Hi I use these ands daily as part of my physio exercises which have been prescirbed by the clinical specialist physio at my hospital (who' area is shoulders and knees). I've also used them within 1:! pilates classes again with a focus on stabilising my shoulders, and working all those small rotator band muscles. It's also a piece of equipment that I used to use a lot when I had a personal trainer. The feeling you get with using one is like a burning pain, but that's what it feels like to work your muscle to that state of tiredness! I've found that when using them because you are targetting such smaller muscles that wouldn't normaly get used, they do fatigue quickly, and so maybe you can only do 5 reps to start with, and build up from this, but you will feel the after effects in terms of normal muscle fatigue, which gets less, with an increase in reps & therefore strength. I now do about 50 in one go - of each exercise, (alternate sets of 10 on each side), but I started with 10 reps 3 times a day. It's worth continuing with under the guidance of a physio/pilates instructor, as i've found it really key in stabilising my shoulder joint and shoulder blades, and in increasing my own awareness of what my shoulder/shoulder blades and surrounding muscles are doing in various positions, even without using the band e.g., lifting my arm up I can now tell when the humeral head is going to sublux posterially & can ensure most of the time that I correct this before it happens.