We have developped a custom-made mouthguard model which seems to be a potential protective device to avoid or limit the cumulative brain effects of head accelerations during repeated sport-related impacts, as found previously in a first experimental study. We want to continue the development of this mouthguard in order to integrate measurement sensors (accelerations and pressure) of exposure to sport-related head impacts, in order to be able to study the link between these impacts and brain modifications, suspected of lead to neurodegenerative diseases. The objectives and methodology are divided into 3 workpackages (WP). WP1 will consist of the experimental development of a connected mouthguard: the objective is to develop the measurement system, from the selection of the sensors (inertial unit and pressure sensor) to the integration into our 3D-printed mouthguard model after checking the reliability of the recorded data and adaptating the 3D printing procedure, and with a rechargeable battery and wireless transmission of energy and data. The objective of WP2 will be the validation of this numerical tool for monitoring head impacts and accelerations suffered during sports practice in real conditions: the prototype will be tested with rugby and soccer players, to check the ability of the system to measure head accelerations correctly, by calibrating the data first through non-contact runs and gradually integrating voluntary contacts at different intensities, and then impacts in real conditions. The WP3 aims to assess brain and cognitive hyper-acute and long-term changes in high-level athletes, depending on their exposition to head impacts monitoring by the numerical mouthguard. Neurocognitive and functional near-infrared spectroscopy data will be compared pre and post heading, between 2 groups equipped with either our mouthguard or another connected mouthguard or without mouthguard. Possible correlations with peak linear and angular head acceleration or with muscles activity recordings will be studied. Besides, a prospective cohort of 100 athletes exposed to high risk of head impacts will be followed over 3 consecutive years with an accurate monitoring of all head impacts through our connected mouthguard. The primary endpoint will be the season-to-season evolution of brain activation changes correlated to number of head impacts and mean peak of head acceleration during these impacts. Ultimately, the goal will be to transfer this technology to industry to make it accessible to all and allow users to both monitor their exposure and protect their health.