Question

If I exercised at a high intensity for 5 minutes, at that point, what would be contributing the most energy production?

A. Glucose in the Liver

B. Glycogen in the Muscle

C. Glycogen in the Liver

D. FFA in the blood

Answer 1

Muscle and liver are the stores of glycogen in the body. Further free fatty acids from stored fats also provide ATP. At low intensity exercise, free fatty acids are mobilized due to breakdown of fats by lipolysis. These free fatty acids present in the circulation will be used by the muscle as sources for ATP. However, as exercise intensity increases, free fatty acids are no longer available due to decreased lipolysis. In this case, the muscles use muscle glycogen for ATP generation due to aerobic respiration. However, this muscle glycogen can only support ATP generation for moderate intensity exercise (65-75% of VO2 max).

The muscles then use the liver glycogen for generation of ATP by glycogenolysis when there is high intensity exercise (85% of VO2 max). Liver glycogen is used for ATP generation by aerobic respiration. However, when high intensity exercise occurs for longer duration, the glucose generated from glycogen of liver is used for anaerobic respiration to produce lactate. Lactate is then transferred to liver and converted to glucose in liver by Cori cycle.

Right choice: C. Glycogen in the Liver.