Conceptual Design of an Extended Reality Exercise Game for the Elderly

Round 1

Reviewer 1 Report

In this manuscript, the authors describe a VR-based game for the elderly. From reading the abstract, I first thought authors “only” designed and implemented a VR game, following existing design principles. In particular, I miss a description of contributions or a research question. Thus, I would first recommend rewriting the abstract, making the contributions clear and describing the purpose of the study. Similarly, the research gap should also be already mentioned in the abstract.

In the introduction, the researchers try to describe the research gap, however, fail to explain why VR-based games need to be designed differently for the elderly. Simply stating that there are no games, which are intentionally implemented for the elderly, is weak. For example, are games such as Beat Saber or Exercube [1, 2] not proper for the elderly, although you can choose the level difficulty? In Beat Saber, you can even customize songs or choose between the song genres. Also, Exercube adapts to the player's ability.

In section 3.1, the authors mention some of the most important design principles for serious games. Nevertheless, I am missing some important criteria particularly for exergames, such as accurate tracking to prevent cheating or injuries (see also Caserman et al. [1]). In 3.2.1. the authors mention that they track hands with controllers and feet with some sensors, but it’s unknown which one. I especially appreciate that full-body movements are tracked, as most of the current games focus only on upper- (or lower-) body movements. Nevertheless, I would suggest to describe more specifically how the full-body movements are tracked and how does the game ensures that the movements are performed as intended by the designer.

Minor issues:

• In the Background, the authors already classify the implemented game VRrowing as an exergame, however, the description of the game is first provided later.
• Table 1 and Figure 3 are never mentioned in the text and just pop up. I think there is a typo in “Figure 3. shows the type of players that VRrowing can attract under different modes and character 332 arrangements.” It should probably be Figure 2.

[1] Martin-Niedecken, A. L., Rogers, K., Turmo Vidal, L., Mekler, E. D., & Márquez Segura, E. (2019, May). Exercube vs. personal trainer: evaluating a holistic, immersive, and adaptive fitness game setup. In Proceedings of the 2019 CHI Conference on Human Factors in Computing Systems (pp. 1-15).

[2] Martin-Niedecken, A. L., Mahrer, A., Rogers, K., de Bruin, E. D., & Schättin, A. (2020). “HIIT” the ExerCube: Comparing the Effectiveness of Functional High-Intensity Interval Training in Conventional vs. Exergame-Based Training. Frontiers in Computer Science, 33.

[3] Caserman, P., Hoffmann, K., Müller, P., Schaub, M., Straßburg, K., Wiemeyer, J., ... & Göbel, S. (2020). Quality criteria for serious games: serious part, game part, and balance. JMIR serious games, 8(3), e19037.

Author Response

Thank you very much for your detailed and comprehensive review, it helped a lot to improve the article. Below are our responses and actions to each comment.

Comment 1: In this manuscript, the authors describe a VR-based game for the elderly. From reading the abstract, I first thought authors “only” designed and implemented a VR game, following existing design principles. In particular, I miss a description of contributions or a research question. Thus, I would first recommend rewriting the abstract, making the contributions clear and describing the purpose of the study. Similarly, the research gap should also be already mentioned in the abstract.

Response: We have a few sentences in the abstract about purpose (“……this paper proposes a conceptual design of a VR rowing game, VRrowing, to provide a home exercise game for the elderly, which benefits both physical and mental health.”), contributions (This research has reference value for scientific research or development personnel in VR game applications and evaluations). But we did not highlight the research gap. Thus, we have updated a sentence to make it clear.

Action: Add the sentence “……, which fills the void of home VR rowing games for seniors exercise.” to highlight the research gap, and “……, especially such games targeting the elderly” to rich the contributions.

Comment 2: In the introduction, the researchers try to describe the research gap, however, fail to explain why VR-based games need to be designed differently for the elderly. Simply stating that there are no games, which are intentionally implemented for the elderly, is weak. For example, are games such as Beat Saber or Exercube [1, 2] not proper for the elderly, although you can choose the level difficulty? In Beat Saber, you can even customize songs or choose between the song genres. Also, Exercube adapts to the player's ability.

Response: We agree with this comment. We missed the part of motivation explanation about the elderly exercise game should be different to VR games targeting the general user.

Action: Add sentences “Relevant elderly XR games have focused on treatment/rehabilitation/prevention of specific diseases by physical training, which may miss some users who are not at risk of such diseases. Moreover, XR exercise games (especially XR rowing games) usually do not target the elderly user, which might ignore the significantly different between the elderly and other age groups such as motor, cognitive, and perceptual, thereby may affect the acceptance and satisfaction among the elderly users [57].”

Comment 3: In section 3.1, the authors mention some of the most important design principles for serious games. Nevertheless, I am missing some important criteria particularly for exergames, such as accurate tracking to prevent cheating or injuries (see also Caserman et al. [1]). In 3.2.1. the authors mention that they track hands with controllers and feet with some sensors, but it’s unknown which one. I especially appreciate that full-body movements are tracked, as most of the current games focus only on upper- (or lower-) body movements. Nevertheless, I would suggest to describe more specifically how the full-body movements are tracked and how does the game ensures that the movements are performed as intended by the designer. 

Response: We agree with this comment.

Action: Add some sentences in Section 3.2.1 to describe whole-body movement tracking.

Comment 4: In the Background, the authors already classify the implemented game VRrowing as an exergame, however, the description of the game is first provided later.

Response: We agree with this comment.

Action: Remove VRrowing in this section.

Comment 5: Table 1 and Figure 3 are never mentioned in the text and just pop up. We have I think there is a typo in “Figure 3. shows the type of players that VRrowing can attract under different modes and character 332 arrangements.” It should probably be Figure 2. Did find found

Response: Table 1 (Page 5, the first paragraph) and Figure 3 (page 10, section 3.2.5) are mentioned in this paper.

          We made a mistake in Figure 2 and 3.

Reviewer 2 Report

Presented article with Title ”Conceptual design of an extended reality exercise game for the elderly” is writing on 16 pages with 4 figures, 3 tables and 63 references. The paper is written clearly. The structure is very clear (introduction, bacground, methodology, discusion, conclusion).

Suggestions:

• Introduction is written clearly.
• Please more describe Game Flow on the figure 3.
• In the article is missing an image showing the application in VR. Figure 4 is unclear.
• Was the presented application tested on a selected sample of users?
• Conclusions, please describe more your future directions.

All the specific comments can be followed in reviewed copy of the manuscript.     

I recomend this paper publish in journal after minor revision.

Author Response

Thank you very much for your detailed and comprehensive review, it helped a lot to improve the article. Below are our responses and actions to each comment.

Comment 1: Please more describe Game Flow on the figure 3.

Response: We agree with this comment.

Action: Update Figure 3 and add more details in Section 3.2.5 to describe it.

Comment 2: In the article is missing an image showing the application in VR. Figure 4 is unclear.

Response: This paper is a conceptual design of VRrowing, and figure 4 is a user interface concept design. We don’t have the application VR image yet.

Action: Change the name of Figure 4 to “A concept user interface design of VRrowing” and add sentences in Section 3.2.6 to explain Figure 4 is a user interface concept design. In addition, we updated more explanation about UI design in Section 3.2.6.

Comment 3: Was the presented application tested on a selected sample of users?

Response: We have not conducted a test with users. The evaluation section will continue after the implementation and descript in the following paper.

Action: No action.

Comment 4: Conclusions, please describe more your future directions.

Response: We agree with this comment.

Action: Add sentences to explain our future work in the Conclusion section.

Round 2

Reviewer 1 Report

The authors partly improved the manuscript; however, there are still some inconsistences. For example, in introduction, authors write “Unlike the above studies…” but do not specify any references. Probably, the authors should here specify some of the games which were analyzed in their previous surveys (previously published by the authors).

I like the idea that full-body movements are tracked accurately to ensure that players perform game activities as intended by designer. However, I am still concerned about the sensors used for motion tracking. As described. In Section 3.2.1, players need to hold two controllers (in their hands) and have to attach additionally five sensors (on the waist, tight and ankles). Is the sensor position / orientation important? How does the calibration work? Please discuss how do you ensure that elderly (or any other players) will attach all these sensors properly? Furthermore, some of the proposed tracking technologies require that you stand at least 3 m in front of the sensor. Is the proposed game supposed to be played at home? This might be difficult, as probably not all players have enough place or knowledge to setup the system.

I also like the idea to support different player types. Nevertheless, authors do not discuss how they aim to achieve this. From the Figure 2, it seems as if in the single mode, every player is achiever when training. What if a player performs better as “killer” during the training phase? Are different player types fixed based on the intensity? Please discuss how the player intensity is determined?

Author Response

Comment 1: The authors partly improved the manuscript; however, there are still some inconsistences. For example, in introduction, authors write “Unlike the above studies…” but do not specify any references. Probably, the authors should here specify some of the games which were analyzed in their previous surveys (previously published by the authors).

Response: We agree with this comment.

Action: Add three example games as the cite for “Relevant elderly XR games have focused on treatment/rehabilitation/prevention of specific diseases by physical training” and “XR exercise games (especially XR rowing games) usually do not target the elderly user”.

Comment 2: I like the idea that full-body movements are tracked accurately to ensure that players perform game activities as intended by designer. However, I am still concerned about the sensors used for motion tracking. As described. In Section 3.2.1, players need to hold two controllers (in their hands) and have to attach additionally five sensors (on the waist, tight and ankles). Is the sensor position / orientation important? How does the calibration work? Please discuss how do you ensure that elderly (or any other players) will attach all these sensors properly?

Response: We agree with this comment.

Action: Add sentences in Section 3.2.5 to descript how to guide users to attach all devices and check and debug the linking.

Comment 3:Furthermore, some of the proposed tracking technologies require that you stand at least 3 m in front of the sensor. Is the proposed game supposed to be played at home? This might be difficult, as probably not all players have enough place or knowledge to setup the system.

Response: We agree with this comment.

Action: Add sentences in Section 3.2.1 to explain the necessary space for VRrowing playing at home.

Comment 4:I also like the idea to support different player types. Nevertheless, authors do not discuss how they aim to achieve this. From the Figure 2, it seems as if in the single mode, every player is achiever when training. What if a player performs better as “killer” during the training phase? Are different player types fixed based on the intensity? Please discuss how the player intensity is determined?

Response: We agree with this comment.

Action: Update Figure 2, and add detail about how to match the different player types and how to determine the player intensity.

Round 3

Reviewer 1 Report

The authors answered all my questions and also improved their manuscript.