This is a video of a nifty muscle rippling phenomenon. I’ve waited for an opportunity to film it in my own quadriceps, where I have seen it a few times, but it’s hard enough to induce that I haven’t had a chance yet. Hat tip to reader Chris for finding this video of it:
That’s very similar to what I’ve seen in my own muscles, but much more languid. It’s always been at least triple that speed in my flesh! Could just be natural variation in the phenomenon, or something else altogether, but this definitely looks more like it than anything else I’ve seen.