P 4 Describe the Function of the Muscular

P 4 – 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 1. Energy (ATP) 2. Calcium (on/off switch) 3. 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 Tibialis anterior

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 (2 a & 2 b) 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 2 a Fast contraction Medium force Slow to fatigue Middle distance Good blood supply Red in colour Aerobic Type 2 b 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 2 a = � Type 2 b =