Back in the day, in high school, I was all into the online exercise research. I’d do homework, hit the basement with the weight set and cardio equipment, then hit the internet to research a million different things.
Sadly… I can’t find any of the cool articles from that era any more. Another instance of the modern search algorithms not comparing well with the old internet for me… lol
Anyways, there was a neat article that tried to develop a protocol for realistic “spot reduction” and abs. A trainer (I don’t remember the name) was using cardio intervals to help spike the metabolism and try to get a sort of carryover effect for the abs.
So he would do a few intense minutes of either an exercise bike or a rowing machine and then cut to some abdominal exercises, and then repeat for a whole training session. Apparently it was effective for increasing muscle and reducing fat especially in the waist/abs region.