NEURAL ADAPTATION TO RESISTED EXERCISE

Presented by fahis apMPT 1st semphysiotherapist

It is the adaptive changes that occurs in nerves system due to exercise training and it will enhance desired physical activity.

NEURAL ADAPTATION

Neural adaptation to resistive exercise generally accepted that neural factors play an important role in muscle strength gains

Neural adaptations always accompany the strength gains that result from resistance training, but hypertrophy may or may not be present.

NEURAL ADAPTATION

Resistance training actions can use static or dynamic actions.

Dynamic actions include the use of free weights,

variable resistance, isokinetic actions, and plyometrics.

Strength gains are highly specific to the speed of training and the movement patterns used in training.

For maximum benefit, a resistance training program must include activities quite similar to those experienced by the athlete in actual performance.

Resistance Training

Resistance training can benefit almost everyone, regardless of a person’s gender, age, or athletic involvement.

Resistance Training

Select mode of exercise free weights, etc.

Select the exercise movement Select the order of exercises Select number of sets/reps

Designing Resistance Training Programs

Neural mechanisms leading to strength gains can include.

1. Increased recruitment of more motor units.2. Increased motor unit synchronisation. 3. Increased motor uinit firing.4. Autogenic inhibition from Golgi tendon

organs.

Neural mechanisms

Neural mechanisms

•Recruitment• Synchronization• Inter-Musc Coordination• Intra-Musc. Coordination

Motor unit: Neuron and muscle fibers innervated.

Increasing force via recruitment of additional motor units Number coding.

Neural Adaptations

Representative motor unitssmall twitch oxidative(os)motorunit-recruited at low forcelargest high threshold fast twitch glycolytic motor unit(FG).Fast twitch oxidative glycolytic motor unit(FOG)

Increasing force via greater neural discharge frequency Rate coding.

Maximum force of any agonist muscle requires:◦ Activation of all motor units◦ Maximal rate coding

Neural Adaptations

Neural AdaptationsTimeline.•An increase in muscular strength without noticeable hypertrophy is the first line of evidence for neural involvement in acquisition of muscular strength.

•Neural factors is particularly strong during the early phase of strength training. the muscle hypertrophy are not observed until the 8th week of exercise training. this delay has led some to suggest that neural factors are important.

Increased activation of agonist motor units:

Untrained subjects are not able to activate all potential motor units

Resistance training may:1. Increase ability to recruit highest threshold

motor units2. Increase rate coding of all motor units

Neural Adaptations

Neural facilitation

◦ Facilitation = opposite of inhibition◦ Enhancement of reflex response to rapid eccentric

actions

Neural Adaptations

Neural facilitation movement.

When box jumbing (plyometric exs)the trained person has increased EMG activity in the legs compared to the untrained person .upon landing the untrained person is neuraly inhibited (decreased EMG activity),while the trained person is neurally facilitated (increased EMG activity)

Co-contraction of antagonists

◦ Enhancement of agonist/antagonist control during rapid movements

◦ Joint protection◦ Evidence: Sprinters greater hamstring EMG during

knee extension compared to distance runners

Neural Adaptations

Golti tendon organs (GTO):◦ Location: Tendons◦ Role: Inhibition of agonist during forceful movements◦ Examples:

Muscle weakness during rehabilitation Arm wrestling 1RM.

When the tension on a muscle’s tendons and internal connective tissue structures exceeds the threshold of the imbedded Golgi tendon organs, motor neurons to that muscle are inhibited. ◦ This reflex is called autogenic inhibition.

Progressive resistance training may inhibit GTO.

decresed sensitivity of the golgitendon organ to tension it may leed to injury

Neural Adaptations

1. High muscle tension

2. High tendon tension

3. GTO activation

4. Inhibition of agonist

GOLGI TENDON REFLEX

Neural Adaptations weight training vs. plyometric training

•Weigth training and plyomrtics develop different aspects of strength.

•plyometrics training results in inncrease in motor unit recrutment

•Weigth training increase isometrics force capacity and the cross- sectional area.

Increased motor unit recruitment Coordination of motor unit recruitment (synchronous) Decreased autogenic inhibition

◦ Decreased sensitivity of the golgi tendon organs to tension ◦ may lead to injury.◦ Inhibition of antagonist.◦ Neuromuscular inhibition(GTO,etc)

Increased synergestic co- contraction. Motor neuron excitability. Learn movement/motor learning.. Increased co-ordination of motor unit . Increased synchronised firing.

Adaptations to Resistance Training are:

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