Nugraha, A. D., Y. Yudanto, and S. Bahri. “The Impact of Using Surgical Masks and Non-Masks When Exercising on Heart Rate, Calories and VO2max During the Covid-19 Pandemic”. Jurnal SPORTIF : Jurnal Penelitian Pembelajaran, Vol. 7, no. 1, Apr. 2021, pp. 84-92, doi:10.29407/js_unpgri.v7i1.15698.