Muscle Synergies in Pain and Pain Anticipation

Official title

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

Overview

This study investigates how the anticipation of pain affects muscle synergies. One group will be recruited who will first experience actual pain from capsaicin cream and are then presented with a harmless cream deceptively labeled as capsaicin. The changes in muscle synergies will be measured during walking tasks.

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 experimental Group ("Prior Experience"): Individuals who report a prior painful experience with capsaicin cream.

Participants will complete a first session consisting on 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).

Then, a capsaicin 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 participants will come to the laboratory a second time to measure the same outcomes but, instead of applying capsaicin again, they will receive an inert cream presented as capsaicin (neutral massage cream MEDICAFARM). The procedure will be repeated.

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.

Interventions

• 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.

Primary outcome measures

• Distribution of muscle synergies derived by non-negative matrix factorization [Time frame: Before intervention, after intervention (10 minutes after cream application)]
• Changes in Muscle Synergy Composition derived by non-negative matrix factorization. [Time frame: Before intervention, after intervention (10 minutes after cream application)]

Secondary outcome measures (1)

• Tampa Scale for Kinesiophobia (TSK) [Time frame: Before intervention.]

Eligibility criteria

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

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: Yes

Study design

Allocation

N/A

Model

Single group

Masking

Open label

Primary purpose

Basic science

Study locations

Canada · 1 center

• Centre de Recherche sur le Vieillissement — Sherbrooke

France · 1 center

• Université de Picardie Jules Verne — Amiens

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. PMID 34045515
• 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. PMID 34145580
• 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. PMID 33503586

Identifiers

NCT: NCT07251387 · 2025-5551-1H

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗