This month, we’ve been exploring the different ways we generate power in our Karate. Like many themes in Karate, this one keeps coming back—but I’m always amazed how, every time we revisit it, I walk away with a new understanding, perspective, or even a small epiphany.
This time around, we got stuck on vibration. Not stuck as in lost or unable to move forward, but stuck in the sense that it felt worth pausing to explore more deeply. I remember learning a long time ago to mimic others who were doing it. I don't recall ever being told why I should. It was something I had to decide to uncover on my own through reading and other reference materials over the years. But even then, it still doesn't seem well understood in general just from my personal observations. That got me wondering—does anyone really get it? Do I really get it? So, a few weeks ago, I posed some questions to my students.
The first was simple: “What is vibration?”
The answers I received were along the lines of “rotation on a small scale.” But is that all it is? If so, why distinguish it from rotation at all? After all, does the word “rotation” imply a specific size or scale? I don’t think it does, which suggests that vibration must involve something more. Technically, vibration is defined as rapid back-and-forth movement, but that can come in various patterns. Rotational vibration, linear, or a more wave-like oscillation.
So my next question was, “How does vibrating our hips make any technique more powerful?” This one was met with much less confidence. Which naturally led us to wonder: “Does it even make our technique more powerful?”
I’m known for putting things to the test if we’re not sure. Usually, it’s as simple as, “Hit me both ways and I’ll tell you which felt stronger.” It’s not exactly a foolproof scientific method, but since we’re trying to convince ourselves—not publish a research paper—it’s sufficient.
We tested two punching methods, starting with stationary choku-zuki. Before anyone punched me, I made sure they understood how to properly vibrate their hips. I watched their punches from all angles, paying close attention to what both hips were doing at the start of each punch and at the moment of kime. I also reviewed hours of video footage of our classes, going frame by frame to analyze their choku-zuki. One result stood out: we needed to adjust how vibration was being performed.
I tend to favor the method J.D. Swanson describes in Chapter 14 of Karate Science. He emphasizes that it’s a mistake to vibrate the hips by rotating around the spine as the axis. Why? Because doing so causes one side of the body to retreat as the other moves forward, leaving the body’s center of gravity (CoG) neutral. For maximum effect, we want the CoG moving toward the target at the moment of impact so the hit carries momentum. Momentum is the product of velocity and mass. If the CoG isn’t moving, there’s no momentum. A 200-pound person with a 10-pound arm can only hit as hard as the speed of that 10-pound arm allows if the other 190 pounds remain neutral.
Swanson instead suggests, from shizentai while making choku-zuki, the attacker should push the punching-side hip forward at the initiation of the punch, then subtly push the opposite hip forward to catch up at the moment of kime. At no point should either hip pull back until the technique is completed, at which point, the hips relax back to neutral. It’s a small forward movement—an inch or two—but enough to ensure the CoG is moving toward the target, if only briefly.
But can an inch or two really make a difference?
Well... yes and no.
When my students tried punching me with the described vibration, two things happened. First, as mentioned, their CoG was slightly moving forward on impact. Second, and maybe more importantly, the vibration ensured proper core compression—the key to producing kime and connecting the entire body from the floor, up through the legs and core, to the striking limb. You cannot execute proper hip vibration without engaging the core. The intra-abdominal muscles have to activate to rapidly send the initial hip forward, stop it without retracting, and bring the second hip in—all within a fraction of a second. So in that sense, vibration does make a difference.
However, my experienced students are already adept at engaging their core without relying on hip vibration to do so. Comparing their choku-zuki with and without vibration—but maintaining core compression either way—I couldn’t perceive much difference in power.
We also tested oi-zuki, with and without vibration. As long as core compression was present and timed correctly, again, I couldn’t feel a significant difference. That said, oi-zuki punches were naturally stronger overall than choku-zuki punches, thanks to the linear power generated by the body's lunging motion.
In both cases, if hip vibration added any advantage, it was too subtle for me to feel clearly. But I also didn’t notice any downside—as long as the vibration was performed correctly, without pulling back the opposite side. Any slight extra momentum, even marginal, is a plus. More importantly, hip vibration ensures that core engagement is there, especially for those who struggle with timing and compression. Vibration is therefore a useful tool.
However, as students progress and refine their body control, they may find they can achieve the same effect without the need for visible vibration. Like many tools in Karate, hip vibration helps instill a “feeling” early on—something that, over time, becomes internalized and no longer relies on the tool itself.
So, what do you think? Is it hip to vibrate?