I noticed some good things in this video.
Even though your left hand was lagging a little bit behind the right, you kept trucking along and keeping up with the tempo of the song. That's good, because when you're actually playing music with a band, you can't stop or slow down to think -- what you just played is in the past. The song must go on!
Check out the Strumming lesson on Free Ride, taught by Anders Mouridsen, under the Songs. I don't think you were stiff, you were just strumming with more of your elbow instead of your wrist.
As a sort of similar example, imagine if you turned the steering wheel of your car with your shoulders instead of your elbows. Try it right now and see what I mean. Keep your elbows and wrists locked and just turn to turn the imaginary steering wheel with your shoulders. You'll see it looks "stiff."
The point is, you don't *need* to be moving a larger part of your body (shoulders, back, elbows) if you can get the same sound from moving a smaller one (wrist, fingers). It takes more energy to move your elbow (and your whole forearm and hand which are connected to it) than it does just your wrist. You can also get more control and nuance out of your wrist than your elbow.
I see a little bit of combination of wrist and elbow in your video, which is good. When you're learning, it's good to take apart the mechanics of your arm and see where you're losing energy. It's like martial arts.
You can think about it this way: The area you are actually "playing" with your right hand, from low E to high E is really only about 2 inches across at its widest. If you take that into consideration, why should a stroke be *drastically* longer than that? If you make your stroke 18 inches long from top to bottom, what are you really doing but strumming 16 more inches of strings that aren't there? If you were to build a machine to strum guitar strings, you wouldn't want to spend the extra money and energy making it's "arm" move that much. There would be the extra cost of repairs, the extra materials, but the result would be the same. There's only so much energy that the strings can actually absorb, and at some point the extra stroke doesn't do anything. I'm not saying to only make your stroke 2 inches long. Just think about the idea of it and experiment.
If you watch a lot of rock videos and live bands you'll see them strumming like crazy with their whole arm, but that's really just for show (or for the feel of the player). Same thing with drummers. (Raising the sticks above their heads and swinging all the way down doesn't really do anything other than look cool and feel fun.)
You could practice both ways of strumming (wrist and elbow) and learn how to switch between them to get the best control and best sound. Drummers practice separately with shoulder, elbow, wrists, and fingers and integrate them for different purposes. It's strange that these same techniques are not essential for guitarists.
-Carl.
Carl King
Director of Content
GuitarTricks
Los Angeles, CA