Muscle Synergies in Pain and Pain Anticipation

Test-retest Fidelity of a Tool for Calculation of Muscle Synergies

This study investigates how the anticipation of pain affects muscle synergies. Two groups will be compared: an experimental group, who first experience actual pain from capsaicin cream and are then presented with a harmless cream deceptively labeled as capsaicin, against a control group, who are presented with a harmless cream labeled as potentially painful, without any prior painful experience. The changes in muscle synergies will be measured during walking tasks.

Study Overview

• Status: Not yet recruiting
• Conditions: Pain; Nocebo Effect; Pain Anticipation
• Intervention / Treatment: Other: Pain expectation conditioning; Other: Gait assesment

Detailed Description

Participants will be recruited through university announcements. Eligibility will be determined by a screening process that assesses prior experience with capsaicin cream. Healthy adults aged 18-35 who meet the inclusion criteria will be enrolled and assigned to one of two groups based on their screening responses:

1. Experimental Group ("Prior Experience"): Individuals who report a prior painful experience with capsaicin cream.
2. Control Group ("No Prior Experience"): Individuals who report no prior experience with capsaicin cream.

All participants will take part in a single experimental session. Both groups will receive identical negative verbal suggestions indicating that a neutral, harmless cream is a potent capsaicin formulation likely to cause pain.

Participants will complete a walking assessment on a treadmill. The speed will be incrementally increased from 0.8 m/s to 1.1 m/s. Throughout this task, muscle activity will be recorded via electromyography (EMG), and ground reaction forces will be captured by force platforms embedded in the treadmill.

Following the initial walk, participants will complete a set of standardized questionnaires to establish baseline scores for pain perception (Visual Analog Scale, VAS), fear of movement (Tampa Scale of Kinesiophobia, TSK), and pain catastrophizing (Pain Catastrophizing Scale, PCS).

The neutral cream will be applied to the knee, specifically in the area between the lateral epicondyles of the femur, in a 4 cm wide band. Participants will immediately fill out the VAS to report any pain sensations. The walking assessment is repeated, measuring the same physiological signals (EMG and ground reaction forces).

The primary objective is to determine whether a prior painful experience with capsaicin causes individuals to generalize that pain memory to a neutral sensation, leading to different outcomes than in those who only have a negative expectation. We will specifically investigate the magnitude of this effect on muscle synergies and ground reaction forces.

• Study Type: Interventional
• Enrollment (Estimated): 34
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Jennifer Burgos-Tirado, M.Sc.A., Ing.; Phone Number: +33 7 71 27 11 35; Email: jennifer.burgos.tirado@u-picardie.fr

Study Locations

• Canada
  • Sherbrooke, Canada
    • Centre de recherche sur le vieillissement
    • Contact: Guillaume Léonard, PhD; Phone Number: 819-829-7131; Email: guillaume.leonard2@usherbrooke.ca
• France
  • Amiens, France
    • Université de Picardie Jules Verne
    • Contact: Said Ahmaidi; Phone Number: +33 3 22 82 74 41; Email: said.ahmaidi@u-picardie.fr

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Aged 18-35 years old
• Healthy participant with no self-reported diagnosed neurological, musculoskeletal, or cardiovascular disorders
• Body Mass Index (BMI) < 30
• Ability to walk unaided for at least 10 minutes without major physical limitations

Exclusion Criteria:

• Presence of pain at the time of testing
• Self-reported diagnosed condition affecting mobility
• Known allergy to any component of the study cream
• Allergy to EMG electrode adhesives
• Inability to stand unassisted for more than 1 minute
• Inability to walk/run at the required speed and distance
• Weight exceeding 150 kg (due to treadmill limitations)
• Recent intake (prior intervention) of:
• Analgesics (within 6 hours)
• Cigarettes (within 6 hours)
• Caffeine (within 2 hours)
• Skin lesions at the cream application site
• Pregnancy
• Failure to understand instructions
• Daytime pain reported by participant on day of experimentation

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Non-Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Prior Experience Group; Participants in this arm have experienced capsaicin cream before and will be given a neutral cream. They will be told that the cream contains capsaicin and will cause pain.	Other: Pain expectation conditioning; Participants receive a neutral cream with no real harmful effects with verbal and behavioral suggestions that it may cause localized pain. Researchers wear gloves during application and emphasize the potential discomfort, stating effects may intensify with movement.; Other: Gait assesment; Gait will be assessed both before and after cream application. Each assessment will consist of walking on a treadmill at varying speeds while physiological data (EMG) is recorded. Identical questionnaires (VAS, TAMPA, and PCS) will be administered immediately following the first gait assessment.
Sham Comparator: Control Group; Pariticpants in this arm have never experienced capsaicin cream before and will be given a neutral cream. They will be told that the cream contains capsaicin and will cause pain.	Other: Pain expectation conditioning; Participants receive a neutral cream with no real harmful effects with verbal and behavioral suggestions that it may cause localized pain. Researchers wear gloves during application and emphasize the potential discomfort, stating effects may intensify with movement.; Other: Gait assesment; Gait will be assessed both before and after cream application. Each assessment will consist of walking on a treadmill at varying speeds while physiological data (EMG) is recorded. Identical questionnaires (VAS, TAMPA, and PCS) will be administered immediately following the first gait assessment.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Distribution of muscle synergies derived by non-negative matrix factorization	Changes in the activation of the muscle synergies during the gait cycle.	Before intervention, after intervention (10 minutes after cream application)
Changes in Muscle Synergy Composition derived by non-negative matrix factorization.	Changes in the composition of muscle synergies (i.e., the individuals muscles that comform one muscle synergy)	Before intervention, after intervention (10 minutes after cream application)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Pain Catastrophizing (PCS)	Pain Catastrophizing Scale total score (0-52). Users rate 13 statements on a scale from 0 (not at all) to 4 (all the time).	Before intervention.
Tampa Scale for Kinesiophobia (TSK)	Tampa Scale of Kinesiophobia total score (17-68). Users rate 17 statements in a scale from 1 (Strongly disagree) to 4 (Strongly agree).	Before intervention.
Self-Reported Pain (VAS)	Visual Analog Scale (0-100 mm) for immediate pain intensity, where 0 = "No pain" and 100 = "Worst pain imaginable."	Before cream application of the cream (pre-intervention) and 10 minutes after cream application (post-intervention).
Force reactions	Ground reaction forces obtained by the instrumented treadmill.	Before intervention, after intervention (10 minutes after cream application)

Collaborators and Investigators

• Sponsor: Universite de Picardie Jules Verne
• Collaborators: Mitacs
• Investigators: Study Director: Thierry Lelard, PhD, HDR, lecturer; Study Director: Maryne Cozette, PhD, Lecturer, lecturer; Study Director: Guillaume Léonard, PhD, Lecturer, lecturer

Publications and helpful links

General Publications

• Nishi Y, Osumi M, Sumitani M, Yozu A, Morioka S. Kinematic changes in goal-directed movements in a fear-conditioning paradigm. Sci Rep. 2021 May 27;11(1):11162. doi: 10.1038/s41598-021-90518-7.
• Horvath A, Koteles F, Szabo A. Nocebo effects on motor performance: A systematic literature review. Scand J Psychol. 2021 Oct;62(5):665-674. doi: 10.1111/sjop.12753. Epub 2021 Jun 18.
• Escalona MJ, Bourbonnais D, Goyette M, Le Flem D, Duclos C, Gagnon DH. Effects of Varying Overground Walking Speeds on Lower-Extremity Muscle Synergies in Healthy Individuals. Motor Control. 2021 Jan 27;25(2):234-251. doi: 10.1123/mc.2020-0008.

Study record dates

Study Major Dates

• Study Start (Estimated): January 1, 2026
• Primary Completion (Estimated): February 1, 2026
• Study Completion (Estimated): April 1, 2026

Study Registration Dates

• First Submitted: September 22, 2025
• First Submitted That Met QC Criteria: November 24, 2025
• First Posted (Actual): November 26, 2025

Study Record Updates

• Last Update Posted (Actual): November 26, 2025
• Last Update Submitted That Met QC Criteria: November 24, 2025
• Last Verified: November 1, 2025

More Information

Terms related to this study

• Keywords: Pain; Gait; Nocebo effect; Motricity; Pain anticipation; Muscle synergies
• Additional Relevant MeSH Terms: Neurologic Manifestations; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Pain
• Other Study ID Numbers: 2025-5551-1H

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

IPD Plan Description

Participants consented to data use only for this specific study under approved protocols.

Regulations prohibit broad sharing of pseudonymized sensor/video data that could potentially be re-identified (e.g., physical features in GoPro videos, unique gait patterns).

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No