Here's a concept: Every single researcher who wants to conduct these kinds of experiments needs to, as a prerequisite, read Starting Strength [0] and then go to a certified gym for a year or more before even remotely being able to say anything useful about the subject.
Yes, sure, Starting Strength isn't perfect. I am not presenting it as the sum of all knowledge and the one-and-only true anything. However, there is a vast difference between someone who think they understand strength training and someone who reads this book and actually does it (under trained supervision) for as little as a year.
Someone mentioned dumbbell exercises being harmful and unnecessary. Absolutely agreed. The isolation exercises and machines are dangerous gimmicks for almost everyone going to the gym. There are people for whom they might have value. For the average person who wants to get fit and strong, these exercises and machines are a horrible idea.
My own story: I thought I knew how to lift. I was frustrated because I was not able to make progress. Someone at work introduced me to Starting Strength. I read the book and found a local certified trainer. The difference was like night and day.
I remember the first time I went back to a regular gym after about a year on Starting Strength. I had not touched a dumbbell in probably two years, if not more. Not once. I decided to see what I could do. Long story short, I got all the way up to the 120 lb dumbbells and could not go further 'cause that's the heaviest they had. Anyone looking at me would not, in a million years, have guessed I could go pick-up two 120 lb dumbbells and workout using them. I had guys coming to ask "WTF?", because they were struggling with weights less than half that much.
This goes with my favorite quote: "A man holding a cat by the tail learns something he can learn in no other way" - Mark Twain. These researchers need a cat to hold before they think they know what they are talking about.
[0] https://startingstrength.com/
PS.: Rip is an interesting character. Trained with him. Even had discussions about the use of his approach in space travel applications. Nice guy.