Background: Physical exercise can improve antioxidant defense system of organis. But long and heavy exercise can disrupt the balance of oxidant-antioxidant. Low glutathione peroxidase is associated with free radicals. Plant purple sweet potatoes (Ipomoea batatas L.) contain anthocyanins high enough that act as antioxidants. This stuÃÂdy aimed to determine the effect of extracts of tubers of purple sweet potato (Ipomoea Batatas L.) on the activity of glutathione peroxidase (GPx) liver of mice (Mus Musculus) treated with maximal physical exercise.Subjects and Method: This was a true experimental study. This conducted with the design of the control group post-test only in vivo on 24 white male mice (Mus musculus), DD Webster strain. DaÃÂta analysis was using SPSS software 19. Statistical testing decision taken 5% significance level (p=0.05). Results: The results showed that the average enzyme activity of GPx in the P5 is the highest enzyme activity GPx (mean=19:39 ñ SD=7:06, p=0.024), which means there are significant differÃÂrences in the enzyme activity of GPx values between groups.Conclusion: This study showed that the extract could increase the activity of GPx hepatic enzymeÃÂes mice significantly.Keywords: physical exercise maximum, free radicals, purple sweet potato, anthocyanin, GPxCorrespondence:àAyu Elvana. School of Health Sciences (STIKes) Siti Hajar, Medan, Indonesia.Indonesian Journal of Medicine (2016), 1(2): 116-120https://doi.org/10.26911/theijmed.2016.01.02.05