Without the Nervous System – Muscles will not contract.

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Nerve-Muscle Interaction

Skeletal muscle activation is initiated through neural activation

The Nervous system can be divided into central (CNS) and

peripheral (PNS)

It can also be divided in terms of function: motor and sensory

activity

Sensory: collects info from the various sensors located

throughout the body and transmits the info to the brain

Motor: conducts signals to activate muscle contraction

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Activation of motor unit and its innervation systems

1. Spinal cord 2. Cytosome 3. Spinal nerve 4. Motor nerve 5. Sensory nerve 6. Muscle with muscle fibres

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Motor Unit

Motor nerves extend from the spinal cord to the muscle fibres Each fibre is activated through impulses delivered via motor end plate Motor unit: a group of fibres activated via the same nerve All muscle fibres of one particular motor unit are always of the same

fibre type Muscles needed to perform precise movements generally consist of a

large number of motor units and few muscle fibres Less precise movements are carried out by muscles composed of

fewer motor units with many fibres per unit

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All-or-none Principle Whether or not a motor unit activates upon the

arrival of an impulse depends upon the so called all-or-none principle

An impulse of a certain magnitude (or strength) is required to cause the innervated fibres to contract

Every motor unit has a specific threshold that must be reached for such activation to occur

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Intra-muscle Coordination

The capacity to apply motor units simultaneously is known as intra-muscle coordination

Many highly trained power athletes, such as weightlifters, wrestlers, and shot putters, are able to activate up to 85% of their available muscle fibres simultaneously (untrained: 60%)

Force deficit: the difference between assisted and voluntarily generated maximal force (trained: 10%, untrained: 20-35%)

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Intra-muscle Coordination cont.

Trained athletes have not only a larger muscle mass than untrained individuals, but can also exploit a larger number of muscle fibres

Athletes are more restricted in further developing strength by improving intra-muscular coordination

Trained individuals can further increase strength only by increasing muscle diameter

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Inter-muscle Coordination

The interplay between muscles that generate movement through contraction (agonists) and muscles responsible for opposing movement (antagonists) is called inter-muscle coordination

The greater the participation of muscles and muscle groups, the higher the importance of inter-muscle coordination

To benefit from strength training the individual muscle groups can be trained in relative isolation

Difficulties may occur if the athlete fails to develop all the relevant muscles in a balanced manner

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Inter-muscle Coordination cont. High-level inter-muscle coordination greatly improves

strength performance and also enhances the flow, rhythm, and precision of movement

Trained athlete is able to translate strength potential to enhance inter-muscle coordination

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Muscle’s Adaptation to Strength Training

Individual’s performance improvements occur through a process of biological adaptation, which is reflected in the body’s increased strength

Adaptation process proceeds at different time rates for different functional systems and physiological processes

Adaptation depends on intensity levels used in training and on athlete’s unique biological make-up

Enzymes adapt within hours, cardiovascular adaptation within 10 to 14 days