L-leucine might have some benefit when combined with creatine and L-carnitine in older adults. I’ve personally tried that combo as well as BCAAs alone. I don’t really see the point to be honest in taking anything like that. Did I get a “boost” in any way from any supplement? Maybe. Was it a placebo effect? Maybe. Cost a lot of money in my training career for maybes and I’d say I’m not better off currently having taken tons of different supplements.