Music Induced Modulation of Pressure Pain Sensitivity and Affective Valence, Comparing Silence and Self-Selected Levantine Music

Title: A Pilot Study of Music-Induced Modulation of Pressure Pain Sensitivity: Comparing Silence and Self-Selected Levantine Music Introduction Pain is an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage. Pain perception is strongly influenced by an individual's emotional state. Among the non-pharmacological methods used to influence pain perception, music has gained growing attention because it can rapidly and robustly alter affective state and attention, which in turn modulates pain processing. Music listening is strongly associated with stress reduction through decreased physiological arousal, as indicated by reduced cortisol levels, lowered heart rate, and decreases in mean arterial pressure. These effects suggest that music may influence pain through emotional and physiological pathways. The emotional and analgesic effects of music are not universal and may vary according to cultural and musical systems. Middle Eastern or Levantine music is based on the system of maqams, melodic modes that define the tonal-spatial organization of a piece. Unlike Western scales, maqams include microtones (such as quartertones) and are closely tied to emotional expression. Since the 9th century, scholars such as Al-Farabi have associated specific maqams with distinct emotional states. For example, Maqam Rast is linked to happiness and confidence, Maqam Saba to sadness and pain, Maqam Bayati to vitality and warmth, and Maqam Hijaz to spirituality and longing. Understanding these emotional associations underscores the importance of evaluating how such music may impact pain sensitivity. Emotional valence plays a central role in shaping the subjective experience of pain. It refers to the value associated with a stimulus as expressed on a continuum from pleasant to unpleasant or from attractive to aversive. Music that promotes positive emotions may reduce pain sensitivity, whereas music associated with negative emotions may increase it. Pain can be assessed using both subjective self-report measures and physiological measures such as pain pressure threshold (PPT). Studies have shown that PPT is a reliable method for assessing pain. PPT assesses deep muscular tissue sensitivity by determining the amount of pressure over a given area at which a steadily increasing, non-painful pressure stimulus becomes painful. The neurobiological mechanisms underlying music-induced analgesia (MIA) are not yet fully understood; factors such as emotional and cognitive shifts, individual expectations, and autonomic nervous system activity are thought to contribute to the effects of self-selected music. Studies showed that self-selected music, aligned with individual preferences, is most effective in MIA. Although previous research has demonstrated that music can modulate pain perception and emotional responses, several gaps remain. Most studies have focused on Western populations and mainstream music genres, leaving limited evidence on the effects of culturally specific music, such as Levantine music, on pain sensitivity and emotional valence; in addition to this, most previous studies focused on patients with pain and certain cases, but there is a lack of studies on the effect of music on healthy individuals. This study contributes to improving healthcare outcomes and holds value for practitioners. Pressure-pain sensitivity is an important measure in non-pharmacological pain management, and identifying effective, low-cost, and culturally appropriate interventions that can improve patient care. This study aims to assess the effect of Self-selected Levantine Music on pain pressure threshold compared to silence on healthy Lebanese university students. Hypotheses: Self-selected Levantine music may result in a greater increase in PPT than silence. Depending on the data, positive valence and lower arousal (or optimal arousal) will partially mediate the PPT change. Methodology Design This randomized crossover counterbalanced pilot study will follow a double-blinded, experimental design aimed at examining the modulation of PPT and affective valence induced by two auditory conditions: silence and self-selected Levantine music. The study was reviewed and approved by the Antonine University Ethics Committee and was registered at www.clinicaltrials.gov . Participants Inclusion: healthy Lebanese adults, aged between 18 and 25, no chronic pain, no hearing impairment, no current analgesic medication. Exclusion: neurological disorders, recent injury at PPT sites. Subjects were also excluded in case of regular use of medication, pregnancy, severe allergic reactions, systemic, neurological, metabolic, cardiovascular pathologies, chronic pain, psychiatric disease (being under pharmacological or psychiatric treatment), or suffering from hypertension (\>140/90 mm Hg). Sample Size This pilot study includes 12 participants divided into two groups of 6. The primary aim of this phase is to assess the protocol's feasibility, refine procedures, and generate preliminary effect-size estimates to inform a future full-scale trial. A formal sample size calculation using G\*Power, based on the main outcome measure (changes in PPT), indicated an effect size of 0.5, an alpha level (α) of 0.05, and a desired power (β) of 80%, yielding a minimum of 16 participants per group. Accounting for a 20% dropout rate, the estimated sample size for the full trial would be 20 participants per group. The current pilot sample was determined pragmatically to allow initial testing of the protocol prior to full-scale implementation. Recruitment To gather eligible participants, a recruitment form was advertised via social media, in addition to on-campus recruitment. Consent was obtained through Google Forms. To minimize the risk of bias, all testing was completed in a single experimental session conducted at the same time of day, with lighting standardized throughout the procedure, and to control ambient noise, a Sony WH-1000XM6 headset was used for its active noise cancellation. While scheduling appointments, participants were asked to consume a light meal must no later than two hours (heavy meals no later than four hours) before the initiation of the experiments, and requested to refrain from physical exertion 24 hours before the experiments, to abstain from analgesic medications 48 hours before the experiments, and to refrain from smoking, alcohol, and caffeine in the two hours before the experiments. Randomization and Allocation Participants were randomly assigned to one of two intervention sequences using stratified randomization by gender to ensure equal representation of males and females in each sequence. Two strata were created based on self-reported gender, and participants were randomly allocated within each stratum to determine the order in which they received the interventions. Randomization was performed using a computer-generated sequence with variable block sizes to maintain balance and minimize predictability. This procedure ensured that each intervention sequence had a similar distribution of participants by gender, supporting comparability across sequences. To protect participant identity and privacy, participants were allocated a code consisting of two letters and two numbers instead of using their birth name. Only one member of the research team, who was responsible for randomization, had access to the data. The data were securely stored on an external hard drive and will be deleted two years after publication of the study. Procedure Both groups were assessed at baseline; the participant was seated, and only standard formal interaction occurred. The participant was then fitted with the Sony headphones. A 15-minute rest interval was implemented between sessions to minimize potential carryover effects. If participants were allocated to Group 1, they were first exposed to the silence condition, followed by the self-selected Levantine music. If allocated to Group 2, they were exposed to the Levantine music condition first, followed by the silence condition. This sequence was implemented to examine whether the order of conditions had a significant effect on pain and anxiety reduction. PPT was then recorded at two anatomical sites on the non-dominant side of the body: The middle of the upper trapezius muscle, located midway between the C7 spinous process and the acromion. The middle of the lateral calf, located midway between the head of the fibula and the lateral malleolus. Two trials were performed at each site at approximately 1 kg/s using a Wagner digital algometer, and the mean value was used as the baseline PPT. Baseline affective valence was measured using the Self-Assessment Manikin (SAM). During each audio exposure, pressure pain threshold (PPT) was measured at both anatomical sites. In addition, during the PPT procedure, participants were asked to rate their perceived pain intensity using the Numeric Pain Rating Scale (NPRS). Immediately following each condition, participants completed the Self-Assessment Manikin (SAM) scale. Blinding and assessor procedures The PPT assessor was blinded to the auditory input and was trained to apply pressure at a steady, consistent rate using the same algometer and probe. Outcome measures Primary outcomes PPT PPT assessment is considered a reliable method for measuring mechanical pain thresholds. PPTs were assessed in a sitting position using a digital algometer (FPX 50, Wagner Instruments, Greenwich, USA) unilaterally (at the side of the non-dominant hand) at two different body sites. The investigator applied pressure perpendicular to the muscle while increasing the force at a rate of 1 kg/s until the participant indicated that they should stop when the sensation became intolerable. The pressure marked at that moment was determined as the PPT, measured in kg/cm2. The first location was the trapezius belly, with PPTs being assessed at mid-distance between the acromion and the spinous process of the seventh cervical vertebrae. The trapezius muscle is a reliable location for measuring the PPT. The second location was on the calf belly, with PPTs being measured at the proximal one-third of the calf. The PPT was measured at the two anatomical sites with an interval of 30 seconds until the circuit was repeated a total of two times, starting with the trapezius as the first measurement and then proceeding with the measurement of the calf. The time between two PPT measures of the same body location will be enough to prevent the pain wind-up effect that might be induced by temporal summation. Four PPT measurements were performed, from which a mean PPT was calculated using the following formula: (PPT calf 1 + PPT calf 2 + PPT trapezius 1 + PPT trapezius 2) / 4. PPT was measured under both experimental conditions - silence and self-selected Levantine music - to evaluate the modulatory effects of music on pressure pain sensitivity, with higher PPT values indicating reduced pain sensitivity. To determine whether observed changes exceed measurement error and represent meaningful improvement, both relative change criteria and measurement reliability principles were considered. A responder was defined as a participant demonstrating a ≥10% increase in PPT from baseline. This threshold was selected as a conservative value that may exceed typical measurement error when standardized protocols are followed, given evidence that PPT demonstrates good to excellent reliability (ICC generally \> .85). Interpretation of change scores will additionally consider the minimal detectable change (MDC), which reflects the smallest change exceeding measurement error. When reliability coefficients are available, the MDC will be calculated using the standard error of measurement (SEM) as follows: MDC95 = SEM × 1.96 × √2 where SEM is derived from the standard deviation and intraclass correlation coefficient (ICC). Changes exceeding the calculated MDC will be interpreted as true change beyond measurement error. Primary analyses will evaluate continuous changes in PPT values, while responder status (≥10% increase from baseline) will be examined as a secondary, clinically interpretable outcome. Numeric Pain Rating Scale (NPRS) Pain intensity was assessed using the NPRS, an 11-point self-report measure in which participants rate their pain on a scale from 0 to 10, where 0 represents "no pain" and 10 represents "worst possible pain." The NPRS is a unidimensional measure designed to quantify subjective pain intensity. The scale was selected due to its ease of administration, minimal burden on participants, and suitability for repeated measurement. It can be administered verbally or in written form and produces numerical data appropriate for statistical analysis. Secondary outcomes Self-Assessment Manikin (SAM) (affective valence) The Self-Assessment Manikin (SAM) is a non-verbal, pictorial questionnaire used to measure a person's emotional response to stimuli like images or events. It uses a series of cartoon figures to have individuals rate their feelings along three dimensions: pleasure/valence (positive to negative), arousal (high to low energy), and dominance/control (low to high control). Reliability: Cronbach's α = 0.83. Blood Pressure and Heart Rate (parasympathetic response) Heart rate (HR) and blood pressure (BP) are established noninvasive markers of autonomic cardiovascular regulation, as cardiac activity is modulated by parasympathetic (vagal) pathways and arterial pressure is maintained through integrated autonomic and baroreflex mechanisms. BP and HR were measured using a digital sphygmomanometer and an oximeter, allowing for continuous and accurate monitoring of cardiovascular responses during the auditory interventions. Statistical analysis plan to be checked with Dr Samah at the physical therapy department Descriptive: mean ± SD of baseline and post PPT per condition; plot with individual change lines. Primary inferential: repeated-measures ANOVA. Preferred alternative: linear mixed-effects model with random intercept per participant and condition as fixed effect. Post-hoc: pairwise comparisons (preferred vs silence; preferred vs each oriental style; silence vs each style) with Bonferroni correction. Mediation/exploratory: test whether valence and/or arousal change mediate the relationship between Condition and PPT change