Mice that had two specific liver genes turned off couldn't keep their blood sugar stable after exercise, and their sugar levels dropped a lot compared to normal mice.

When two specific genes are turned off in the livers of mice, their bodies make less blood sugar—both when resting and exercising—because the liver can't use certain fuel sources as well. This shows those genes are important for keeping blood sugar levels up when the body needs more energy.

In mice, turning off one of two specific liver genes doesn’t hurt their stamina or blood sugar control after exercise, because their bodies can use backup systems to keep making glucose.

When mice are genetically changed so their liver can't take in two key energy-related molecules at the same time, they get tired faster during exercise — but only when both are blocked, not just one.

In mice, when two specific liver genes are turned off, their liver cells don't process energy as well—even during exercise—because they can't get enough fuel, not because they're missing the tools to do the job.

During prolonged moderate exercise, low blood sugar caused by reduced glucose in the liver and bloodstream is the main reason for early fatigue, not low muscle sugar stores.