Exergame designers should include some type of spectator support and encouraging messages whenever players are making good progress, e.g., (1) when their performance has achieved a certain level, (2) when their performance has resulted in good outcomes, and (3) when their performance has prevented the opponent from performing well.

Here we list examples of how the spectator NPCs can be added to the games based on the degree of locomotion the player has in VR:

• (1) Low: in exergames that the player mostly remains at the same location [e.g., VirusBoxing, Beat Saber4, Hot Squat, spectators/supporters can be added behind the player, alongside the objects’ flying area, or placed at a higher location where the game objects are initialized.
• (2) Medium: in exergames where players only need to move in a limited in-game distance (Eleven Table Tennis VR), spectators can be added around the users but with a small distance. A good example is the Creed: Rise to Glory.
• (3) High: in exergames where players need to move their in-game position on a large scale (e.g., VR cycling games), the spectator could be placed alongside the playing or track field (e.g., placing the spectators next to the street for VR cycling games).

Based on our fndings in , including an audience (even composed of generic NPCs) and its feedback reacting to the players’ movements can improve the performance and enhance the gameplay experience for elderly players. We suggest including an audience and providing positive feedback whenever the elderly players are making good progress, the term "good progress" can be varied across games, please define this based on the game you are designing. In addition, more NPC models and a diverse range of visual and audio feedback are needed.

When all movements can achieve the desired exertion of the exergame: (1) providing the players with a list of movements and enabling them to select their preferred gestures, or (2) allowing the players to customize the gestures; both approaches could lead to a better and more personalized experience.

When some movements cannot achieve the desired exertion level but are necessary to help players reach a certain exertion level, a possible approach is to apply an adaptive exertion level for each participant based on each individual’s physical ability level, exercise demands, and performance in the game.

• As Perceived Usefulness had a positive effect on Chinese older adults’ intention towards VR exergames, VR game desginers of these games should (1) ensure a game is sufficient to provide health benefits, and (2) highlight the health benefits people could obtain and how effective of it.

• Use natural and simple motions (e.g., punching, slicing, dancing) for VR exergames as these motions are easy to use–Perceived Ease of Use is a positive predictor of Chinese older adults’ intention to use VR exergames. No additional tutorials are needed when the game only uses easy-to learn and natural motions.

• VR exergame producers should provide various in-game achievements to encourage further gameplay. One way to achieve this is to use a badge system.

• VR exergames should enable social interaction within these games and encourage older adults to play together in groups or at least with another friend. Studies suggest that social interaction could help older adults exchange tips for better performance and, as such, could make them more engaged in a game.

• Consideration should be given to the demographics of the population. e.g., if it's Chinese older adults, dancing games should involve some type of Chinese style dances. Chinese songs can also be provided in rhythmic-based and dancing games. Multiplayer features should be supported since the Chinese elderly are quite social and prefer to play with their peers.