# Practical Approach to Designing and Implementing a Recommendation System for Healthy Challenges
## 2 Materials and Methods
### Recommendation Algorithm Design
\begin{table}
\begin{tabular}{l l} \hline \hline \multicolumn{1}{c}{**Feature/Dimension**} & \multicolumn{1}{c}{**Set of Possible Values**} \\ \hline SF & Rating for the social function dimension (0–10) \\ MH & Rating for the mental health dimension (0–10) \\ FC & Rating for the fruit consumption dimension (0–10) \\ LVC & Rating for the legume and vegetable consumption dimension (0–10) \\ WGC & Rating for the green vegetable consumption dimension (0–10) \\ ASC & Rating for the dimension of consumption of added sugars (0–10) \\ WGC & Rating for the whole grains consumption dimension (0–10) \\ DC & Rating for the dairy consumption dimension (0–10) \\ SSS & Rating for the subjective sleep satisfaction dimension (0–10) \\ IS & Rating for the challenge in the insomnia dimension (0–10) \\ HS & Rating for the challenge in the hypersonmia dimension (0–10) \\ ER & Rating for the effort required to carry out the challenge (0–10) \\ \hline \hline \end{tabular}
\begin{tabular}{l} BMI: Body mass index; PF: Physical function; BP: Bodily pain; GH: General health; V: Vitality; SF: Social function; MH: Mental health; FC: Fruit consumption; LVC: Legume and vegetable consumption; ASC: Added sugar consumption; WGC: Whole grains consumption; DC: Dairy consumption; GVC: Green vegetable consumption; SSS: Subjective sleep satisfaction; IS: Insomnia; HS: Hypersonmia; ER: Effort required. \\ \end{tabular}
\end{table} 
Table 2: _Cont._Figure 1: Profile of the tester A included in the RS. Colors highlight the dimension scores, from 0 to 3.33 are in red, from 3.34 to 6.66 are in yellow and from 6.67 to 10 are in green. \begin{table}
\begin{tabular}{l l} \hline \hline \multicolumn{1}{c}{**Feature/Dimension**} & \multicolumn{1}{c}{**Provided Data**} \\ \hline Age group & 18–64 years. \\ Gender & Male. \\ BMI & 18.5–24.9 = normal weight. \\ Special groups & Skin diseases. \\ Injuries & None. \\ Daily time available & \(>\)30\({}^{\prime}\). \\ Possible spots & Pool. Sea. Country or city. Indoor house. Gym. \\ Material available & Bicycle. Barbells. \\ PF & 9.5 \\ BP & 4.8 \\ GH & 8.7 \\ V & 8.0 \\ SF & 10.0 \\ MH & 6.4 \\ FC & 6.5 \\ LVC & 10.0 \\ GVC & 6.2 \\ ASC & 10.0 \\ WGC & 2.5 \\ DC & 4.2 \\ SSS & 5.0 \\ IS & 6.1 \\ HS & 8.3 \\ AE & 7.95 \\ \hline \hline \end{tabular} BMI: Body mass index; PF: Physical function; BP: Bodily pain; GH: General health; V: Vitality; SF: Social function; MH: Mental health; FC: Fruit consumption; LVC: Legume and vegetable consumption; ASC: Added sugar consumption; WGC: Whole grains consumption; DC: Dairy consumption; GVC: Green vegetable consumption; SSS: Subjective sleep satisfaction; IS: Insemoia; HS: Hypersomia; ER: Effort required.  
\end{table} 
Table 3: The complete profile of the tester A included in the RS. Filtering  
Comparing the data of the user under consideration with each challenge in the pool, those challenges unsuitable for this particular user are excluded from the process. This decision is based on factors such as age group, incompatible BMI, belonging to ill-advised groups, time constraints, location incompatibility, and lack of necessary equipment. This filtering is based on explicit data gathered directly from the user profile. Also, a second filtering step is performed. The algorithm compares the user's AE (estimated as previously mentioned) with the ER by each challenge according to the evaluations by experts. Challenges that exceed the user's AE level are eliminated from the recommendation process. A 10% increase in the ER is applied to ensure the inclusion of challenges in the limit of the user. For the user tester A described in Table 3, the following challenges shown in Supplementary Materials are not compatible:  
* Challenge 8: this challenge is not compatible with skin diseases and the ER is higher than the tester A's AE. The AE of the tester A after the 10% increase goes up to 8.745. * Challenge 13: the use of a jumping rope is necessary to perform that challenge.