You can watch a live action demo from one of my students in the video clip to the right. Although he moves across a room, this can be done backwards and forwards on the spot just as easily. You can also make the excerise harder or easier by changing the surface you work on.
The sidewinding action simulates the movement of a snake and allows us to develop a natural movement on the ground without the direct use of our hands and legs for leverage or traction. So why is this useful? Two main reasons: 1) Especially whilst executing BJJ / ground-based techniques, our arms and legs may well be busy; and 2) Throughout all the different aspects of martial arts, shoulder and hip rotation / twist is a vital movement. Sidewinding is also excellent for building core strength.
The drill looks very simple and is, in reality, very simple to perform. However, almost all students that are new to this drill will struggle at first. The trick is to keep trying, although the drill can be very tiring when it's not done correctly. Don't be tempted to use your hands, feet or elbows as this defeats the point of the exercise and will just slow you down by interrupting the natural flow of the movement. Begin by transferring your hips out to the side and following with your shoulders. Repeat and gather speed. Allow your arms and legs to move, don't try to keep them rigid. I find the movement very similar to doing the Twist (first 20 seconds only) in a horizontal position.