I recently read a post on a forum where the thread starter asked if it was okay to cross your feet while trying to armbar from the top position. He said his instructor told him not to, but that he saw lots of top level competitors doing it.
First thing is first, to all those new to BJJ (or old, you never know), always listen to your instructor when he tells you to do something in regards to the execution of technique. I think this instance is a prime example of how top level competitors can deceive you into thinking your instructor is wrong.
Yes, Roger, Marcelo, the Mendes Bros., etc., might cross their feet when armlocking from on top; they have every right to, because they are world-class black belts. But, that’s just the thing! They are world-class black belts! They are much more technical and have practiced techniques a thousand times (or more), so in certain areas they are allowed to “fudge” in order to accomplish what they are doing. They know the technique backwards to front. I like to compare it to riding a bicycle.
You don’t start off riding a bicycle by standing on the seat. You learn to ride by sitting your butt on the seat and placing your feet on the pedals. That’s the basics. If you’re extremely proficient at riding, then you can start to stand on the seat and ride the bicycle that way. You don’t just start riding by standing on the seat. That would be insane!
If your instructor tells you to do something, it is most likely for a reason. Most instructors tell you to never cross your feet for several reasons. The first being that you’re a beginner at armbars. Crossing your feet is like trying to run before you can even walk! Secondly, crossing your feet can only be done from on top and if you start practicing that as a beginner, crossing your feet from the bottom, which is something you’ll never see Roger, Marcelo, or the Mendes Bros. do, can become habit and that can be detrimental. Crossing your feet from the bottom naturally brings your knees apart, which then makes it much easier for the person on top to pull their arm out and it makes it easier to get stacked and crushed.
So, in summary, just because you see top levels guys doing it doesn’t mean it’s the right thing for you right now. And you should always put trust in your instructor when it comes to techniques. He’s been around longer than you. Remember that!