After a weightlifting workout, the main leg muscle loses a lot of its stored sugar energy—about 21% on average—which can make you feel tired and affect how well you do in your next workout.

Lifting weights once can use up a lot of the sugar stored in your thigh muscles, which your body needs for energy during hard exercise.

People who don’t lift weights regularly lose more muscle sugar during a workout than those who train regularly—likely because their bodies are less efficient at using energy.

The more sets you do in a weightlifting workout, the more your muscle sugar stores get used up—each extra set burns about 11 more units of energy.

The longer you lift weights in one session, the more your muscle sugar gets used up—every extra minute burns about 1.3 more units of energy.

Mixing up heavy and light weights in a workout burns more muscle sugar than sticking to one weight the whole time—likely because you do more total work.