The Effect of High-Intensity Intermittent Exercise on Chronic Stress and Potential Biomarkers: a Pilot Study

Abstract

Persons employed in highly stressful occupations are at a heightened risk for developing chronic stress-related disorders. These disorders are associated with immunosuppression, disease progression and psychological illness. Exercise has previously been used to combat depression; however, police personnel are already moderately active yet still stressed. Therefore, this pilot study aims to determine if high-intensity intermittent training (HIIT) could be a potential stress-reducing strategy in already trained persons, and which biological markers could be measured in a larger study. Using three single case studies, this study employed a 10-week HIIT intervention and measured markers of stress via Perceived Stress Scale (PSS) scores, cortisol levels and associated inflammation blood markers at baseline and post-intervention. The PSS scores reduced after HIIT (36–40%). Cortisol secretion pre-intervention indicated a flat profile during daytime hours; post-intervention showed increased levels in the morning and an overall normal daytime profile. Of the inflammation blood markers, eosinophil cell counts were halved post-intervention. HIIT, therefore, is a potential stress-reducing strategy in already trained individuals. The decreased psychological stress was associated with normalization of cortisol hormone function and reduced systemic inflammation via lower eosinophil counts, which highlighted the specific physiological markers as indicators of chronic stress.