UTAMA, Jana; HANDOKO, Yeffry; SAEFULLOH, Candra. Design of an Electrocardiogram System for Physical Fitness Analysis using Heart Rate Variability and Maximal Oxygen Volume. IJIES (International Journal of Innovation in Enterprise System), [S. l.], v. 9, n. 2, p. 134–150, 2025. DOI: 10.25124/ijies.v9i02.9790. Disponível em: https://journals.telkomuniversity.ac.id/ijies/article/view/9790. Acesso em: 13 jan. 2026.