Although it is difficult to compare our findings with the previous studies due to different exercise protocols, difference assessment of biomarkers and disease status (i.e. breast cancer vs type 2 diabetes), our study suggests that HIIT may partly contribute to the level of MMP-9 with a lower volume of exercise (90 min vs 150 min per week) over fewer number of weeks (8 vs 16 weeks). The gene discussed is MMP9; the disease is breast carcinoma.