Molecular Exercise Physiology Resistance training Presentation 6 Henning Wackerhage

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Molecular Exercise PhysiologyResistance training
Presentation 6Henning Wackerhage
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Learning outcomes

• At the end of this presentation you should be
  able to
• Describe resistance training methods and other
  interventions that achieve a skeletal muscle
  hypertrophy.
• Describe the changes in neuromuscular activation
  and muscle size that occur in response to
  resistance training.

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Adaptation to resistance training Part 1Basics
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What is strength?
Strength can be defined as the ability of the
neuromuscular system to produce force.
Strength can occur in different situations 1)
Isometric muscle produces tension but length is
unchanged. 2) Concentric muscle produces tension
and shortens. 3) Eccentric muscle produces
tension and lengthens. 4) Plyometric concentric
action immediately preceded by an eccentric
action.
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The relevance of the two sections of the
neuromusular system for force production
Strength (force production)
depends on
Neuromuscular activation a) The firing rates of
the a motor neurones involved b) The number of a
motor neurones that innervate a muscle c) The
co-ordination of the movement (innervation of
agonist versus antagonist, technique).
Force production by innervated muscle fibres a)
Fibre size (hypertrophy) b) Fibre phenotype
(type I, IIa, IIb/x).
Central nervous system
a motor neurones
muscle fibres
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Strength response to standard resistance training
Strength increases due to strength training
result from increased neural activation (early
response) and fibre hypertrophy (delayed
response) (Sale et al. 1988).
Strength
Hypertrophy
Strength
Neural activation
Time
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Resistance training Part 2Training for
hypertrophy
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Resistance training

• Resistance training research results
• Increases in the cross-sectional area of muscle
  fibers range from 20 to 45 in most training
  studies (Staron et al., 1991).
• Type II (fast) muscle fibres show greater
  increases in size compared to type I (slow)
  fibres (Hather et al. 1991) .
• More than 16 workouts are needed to produce
  significant muscle fibre hypertrophy (Staron et
  al., 1994).
• Increases in strength occur near the velocity of
  training (e.g. slow-speed training increases
  strength at slow speeds) (Behm Sale, 1993) .

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Resistance training for hypertrophy
Hypertrophy training Do it if you can afford a
high body mass and if high absolute strength is
important. Yes Throwers, super heavyweight
weightlifters, body builders. No or limited
amount high jumpers, weight class athletes.
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Resistance training for hypertrophy

• Hypertrophy training parameters
• Load 70-80
• Number of repetitions per set 8-12 is usually
  recommended
• Number of Sets 4-6 (8)
• Rest intervals 3-5 minutes
• Speed of execution medium

• Variations
• Split routine (e.g. arms, legs and abdominals on
  Monday, Wednesday and Friday chest, shoulders
  and back on Tuesdays, Thursdays and Saturdays).
• Single or multiple sets per exercise.
• Training with varying weights and repetitions per
  exercise low-to-high or high-to-low weights,
  pyramid training.

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Net protein synthesis and hypertrophy
Skeletal muscle hypertrophy requires a net
protein synthesis. However, it is not sufficient
just to measure protein synthesis because Net
protein synthesis protein synthesis protein
breakdown. Both protein synthesis and protein
breakdown increase in response to resistance
training.
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Lower effect in trained subjects
Protein synthesis
Protein breakdown
The figures show that untrained (UT) subjects
have a higher protein synthesis and protein
breakdown after resistance exercise compared to
trained subjects (T). This confirms that
untrained subjects respond more to resistance
training than trained subjects who are closer to
maximal hypertrophy (Phillips et al. 1999).
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Lower effect in trained subjects
Total
Both trained and untrained subjects suffer a net
protein breakdown at rest and during exercise in
a fasted state (Phillips et al. 1999). The amino
acid concentration needs to be sufficiently high
to yield a net protein synthesis. In addition,
growth factors like insulin, androgens and IGF-1
will cause a net protein synthesis.
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Feeding is necessary for net protein synthesis
These data show that a resistance training with
no feeding (placebo, PLA) causes a net protein
breakdown while resistance training with
ingestion of 40 g of mixed amino acids (MAA) and
40 g of essential amino acids (EAA) causes net
protein synthesis (Tipton et al.
1999). Important A normal meal would be
sufficient for protein synthesis. Protein drinks
are probably not necessary.
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Feed directly after resistance exercise!
Cross-sectional area of quadriceps femoris
Two groups of old subjects (70-80 years)
performed a period of endurance training. Both
groups received a gel containing 10 g protein
(from skimmed milk and soybean), 7 g carbohydrate
and 3.3 g lipid either directly after exercise
(P0) or 2 h after exercise (P2). Only ingestion
directly after exercise caused hypertrophy
(Esmarck et al. 2001).
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Task
Assume you would like to become a body builder.
Outline a 6 months training programme for maximal
hypertrophy.
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Resistance training Part 3Neuromuscular
activation
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Neuromuscular activation
The force generated during a movement depends on
the neuromuscular activation of the muscles
involved and on the force produced by the
skeletal muscle fibres innervated. Neuromuscular
activation includes a) The firing rates of the a
motor neurones involved. b) The number of a motor
neurones that innervate a muscle. c) The
co-ordination of the muscle (innervation of
agonist versus antagonist, technique).
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Innervation of a motor neurones
The firing of a motor neurones depends on the
input of higher centres (e.g. motor cortex) and
reflex inputs (see figure). If there is
sufficient excitatory input, then the threshold
is reached, the a motor neurone fires, muscle
fibres contract and a force is generated.
Other peripheral sensory receptors
Ib
Reflex inputs
II
Higher motor centres
Ia
a motor neurone
Muscle fibres
Modified after Leonard (1998)
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Three types of motor units

• Fast fatiguing
• very high tension
• fast fatiguing
• Large a motor neurone, type IIb/x fibres

• Fatigue resistant
• high tension
• slow fatiguing
• Intermediate size a motor neurone, type IIa fibres

• Slow
• low tension
• fatigue resistant
• Small a motor neurone, type I fibres

Burke et al. (1973)
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Task
Explain the difference between myosin heavy chain
isoforms, fibre types and motor units.
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Three types of motor units
A motor unit is an a motor neurone and the muscle
fibres innervated by it. Three types of motor
units can be distinguished slow (S), fatigue
resistant (FR), fast fatiguing (FF). The a motor
neurones of the slow motor units are the smallest
and have a low threshold while the a motor
neurones in fast fatiguing motor units are large
and have a high threshold.
Fast fatiguing motor unit
Fatigue resistant motor unit
Slow motor unit
Type I fibres
Type IIa fibres
Type IIb/x fibres
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Henneman Size Principle
Stimulation voltage
The first, large spike seen on the left of each
trace is a stimulation artefact. The smaller
spikes to the right originate from firing a motor
neurones. The larger the a motor neurone, the
larger the spike. Firing slow motor units
correspond to small spikes, interme-diate to
intermediate spikes and fast fatiguing to large
spikes.
Only slow motor units fire (small spikes)
Fast fatiguing and intermediate motor units
(large spikes) fire additionally only after
intense stimulation
Electrical stimulation artefact
Henneman (1957)
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Henneman Size Principle
The results shown on the previous slide allow the
following conclusion The susceptibility of a
motor neuron to discharge is a function of its
size. Smaller a motor neurons (part of slow
motor units) have a lower threshold than larger
ones (part of fatigue resistant or fast fatiguing
motor units).
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Henneman size principle conclusion
Slow motor units are easily activated and
trained by any training that activates the
muscle. Intense stimulation (near maximal
resistance training, sprinting, jumping) is
required to additionally innervate and thus train
fatigue resistant and fast fatiguing motor units.
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How to specifically train neuromuscular
activation?
Choose near maximal weights that allow you to
perform 1-6 repetitions. Mainly olympic lifts
(clean, snatch, jerk) with dumbbells or barbells
esp. for advanced athletes. Alternatively, work
with lower or no weights and near maximum
velocity (e.g. plyometric training, sprints,
jumps, throws).
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Neuromuscular activation training
U
t

• Physiological basis
• Normal firing rates of a motor neurones range
  from 10 to 60 action potentials s-1.
• Maximum forces are achieved with firing rates
  around 50 s-1. Maximal firing rates during
  ballistic exercises in trained subjects are
  higher than 100 s-1.
• However, firing rates higher than 50 s-1 speed up
  the force increase at the beginning of a
  contraction.

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Neuromuscular activation training
Explosive, ballistic strength training increases
maximal strength but especially develops a
quicker force development. Heavy resistance
strength training develops especially a higher,
maximal force (Häkkinen Komi 1985 RFD rate of
force development).
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Task
What is plyometric training? Why might it be
useful to develop neuromuscular activation?
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The End