Effect of HIIT versus endurance training on oxidative stress markers

Introduction. To avoid conceptual ambiguity, endurance training in this study is referred to as MICT, which reflects sustained efforts at moderate intensity (zone 2 of Seiler’s triphasic model). By contrast, HIIT is classified as vigorous intermittent exercise (zone 3). This differentiation is essential for comparing the physiological adaptations of both modalities (Seiler, 2010). Oxidative stress, arising from an imbalance between reactive oxygen species (ROS) production and antioxidant capacity, can cause cellular damage and contribute to chronic diseases. Biomarkers such as malondialdehyde (MDA), catalase (CAT), and superoxide dismutase (SOD) are used to assess this imbalance. Physical exercise, particularly high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT), modulates redox homeostasis, but their comparative effects remain underexplored. Objective. To compare the effects of a HIIT protocol versus an moderate-intensity continuous training (MICT) protocol on oxidative stress markers (MDA, CAT, SOD) in healthy athletes, enhancing understanding of exercise-induced physiological adaptations. Methodology. Twenty healthy male athletes (aged 18–35 years) were randomized into two groups (MICT, n=10; HIIT, n=10) following a 4-week training protocol (3 sessions/week, 60–80% VO₂max). MDA, CAT, and SOD levels were measured via colorimetry before and after exercise at the start and end of the program. Repeated-measures ANOVA assessed the effects of exercise, training program, and their interactions, with a significance threshold of p<0.05. Findings. Both training modalities increased CAT activity (MICT: +5.4% at rest, +10.0% post-exercise; HIIT: +6.4% at rest, +11.0% post-exercise) with no inter-group differences. SOD levels increased in the MICT group at rest (+5.3%) and post-exercise (+6.0%), but only post-exercise in the HIIT group (+8.4%). MDA levels decreased at rest in both groups (MICT: -15.2%; HIIT: -17.3%) and post-exercise in the HIIT group (-13.0%), but not in the MICT group post-exercise.