These things are sitting machines. If you’re going to spend money on one of them, read the manual, set it up properly for your body (seat height, depth and tilt, backrest tension if it’s not autoregulated, lumbar support, armrest width, height, angle, and/or depth…), and learn to use it as intended. If you do, it’s money well spent (orthopedists and chiropractors are way more expensive); if you don’t, it’s a waste of money and intervertebral discs.