Part of the problem with this study is the same as that seen in most studies in exercise science -- they only study untrained participants and last, say, 10 weeks (or 8, in this case) And then there are the tiny tiny sample sizes (14 individuals??). The fact is, doing almost anything is better than doing nothing. That's good news for the people who do nothing, I guess, because you can literally start parking two blocks from work every day and start seeing improvement.

But because of this novice effect, we don't really get a sense from the studies what the actual optimal ways of exercising are. It's after that initial period (say, 10 weeks) of going from doing nothing to doing something that you start to hit plateaus and have difficulty improving. This is the point where the difference between various forms of exercise would start to become clear, and yet that's when studies always stop.

Is doing 3 sets of 5 better than 5 sets of 5? Is HIIT better than long, slow distance for cardiovascular conditioning? We have lots of anecdotal evidence of how to improve physical conditioning past the initial novice period, but very little in the way of rigorous studies. So for now and the foreseeable future, if we are to decide what to do once doing literally anything is no longer enough to make improvements, we'll just have to rely on "bro science" and the experience of various coaches who see a lot of trainees to decide how best to exercise.