Muscles

Consist of collagen fibres & very strong Attach skeletal muscle to periosteum covering bone

-Surrounds muscle, muscle bundle & fibres -These layers give muscle shape & smooth surface to allow other muscles, muscle bundles & fibres to glide during contractions -All 3 layers of connective tissue connected to each other & tendon allowing moment to place muscle contracts

Consist of long lines of sacromeres - basic operational building blocks for muscle contractions

Motor units consisting of motor neuron & groups of muscle fibres

• Cell body containing cell nucleus, cytoplasm & mitochondria • Dendrites which receive electrical impulses from spinal chord & transmit them to cell body • Axon links cell body to muscle fibres, as it reaches muscle, axon splits into branches to myelin allow single cell to control many muscle fibres • Motor end plates connect axon to muscle cell allowing motor nerve to stimulate muscle fibres & cause muscle contractions

Occur when neural messages transmitted by electrochemical process from CNS to muscle fibres via motor unit

Smaller & contract at about 1/5 of rate of fast twitch fibres High oxidative structures makes them very resistant to fatigue

Larger, produce greater force faster but tire rapidly

-Fast twitch fibres can be made faster & stronger with correct training methods (speed, power, plyomertric training) -Fast twitch can become ‘slower’ through prolonged low intensity training -Type 2B muscle fibre can be converted to type 2A muscle fibres

-Strength of movement controlled by number of motor units recruited by CNS to complete required movement & by freq of contraction -Not all motor units within muscle needed for fine skill or gentle movement, whilst all motor units may be needed for gross skill or dynamic movement -Slow freq of contractions produce light or weak contractile forces, whilst rapid freq will produce stronger contractions -Slow twitch fibres normally recruited first in any movement, fast twitch muscles only recruited when intensity of movement reaches certain level

Contractile strength increased if motor unit continuously activated by stimulus before it’s completely relaxed from previous contractions Known as wave summation - force produced grows in series of waves until point stimuli so fast there’s no relaxation possible This is termed a Tetanic & Absolute Contraction

Wave = typically fast twitch 2B Spatial = Long distance/continuous activity

-Motor units within muscle activated slightly different times & not all together -By spreading out contraction & relaxation, muscle able to sustain continuous contraction over period of time; not just split-second -Staggering contractions within muscle called spatial summation

Flexors = bend a joint Extensors = straighten joint

Muscle that shortens/contracts to move joint E.g. bicep muscles in lifting phase of curl

Muscle that lengthens/relaxes to move joint E.g. triceps in lifting phase of curl