Exercise Physiology: Energy systems: ATP-PCr, glycolytic, oxidative — ATP and the Phosphagen System
How muscles get instant energy from ATP and phosphocreatine, why it runs out in seconds, and what that means for sprints, rest and creatine.
Try 3 questions
1. How does ATP release the energy that powers muscle contraction?
- By splitting off its last phosphate group
- By converting directly into glucose
- By combining with oxygen from the blood
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Answer: By splitting off its last phosphate group
Hydrolysis of the terminal phosphate bond turns ATP into ADP and phosphate, releasing the energy myosin uses to pull on actin.
2. How long could the ATP already stored in muscle fuel an all-out sprint on its own?
- About 20 to 30 minutes
- About 2 to 3 seconds
- About 2 to 3 minutes
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Answer: About 2 to 3 seconds
Muscle holds only a small pool of ATP, enough for a couple of seconds of maximal work, so it must be rebuilt constantly.
3. Roughly how much ATP does an adult recycle in a single day?
- Around their own body weight
- About ten grams
- About a teaspoonful
Show the answer
Answer: Around their own body weight
The body holds well under 100 g of ATP at any moment but rebuilds each molecule over and over, turning over tens of kilograms daily.
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