Hand Gesture Arm Fatigue, Part II

Why Drumming Tells Us Everything We Need To Know

7 min readAug 24, 2021

Welcome to Part II of a three-part series on spatial computing ergonomics. Here are the links to the other parts:

Part I: Is Arm Fatigue a Non-Starter for Spatial Computing?

Part II: Why Drumming Tells Us Everything We Need to Know (you are here)

Part III: Anatomy and Best Practices

In Part I, we covered that spatial computing is a young industry full of ergonomic problems, and one of the most prevalent early problems is rampant shoulder fatigue. We need to branch outside of our niche field to find examples of how to use our bodies without hurting ourselves.

Drumming is one of the best places to look.

On a drum set, your hands are always directly in front of you, executing rapid short-to-mid-range translation and rotation. You may be surprised to learn that drum technique is not high impact for your hands. It’s high impact for those poor drumheads, but if the impact absorbs into your hands, you’re doing it wrong. It’s fast, all-day, low-impact hand activity.

A perfect corollary to spatial computing!

And luckily, before my career as a spatial computing engineer, I taught over 300 students how to play the drums, so I tripped over a problem or two that can arise when you’re first learning these techniques.

Simultaneous and coordinated activation of fingers, wrists, and arms remain constant for performances that can last several hours on drums. If you drum correctly, you can play loud and fast for a whole eight hour shift at work, and come back again the next day to do it again. You’ll need lunch before you need to rest your arms, IF your technique is correct.

Most drumming activity creates the same ranges of rotation angle for all the joints, and the same travel distance for the position of the hands as we need in spatial computing. The latter is how I always knew spatial computing hardware is not yet ready for long-term use. Hand tracking sensors generally require you to place and hold your hands too far away from your body at all times. We’ll see how common a problem this is in young drummers in a moment, and what it does to their arms.

Human Resources professionals often specialize in the ergonomics of using computers in an office setting all day. These pros know a lot about PC best practices, but very little about spatial computing, not that I’d expect more from them until we see greater adoption of immersive hardware.

In a chicken/egg loop, ergonomic specialists can’t bother to study hardware no one uses, and no one will use hardware that has bad ergo. We’ll break this loop one day.

Spatial computing ergo specialists will then advise proper coordinated flex from the fingertips all the way up to the shoulder for extended, repetitive actions, just like a drum teacher.

In drums, we activate the hands more rapidly than in hand-tracking apps on average, and yet we can do so all day with no fatigue. If drummers can do it, so can spatial UI users. The human body is the human body.

If hand gesture technique is the same as drumming but slower, it’s easier. If it’s known to be ergonomically safe at high speed, then it’s confirmed to be even safer at low speed.

I’m currently using my knowledge as a former drum teacher to design ergonomically sound hand tracking techniques as I prototype a VR and AR replacement for a QWERTY keyboard. Text entry is very repetitive, and it needs to be fast. Drumming is even faster. From music, I brought over some tricks that are little known in the spatial computing industry.

For instance, when a drum student begins their journey, most of them run over the same speed bump in their first month:

I call it the “reach” problem.

In their third weekly drum lesson, they say, “I love playing, but my arms get really tired after about twenty minutes.”

Sound familiar, Tom Cruise?

Tom Cruise’s agent called. His shoulders do not fatigue. Move over, Chuck Norris.

So I ask my drum student:

“Which muscle is the one that’s getting tired?”

I already have an idea where they’re going to point. It’s that little muscle on the front of their shoulder cap. I now know it’s called the coracobrachialis. More on that little devil of a muscle later.

When the student points to that muscle, I say, “Yup, that’s what I thought.”

Most beginning drummers set up their 1st drum kit like this.

And then I ask them to show me how their drums are set up at home. They’re usually confused by this. They’re new to drums, so they don’t really notice any difference between the drum set at the music store versus their kit at home.

This is correct setup. Notice the batter heads pointing upward.

So I show them. I grab the high tom on my drum set and tilt the batter head toward me, which causes the bottom head to swing away. The drum is now MUCH farther away from my body.

And I ask them, “Are your drums set up like THIS at home?”

And they ask, “How’d you know?”

I tell them, “That’s how everyone does it at first, because the drum heads are easier to see when the strike zone is parallel to your face, but it actually works against you because the drums are much harder to reach, see?”

I show them my arm has to fully extend in order to hit the head, not just because it’s farther away, but because the tone and bounce response is better the farther you move forward to compensate for that sharp batter head angle. The drum pulls your hands toward it by feeding your ear a better sound as your elbows drift further and further. I carefully point out how far forward my elbows now extend. Just like Tom Cruise in Minority Report. Allegedly.

Then, I explain the key to ergonomic comfort is one simple trick, a trick everyone intuitively knows since we use it to improve all kinematic skills:

Never use muscle you don’t need.

If the drum encourages your elbow to move a lot, it’s probably in the wrong position. It should be moved closer to your body and angled to enable stasis and rest in your upper arm.

In a perfect one-to-one correlation, if the tracking cone of your spatial computing hardware requires your elbow to move outward away from your body, it should probably be repositioned. If interaction with a spatial UI forces your elbow to move away from your body, it should probably be moved closer. This simple idea drastically affects the decision processes of everyone involved in both hardware and software development in spatial computing.

If the elbow moves, the shoulder flexed to move it. If the shoulder flexed at all, there’s probably a different way, a way that allows the shoulder to completely relax.

But in hand tracking systems, we HAVE to move the elbow, at least a little bit. Don’t we?

100%. It’s the same story between hand tracking and drumming. To reach all the drum and cymbal positions or all the UI elements, you do have to move your elbows, but there’s an elbow range threshold that your shoulder can handle for extended multi-hour use.

Drum teachers grow familiar with this “safe” range by observing which elbow positions alleviate fatigue in dozens or hundreds of students. If you cross the threshold, your shoulder will fatigue in ten minutes. If you don’t cross the threshold, you can hit those drums or do those UI gestures all day long.

So where is that threshold?

To not only find it, but find out why it’s so constrained, we’ve got to explore that annoying little muscle, the coracobrachialis, which is exactly what we’ll do in Part III, the final part of this series.

In Part III, we’ll observe the difference between human muscles and those of a certain primate who definitely pumps more iron than we do. Our tree-swinging buddy’s anatomy will reveal the root cause of our fatigue, which will be the key to eliminating it.

Follow me on Twitter to see when the finale of this series goes live tomorrow.