When eight trained bodybuilders did arm curls with heavy weights, their muscles used up a bit of stored sugar—12% after one round and 24% after three rounds—showing that even short, intense weightlifting burns some muscle fuel.

When eight trained bodybuilders did arm curls with heavy weights, their muscles made more lactic acid the more sets they did — which means their bodies were working so hard they had to rely on a fast, oxygen-free energy system.

When eight trained bodybuilders did heavy arm curls, their muscle energy stores dropped a lot after just one set and still stayed low after three sets, showing their muscles were burning through quick energy fast.

Glycogen depletion during resistance training is negligible in non-fasted individuals performing ≤10 sets per muscle group per session.

Typical resistance training sessions deplete muscle glycogen by no more than 40%, even under high-volume conditions.

After a short, super-hard workout, your muscles refill their energy stores way faster than after a long, slow one—even if you eat the same amount of carbs.