Nerve-Muscle Interaction

Skeletal muscle activation is initiated through neural activation

NS can be divided into central (CNS) and peripheral (PNS)

The NS can 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

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

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

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

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%)

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

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

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

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

Make a table with muscles through the unit – only movers of main jointsMuscle Name Function Describe

movementsOrigin Insertion

Bicep

Brachii

Prime mover Flexes lower arms Coracoid Process

Head of Humerus

Radius

Key Terms Skeletal muscle

Smooth muscle Cardiac muscle Biomechanics Muscle fibres Myofilaments Motor unit Sarcomeres Cross bridge formation

Slow twitch fibres Fast twitch fibres Muscle biopsy Isometric contraction Isotonic contraction Isokinetic contraction Concentric contraction Eccentric contraction Plyocentric contraction