What energy system is required for sustained activity, and why can the other energy systems not support sustained activity?
What will be an ideal response?
The muscles rely on the aerobic system to provide ATP for muscle contraction to meet the more prolonged demands of sustained activity. This is the one system that uses oxygen, and therefore is able to provide ATP more efficiently and for sustained periods far beyond the capabilities of the phosphagen system and the lactic acid system. In addition, after 20 minutes of sustained activity, the aerobic system starts to use a higher percentage of fat for fuel and less glucose which conserves the body’s glycogen stores.
The phosphagen system relies on the immediate breakdown of creatine phosphate. When creatine phosphate is split anaerobically, it releases phosphate which can be used to replenish ATP. However, creatine phosphate amounts are very limited and require rest for more to be produced, making it an energy source for approximately 10 seconds.
The lactic acid system is called on by muscle cells to produce more ATP as the phosphagen system diminishes. The lactic acid system involves the anaerobic breakdown of glucose to pyruvate (and then of pyruvate to lactate). The primary source of glucose is muscle glycogen. This system can generate a small amount of ATP quickly for high-intensity activity lasting up to 3 minutes, but when the rate of lactate production exceeds the rate of clearance, intense activity can be maintained for only 1 to 3 minutes (as in a 400- to 800-meter race or a boxing match).
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a. True b. False Indicate whether the statement is true or false
Which of these statements is FALSE?
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