Without the Nervous System – Muscles will not contract.

1. Without the Nervous System – Muscles will not contract. Sport Books Publisher

2. 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 Sport Books Publisher

3. Activation of motor unit and its innervation systems • Spinal cord 2. Cytosome 3. Spinal nerve • 4. Motor nerve 5. Sensory nerve 6. Muscle with muscle fibres Sport Books Publisher

4. 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 Sport Books Publisher

5. 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 Sport Books Publisher

6. 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%) Sport Books Publisher

7. 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 Sport Books Publisher

8. 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 Sport Books Publisher

9. 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 Sport Books Publisher

10. 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 Sport Books Publisher