Mark Martin blazed the trail on weight training for NASCAR which is why he can still make the occasional appearance in victory lane at 50 years old. It seems to be about upper body strength required for pulling considerable Gs hundreds of times. Plus there’s the heat that must be contended with. Temperatures inside the cars can reach 150 degrees or better. You also have to consider how many races there are in a year (36), plus the crossover races.
I remember seeing Ricky Rudd win at Bristol and give his post race interview from a stretcher because he collapsed as soon as he got out of the car.
I’m not going to beat up on any sport, because they all have their own physical requirements.
I was just replying to another poster who didn’t seem to think NASCAR was a sport, because the car does all the work, or something.