I've looked at a lot of this data and while I'm not completely convinced that we've got as clear a picture about it as some would like to suggest, I think it is generally accurate enough to be useful. The question it raises for me, and I read articles all the time on this topic so I know I must be missing something that's obvious to most people, is why anyone would want to lift lighter if it is no more effective than lifting heavier (and I've seen no studies to indicate that lighter is better, merely, possibly equivalent)? I'm sure some of it relates to the wide variation in the definition of the term "failure" and some of it probably relates to fear of heavy weights, but I still don't get it.
If I'm training to what I define as failure I've got a lot of grit to really, really push myself to "real failure" if I keep the weight heavy enough that I fail in 45-60 seconds of continuous movement. I can maintain my determination and almost always achieve what I consider to be "real failure" with times around 90 seconds, but I admit I can be intimidated by doing a large volume workout with that kind of target time. I can consistently get to something that is a reasonable approximation of failure at times around 2 minutes but it's utterly miserable. Anything beyond that and I'm always wondering whether I lost my grit, overheated, just plain gave up, or managed to hit something like a good approximation of real failure and I look forward to my workouts with unmitigated dread. Having experimented extensively with all of the above, I personally get slightly better results utilizing a target time of 60-90 seconds to failure for most movements and as little as 45 on a select few. Much more importantly, when I run with weights that are this heavy I find my workouts to be a serious but interesting challenge that I don't want to miss. When I've worked with lighter weights I only work out from a sense of obligation.
Do you prefer lighter weights, and if so, what is it that you like about them? Do you train to failure or to some other metric? Anything you think I'm missing?