## 3 Materials and Methods
### Evaluation and Automatic Progression Adaptation  
Minigame scores reflect the performance of the player on a specific task, for instance, based on the number of right answers and average reaction time, the number of elements picked or, if applicable, the number of pelvic floor muscle contractions correctly performed. The performance of strength training-related tasks is not evaluated within VITAAL, being maximum score achieved upon completion of the task. The team considered that by mirroring the movements of the avatar, older adults would challenge and strengthen their muscles--even without an objective evaluation and feedback for movement correctness. Reducing system complexity (using only two inertial sensors that evaluate the movements of the feet) was preferred over the use of additional sensors for full-body movement evaluation. The exergame employs automatic progression adaptation that manipulates task difficulty and load. Each minigame includes a set of difficulty levels (a set of predefined game \begin{table}
\begin{tabular}{p{85.4 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Minigame** & **Training** & **Description** \\ \hline Shopping list & Cognitive training (short-term memory) & Users have a limited time to memorize a list of products and then confirm whether the products on the shelf correspond to those previously visualized or not. \\ Shopping & Cognitive training (flexibility, divided attention) & In this game, the player needs to select whether two presented objects match in shape or in color. The correct answer evaluates the trueness or falseness of a sentence referring to the objects. \\ Healthy food & Cognitive training (inhibition) & The player must select healthy food as fast as possible, avoiding the selection of unhealthy food. \\ Pizza & Cognitive training (flexibility, selective attention) & The player must select the pizza slice that is pointing in the wrong direction while suppressing the impulse to select the most common direction. \\ Wide squats & Strength training & The player should follow the movements of a virtual instructor who performs Tai Chi-inspired exercises based on wide squats. \\ Narrow squats & Strength training & The player should follow the movements of a virtual instructor who performs Tai Chi-inspired exercises based on narrow squats. \\ Labyrinth & Balance training & The player must guide [PERSON] inside the labyrinth to avoid the worm and catch the maximum number of apples as fast as possible. \\ Mommy chicken & Balance training & The player should catch as many eggs as possible, stealing them from the respective nests. Caution is required to avoid being caught by the chickens. \\ Falling books & Pelvic floor muscle training and/or balance training & The player should catch the maximum number of books, preventing them from falling off the bookshelves. \\ Music & Pelvic floor muscle training and/or balance training & In this game, the player must collect as many records as possible to score points. Special records will score additional points and switch to a different music style. \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Minigames for motor-cognitive and pelvic floor muscle training. parameters that affect the difficulty of the game) and criteria (a set of predefined rules that describe when the player level should maintain, increase, or decrease). Difficulty levels were defined by game designers, with the support from clinicians and movement scientists, to ensure their adequacy concerning different training needs and end-user characteristics. Strength training exercises were arranged in a progressive order of difficulty, as defined by clinicians and movement scientists. The continuous adaptation of difficulty levels would ensure a progressively increasing training load and optimal challenge to prevent under- and overload [49]. The progression to the next (or previous) difficulty level is based on the scores achieved in previous training sessions. By default, all players start at the minimum difficulty level.