Effort changes
• Synergist muscles
• Greater movement options

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Variable Resistance
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Variable Resistance

• Machine matches the increases and decreases in
  strength (strength curve) throughout the range of
  motion
• Three types of strength curves
• increasing (squat)
• decreasing (upright rows)
• bell shaped (elbow curls).
• Perfect matches are impossible due to variations
  in limb length, points of tendon attachment, etc.
• No more effective than free weights

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Eccentric Loading
Increase in length of pectoralis major as the
weight is lowered
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Eccentric Loading

• 120 of 1RM is used as an upper limit
• Effective but not superior to isotonic techniques
• Maximal eccentric loading recruits mostly fast
  twitch fibers

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Plyometric Loading
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Plyometric Loading

• Stretch-shortening cycle
• Stores elastic energy
• Activates muscle spindles
• Therefore, greater or quicker fiber recruitment
• Eccentric contraction and loading followed by
  concentric contraction
• Focuses on neural and elastic components

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Speed Loading

• Not as effective in developing strength fewer
  cross bridges
• Improves movement speed
• Need to train at peak power output (weight x reps
  / time)

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Isokinetic

• Speed kept constant with accomodating
  resistance
• Most effective gains come at slower (60 degrees /
  sec) speeds
• No more affective than traditional isotonic
  exercises

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Factors in Muscle Adaptation

• Overload
• Specificity
• Reversibility
• Individual differences

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1. Overload

• Strength
• Power (speed)
• Hypertrophy
• Endurance

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Strength
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Strength Overload

• Strength overload leads to hypertrophy but of
  differing degrees
• Muscle protein accumulation occurs when
• increase in protein synthesis
• decrease in protein degradation
• both
• Amino acid transport into a muscle in influenced
  by intensity and duration of muscle tension
• Ideal tension comes from doing 4 to 8 reps and 3
  or more sets
• However, increase in IIx myosin heavy chain mRNA
  isoform and repression of IIb which slow the
  contractile velocity.

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Power Overload

• Speed overload increases neural stimulation and
  attenuates the slowing effects of hypertrophy
• Athletes must improve the speed that the nervous
  system can turn-on the muscle fibers in the
  motor units in order to counter the slowly effect
  of hypertrophy
• Plyometrics and speed exercises are most
  effective for enhancing neural activation than
  intense progressive strength exercises.

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Hypertrophy

• More sets
• More reps
• More exercises
• Effective?

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Endurance

• Less resistance - More reps
• Why?
• Aerobic sport performance yes
• Toning - no

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Rest and Recovery

• Between sets
• ATP-PC
• Longer recovery periods
• Lactic acid
• Shorter recovery periods
• Between workouts
• 48 hours
• Protein repair and synthesis
• Adequate time
• Adequate energy

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2. Specificity

• Muscle group
• Energy systems
• Fiber types and motor units
• Movement patterns

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Muscle Group
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Energy Systems

• Power (strength)
• Speed
• Endurance

Power/strength
Speed
Endurance
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Fiber type

• IIb
• IIa
• I
• Does training for both endurance and strength
  limit strength gains? Some studies say, yes.
  Others, no.

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Type of exercise/movement

• Mimic movement patterns of a sport
• 2A. Closed chain exercises
• Typical of free weights
• Better transfer to motor skills
• Multiple joint movement
• 2B. Open chain exercises
• Typical of machines

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Type of exercise/movement

• Type of exercise matters even in the same muscle
  groups
• Percent improvement in strength (Figure 20-6)

Squat Leg Press Knee Extension
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3. Reversibility

• Slow twitch fibers atrophy the fastest
• Decrease energy reserves (CP, glycogen, etc)
• Return of strength after periods of inactivity
  (below)

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4. Individual Differences

• Fiber types and strength gains are genetically
  determined
• However, shot putters have a diverse muscle fiber
  composition

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Adaptations for Muscle Strength

• Neural
• Contractile
• Elastic

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Neural Adaptations

• Increase electrical activity
• Inhibition of GTO
• Increase coordination of antagonist muscle groups
• Cross training between muscles on left and right
  sides of body
• Increased motor unit synchronization
• Increase rate of motor unit stimulation
• Recruitment of even more IIb motor units

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Increase electrical activity

• Figure 20-8

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Inhibition of GTO

• Golgi tendon organs inhibit continued contraction

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Co-contraction of Antagonists

• Greater activation of anatagonist
• Added control
• Prevents Injuries

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Neurological cross-training

• Training an uninjured limb produces small
  training effects in the injured, untrained limb
• 0-40 increase in strength in the non-trained
  limb
• Why?

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Enhanced synchronization

• Stronger contraction
• Longer contraction

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Increase rate of motor unit stimulation

• Larger, stronger motor units have a faster firing
  rate
• Fast firing rates leads to more action
  potentials, calcium release, cross bridge
  formation, power strokes, and tension (force)
• 300-1500 increase from minimal to maximal
  stimulation
• Firing rates improved with plyometric /speed
  training

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Increase Rate of Motor Unit Activation

• Motor units are turn on sooner e.g. when the
  muscle is suddenly shortened (Figure 20-10)

Trained
Untrained
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Recruitment of even more IIb motor units

• IIb fibers are activated for a longer period of
  time
• Motor units are trained in direct proportion to
  its recruitment
• High intensity training is required in order to
  recruit additional IIb motor units

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Summary of Neural Adaptations to Strength
Training (p. 436)

• PHYSIOLOGICAL EFFECT
• Increase electrical activity
• Inhibition of GTO
• Increase coordination of antagonist muscle groups
• Cross training between muscles on left and right
  sides of body
• Increase rate of MU activation
• Increased motor unit synchronization
• Increase recruitment of high-threshold (IIb)
  motor units
• Increase duration of high-threshold (IIb) motor
  units

• SIGNIFICANCE
• Increase force
• Disinhibition of maximal contraction
• Increase effectiveness of force
• Improved balance
• Increase rate and strength of force development
• Increase rate and strength of force development
• Increase force and efficiency
• Increase time maximal force can be maintained

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Contractile Adaptations (Table 20-2)

• Physiological Effect
• Increase muscle mass
• Increase cross-sectional area (myofibrils)
• Increase heavy chain IIb and IIx forms
• Increase angle pinnation
• Increase in I and/or II fiber area
• Capillary density decrease in BB and increase in
  PL
• Decrease in mitochondrial density no change in
  mitochondrial volume
• Increase intracellular lipids
• Increase intracellular glycogen
• Increase intracellular phosphate pool
• No change in glycolytic enzymes
• Increase androgen receptor sites

• Significance
• Increase muscle strength
• Increase contractile capacity
• Slows myosin cycling rate
• Increase muscle size
• Reflects selective recruitment (II fiber area 20
  greater in powerlifters v. body builders)
• No effect with BB. Decrease diffusion capacity in
  PL
• Decrease oxidative capacity
• Increase lipid oxidation
• Increase glycolytic energy
• Improved phosphagan metabolism increase maximum
  muscle capacity
• Increase effectiveness of androgens in promoting
  muscle hypertrophy

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Contractile Adaptations (Table 20-2)

• Physiological Effect
• Increase muscle mass
• Increase cross-sectional area (myofibrils)
• Increase angle pinnation
• Increase intracellular glycogen
• Increase intracellular phosphate pool
• Increase androgen receptor sites

• Significance
• Increase muscle strength
• Increase contractile capacity
• Increase muscle size
• Increase glycolytic energy
• Improved phosphagan metabolism increase maximum
  muscle capacity
• Increase effectiveness of androgens in promoting
  muscle hypertrophy

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Hypertrophy or Hyperplasia?

• Muscle cell hypertrophy accounts for 95-100 of
  overall muscle hypertrophy
• The remainder is the result of hyperplasia and,
  to a lesser extent, changes in fiber angle

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Elastic Adaptations
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Elastic Adaptations

• Series elastic components
• Cross bridges
• Tendons
• Parallel elastic components
• Myofilaments
• Fascia
• Increase elastic properties enhances (elastic)
  energy production from the stretch-shortening
  cycle

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Other Topics

• Muscle soreness
• Training programs
• Inactivity/Injury
• Gender/Age Differences
• Flexibility

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Muscle Soreness

• Acute
• Delayed Onset Muscle Soreness

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Delayed Onset Muscle Soreness (Figure 20-12)

• Damage to the muscle due to high tension,
  particularly during eccentric, intense, or
  prolonged exercise
• Injury leads to tissue edema and inflammation
  (e.g. increase neutrophils, leukocytes,
  monocyctes, macrophages, histamines, PGE2,
  cytokines)
• Increased cell tension and strain from edema and
  agents, such as prostaglandins and histamine,
  cause pain
• Additional muscle tissue breakdown and pain occur
  due to formation of proteases, phospholipases,
  and oxygen radicals
• Cells repairs themselves and form protective
  proteins that prevent muscle soreness during
  subsequent workouts.

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Inactivity

• Protein synthesis deceases after 6 hours of
  inactivity
• Noticeable atrophy within 3-4 days
• Greater with immobilization and weightlessness
• Muscle weakness and fatigue levels may exceed
  atrophy

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Muscle Injury/Damage

• Many factors can cause injury/damage
• Very common are eccentric muscle contractions
• Two phases of injury
• Immediate and mechanical
• Delayed and biochemical
• Calcium
• Oxygen free radicals
• Injury leads to degeneration
• Healing leads to regeneration

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Gender Differences

• Intrinsic properties of muscle tissue are the
  same
• Absolute strength men are stronger
• Relative (per amount muscle mass) strength women
  are equal

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Age-Associated Changes

• 25-30 decrease in muscle mass by age 65
• Fiber diameter decrease
• Fiber number decrease hypoplasia
• Motor unit remodeling
• Shift from type II to type I
• Fewer motor units

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Age-Associated Changes

• Decrease strength
• Partially due to inactivity
• Partially due to weaker muscles
• Decrease in power
• Decrease in sustained power
• Able to train at relatively high intensity levels

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Any questions?
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Training for Flexibility

• Static flexibility - easy to measure
• Dynamic flexibility - more important

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Benefits of Flexibility

• Joint health
• Decrease risk of injury
• Decease DOMS
• Etc.

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Factors Determining Flexibility

• Joint structure
• Muscle elasticity
• Regular stretching adds sarcomeres and lengthens
  connective tissue
• Connective tissue has limits
• Nervous system activity
• Muscle spindles sudden stretch and they contract
  the muscle
• Spindle activity decreases after 10 seconds

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Principles of Training for Flexibility (Table
20-5)

• Warm the muscle first
• Static stretch for 10-30 seconds and dont bounce
• Feel a mild stretch
• Both sides of the body
• Watch the lower back
• Regular attention (at least 2-3 days/week)

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PNF

• Proprioceptive Neuromuscular Facilitation
• Contract muscle to stimulate GTO
• GTO cause muscle to relax
• Stretch relaxed muscle further

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Stretching

• Passive stretching - outside force
• Active stretching - opposite muscle

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Any Questions?