When your muscles swell up after a workout because of increased blood flow, that puffiness itself doesn’t actually make your muscles grow bigger over time.

Just because your muscles feel swollen and pumped after a workout doesn't mean they're going to get bigger over time—studies show that even if some people get way more pumped than others, they all end up with about the same muscle growth in the long run.

When you do blood flow restriction training, your muscle cells might swell up, and that swelling could be what makes your muscles grow — even if there’s not much buildup of fatigue-related chemicals.

When you lift weights until your muscles burn, the buildup of waste products might help your muscles grow bigger, but scientists aren't sure yet if it's actually causing the growth or just happening at the same time.

Muscle swelling induced by resistance training may persist for up to 72 hours post-exercise, potentially confounding hypertrophy measurements if assessed within this window.

When you lift weights until your muscles burn and feel fatigued, the buildup of waste products might help your muscles grow bigger, but the main reason they grow is still from the physical force you're using.