Without the Nervous System – Muscles will not contract. Sport Books Publisher1

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 Publisher3 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

Sport Books Publisher4 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 Publisher5 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 Publisher6 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 Publisher7 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 Publisher8 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 Publisher9 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 Publisher10 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