Mobile devices are widely used among young people, and their use for health promotion is in-creasing. Healthy Jeart is a mobile application aimed at promoting healthy life habits among people aged 8-16 years. The aim of this study was to develop and validate an instrument that allows evaluating the healthy knowledge, habits and attitudes learned by adolescents aged 12-16 years through the Healthy Jeart application. Attending to the content of Healthy Jeart, a first version of the evaluation instrument was generated. It was subjected to expert judgement. The second version was administered to 429 adolescents from six educational centres of Andalusia to carry out the validation of the construct through exploratory and confirmatory factor analyses. After exploration, a six-factor model was confirmed, with a very adequate level of fit and good internal consistency. The six factors were: (1) knowledge about eating and physical activity, (2) habits about eating and physical activity, (3) emotional health, (4) consumption of alcohol and drugs, (5) social relationships and (6) sexual activities and use of technologies. There are at least four instruments that could be used to measure health-promoting behaviours. However, this new instrument was created ad hoc. It measures exactly the results that can be expected. Healthy Jeart will now have a valid and reliable evaluation instrument: Ev-HealthyJRT v.1.0. Young people, teachers and other professionals who carry out health-promotion interventions based on Healthy Jeart with adolescents will have at their disposal an instrument integrated in this app that allows verifying the learning results. However, the validated instrument can be used for evaluation in other interventions, as long as the multiple and essential aspects of a healthy living are addressed as in Healthy Jeart.
Keywords: adolescents; eHealth app; health interventions; health promotion; instrument development.