The Seated Torso Rotation Over-Twist
This machine is designed to shape the obliques and eliminate love handles, making it popular with gym-goers looking to whittle their waists. However, it requires you to lift a stack of weights by twisting only your upper body and keeping your pelvis facing forward (try it in your chair; awkward, isn't it?). Isolating the back in this way puts an excessive amount of rotational force on the spine. Over time, it can result in a disk-related injury, says Matthews. Some devotees of this machine have found themselves hobbling to the chiropractor with nerve damage that causes shooting pain in the legs.