So why assume that studies of drugs have better technique? It's a lot easier to study exercise.
I think a lot of X correlates with Y studies are just kinda crap for a number of reasons, including that we don't have extremely good baselines -- e.g. continuous 24 hour monitoring across a wide population in a multitude of circumstances.
I don't think we should make any such assumption. What this looks like to me is that researchers have seen a couple different ways to trigger something that might be the same mechanism, but the overall way it works is still enough of a mystery that it's hard to say what the overlap is.
I think a lot of X correlates with Y studies are just kinda crap for a number of reasons, including that we don't have extremely good baselines -- e.g. continuous 24 hour monitoring across a wide population in a multitude of circumstances.