The couch stretch, as popularised in the Crossfit community by Kelly Starrett is a mobility exercise that most of us would benefit from doing daily.
Our modern world is designed for far too much sitting. Spending significant time with flexed hips and knees creates adaptations that make it more difficult to stand properly upright. Usually you get back pain as the result. With a lifetime prevalence for non-specific lower back pain estimated at 60-70%, and with the British NHS citing lower back pain as the leading cause of disability, the couch stretch is a simple way for you not to be one of those statistics.
As mentioned in the video, one of the key points to do the couch stretch well is to make sure that you contract your glutes (butt muscles). This teaches your nervous system that there is a connection between contracted glutes and lengthened hip flexors.
I shot this video at Christmas 2015, thus the much younger version of me.