But where does all of the energy to do this contraction come from? That is the difference between our two athletes.  

Both of their muscles use large amounts of ATP, but the sprinter needs to make , while the mile runner needs to make .

 

Our sprinter probably gets a quick burst of energy from his muscles' stores of , but for the rest of his sprint he will be quickly (and inefficiently) "burning" glucose without oxygen to make ATP in a process called . The by-product of this metabolic process is a molecule called , which has to be ejected from the cell or it will cause muscle "burn".

 

Because of this, he is mostly building up muscle fibers known as (<-- two-word name), or (<-- two letter abbrev.), fibers, which store a lot of reserve fuel in the form of

 

Our mile runner, however, needs to burn her fuel more efficiently. She burns glucose using oxidative, or , metabolism, with the help of cellular organelles called .

 

The muscle fibers she is building up will be pink, because they store oxygen between contractions on a protein called . These muscle fibers are (<-- two-word name), or (<-- two letter abbrev.), fibers.

 

·        ATP slowly over a long time

·        a lot of ATP in a hurry

·        aerobic

·        creatine phosphate

·        fast glycolytic

·        fast oxidative

·        FG

·        FO

·        glycogen

·        glycolysis

·        lactic acid

·        mitochondria

·        myoglobin

·        slow oxidative

·        SO

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