THis is definitely what I'm most interested at the present moment; I actually perform mental training on all non-training days, for around 10 minutes minimum, and I've thought of more unique exercises to perform, but haven't seen significant strength gains or anything. THe only time I noticed a different was when I did a lot of trampoline trianing in my head, a lot of overspeed training using springboards, trampolines, other bouncy platforms, and my SVJ became a lot faster with minimal ROM.
What I'd like to see is these studies performed on trained athletes who have already learned to recruit 90%+ of their muscle fibers. In untrained ppl it makes sense to see these gains, but I wonder if it's possible to see gains in MUSCLE through mental training. What if we could trick the body into building more muscle by thinking about it. That would be really cool.