Placebo in sports and exercise: prevalence, conditioning and open-placebo

Abstract

Historically in research, placebos have been used as a control treatment that is indistinguishable from the active intervention but has no active component. This allows the intervention arm to be compared to the non-active placebo treatment which, theoretically, should allow determination of the "true" effect of the intervention, through reducing the potential that expectancy, or belief, about the intervention may artificially inflate the estimated response to that intervention. However. placebo effects in sport and exercise nutrition are apparent with studies (including from our group) showing small to moderate positive effects on exercise outcomes and up to 60% of the ergogenic effect shown with nutritional supplements explained by placebo effects. Placebo effects are induced by administering an inert intervention (e.g., sham drugs, nutrients, or equipment), which can elicit a neurobiological response due to verbal suggestions, explicit expectations, or implicit experience. Very little is understood about the physiological effects that occur that explain these performance changes with placebo. This project aims to bridge several important gaps in our knowledge relating to the placebo and placebo effects in sports, health and exercise. Specifically, we aim to elucidate some underlying questions regarding the prevalence of placebo techniques in sport, physiological and metabolomic responses to conditioning and placebo, and the potential for open-label placebo in sport. Study 1 will investigate the effect of caffeine conditioning on physiological parameters and cognitive and exercise performance. Study 2 will employ a metabolomics approach to determine metabolic pathways that are similar when individuals receive caffeine and placebo - the hot-topic called "placebomics". Study 3 will investigate the efficacy of an open-label placebo intervention on exercise performance in men and women and potential mechanisms. Study 4 will determine changes in functional magnetic resonance imaging of the brain following supplementation with caffeine and placebo perceived to be caffeine. These findings will generate important practical information as to the main physiological mechanisms through which placebos work and whether we can optimise these effects for health and performance and predict responses both within and between individuals. Results from these studies will also yield further research, shaping future study designs to better control for this complex phenomenon, with practical implications in sports, health and exercise science. (AU)