Many of you have asked how to maintain better balance with the single leg RDL and here's your answer. One of the BIGGEST mistakes people make when performing a single leg RDL is LOOSING HIP CONTROL AND LETTING THE PELVIS ROTATE!! I cannot tell you the amount of times I've seen people performing a single leg RDL (happy they are doing it) but with improper PELVIC CONTROL!
You must aspire to keep your hips and pelvis level (flat) when performing the single leg RDL. Far too often when people descend in the single leg RDL, they will let their hips turn outward. You can see this if the hips of the back leg (in this example my right leg) ELEVATE higher than my left hip. This is a sign of a lack of hip/pelvis neuromuscular control and/or hip weakness.
To fix this, a coaching cue I like to use first is to tell the client to "keep the back foot pointed down towards their stance leg". This encourages the client to keep the hips neutral, as letting the foot point outwards to the side is indicative of a loss of pelvis control. Wherever your foot goes your pelvis will follow, and vice versa.
A second great manual cue can be accomplished with a foam roller. The foam roller essentially connects your hand to your foot. And by bringing your arm DIRECTLY IN A STRAIGHT LINE BACK, it forces your foot to follow in a similar bath, directly back, in addition to keeping the foot pointed down.