Novel use of the Nintendo Wii board as a measure of reaction time: a study of reproducibility in older and younger adults

The NWB could have potential to become a good clinical tool for assessment of RT in a wide range of populations, as it is inexpensive, portable, and reliable. Overall, the results indicate that the RT tests can differentiate older adults from younger adults. Secondly, that no learning effect within- and between day could be observed for any of the tests with exception of the lower extremity RT test between session 1 and 3 for the younger participants. Finally, that a good reproducibility could be achieved within- and between day for both the upper and lower extremity test using the fastest of three trials in both the older and younger participants.

This was the first study to explore RT measured with standard NWB using custom software. Previously, researchers have primarily measured RT using expensive laboratory equipment [8, 16‐20]. The results from the current study showed that for both the upper and lower extremity test the younger adults were markedly faster on average than the older adults (−170.7 ms ~24 % difference and −224.3 ms ~23 % difference, respectively). This was anticipated and not a surprise as numerous studies have shown this previously [16, 21‐23].

The mixed effect model used in the present study showed that there was no systematic effect comparing any of the sessions for the RT test in both the upper and lower extremities for both the older and younger adults. The only exception was in the lower extremity test where a significant decrease (−35,5 ms; 4,6 %) in RT was observed for the younger adults between session 1 and 3. However, in the older group a similar trend was seen between session 1 and 3 in the lower extremity test. This possible learning effect might be related to the nature of the lower extremity test, which is weight Bearing contrary to the upper extremity test. If the visual cue i.e. was presented on the left side of the computer screen and the participant was predominantly or fully weight supported on the equivalent leg (left leg) then the RT would be slower compared to if the participant had an equivalent weight distribution on the legs. If this was the case in session 1 and 2 then the participant would have to shift their weight i.e. onto the right leg in order to react appropriately to the visual stimulus (left side). In session 3 the younger adults may have adapted towards this by having a more equivalent weight distribution on their legs resulting in a faster RT compared to session 1. In the future this medio lateral swaying may be avoidable by giving clear and very specific instructions on having their weight equally distributed on their legs. Another possible explanation for the trend between session 1 and 3 in the older group might be that older adults tend to improve speed, accuracy, and consistency of their motor response between sessions [35, 36]. In support of the above and in the present study, the standard deviation in general became smaller with increased number of recordings and across sessions (time 1, 2, and 3) for both groups in the lower extremity test. This underpins that a learning effect across sessions has taken place in the lower extremity test, and that future test protocols should focus on this problem.

In the present study, a good reproducibility (ICC, CV and TE) was achieved within- and between day for both the upper and lower extremity RT test in both groups. However, in 2013 Spiteri et al. [20] reported slightly better Coefficient of Variation (CV) values ranging from 1.48 to 3.35 % but similar or lower ICC values ranging from .71 to .83 and for a simple lower extremity RT test in 5 young adults (University sports science students) when averaging 10 trials compared to the present study. These slightly better CV values compared to the current study might be explained by Spiteri et al. handpicking 5 out of the original 30 participants for the sub study on reproducibility. Moreover, participants were allowed two practice trials prior to each test before commencing the counting tests. In the current study, this type of participant selection did not occur and not surprisingly, we found slightly higher CV percentage values for both the young (6.2 %) and older (7.3 %) adults. However, the present study produced similar or higher ICC values compared to Spiteri et al. when averaging 10 trials. These similar or higher ICC values might be explained by the current study consisted of a much more heterogeneous study-population in both groups than the very small study-population in the Spiteri et al. study. In another reproducibility study Mercer and coworkers [15] evaluated a simple, inexpensive, and portable ruler-method for measuring RT on 30 community-dwelling older adults using an intra-day (20 min pause) design. They found the method to be outside of an acceptable reproducibility range as ICC was .53 between sessions. In addition, they observed a significant learning effect between sessions, which further disqualified the method. However, the Mercer study did only report ICC values with respect to reproducibility and this may have played to their disadvantage, as other statistical methods (which are effected to a minor degree by the study-population) could have shown greater reproducibility. The ICC calculation is depends on the ratio of the variability between participants to the total variability, and is thus affected by factors related to the study sample itself. The CV percentage or similar (Bland-Altman plots, Limits of Agreement) are less effected by study sample and are important to report as they will give an indication either in percent or absolute values to the measurement error of the method [29]. This becomes of great importance when evaluating the effect of an intervention study or a rehabilitation course, as some of the potential effect achieved may/should be attribute to measurement error. Based on the measures of reliability (ICC) and agreement (CV, TE) the authors recommend using the fastest trial of three in both the upper and lower extremity RT test in both groups in order to minimize measurement error and at the same time be time efficient. However, to avoid a learning effect across days of testing it is recommended that habitation trials are applied for both young and old adults when testing RT in the lower extremities.

The strength of the current study is the availability of the NWB’s. Presently approximately 43 million Wii-boards have been sold across the world. In addition, it is a very cost-efficient and portable method compared to existing methods. Moreover, we were able to test both upper and lower extremities, and explore within- and between day reproducibility in one study. Finally, the present study concurred with internationally accepted guidelines in terms of reporting reproducibility studies as several measures of both reliability (ICC) and agreement (CV and TE) were reported [29]. A weakness in the current study is the lack of validation. This study did not correlate results with a ‘gold standard’ within reaction time testing, which would have added to the potential future use of the test in clinical settings. Finally, the custom software prepared for the current study is not yet widely available limiting the usefulness of the study. However, in the near future the authors plan to validate the Wii-RT test against a ‘gold standard’ method and make the software widely available to clinicians and researchers.