Impact of high intensity interval training (HIIT) and/or selenium (Se) supplementation on oxidative stress and antioxidant status in active females.
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Background: Cells continuously produce free radicals (FR) and reactive oxygen species (ROS) as part of metabolic processes. These free radicals are neutralized by an elaborate antioxidant defence system consisting of enzymes. An imbalance between ROS / FR and antioxidants is often referred to as oxidative stress and is involved in the pathogenesis of various disorders including cardiovascular disease, neurodegenerative diseases, diabetes and several types of cancer (Campbell et al. 2010). Selenium (Se), as part of the glutathione peroxidase (GPx) family of enzymes, has the ability to detoxify these ROS / FR, increasing protection against this stress. Regular training has been shown to increase antioxidant capacity; it is through adaptation that increased antioxidant capacity may alleviate oxidative stress. Objectives: The present investigation is designed to test the hypothesis that Se supplementation and / or regular High Intensity Interval Training (HIIT) can alleviate exercise - induced oxidative stress following a single bout of HIIT. Design: Randomised Open Label Trial. Method: Twenty-two healthy female participants, who participated in intermittent sports, were recruited. In a randomised manner, participants were equally allocated to either a Se only group (250 ug sodium selenite/day) or a Se + HIIT group (250 ug sodium selenite / day + 2 sessions HIIT / week) for 3 weeks. Measures of fitness, malondialdehyde (MDA), glutathione peroxidase (GPx) in plasma and red blood cells (RBC) and total antioxidant capacity (TAC) were assessed before and after an initial (baseline) and last bout of HIIT. Results: No statistically significant changes were identified for any of the measured markers of oxidative stress or antioxidant capacity, although a number of trends toward altered activity were noted. Following the intervention, Se + HIIT group demonstrated a 9% decrease in MDA response to a single bout of HIIT, whilst the Se only group decreased by 12%. GPx3Activity in plasma increased by 15% in the Se group and decreased in the Se + HIIT group by 2% pre to post intervention. Additionally, GPx1 Activity in RBC increased in both groups by 6% and 2% respectively. TAC elicited similar responses increasing by 40% in the Se + HIIT group and 66% in the Se only group. Furthermore, there was an improvement in a number of fitness components in the HIIT trained group post intervention, namely speed and maximal aerobic capacity. Conclusion: This is the first study to examine the impact of HIIT and/or Se supplementation on oxidative stress and antioxidant capacity in active females. Whilst there were no significant differences observed, there were some promising trends highlighting a potential benefit of Se (and possibly HIIT) in reducing oxidative stress and increasing antioxidant status post high intensity interval exercise in females engaged in intermittent sports.