“Analysis of Abdominal Strength on Heading Quality in Football Athletes of the Persela Lamongan Academy”. COMPETITOR: Jurnal Pendidikan Kepelatihan Olahraga 17, no. 2 (August 6, 2025): 1549–1555. Accessed December 7, 2025. http://competitor.ojsunm.ac.id/index.php/competitor/article/view/141.