Unit 1 – Anatomy & Physiology P4 – Describe the Function of the Muscular System & the Different Fibre Types Unit 1 – Anatomy & Physiology

Function of the Muscular System (skeletal muscle) = Generate movement Needs 3 things Energy (ATP) Calcium (on/off switch) Stimulus (signal from brain/spinal cord)

Movement Muscles cross joints Muscles contract and pull on the bones Muscles are ‘ready to go’ always slightly contracted waiting for a message from the nervous system (muscle tone) Without this we would fall over! Muscles work ‘all or nothing’ How strong the contraction is depends on how many muscle fibres are used Muscles use a lot of energy

Basic Muscle Rules Muscles can only pull on their bony attachment – never push All muscles work in pairs. When 1 muscle contracts (agonist) the other muscle must relax (antagonist) = reciprocal innervation

Major Muscle Pairs AGONIST ANTAGONIST Pectoralis Major Trapezius, Rhomboids Latissimus Dorsi Deltoids Biceps Triceps Rectus Abdominus Erector spinae Gluteus Maximus Hip flexors Gluteus Medius / Minimus Adductors Quadriceps Hamstrings Gastrocnemius Tibialis anterior Soleus

Muscles work together! Agonist – the main muscle generating the movement – prime mover Antagonist – opposite muscle to the agonist – relaxes to allow the movement to happen Fixator – the muscle or muscles that contract isometrically to fix a nearby or adjacent joint to prevent any unwanted movement Synergist – the muscle or muscles that assist the agonist to generate the movement

Bicep Curl Agonist = Antagonist = Fixator = Synergist =

Types of Contraction

Types of Contractions Isometric – muscle length stays the same, no movement, static contraction, easy to do but fatigues quickly. e.g. Plank Concentric – muscle shortens, joint moves, also known as the positive phase of contraction. e.g. Upward part of bicep curl Eccentric – muscle returning to original length, under resistance, after shortening, muscle works against gravity as a breaking mechanism, known as the negative phase of contraction. e.g. Downward phase of bicep curl Isokinetic – muscle contracts & shortens at a constant speed, needs specialised equipment that detects the speed of the movement & increases or decreases the load to keep it at the same speed.

Isokinetic Training Machine

Types of Muscle Fibres Muscle fibres are classed by the speed of their contraction. Slow Twitch = Type 1 Fast Twitch = Type 2 (2a & 2b) All skeletal muscles = different mix of fibres – down to genetics but training can change the characteristics!

Types of Muscle Fibres Muscle fibres are classed by the speed of their contraction. Slow Twitch = Type 1 Fast Twitch = Type 2 (2a & 2b) All skeletal muscles = different mix of fibres – down to genetics but training can change the characteristics!

Type 1 Muscle Fibres Slow contraction Produce minimal force Slow to fatigue Good blood supply Aerobic High number of mitochondria Red in colour Suited to endurance based aerobic activities

Type 2 Muscle Fibres Type 2a Fast contraction Medium force Slow to fatigue Middle distance Good blood supply Red in colour Aerobic Type 2b Fast contraction High force Quick to fatigue Short duration/stop go Speed & strength based Low blood supply White in colour Anaerobic

Muscle Fibres & Sports Type 1 = Type 2a = Type 2b =