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\section{Conclusion}
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\label{sec:conclusion}
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Since keyboards are still the main data input device while using a computer and
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are also found to be related to discomfort or even \glsfirst{WRUED}
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\cite{pascarelli_wrued}, we tried to evaluate a possible modification to the
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existing keyboard design, that does not require the consumers to extensively
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adapt their typing behaviour, nor the producers to massively deviate from
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existing manufacturing processes. To reduce the load on weaker fingers, we
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created a keyboard that used keyswitches with actuation forces, related to the
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specific finger the keyswitch is operated with and hoped to thereby decrease the
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risk for \gls{WRUED}. The evaluation of the impact of different actuation forces
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on typing speed, error rate and satisfaction revealed, that higher actuation
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forces reduce error rates compared to lower actuation forces and that the typing
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speed is also influenced―\textbf{at least indirectly}―by differences in
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actuation force. Especially the keyboard with very low actuation force,
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\textit{Nyx (35\,g)}, which also had the highest average error rate was
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significantly slower than all other keyboards. Therefore, we investigated, if
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there is a connection between high error rates and stagnating typing speed and
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found, that in general, the error rate was a factor for lower input
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rates. Neither the satisfaction nor the muscle activity was significantly
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influenced solely by the actuation.
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In conclusion, our study showed, that the keyboard with non-uniform actuation
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forces―\textit{Hera (35 - 60\,g)}―was not able to improve the overall typing
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experience significantly enough to supersede existing designs, but was still a
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viable alternative to all traditional keyboards we tested. It could be possible,
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that due to the unconventional force distribution, that is similar to keyboards
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with very light actuation force, the muscle activity while using \textit{Hera}
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could decrease when users are given more time to adapt to this keyboard
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\cite{gerard_keyswitch}. Additionally, we found that keyboards with either very
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high (80\,g) or very low (35\,g) actuation forces had the most influence on typing
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related metrics, when compared to the more commonly sold keyboards with around
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50\,g to 60\,g actuation force. In the next sections we identify possible
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limitations and propose some ideas on how to reevaluate custom keyboard designs
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in future studies.
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\subsection{Limitations}
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\label{sec:limitations}
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The first limitation of our study design was the rather short time period of in
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total 10 minutes, for every participant to adjust to each keyboard. With
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prolonged typing session, familiarization, especially for keyboards with lighter
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actuation force, would have been more realistic to a real life scenario where a
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person bought a new keyboard. Furthermore, the laboratory test environment where
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the researcher was in the same room, the limited time for the individual typing
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tests and the rather short breaks in between typing tests, could have influenced
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some subjects by inducing unnecessary stress. Another limitation related to the
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preliminary finger strength study, was the very small number of participants (n
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= 6). Although we measured the finger strengths in different positions for 50\,\%
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female and male participants, the age distribution was not diverse (M = 24) and
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with a higher number of subjects, the results would have been much more
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reliable. Similarly, the number and diversity in occupation of participants
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could have been higher for our main study (n = 24) to yield even more meaningful
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results. The low number of participants in general was partly due to the ongoing
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COVID-19 pandemic. Lastly, we could have used more linear mixed models during
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our statistical analysis, to be able to make statements about the influence of
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other factors e.g., age, gender, average daily keyboard usage, etc., on speed,
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error rate and satisfaction.
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\subsection{Future work}
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\label{sec:fw}
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We propose, that in further research related to keyboards with non-uniform
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actuation force (adjusted keyboards), participants should test several different
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adjusted keyboards and the results should be compared to one identical looking
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keyboard that utilizes a uniform layout of keyswitches with an actuation force
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of 50\,g to 65\,g. Further, different adjusted layouts, with e.g. higher or lower
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base actuation force than 50\,g could be used to calculate the individual spring
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resistances used for each key or a similar layout to the one used in
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Realforce\footnote{\url{https://www.realforce.co.jp/en/products/}} keyboards,
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could be compared to each other. Furthermore, long term studies with adjusted
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keyboards, where participants use the adjusted keyboard for 3 to 4 months and
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then use a uniform keyboard they prefer for another 3 to 4 months as their daily
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driver, could yield more accurate results, due to the chance to fully adapt to
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the individual keyboards. During those months \gls{EMG} and typing related
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metrics should be measured on a regular basis. Lastly, it would be interesting
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to investigate if an adjusted keyboard can reduce pain or at least enhance
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comfort for typists with pre-existing diseases influenced by typing activities
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(disorders of the upper extremity), since one of our participants with a similar
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disease reported a great reduction in pain while using \textit{Hera}.
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