3) Two elite swimmers agree to be test subjects in a metabolism experiment. They

Question

3) Two elite swimmers agree to be test subjects in a metabolism experiment. They compete in a race that lasts roughly 90 seconds. Although they complete the event in about the same amount of time as each other, Swimmer A starts much faster than Swimmer B, but B swims faster than A at the end of the race. From muscle tissue samples taken shortly before the event, you assay their a) levels of creatine kinase activity b) percentage of fast-glycolytic fiber in the muscle levels of lactate dehydrogenase activity The swimmers had different profiles for all three of the above items. What differences would be consistent with their relative racing abilities? Briefly explain your reasoning in each case.

Explanation / Answer

The energy source for high intense activity at the start includes ATP and creatine phosphate. Once these two get depleted, anaerobic respiration takes over to produce energy for the activity.

So swimmer A must have higher levels of creatine kinase and higher percentage of fast glycolytic fiber in the muscle. The levels of lactate dehydrogenase which is needed for anaerobic respiration must be low.

The conditions are exactly opposite for swimmer B. The levels of creatine kinase and percentage of fast glycolytic muscle fiber must be low and lactate dehydrogenase activity must be high.

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