Muscular

• Isotonic muscle contraction is when a muscle changes length during it's contraction. There are two types. Concentric is when a muscle contracts and shortens.Eccentric is when the muscle contracts and lengths.
• Isometric is when a muscle contracts but does not change length.
• A skeletal muscle contraction can only happen when stimulated by an electrical impulse sent from the CNS.

  The part of the nervous system it gets it signal from is a motor neuron.
• A motor neuron is a specialized cell which transmit nerve impulses to a group of muscle fibres.

  They have a cell body in the brain and spinal cord iwth an extending axon which branches to connect motor end paltes to a group of muscle fibres.
• A motor unit is a motor neuron and the muscle fiber. The motor unit functions to carry nerve impulse from the brain and spinal cord to muscles, initiating contractions.
• A skeletal muscle contracts by a nerve impulse from the CNS travels down the axon of the motor neuron known as the action potential.

  The action potential arrives at neuromuscular junction at the end plate of the motor neurone.

  Acetylcholine (neurotransmitter) is secreted which transmits the impuls across the synaptic cleft.

  If the impulse/action potential is above the threshold, all muscle fibres will contact in an all or none threshold.
• The neuromuscular junction is the point where the axon's motor end plate meets the muscle fibre.
• The gap between the end plate and the muscle fibre is known as the synaptic cleft.
• If a motor unit recieves a stimulus to crate an action potential that has reached threshold all the muscle fibres within the motor unit will contract at the same time and with maximum force.

  If the action potential does not reach threshold, none of the fibres will contract.

  This is known as the all or none law.
• There are 3 type of fibres, slow oxidative, fast oxidative glycolytic and fast glycolytic.
• Slow oxidative fibres structure:

  Neuron size - Small

  Fibres per neuron - Few

  Capillary density - High

  Mitochondria density - High

  Myoglobin content - High

  Phosphocreatine stores - Low
• Slow oxidative fibres functional:

  Speed of contraction - Slow

  Force of contraction - Low

  Fatigue resistance - High

  Aerobic capacity - High

  Anaerobic capacity - Low
• Fast Oxidative Glycolytic fibres structure:

  Neuron size - Large

  Fibres per neuron - Many

  Capillary density - High

  Mitochondria density - Moderate

  Myoglobin content - Moderate

  Phosphocreatine stores - High
• Fast Oxidative Glycolytic fibres functional:

  Speed of contraction - Fast

  Force of contraction - High

  Fatigue resistance - Moderate

  Aerobic capacity - Moderate

  Anaerobic capacity - Moderate
• Fast Glycolytic fibres structure:

  Neuron size - Large

  Fibres per neuron - Many

  Capillary density - Low

  Mitochondria density - Low

  Myoglobin content - Low

  Phosphocreatine stores - High
• Fast Glycolytic fibres functional:

  Speed of contraction - Fast

  Force of contraction - High

  Fatigue resistance - Low

  Aerobic capacity - Low

  Anaerobic capacity - High
• Work relief ratio is the volume of relief to the volume of work performed.
• Work:Relief are very low for SO muscle fibres to maximise the use of SO fibres a 1:1 or 1:0.5 work/relief is commonly used.
• Work:Relief are very high for maximal weight training. A 1:3+ work:relief ratio is used.
• The agonist during flexion at the hip is iliopsoas
• The agonist during extension of the hip is gluteus maximus.
• The agonist during adduction hip are the adductor brevis, adductor longus and adductor mangus.
• The agonist during abduction at the hip are gluteus medius and gluteus minimus.
• The agonist during lateral rotation at the hip is the gluteus maximus.
• The agonist during medial roation at the hip is the gluteus maximus and gluteus medius.
• The agonist during flexion at the knee are the bicep femoris,semimembranosus and semitendinosus.
• The agonist during extension at the knee are rectus femouris, vastus lateralis, vastus intermedius and vastus medialis.
• The agonist during dorsi-flexion at the ankle is the tibialis anterior.
• The agonist during plantar flexion ankle is the gastrocnemius and soleus.
• The agonist during flexion of the wrist is the wrist flexors.
• The agonist during extension at the wrist is wrist extensors.
• The agonist during flexion at the elbow is the bicep brachii.
• The agonist during extension of the elbow is the tricep brachii.
• The agonist during flexion at the shoulder is the anterior deltoid
• The agonist during extension at the shoulder is the posterior deltoid.
• The agonist during abduction at the shoulder is the middle deltoid.
• The agonist during adduction at the shoulder is the latissimus dorsi.
• The agonist during medial rotation at the shoulder is the teres major and subscapularis.
• The agonist during lateral rotation at the shoulder is teres major and infraspinatous.
• The agonist during horizontal flexion at the shoulder is the pectoralis major.