There are lots of studies about what affects performance in sports (food, biomechanics, training methodologies, psychology, metabolism, genetics...) combat sports included. Martial arts studies about performance are few and far between.
Try this for instance:
-Go to google scholar
-Search: judo performance training
-Search: aikido performance training
I haven't done the searches. I can guess, though, that there's a lot more research done into Judo because there's world and Olympic championships at stake. It matters (at some level) who wins. Think of the money that's sunk into winning in Formula 1 racing. It matters (to those with the deep pockets), so there's a lot of research done. There's quite a bit of physiology, strength, fluid-dynamics, training, sport psychology, nutrition, recovery, materials study that goes into my sport (Rowing) where there's virtually no financial gain available - the money in F-1 must be amazing... Think about it - a steering wheel for those cars costs more than most people's entire car.. Because there's a winner at the end of the day and performance matters.
We don't really measure "performance" in Aikido, so there's not a lot of scientific method in it - no sponsors who need a result, who need to find out the facts - so there's a lot of speculative musing about things like... 'tensegrity' and so on.