Yeah, i thnik they did studies before, it's basically like altitude training, just a bit different in the number of days for adaptation and then after that duration that you can hold that before losing the edge.
Think it is like 10 days before you adapt.
But of coz in order to take full advantage of that for PRs, you'd need to train in SG weather and then go to cooler climates to run races lah. For eg you go KLSCM it's basically walking 3 steps front and then 3 steps back. Only pro is that you do no DNF, while if you are sufficiently heat prepped then maybe still can run same as training runs in SG. Of coz for full effect, train hot and run cool.
It's the same as altitude training, you train at 6k ft AMSL but race at 5k ft, really no diff.
And of coz like for me, office / server cold, and then home also AC. And training all shaded....... you race fast pace say mid 3 min paces here in SG, surely physics would still screw me one.
Not sure if you watch triathlons like T100. Lucy charles barclay loves hot climates. She usually no issue with Ironman Kona or T100 SG or similar hot venues.