Having just started playing the saxophone very recently, I am still on the easiest setting of the U-trainer and I found it easy enough to do a recommended three-minute workout. At the same time I could feel that my muscles were being challenged. I hold it for one minute, followed by 10 seconds of rest (3 minutes in total).
I am glad that this tool is so time efficient, easy to use, and that it's one of the few saxophone exercises my neighbours can't hear