A standardised exercise protocol to induce oxidative stress in humans: validation with a dietary polyphenol intervention

Abstract

Background: Generating oxidative stress in a predictable and controllable way without the risk of causing harm is important for enabling the safe validation of interventions such as dietary polyphenols and ensuring ethical standards in human studies, while also advancing mechanisms involved in the induced oxidative stress. Although, many experimental animal and in vitro models have been developed to conduct oxidative stress-based research, to date, very few reliable human models are available. Objective: This study’s main objective was to establish a standardised exercise model to induce oxidative stress in a repeatable and controllable manner and was tested with dietary polyphenols. Method: We applied a single blinded, randomised, cross-over, placebo-controlled trial with adult (25.95 ± 6.25 years) males (N = 40) where the induction of oxidative stress was achieved by an incremental aerobic exercise activity followed by a maximal anaerobic activity until exhaustion. To assess the model, rooibos polyphenolics was used as one of the interventions, while markers of safety and oxidative stress were measured on various occasions during the trial period. Results: The exercise regime reliably and repeatably induced oxidative stress, evidenced by increased levels of oxidative damage markers, i.e., oxidised glutathione (p = 0.003), malondialdehyde (p = 0.004), and a Comet assay tail moment (p < 0.05), while unconjugated bilirubin (p = 0.002) and the ferric reducing antioxidant potential (p < 0.001) increased over the study period, in the male study participants, irrespective of the oral intervention. Conclusions: This model showed an exercise regime that could be adapted to induce oxidative stress in a reliable and repeatable fashion without risk of causing harm. This study also demonstrated that a dietary polyphenolic intervention with rooibos did not complicate the onset of oxidative stress.