The Area of Pressure-Induced Referred Pain Is Dependent on the Intensity of the Suprathreshold Stimulus: An Explorative Study

Abstract

Objective To investigate the pain referral area (number of pixels) and extent (vector length) as elicited from increasing intensities of pressure-induced pain at the shoulder. Design Cross-sectional design. Setting Clinical laboratory setting. Participants Twenty-two healthy men and women participated in two experimental sessions. Methods Delayed onset of muscle soreness (DOMS) was induced in the dominant shoulder and assessed 24 hours later. Participants rated the level of DOMS on a 6-point Likert scale. Four different intensities (pressure pain threshold [PPT]+20%, PPT+30%, PPT+40%, and PPT+50%) were applied to the infraspinatus in a randomized, balanced fashion for 60 seconds from low to high intensity or vice versa. The resulting location, area, and extent of referred pain as drawn by the participants on a digital body chart were extracted and expressed in pixels. The extent of pain was defined as the vector length extending from the ipsilateral earlobe to the most distal location of the pain. Results The referred pain area from PPT+20% was smaller than PPT+30%, PPT+40%, and PPT+50%. The extent of referred pain did not differ between the pressure pain intensities. Conclusions Pressure intensity at PPT+30%, but no more, produces the greatest referred pain area as compared with the traditional pressure intensity of PPT+20%. Thus, the intensity of PPT+30% may be ideal for exploring the mechanisms of referred pain. The extent of the pain represents an independent expression of the intensity of the provoking stimulus and may be more closely related to the location of the stimulus.

Referred sensation location can be altered by a strong heterotopic nociceptive stimulus: implications for clinical pain conditions

“…This indicates that the development of RS is likely dependent on how painful the stimulus is, and this has been shown for both the trigeminal and spinal systems. 11,27 Moreover, this study found a higher percentage of participants who developed RS when being palpated with 2 kg than in previous studies. 10,11,23 This can be explained by the fact that, in this study, the palpation was performed in the most sensitive part of the masseter muscle which led to an increase in mechanical sensitivity when compared with previous studies.…”

Modulation Of Experimental Prolonged Pain and Sensitization Using High-Definition Transcranial Direct Current Stimulation: A Double-Blind, Sham-Controlled Study

“…This is a fairly new assessment method and should be interpreted with care. Previous studies have performed similar assessments by applying pressure stimulation at 120% of the pressure pain threshold to investigate the effects of suprathreshold pressure stimulation 21,58 . As the pressure is held at threshold level for a few seconds while posing the question of pain rating, it is expected that the assessment will produce a low-to moderate pain at baseline level, much like temporal summation at pain threshold level 10,36 .…”

Pain referral area is reduced by remote pain

“…Another factor to consider is the variance in pain referral patterns between individuals as observed in this study and others (Boudreau et al., 2017, 2018; Domenech‐Garcia et al., 2016; Gibson et al., 2006b; Palsson et al., 2018). Recently, it was demonstrated that variability in pain referral is greater with lower stimulation intensities (Palsson et al., 2020) where the optimal stimulation intensity, based on variability of pain referral, is above 30% of the PPT as also used in the present study (Table 1). In the Palsson et al’s study, higher intensities did not reduce the coefficient of variance for pain referral additionally.…”

“…Previously, it has been suggested that the size of pain referral patterns could be a useful proxy for evaluating the sensitivity of central pain mechanisms (Domenech‐Garcia et al., 2016; Graven‐Nielsen & Arendt‐Nielsen, 2010). There are a number of limitations to this premise: The stimulation intensity is difficult to standardize with manual palpation, but the size of referred pain areas is related to stimulation intensity (Arroyo‐Fernandez et al., 2020; Palsson et al., 2020). Therefore, even though referred pain can be induced by manual stimulation (Schiffman et al., 2014), it would be unrealistic to believe that manual stimulation can be standardized across individuals and clinicians making the quantification of day‐to‐day differences unreliable.…”

“…Any pain subsequently perceived beyond the site of the applied painful stimulus is considered referred pain and can vary in size and distribution. In some cases, healthy individuals only report local pain at the site of the applied stimulus while others report an extensive spread of referred pain (Domenech‐Garcia et al., 2016; Doménech‐García et al., 2018; Palsson et al., 2020).…”