This article was made possible by the excellent and very interesting study linked below.
Coppola, Sarah M., Philippe C. Dixon, Boyi Hu, Michael Y.C. Lin, and Jack T. Dennerlein. 2019. “Going Short: The Effects of Short-Travel Key Switches on Typing Performance, Typing Force, Forearm Muscle Activity, and User Experience.” Journal of Applied Biomechanics 35 (2): 149–56.
One of the longest-running metrics for keyboard quality, especially on laptops has been key travel. While key travel plays an incredibly important part, I’ve had a hard time believing it was the only one. I know for example that there are many fans of what is considered the classic IBM/ThinkPad 7-row keyboard before it was changed to the design we have today. When that design changed occurred, strong opinions emerged and that didn’t result in any significant change to key travel. If you want an in-depth look at the differences between these two keyboards, I strongly recommend this article from Laptopmag.com: https://www.laptopmag.com/articles/thinkpad-type-off-is-lenovos-new-island-style-keyboard-better-or-worse
Lenovo at the time also published a 5-pager which you can read here: Lenovo-Keyboard_Change-Is-Hard-Why-You-Should-Give-In-to-the-New-ThinkPad-Keyboard They outline the work that went into the redesign of the keyboard if you have never read it.
In the article above they examined several different metrics and came to the conclusion that the newer keyboard was not a step backward. In fact, the key travel between the two keyboards is identical, but the strong opinions remain for some, thus another factor must be at work. Now, getting back to our article from the Journal of Applied Biomechanics.
The present results suggest that key travel alone does not predict biomechanical outcomes and that key mechanism and activation force are also important factors in key switch design.
The results from the study were very interesting considering the common trend among reviewers and I suspect the industry as a whole is to discuss key travel as the main metric to measure the quality of the keyboard. Many companies like Dell have come up with some interesting ideas such as the use of magnets on their keyboards to maintain a good tactile feel while reducing travel. Others like Apple have ended up being in the news over their butterfly switches and their failure rate.
Specifically, the 2 devices with the same short travel (0.55 mm) had the largest differences across most muscles, though this difference was relatively small (<1.0% MVC). These 2 devices differed in activation force and mechanism: Tablet S had a dome switch mechanism and a higher activation force than Notebook S, which had a butterfly switch mechanism. Similarly, this study found that key travel distance was not strictly associated with typing force, typing performance, or perceived experience, as Tablet S was associated with the worst results across these measures compared with the other 3 devices.
In short, other factors such as the switch mechanism and how it relates to activation force potentially play a larger role than just key travel alone. Some might wish to equate a longer key travel with a greater activation force but that isn’t how spring mechanisms work.
Let us consider the classic example of a keyboard with an actual spring in the switch for sake of simplicity. If we look at Hooke’s Law which is used to calculate spring constants, F = -kΔx where F= force in Newtons, -k= Spring Constant and Δx= the change in spring length, we can see from this relationship that depending on the spring, we can change how much force is required for a specific change in distance. Now for further math-related content regarding keyboards and force, I strongly suggest you spend some time looking at the work done by Javier De Leon at the University of Alaska.
If seeing classic keyboard switches gutted are your thing, you might want to check out this article that shows the switch designs of several classic ThinkPad keyboards including the 701C
Turning out attention to the ThinkPad X1 Nano, which has key travel of 1.35mm, the mechanism gives it a positive typing experience. One of the “key” criticisms of the newer ThinkPads is the reduced key travel on the thinner models. While thinning a laptop down objectively leaves less room for key travel and some traditional activation mechanisms, we shouldn’t count out innovation to find solutions to these problems.