Sitko, Sebastian Legaz-Arrese, Alejandro Reverter-Masia, Joaquín Moliner-Urdiales, Diego Hernández-González, Vicenç Aixa-Requena, Saül Conesa-Milian, Enric Mayolas-Pi, Carmen Association Between Physical Activity Level and Training Volume in Adolescent Athletes 10.3390/sports13060178 2025 2025