Unsure if this is related, but I’ve heard that taking painkillers for delayed onset muscle soreness will reduce muscle gains.

Painkillers like ibuprofen are NSAIDs which inhibit the enzyme COX1/2, reducing prostaglandin production.

Prostaglandins are an inflammatory hormone that do a variety of things, but specifically PGE2 plays a role in muscle stem cell activation to divide and produce more muscle fibers. The effect is probably realistically small, but you will leave gains on the table by taking ibuprofen after hard workouts.

Are you saying that lifting weights makes more muscle fibers? I was under the impression it does not, that it simply makes your existing muscle fibers bigger and stronger.

The main muscle fiber cells don't divide (usually), but satellite cells reproduce. Those fuse with the fibers though.

Though the science is not completely established here and there are some exceptions (obvious ones like cancer, etc...)

So, literally "no pain, no gain" ?

Anti-inflammatories - not all painkillers.

Just NSAID’s - they’re anti-inflammatory and muscle synthesis happens in response to inflammation.

Same goes for icebaths, they reduce inflammation, which is the whole point of working out.

The whole point of working out is to stress the organism in order to induce a physiological adaptation. Inflammation is NOT the point, but rather an unfortunate side effect.

Does the opposite hold true as well? If I taunt a wasp nest after hitting the gym will I discover the fast route to mad gains?

You'll certainly get swole.

What about ginger? Because that apparently only downregulates COX-2 without affection COX-1 (most inflammation-reducing drugs affect both)

Etoricoxib does just that and is widely available at least in the EU

Interesting, I didn't know. My original question was more about whether that affects muscle gains differently though, do you happen to have any insights into that?

The studies I saw had people taking a lot, it wasn’t looking at people taking 400mg once a week of their knee or shoulder got sore during the workout.