Answer:
The correct answer is- muscle glycogen
Explanation:
During the first few seconds of exercise, the stored ATP in the resting muscles are used to provide energy to the body once the ATP is depleted in few seconds then creatine phosphate is used to provide energy.
ATP and creatine phosphate only provide energy for up to 15 seconds after that the muscle starts anaerobic respiration for providing instant energy because in starting, the rate of respiration is not that much high that instant supply of adequate oxygen can be provided to form ATP.
Therefore muscle switches to anaerobic respiration to form ATP by using glucose of glycogen that is stored in the muscles. It last about 45-120 seconds and after that muscles use aerobic respiration to make ATP.
