Pain-Related Fear and Motor Control in Healthy Volunteers

In the presence of pain, individuals often modify the way they move. However, pain-related motor adaptations cannot be understood solely as responses to nociceptive input, as pain is shaped by a complex interplay of individual and contextual factors. As a result, motor behavior may be influenced not only by pain itself, but also by the anticipation that movement could be painful or harmful, thereby becoming a perceived threat. Within the fear-avoidance framework, fear of movement and pain-related threat are considered important factors influencing motor behavior and autonomic responses. As pain-related apprehension and kinesiophobia may also be present in pain-free individuals, experimental paradigms inducing movement-related threat in healthy participants may help clarify the mechanisms underlying behavioral adaptations associated with pain-related fear and kinesiophobia.

The main objective of this study, which was concealed from participants, was to determine how movement-related threat influences motor behavior. Specifically, the study assessed whether a verbally induced threat affects walking parameters and upper-limb pointing movement time. A secondary objective was to examine whether baseline trait kinesiophobia moderates the effects of movement-related threat on motor behavior.

This study uses a randomized within-subject crossover design to investigate the effects of experimentally induced movement-related threat on motor responses, perceived apprehension, and autonomic responses in healthy adults. Participants complete two experimental conditions during a single experimental session: a control condition and an experimental threat condition. In both conditions, inactive transcutaneous electrical nerve stimulation electrodes are placed in the lumbar region. In the control condition, electrodes are presented as safe and reliable, without any threat-related information. In the experimental condition, participants receive verbal suggestions regarding discomfort, movement-evoked pain, and unpredictable electrical stimulation associated with the device, in order to induce movement-related apprehension.

Motor behavior is evaluated through spatiotemporal gait parameters during walking and movement time during upper-limb pointing movements toward visual targets. Autonomic nervous system responses are assessed using heart rate and heart rate variability analysis from a wearable heart rate monitor. Perceived apprehension is assessed using visual analog scales. Baseline trait kinesiophobia is assessed at the beginning of the session and used as a continuous variable in the analyses.

Inclusion criteria

• Age between 18 and 65 years.
• Ability to understand the experimental instructions and questionnaires.
• No pain at inclusion and during the last 3 months.
• Abstinence from short-term analgesics for 2 hours before testing.
• Abstinence from coffee and cigarette smoking for 6 hours before testing.

Exclusion criteria

• History of chronic pain.
• Motor, neurological, or sensory disorders.
• Cardiovascular conditions likely to affect physiological measurements.
• Clinically significant depressive symptoms or anxiety scores on the Hospital Anxiety and Depression Scale.