I used the sweat patches during a regular 45 minute spinning workout and the other was a 45 minute intense spinning work out. Putting the patch on was easy, just make sure your arm is clean. It did not get in the way of my work out at all. I did notice when doing both workouts, it did not start to fill until the 30 minute mark and I have been sweating pretty good 10 minutes into my workout. This could be because I’m doing my workouts indoors and that I really do not sweat on my arms. Both times it barely filled up to the second line even though I got a good sweat on. You definitely need good natural light when scanning the patch after your work out which is a little hard to do since I am in a dark room after my spinning work out for a few extra minutes to cool down. I did have trouble using the app at first, but the second time it was no problem. I do think I lost more fluid than the patch analyzed. Taking the patch off pulled on the skin a little, but nothing too bad. I did not get any orange ink on my arm like other people who have reviewed this product. I do think that this is a cool and innovative product that can help athletes and active gym goers, but definitely needs some more work. Ultimately for the price point of these patches and how they performed for me, I would not buy them.