2. 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

3. 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

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

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

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%)

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

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

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

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

11. Make a table with muscles through the unit – only movers of main joints Muscle NameFunctionDescribe movements OriginInsertion Bicep Brachii Prime moverFlexes lower armsCoracoid Process Head of Humerus Radius

12. 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