Redox balance during exercise in the heat in healthy adults: A systematic review

Hyperthermia, induced by exercise in the heat, alters the redox status. The physiological significance of these observations remains uncertain but may justify why the consequences of exercising in the heat span from positive health adaptations to negative and even lethal outcomes. Here, we conducted a systematic review to investigate the redox responses during acute exercise in the heat in healthy adults.

We searched MEDLINE, Cochrane Wiley, ClinicalTrials.gov, PEDRO and LILACS for clinical trials investigating pro- and antioxidant responses to exercise associated with hyperthermia and/or sweat-induced dehydration in healthy young individuals. Two independent reviewers extracted data and assessed the quality of the included studies.

A total of 1,014 records were selected, nine full papers were evaluated for eligibility, and eight studies met the inclusion criteria. Overall, results show that hyperthermia promotes oxidative stress both at the tissue level and in the circulation. Exercising in the heat heightens endogenous antioxidant defense systems, attenuating the negative effects of hyperthermia on oxidative damage. Studies also indicate that sweat-induced dehydration promotes oxidative stress, which is attenuated by rehydration.

These findings suggest that changes in redox status play a role in determining whether an acute bout of exercise in the heat lead to adaptive or maladaptive outcomes.