I remember when I first heard about it: I was at a gym doing a photo shoot - it was so long ago I can’t remember which gym it was, or even which magazine I was working for at the time - and a video crew was shooting a choreographed trampoline workout in the next studio.

I thought it was about the dumbest thing I’d ever seen. To me, it just looked like a cheerleading routine performed on trampolines.

But since then, alas, I’ve seen a few things I’d consider even dumber than that.

For ergonomics, I’d say they’re much better than you would think if you just looked at them. When they first came out, I remember thinking that a block-shaped DB couldn’t possibly work as well as a round one. But they definitely do.

For convenience, they’re terrific. A basic set of Powerblocks gives you DBs ranging from 5-50 lbs. but takes up the space of the 50s alone.

My only gripe is that the selectorizing mechanism is never as smooth as you think it will be. I have two different kinds in my basement, and I’ve played around with several other brands in stores or at fitness expos, and I have yet to see one where changing the weights is as fast and easy as changing the weights on a cable machine. With the Powerblocks in my basement, I can change the weight on one of them easily, but the other always puts up a fight—the pins just don’t want to slide in where they’re supposed to go.

Maybe the average consumer doesn’t buy them thinking that changing the weights will be perfectly smooth and as fast as advertised. But if I had to work out with them as my primary equipment, I think I’d be pretty frustrated by the mechanical issues.