A crew was pulling a second string of tubing out of a hole and was warming up a collar to break the connection. A swivel operator was spinning the swivel when an employee placed a 36-inch pipe wrench on the top part of the swivel, then placed a cheater bar on the pipe wrench. The swivel continued to turn clockwise with the pipe wrench and cheater bar attached. The employee was still holding onto the cheater bar when it started turning. The employee was then pulled and thrown off the rig floor, suffering a broken clavicle, broken ribs, collapsed right lung, and broken back.