I have not had an unfortunate experience…YET, thank goodness, but I work with a very experienced and cautious personal trainer. With. -3.2 lumbar and -1.9 femur, I started about 18 months ago with mostly 5 and 8 pound dumbbells and am presently using mostly 12, 15 and 20 pounders. I use these with squats, overhead presses, curls, deadlifts, rows, lunges, etc. I workout once a week with the trainer and duplicate the exercises at home. Since I do not have a barbell set, I’m not using that yet, but I have used a couple of machines at his gym….inclined leg press up to my own weight, and a few cable exercises with anything from 30-60 pounds. So nothing too ridiculously heavy, a very small start and very gradual increase, and adapting when needed for weak wrists and an occasional cranky knee. The MOST important thing is FORM and learning to properly use your core, which requires someone with experience to spot you and give feedback with consistent prompting. I would never attempt anything like this without professional guidance. It’s the best money I have ever spent!