I carefully read the safety instructions and did 10 minutes on a low setting, 10 out of 99. Honestly, it felt very invigorating at first. But then the back pain started. That was over 2 weeks ago. I'm still in constant pain. I can't lift anything, or walk more than a block without pain. In just 10 minutes I went from being able to hike all afternoon, and carry things, and work, to having to ask my neighbors to shovel my walk because it hurts to just pick up the shovel. I'm not saying this will be your outcome. But think very carefully before you try this. If I could warn my past self not to buy this, I would.