# Toward Personalized Vibrotactile Support When Learning Motor Skills
## 4 A Proposal for Personalized Vibrotactile Feedback to Support Motor Skills Learning
Delivering the information through different sensorial channels (as done in [18]) might also be appropriate in some scenarios, but not in others where the other channels are already used (as in [21]). A multisensorial support that can personalize the feedback in terms of light, sound, and/or vibration has been proposed in the AICARP approach to deal with stressful situations that are monitored with physiological sensors [32]. In addition, if a stronger haptic support is to be provided, forced-guidance using exoskeletons might be considered, as proposed in the tangibREC approach [33]. A case study on _Aikido_ defensive martial art has been discussed elsewhere [34]. The idea behind Aikido is to learn techniques that can make entering and turning movements that redirect the momentum of the opponent's attack, and end with a throw or joint lock. To progress in the martial art, learners watch how the teacher (sensei) defends from a specific attack and then practice in pairs the attack and the corresponding defensive technique. Even if the sensei performs the movement very slowly, it is not possible for the learner to perceive and assimilate all the issues to be taken into account when trying to replicate the movement (e.g., movement of feet, turn of hip, position of hand, relaxation of arms...), resulting in an incorrect performance by the learner as it differs from the sensei's. In fact, years and years of practice are required to properly master the performance of the techniques. Moreover, if the learner partner is taller than the partner that has attacked the sensei to show the technique, the technique cannot be performed exactly the same way. For instance, if the sensei asks a taller person to attack her, she may need to make the turn wider so she can take the attacker's gravity center lower than with the previous person. In addition, the learner's body build is different from the sensei's, so even in the case that the attacker is the same, and it would be possible for the learner to perform the same exact movements that the sensei does, both learner and sensei will not produce the same result on the attacker. Thus, the proper execution of the technique cannot be exactly the same as done by the sensei, but needs to be adapted to the user's body build (both attacker or uke, and defender or tori). So, users and movements need to be properly modelled, allowing the error diagnosis algorithms to take into account the individual user's features when comparing learner's movements with the expert's. In addition, the particular context where the learner is placed needs to be modelled, too. Modelling the context implies many issues, such as the user's affective state, the environment conditions (temperature, humidity... ), the kind of session (learning a technique, improving the performance of a technique, free practice, preparing for a belt exam... ), if the user has pain in some joint due to an incorrect previous execution, etc. With all this information, the system should identify the errors made by the user. However, not all errors should be corrected, and the correction should not always be the same one, nor the same one for everybody. Modelled information also needs to be taken into account when deciding the support to be provided. For instance, when a inductive learner wearing a tuned Aikidogi (i.e., the Aikido training uniform) with inertial and physiological sensors as well as actors attached to the sleeves practices the shomen-uchi striking attack for the first time, it might be a good option to guide the learner with the movement to be carried out a couple of times by triggering vibrations on the part of the body that is to be moved and in the direction of the movement. Then, the system can stop the vibration and just monitor several tries of the user in order to identify the errors made (e.g., the arm stops before finishing the movement towards the partner's head). As a result, the system can provide vibration support again, but this time, focused on making the arm complete the movement trajectory.