The Effectiveness of A Training Program Using  Vertical Jump Device (Vertimax) on Some Biomechanical Variables in  Performance of  Undulating Serve Skill in Volleyball for Players. Jurnal Pendidikan Kepelatihan Olahraga: PEJUANG, [S. l.], v. 2, n. 2, p. 27–44, 2026. Disponível em: https://journalpejuang.web.id/index.php/jurnalpkopejuang/article/view/91. Acesso em: 17 apr. 2026.