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08.STRUCTURE AND FUNCTION OFMUSCLE 21. MUSCLE CONTRACTION AND ATPEnergy in the form of ATP is required in order to swivel the myosin heads A. There are 3 potential sources: i. Creatine phosphate ii. Glycolysis iii. Aerobic respiration B. There is some evidence that creatine supplementation can impro...

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08.11.18

STRUCTURE AND FUNCTION OF MUSCLE 2 1. MUSCLE CONTRACTION AND ATP Energy in the form of ATP is required in order to swivel the myosin heads A. There are 3 potential sources: i.

Creatine phosphate

ii.

Glycolysis

iii.

Aerobic respiration

B. There is some evidence that creatine supplementation can improve sprint performance, however this is not conclusive; excess creatine may damage the kidneys

2. MUSCLE FIBRE TYPES A. Slow oxidative B. Fast oxidative - glycolytic C. Fast glycolytic

2

i.

Most skeletal muscles have a mixture of the three types, but the proportions are different depending on the function of the muscle

ii.

The fibres cannot convert fully from one type to another, however they can take on more of the characteristics of another type if put under enough stress of the right kind

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3. FIBRE TYPE DISTRIBUTION A. Distribution in different muscles i.

Most muscles have a mixture of fibre types

ii.

Large postural muscles tend to have a greater proportion of slow twitch fibres, as they make predominantly slower movements with low force development

iii.

Muscles that are used for movement have a higher proportion of fast-twitch fibres, as they make more short-duration movements and develop more force

iv.

The proportions of fibre types in muscles used for movement depends on the individual

B.

Distribution in different individuals i.

The overall proportion of fibre types is genetically determined, although there can be some change in characteristics with training

ii.

In sedentary individuals, a higher proportion of the fibres show slow-twitch characteristics

iii.

Sprinters have a higher proportion of fast twitch fibres

iv.

Endurance athletes have a higher proportion of slow-twitch fibre The proportion of fibres may influence the ability to develop athletic characteristics

4. HOW ARE FIBRES RECRUITED DURING PHYSICAL ACTIVITY?

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i.

At low speed/intensity, slow twitch fibres are mainly recruited

ii.

As speed/intensity increase, more fibres are recruited overall, and a higher number of fast oxidative-glycolytic

iii.

At higher speeds still, the overall number of fibres and the number of fast twitch fibres recruited is increased

5. HOW DOES PHYSICAL ACTIVITY AFFECT MUSCLE?

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i.

Resistance exercise tends to increase muscle fibre size by increasing the amount of protein incorporated into the myofibrils. Strength and/or power are increased according to the specific training carried out

ii.

Aerobic exercise increases the number of mitochondria in the muscle which results in increased capacity to generate energy by aerobic respiration; ability to store myoglobin is also increased; strength and size are not affected unless the training has a power/strength component.

iii.

Training with an anaerobic component increases the ability to tolerate lactic acid and to clear it more efficiently

iv.

Activity of all types increases capillarity of muscle, however this is much more pronounced in aerobic training...