The reverse hyper is good and evil at the same time. One thing we want to make sure we're always doing is utilizing the glutes for hip extension. A sign of glute weakness is the knees flexing when performing any type of prone hip extension movement. This is no exception on the reverse hyper either. A lot of athletes will break at the knees.
Keep the knees straight and emphasize the glutes
Focus on keeping the knees locked out and activating the glutes throughout the entire movement. One way I correct this problem is to execute a pause at the top. This will help to eliminate momentum throughout the movement as well. When performing the reverse hyper we want the entire motion to come from hip extension. Always make sure the lumbar spine is locked into place and we don't have a sagging or dipping motion as we extend the hips.
Loaded hyperextension of the spine
Also, I reinforce the need to be up on the elbows with the chest off the pad as per Dr. Stuart McGill. We want a straight line from the ankles to the shoulders at the top.
Good techniqe is spine sparing
WE DON"T WANT HYPER-EXTENSION OF THE SPINE. I would much rather have an athelte stop short of the top then to look like a reverse V-up at the top.
OUCH!!!