Insomnia exacerbates pain sensitivity and impairs physiological recovery from acute musculoskeletal pain. Repetitive transcranial magnetic stimulation (rTMS) has emerged as a promising non-invasive neuromodulation intervention to alleviate pain and modulate central sensory processing. However, whether rTMS can effectively mitigate insomnia-induced pain hyperalgesia and accelerate the recovery trajectory of acute musculoskeletal pain remains unclear, as does the optimal neuroanatomical stimulation target.
Building upon an established experimental pain model, this randomized, sham-controlled study aims to evaluate the restorative effects of three distinct rTMS interventions - targeting the left primary motor cortex (L M1), the right dorsolateral prefrontal cortex (R DLPFC), and a sham condition - on individuals experiencing insomnia. Following a standardized eccentric exercise protocol to induce muscle soreness, participants will receive three sessions of the allocated rTMS intervention at 0, 24, and 48 hours post-exercise. Pain sensitivity, recovery dynamics, and quantitative sensory testing (QST) metrics will be continuously monitored across the recovery timeframe.
The findings from this trial will clarify the therapeutic efficacy of rTMS in modulating acute pain under insomnia states and identify the target-specific mechanisms of cortical stimulation, offering evidence-based non-invasive interventions for musculoskeletal pain management.
Adults aged 18 to 60 years
Right hand and foot dominant
History of any chronic musculoskeletal pain or presence of existing pain during recruitment
Previous major injuries or surgery involving the lower limbs
Sleep disorders other than insomnia
Clinically diagnosed psychiatric disorders
Parallel
Repetitive transcranial magnetic stimulation (rTMS) on L M1
DeviceHigh-frequency stimulation (10 Hz) will be delivered over left M1 at 90% RMT, consisting of 50 pulses per train, a 25-second inter-train interval, and 30 trains per session, yielding a total of 1500 pulses over 15 minutes.
Repetitive transcranial magnetic stimulation (rTMS) on R DLPFC
DeviceLow-frequency stimulation (1 Hz) will be applied over right DLPFC-rTMS at 90% RMT, with 150 trains of 10 pulses per session, a 2-second inter-train interval, and a total of 1500 pulses over 30 min.
Sham repetitive transcranial magnetic stimulation (rTMS)
DeviceSham stimulation will be administered using identical parameters but delivered via the sham coil, which reproduces the auditory and somatosensory sensations of active rTMS without inducing cortical stimulation.
Muscle damage severity: Muscle pain
Muscle pain will be measured using an 11-point NRS, with 0 representing "no pain" and 10 indicating "worst imaginable pain". The Outcome will be recorded at rest, during a reach for the floor with knees straight, and during a validated hamstring provocative manoeuvre, the "taking-off shoe" test.
Muscle damage severity: Muscle soreness
Muscle soreness will be measured by an 7-point Likert scale, with 0= A complete absence of soreness," 1 = "A light soreness in the muscle felt only when touched/a vague ache," 2 = "A moderate soreness felt only when touched/a slight persistent pain," 3 = "A light muscle soreness when walking up and down stairs," 4 = "A light muscle soreness when walking on flat surface," 5 = "A moderate muscle soreness, stiffness, or weakness when walking," 6 = "A severe muscle soreness, stiffness, or weakness that limits my ability to move."
Pain sensitivity: Thermal pain threshold
Thermal thresholds will be measured with a 30 × 30 mm thermode (TSA 2, Medoc Ltd., Ramat Yishai, Israel). The thermode will be placed gently on the skin without causing deformation. Using the method of limits, temperature will increase or decrease at 1℃/second within a 0 - 51℃ range, with a baseline temperature of 32℃. Participants will press the stop button when the thermal sensation first becomes painful. The mean value of five consecutive trials will be used in the analysis.
Pain sensitivity: Mechanical pain threshold
Mechanical pain threshold will be evaluated using standardised weighted pinprick stimulators (MRC System GmbH, Heidelberg, Germany) with a 0.25mm flat contact area. Seven fixed intensities (8 mN - 512 mN) will be applied. The final threshold will be calculated as the geometric mean of the ascending and descending stimulus intensities from five series.
Sleep Questionnaires: the Insomnia Severity Index (ISI)
The ISI is a 7-item self-report questionnaire assessing the nature, severity, and impact of insomnia. Each item is rated on a 5-point Likert scale (0 to 4). The total score ranges from 0 to 28, with higher scores indicating greater severity of insomnia.
Sleep Questionnaires: The Pittsburgh Sleep Quality Index (PSQI)
The PSQI is a 19-item self-report questionnaire that evaluates sleep quality and disturbances over a 1-month time interval. It generates seven component scores: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleep medication, and daytime dysfunction. Each component is scored from 0 to 3. The sum of these seven component scores yields a global PSQI score ranging from 0 to 21, where higher scores indicate poorer sleep quality.
Sleep diary: Total Sleep Time
Assessed using a daily consensus sleep diary. Total Sleep Time is calculated as the total time spent asleep, derived from the total time in bed (bedtime to rise time) minus sleep onset latency and wake after sleep onset. Higher values indicate longer sleep duration.
Sleep diary: Sleep Onset Latency (SOL)
Assessed using a daily consensus sleep diary. Sleep Onset Latency is the estimated time (in minutes) it takes to fall asleep after turning off the lights. Lower values indicate better sleep onset.
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