More muscles … ugh We’re almost there!! 

Learning goals We are learning to identify the types of muscle fibres. We are learning to examine how to train each energy pathway.

MUSCLE FIBRE TYPE certain muscles in our body are more adapted to one energy system than another according to the dominant type of muscle fibre in the muscle

TYPE 1 (SLOW-OXIDATIVE) contract & relax relatively slowly generate less force, but can last for longer produce ATP aerobically because they contain high levels of: fat (which can only serve as fuel for AEROBIC system) blood vessels (which carry oxygen needed for AEROBIC) myoglobin (the enzyme that stores oxygen in muscle) mitochondria (site of AEROBIC)

TYPE II (FAST-TWITCH) F-T fibres contract & relax 2-3 X as fast as slow-twitch can generate explosive force, but only for short time produce ATP anaerobically because these fibres contain high levels of: phosphocreatine & glycogen (stored version of glucose) which serve as fuels for ANAEROBIC Systems glycolytic enzymes (permit release of glycogen in muscle fibres) larger motor units (so more fibres are recruited at once)

primarily dark meat breast - white legs - dark

TYPE II A (FAST-OXIDATIVE) vs TYPE IIB (FAST-GLYCOLYTIC) Can actually distinguish between 2 types of FAST-twitch IIA – contain both oxidative & glycolytic enzymes Fast contractions, less fatigue resistant than type I IIB – only glycolytic enzymes Fastest contraction speed but limited fatigue resistance The cool thing…IIB’s can become IIA’s if you train them through endurance training

Let’s watch!

most people have a relatively equal # of slow-twitch & fast-twitch fibres in their muscles though certain areas of the body have more S-T (e.g. legs) and others have more F-T (e.g. arms) elite level athletes however, tend to be born with an unequal ratio of fast-twitch & slow-twitch fibres e.g., Usain Bolt = 80% f-t, Simon Whitfield = 80% s-t

I have more S-T I have more F-T

  Size Contraction Speed Fatigue Resistance Color Energy System Mito-chondria Slow Twitch (Type 1) Small Slow High Red Aerobic (Lots of O2) Many Fast Twitch (Type 2) Large Fast Low White Anaerobic (Little O2) Few

Muscle fiber type Average person Sprint trained Aerobic trained Slow   Slow (type I) 40% 55% Fast (IIa) 50% 20% Super-fast (IIb) 10% 5%

training the energy systems even though, our athletic performance is somewhat limited by our genetics (e.g., the ratio of Type I vs II muscle fibres), there are methods of improving the efficiency of our 3 Energy Systems generally, an athlete should match training methods to the Energy System they use during competition

effects of TRAINING on the immediate alactic All training for this system should be powerful (100% intensity) and short (6-12s). The recovery time for this system should be minimal (15s-120s). Examples: Running – 10 repetitions of 30m sprints with 30s recovery Strength Training – 4 repetitions of 90% maximum load with 30s recovery Swim – 8 repetitions of 25m sprints with 30s recovery Effects of training on immediate alactic system: 20-40% increase of creatine phosphate stores increase of ATP stores increase in creatine kinase function

effects of TRAINING on the ANAEROBIC SYSTEMS intense exercise lasting for up to 90 seconds will benefit hockey players, mid-distance runners by: increasing glycogen stores in muscle Enables oxygen to be used sooner Increases speed of Cori Cycle ANAEROBIC THRESHOLD – the point at which lactic acid is accumulating in the blood stream Trained athletes have a higher AT (at 80-90% of max. effort) while untrained athletes have a lower AT (~55% of max. effort).

Let’s watch!

effects of training on THE aerobic SYSTEM cardiovascular exercise lasting 40 min several times per week will benefit endurance athletes by: increasing the # of arteries & veins (vascularization) in muscle tissue increasing the # and size of mitochondria in muscle fibres increasing the activity of the enzymes used in aerobic system (e.g. ATP synthase) promoting fat as a fuel during exercise (instead of glucose) which saves muscles’ limited supply of glycogen

Let’s watch!

Learning goals We are learning to identify the types of muscle fibres. We are learning to examine how to train each energy pathway.