725: The Barefoot LEGO� Brick Test: Can Expectancy Override Physical Reality in a Real-World Task?

Topic: Experimental (Non-clinical) Human Studies
Subtopic: Non -specific to any diagnosis, Placebo/Nocebo, Pain mechanisms (e.g. descending inhibitory control, placebo, inflammation), Pain models (e.g. saline injection, capsaicin, UVB, HFS, incision, exercise, itch)

Background and Aims: Pain is commonly interpreted as a direct indicator of tissue damage, despite evidence that pain is shaped by contextual and expectancy-related factors. Laboratory studies demonstrate placebo and nocebo effects on pain experiences using precise experimental stimuli (e.g., thermal laser). However, it remains unclear whether these expectancy effects extend to ecologically valid, threat-relevant tasks that more closely resemble real-world experiences. Therefore, this study examined expectancy framing associated with stepping on LEGO® bricks while barefoot. Biomechanical measurements were used to determine whether changes in perceived pain and perceived tissue damage occurred independently of altered loading strategies.

Methods: Sixty healthy adults (mean age=29.5 years, SD=12.9; 38 female [63%]) completed five trials. Participants began with a Baseline (no LEGO® brick) trial, followed by an Unexpected (LEGO® present) trial, and then a Control (Expected LEGO®) trial. Then, using inert creams, participants completed protective (placebo) and sensitizing (nocebo) trials in randomized order. Pain intensity and perceived tissue damage (after visual foot inspection) were rated immediately and 30 seconds post-contact using 0–10 numerical rating scales (NRS). Vertical ground-reaction forces and contact time were recorded. Linear mixed-effects models tested planned contrasts across conditions and assessed biomechanical and belief-based moderators.

Results: Unexpected LEGO® brick trials were more painful than baseline (ΔM=+2.95, 95% CI [2.43, 3.47]), and pain ratings remained consistent upon re-exposure (expected LEGO®) (ΔM = −0.08 points, 95% CI [−0.35, 0.18]). Compared with the expected LEGO® brick exposure, sensitizing (nocebo) framing evoked higher pain intensity (+1.22 NRS points, 95% CI [0.96, 1.48]), whereas protective (placebo) framing was not less painful. Perceived tissue damage followed the same directional pattern as pain did, but with attenuated changes. Observed differences in pain remained after controlling for vertical ground reaction forces and belief ratings.

Conclusions: Pain occurred in the absence of participants’ observable tissue injury, with perceived damage remaining low, demonstrating a clear dissociation between pain and harm. Expectancy framing during these ecologically valid barefoot LEGO® brick trials differentially modulated pain, with sensitizing (nocebo) framing evoking more intense pain, whereas protective (placebo) framing showed limited influence. Unlike many experimental paradigms using laboratory-generated pain stimuli, protective expectancy effects were attenuated in this real-world threat context, and this pattern was not explained by altered biomechanics or beliefs. Our results also demonstrate the viability of the barefoot LEGO® brick paradigm for non-injurious, ecologically valid investigation of pain.

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Presenting Author: Sophia Mastrangelo
Submitting Author: David Kennedy

Senior Author: David S. Kennedy

IASP 2026 Global Year theme of Neuropathic Pain: No

• Sophia Mastrangelo: MSc - School of Exercise Science, Physical and Health Education, University of Victoria, Victoria, BC, Canada
• Joshua Pate: PhD - Discipline of Physiotherapy, Graduate School of Health, University of Technology Sydney, Sydney, NSW, Australia
• Biara Webster: MRes - Discipline of Physiotherapy, Graduate School of Health, University of Technology Sydney, Sydney, NSW, Australia
• Anna Oki-Golovkina: BSc - School of Exercise Science, Physical and Health Education, University of Victoria, Victoria, BC, Canada
• Evan Quan: NA - School of Exercise Science, Physical and Health Education, University of Victoria, Victoria, BC, Canada
• Jadin Sjoquist: NA - School of Exercise Science, Physical and Health Education, University of Victoria, Victoria, BC, Canada
• Rocco Cavaleri: PhD - Brain Stimulation and Rehabilitation (BrainStAR) Lab, School of Health Sciences, Western Sydney University
• Matthew C. Bell: PhD - Department of Psychology, Santa Clara University, Santa Clara, California, USA
• Victoria J Madden: PhD - African Pain Research Initiative, Dept of Anaesthesia and Perioperative Medicine, Neuroscience Institute, University of Cape Town, Cape Town, South Africa
• Tasha R Stanton: PhD - Persistent Pain Research Group, Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute (SAHMRI), SA, Australia
• G. Lorimer Moseley: DSc - IIMPACT in Health, Adelaide University, Kaurna Country, SA, Australia
• David S Kennedy: PhD - School of Exercise Science, Physical and Health Education, University of Victoria, Victoria, BC, Canada