Anatomy and Physiology / Unit 5: The Muscular System
5.4 Muscle Energy and Fatigue
Notes
Muscles use ATP, which is regenerated three ways.
- Creatine phosphate: a quick transfer of phosphate to ADP; lasts about 10 seconds.
- Anaerobic glycolysis (without oxygen): breaks glucose to pyruvate, makes 2 ATP per glucose rapidly, and produces lactic acid when oxygen is limited. Lasts up to about 1 minute of intense effort.
- Aerobic respiration (in mitochondria): makes about 30-32 ATP per glucose; used in prolonged exercise.
- Muscle fatigue is when a muscle can no longer contract despite stimulation. Oxygen debt (excess post-exercise oxygen consumption) is the extra oxygen needed afterward to restore ATP, creatine phosphate and process lactic acid.
- Fiber types: slow oxidative (endurance, many mitochondria), fast glycolytic (strong, quick, fatigue fast), fast oxidative (in between).
Practice
A sprinter's muscles depend mostly on which source of ATP in the first seconds of a 100 m race?
Short intense bursts rely on stored creatine phosphate and glycolysis.
A marathon runner's muscles mostly use:
Long events need the high ATP yield of aerobic respiration.
Which fiber type fits postural muscles that contract for hours without tiring?
Slow oxidative fibers have many mitochondria and good blood supply, so they resist fatigue.
Ready for more? Take the Unit 5 test.