Even if your muscles are low on stored sugar (glycogen), your body still builds muscle just as well after lifting weights, as long as you eat enough protein.

In rats, lifting weights for two weeks made their muscles build more protein even though the usual muscle-building signals in their bodies went down. This shows muscles can grow without needing those normal signals.

When you lift super heavy weights until you can't do another rep, your muscles use up a lot of their stored sugar (glycogen) to keep going — this shows your body is breaking down that sugar fast to power your workout.

Doing short bursts of intense exercise can help your muscles make more proteins, especially the ones in energy factories inside cells, but it doesn’t always make your muscles bigger if you only do it for less than six weeks.

When muscle glycogen levels are much lower than normal, the biological signals that trigger muscle growth after weight training are less active.

When muscle glycogen levels drop below one-third of their normal storage capacity, the molecular signals that promote muscle growth after weight training are reduced.