Abstract: Objective: By manipulating psychological factors such as fostering positive expectations about exercise outcomes through verbal suggestions it is possible to induce placebo effects without the use of traditional placebos, such as inert substances (closed-label placebos, CLPs). This can be achieved even when individuals are aware they are receiving a placebo through verbal suggestions (open-label placebo, OLP). This proof of principle study investigated whether the effects of OLPs on affective responses to exercise can be induced solely through verbal suggestions. Methods: Eighty nine healthy volunteers were randomized into three groups during a 30-minute session of moderate-intensity running. The first experimental group was informed that the running session would enhance their mood (CLP: positive verbal suggestion), the second experimental group was educated on the concept of an OLP and its anticipated effects during the running session (OLP: positive verbal suggestion), and the third control group received unrelated information about the study (no verbal suggestion). The primary study outcomes were self-reported affective valence during exercise and postexercise enjoyment. In addition, anticipated affect and remembered affect were assessed. Resting-state functional connectivity (RSFC) in the prefrontal cortex was objectively measured via functional near-infrared spectroscopy (fNIRS). Results: Compared with the control group, both experimental groups presented increased affective valence during exercise, postexercise enjoyment, and anticipated affect, along with lower RSFC in the right prefrontal cortex, and the OLP intervention had a greater effect on remembered affect. Conclusions: The results illustrate a potential role for OLPs in inducing affective response to exercise and suggest that further study of verbal suggestions through an extensive explanation of placebo effects might be promising for practice.

The authors have declared no competing interest.

This study was funded by Xihua University

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This study was approved by the Institutional Review Board of the School of Psychology at Beijing Sports University in China (ethics approval number 20211005).

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ll data produced in the present study are available upon reasonable request to the authors