I filmed a video discussing the single leg RDL. I believe it’s a very important exercise for many reasons. First of all, a couple of studies have shown that sensorimotor training led to improved power production. I’d much rather have athletes perform exercises like single leg RDL’s and single leg squats for sensorimotor training than exercises on wobbly boards, as this approach allows you to kill four birds with one stone by increasing balance, increasing hip stability, increasing hip extensor strength, and hopefully increasing power production.
I believe that the single leg RDL can be placed in the warm-up every single day, where you can mix it up, for example employing a reaching single leg RDL with a medball. I believe that from time to time the single leg RDL should be performed heavily as well, as there aren’t many exercises that challenge balance and coordination while strengthening the hips to the degree that this exercise does. Here’s a video of me discussing some aspects of the single leg RDL.
I realize that some coaches may take issue with my stance on external rotation of the non-grounded leg. I could argue both sides, but I don’t think it’s that big of a deal. If you keep the non-grounded leg straight, I’m fine with your decision. But the true nature of the gluteus maximus when it moves into hip hyperextension (which is where you “lock the leg” if you do it right) is to externally rotate the femur. From a standing position, simply squeeze your glutes as hard as possibly and you’ll feel your legs turn outward a bit and the feet trying to “screw” outward. Why fight this natural tendency?
Mayer et al. (2002) found that back extensions with the hips externally rotated (feet turned out) activated 39% more glute max than hips internally rotated (feet turned in). The glute max activates better with the feet turned out a bit, and in sports, the glute max influences femur, tibia and foot mechanics, so it needs to be strong in external rotation.
But again, I could argue either route so you can make up your mind as to whether you’re picky about the foot turning out or not. That said, you never want tight hip external rotators so you should employ various hip stretches and mobility drills to ensure that they don’t shorten.
I hope you enjoy the video, BC