Transcript neuromuscular response to training

NEUROMUSCULAR
RESPONSE TO
TRAINING
YEAR 12 PE STUDIES
UNIT 2A / 2B
In addition to the cardiorespiratory system,
another system that responds to training
and contributes to improvements in
performance is the NEUROMUSCULAR
SYSTEM.
The neuromuscular system comprises the the
nervous system which sends signals to
initiate movement and the muscular system,
which responds to these signals and
produced movement.
1. NERVOUS SYSTEM RESPONSES
TO TRAINING
 neural adaptations to training occur through a number of
processes; disinhibition, motor unit recruitment, motor unit
synchronisation and the effect of learning
 The MOTOR UNIT is the functional unit that produces
muscle action & movement. It comprises the anterior
motor neuron & the specific muscle fibre it stimulates
 Muscle action results from the individual & combined
stimuli of motor units. Although a muscled fibre generally
receives signals from only 1 motor neuron, a single motor
neuron may stimulate many muscle fibres due to its many
branches.
Disinhibition
The N.S consantly bombards the muscles with signals to
either excite or inhibit muscle action
• Excitatory signals > inhibitory signals = motor unit ‘fires’.
(if the opposite happens the motor unit doesn’t fire)
• When increased force is produced the body has built-in
feedback mechanisms that operate to protect muscles
from injury. ie mechanisms in the muscles have the
capacity to send out inhibitory signals to motor unitswhich
prevent the body from recruiting extra motor units and/or
firing existing ones at their maximal rate. This limits the
force applied by the muscle. There is a reserve of potential
force in the muscles which may not be used in maximal
activities.
 By continually exposing the body to high level of tension eg
strength training, the sensitivity of these inhibiting
mechanisms may reduced through a process called
DISINHIBITION.
 A greater number of motor units can be recruited and each
motor unit is able to fire more rapidly.
Motor Unit Synchronisation
 a single muscle gp contains 100 to 1000 motor units.
When this muscle is activated, these motor units are fired
in a random manner (they are independent of each other)
 A characteristic of strength-trained athletes is
synchronisation of motor unit recruitment ie motor units in
the same muscle coordinate their action to fire at the same
time = stronger contraction.
Effect of Learning
 Training results in a learning effect which produces a
greater efficiency in neural recruitment patterns.
 When first performing a move’t the coordination b/w
various muscles may not be optimal. As the NM system
becomes more proficient, through repeated performance,
the coordination of the muscles improves = enhanced
strength.
 Adaptations of the NS are most dominant in the early
stages of training, and represent the major cause of
strength increase over the first 6 – 8 wks.
2. MUSCULAR SYSTEM RESPONSES
TO TRAINING
The major contributing factor to increases in muscle strength
is an increase in the size of muscle. This is the result of
two mechanisms:
 Muscle Hypertrophy
 Muscle Hyperplasia
Muscle hypertrophy
Refers to an increase in the size of individual muscle fibres
(particularly fast-twitch fibres). This is the major cause of
increases in muscle strength due to the following:
 An increase in the number & size of myofibrils per muscle
fibre
 An increase in the amount of protein filaments
 An increase in the size & length of tendons, ligaments &
connective tissue
Muscle Hyperplasia
 Refers to the splitting of individual muscle fibres to
increase the number of fibres in the muscle
 In order for this splitting to occur, the athlete must
undertake many months of heavy resistance training