Significant Increase In Pressure Pain Threshold Research Articles

Resistance Training-Induced Acute Hypoalgesia in Women With Persistent Pain After Breast Cancer Treatment.

Fogh Rasmussen, GH, Madeleine, P, Arroyo-Morales, M, Voigt, M, and Kristiansen, M. Resistance training-induced acute hypoalgesia in women with persistent pain after breast cancer treatment. J Strength Cond Res 37(3): e16-e24, 2023-The aim of this study was to determine whether a single bout of resistance training (RT) produces acute exercise-induced hypoalgesia (EIH) in breast cancer survivors (BCS) suffering from persistent pain ≥1.5 years after treatment. Twenty individuals with self-reported pain ≥3 on a 0-10 Numerical Rating Scale after treatment for breast cancer completed 3 experimental sessions, (a) familiarization; (b) 1 repetition maximum (1RM) normalization, and (c) training, consisting of 3 sets of 10 repetitions at 60% of 1 repetition maximum. Pressure pain thresholds (PPTs) were measured before and after training for the dorsal and ventral shoulder regions of the affected side. Movement-evoked pain (MEP) and rating of perceived exertion (RPE) were collected immediately after each set. A p -value less than 0.05 was considered statistically significant. The results demonstrated a significant increase in PPTs of the ventral shoulder region after a single bout of RT ( p ≤ 0.05), indicating a localized analgesic response for this area. By contrast, no change was detected in PPTs on the dorsal shoulder region. No significant differences were found in MEP between sessions despite a significant increase in load and RPE during 1RM assessment ( p ≤ 0.05), indicating that MEP was not affected by increase in absolute and relative intensity. In conclusion, a single bout of submaximal RT reduced PPTs for the ventral shoulder region of BCS with persistent pain after treatment and was well tolerated. Hence, RT may be a useful therapeutic tool for managing persistent pain after breast cancer treatment in clinical practice.

Immediate Effects of Dry Needling and Myofascial Release on Local and Widespread Pressure Pain Threshold in Individuals With Active Upper Trapezius Trigger Points: A Randomized Clinical Trial

ObjectiveThis study sought to compare the immediate effects of a single session of dry needling (DN), myofascial release (MR), and sham DN on pressure pain threshold (PPT) and neck pain intensity in individuals with chronic neck pain. MethodsThis was a randomized trial with a blinded outcome assessor. Forty-four individuals with chronic neck pain and unilateral myofascial trigger points in the upper trapezius muscle (UTM) were randomized to receive DN (n = 15), MR (n = 14), or sham DN (n = 15). The PPT over the UTM (ipsilateral and contralateral sides) and the proximal head of the radius (ipsilateral and contralateral to the treated side) and neck pain were assessed immediately and 10 minutes after the intervention. ResultsThere was no significant Group × Time interaction for PPT in the UTM on the treated side (F = 0.63, P = .641) or the contralateral side (F = 1.77, P = .144). However, there was a main effect of time on both the treated side (F = 4.917, P = .001) and the contralateral side (F = 4.70, P = .015), with DN and MR increasing PPT at the UTM. No significant Group × Time × Side interaction was found for PPT at the proximal head of the radius (F = 1.23, P = .276). Within-group analysis revealed a significant increase in PPT on the ipsilateral and contralateral sides in both DN and MR. Neck pain decreased after DN (P < .001), MR (P < .001), and sham DN (P = .008). ConclusionA single application of DN or MR generated local and distant hypalgesic responses superior to placebo. Future trials are needed to examine whether these findings occur in long-term follow-ups.

Effect of manual compressive therapy on latent myofascial trigger point pressure pain thresholds

ObjectiveThis study compared the effects of 90 s of manual compressive therapy (MCT) on latent myofascial trigger points (LTPs) for 3 sessions per week for 4 weeks to determine changes in individual pressure pain threshold (PPT). A total of 30 (15 males, 15 females; age = 22 ± 4 y/o, height = 175 ± 18 cm, weight = 162.5 ± 57.5 kg) symptomatic subjects with LTPs volunteered for the study. MethodsPPT was measured at baseline and pre- and post-treatment for all 12 sessions with a pressure algometer across the 4-week treatment time frame. The MCT was applied to the control group on their LTP at pressure intended to provide a sham condition (1/10 on verbalized analog scale (VAS)). Two experimental groups had MCT applied either directly on the LTP (d-TP) or in close-proximity to their LTP (cp-TP) at moderate pressure (7/10 on VAS). ResultsThere was a significant increase in PPT from the first through twelfth treatment sessions (p < 0.001, partial η2 = 0.914). A significant increase in PPTs between treatment groups was acutely observed from pre- to post-therapy tests (p = 0.001, partial η2 = 0.146). The differences between pre- versus post-treatment PPT measures indicated significant differences (d-TP vs. control, p < 0.001; cp-TP vs. control, p = 0.007). No differences were observed between experimental groups (p = 0.215). ConclusionsPPT continued to increase after several weeks of MCT when applied directly on or within 2.5 cm of an identified LTP compared to control.

Delayed-Onset Muscle Soreness and Topical Analgesic Alter Corticospinal Excitability of the Biceps Brachii.

The interactive effect of delayed-onset muscle soreness (DOMS) and a topical analgesic on corticospinal excitability was investigated. Thirty-two participants completed Experiments A (no DOMS) and B (DOMS). For each experiment, participants were randomly assigned to two groups: 1) topical analgesic gel (topical analgesic, n = 8), or 2) placebo gel (placebo, n = 8) group. Before the application of gel (pregel), as well as 5, 15, 30, and 45 min postgel, motor-evoked potential (MEP) area, latency, and silent period, as well as cervicomedullary MEP and maximal compound motor unit action potential areas and latencies were measured. In addition, pressure-pain threshold (PPT) was measured pre-DOMS and at the same timepoints in experiment B. In experiment A, neither group showed a significant change for any outcome measure. In experiment B, both groups exhibited a significant decrease in PPT from pre-DOMS to pregel. After the application of topical analgesic, but not placebo, there was a significant increase in PPT at 45 min postgel, respectively, compared with pregel and a main effect of time for the silent period to increase compared with pregel. Participants with DOMS had reduced MEP and cervicomedullary MEP areas and increased corticospinal silent periods compared with those who did not have DOMS. These findings suggest that DOMS reduced corticospinal excitability and after the administration of menthol-based topical analgesic, there was a reduction in pain, which was accompanied by increased corticospinal inhibition.

Effects of sternocleidomastoid muscle and suboccipital muscle soft tissue release on muscle hardness and pressure pain of the sternocleidomastoid muscle and upper trapezius muscle in smartphone users with latent trigger points.

Few studies have been performed regarding the reduction of pain in the upper trapezius (UT) muscle by applying interventions to the sternocleidomastoid (SCM) muscle, which is innervated by the same nerves.The purpose of this study was to investigate the effects of soft tissue release intervention on the SCM and suboccipital muscles with regard to muscle hardness and pressure pain threshold (PPT) of the SCM and UT muscles in smartphone users with latent myofascial trigger points (MTrPs) in the UT muscle.Seventeen smartphone users (5 men and 12 women) with latent MTrPs in the UT muscle participated in the study. This study used a single blinding, cross-over design, wherein sternocleidomastoid soft tissue release (SSTR) and suboccipital release (SR) were applied on the subjects in random order one week apart. Muscle hardness and the PPT of the SCM and UT muscles were assessed before and after the intervention.After SSTR was applied, the SCM and UT muscles showed a significant decrease in muscle hardness and a significant increase in PPT. After SR was applied, the UT muscle showed a significant decrease in muscle hardness and a significant increase in PPT. When comparing the amount of change between the SSTR and SR interventions, significant differences were found for SCM muscle hardness and PPT of the UT muscle in the SSTR intervention, compared with the SR intervention.Therefore, we suggest that, to reduce pain in the UT muscle, it may be useful to apply intervention directly to the UT muscle, as well as to the SCM muscle, which is innervated by the same nerve.

Adults with patellofemoral pain do not exhibit manifestations of peripheral and central sensitization when compared to healthy pain-free age and sex matched controls - An assessor blinded cross-sectional study.

Patellofemoral Pain (PFP) is highly prevalent among adults and adolescents. Localized mechanical hyperalgesia around the knee and tibialis anterior have been observed in people with PFP, but limited knowledge of potential manifestations of central sensitisation exists. The aims of this study were to study conditioned pain modulation (CPM) and wide-spread hyperalgesia in adults with PFP. This assessor-blinded cross-sectional study design compared CPM and mechanical pressure pain thresholds (PPT) between 33 adults (23 females) diagnosed with PFP and 32 age and sex matched pain-free controls. The investigator taking the PPT measurements was blinded to which participants had PFP. PPTs were reliably measured using a Somedic hand-held pressure algometer at three sites: 1) The centre of the patella, 2) the tibialis anterior muscle and 3) a remote site on the lateral epicondyle. For the assessment of CPM, experimental pain was induced to the contralateral hand by immersion into a cold water bath (conditioning stimulus), and assessment of PPTs (the test stimulus) was performed before and immediately after the conditioning stimulation. On average, the CPM paradigm induced a significant increase in PPTs across the three sites (6.3–13.5%, P<0.05), however there was no difference in CPM between young adults with PFP compared to the control group, (F(1,189) = 0.39, P = 0.89). There was no difference in mechanical PPTs between the two groups (F(1,189) = 0.03, P = 0.86). Contrary to our a-priori hypothesis, we found no difference in CPM or PPT between young adults with PFP and age and sex matched pain-free controls.

Endogenous Pain Modulation Induced by Extrinsic and Intrinsic Psychological Threat in Healthy Individuals

Many factors interact to influence threat perception and the subsequent experience of pain. This study investigated the effect of observing pain (extrinsic threat) and intrinsic threat of pain to oneself on pressure pain threshold (PPT). Forty socially connected pairs of healthy volunteers were threat-primed and randomly allocated to experimental or control roles. An experimental pain modulation paradigm was applied, with non-nociceptive threat cues used as conditioning stimuli. In substudy 1, the extrinsic threat to the experimental participant was observation of the control partner in pain. The control participant underwent hand immersion in noxious and non-noxious water baths in randomized order. Change in the observing participant's PPT from baseline to mid- and postimmersion was calculated. A significant interaction was found for PPT between conditions and test time (F2,78 = 24.9, P < .005). PPT increased by 23.6% ± 19.3% between baseline and during hand immersion (F1,39 = 43.7, P < .005). Substudy 2 investigated threat of imminent pain to self. After a 15-minute break, the experimental participant's PPT was retested (“baseline 2”). Threat was primed by suggestion of whole arm immersion in an icier, larger water bath. PPT was tested immediately before anticipated arm immersion, after which the experiment ended. A significant increase in PPT between “baseline 2” and “pre-immersion” was seen (t = −7.6, P = .005), a pain modulatory effect of 25.8 ± 20.7%. Extrinsic and intrinsic threat of pain, in the absence of any afferent input therefore influences pain modulation. This may need to be considered in studies that use noxious afferent input with populations who show dysfunctional pain modulation. PerspectiveThe effect on endogenous analgesia of observing another's pain and of threat of pain to oneself was investigated. Extrinsic as well as intrinsic threat cues, in the absence of any afferent input, increased pain thresholds, suggesting that mere threat of pain may initiate analgesic effects in traditional noxious experimental paradigms.

The Effects of Manual Passive Muscle Shortening and Positional Release Therapy on Latent Myofascial Trigger Points of the Upper Trapezius: A Double-Blind Randomized Clinical Trial

Background: Positional release therapy (PRT) has been suggested as an effective treatment for myofascial trigger points (MTrPs). Considering the mechanism of PRT, a new modified technique, known as Manual Passive Muscle Shortening (MPMS), is introduced for the treatment of MTrPs. Objectives: To compare the effects of MPMS and PRT on the sensitivity of latent MTrPs in the upper trapezius and determine the active cervical lateral flexion range. Methods: In this double-blind randomized controlled trial, 30 female university students, who were identified with latent MTrPs of the upper trapezius, were recruited from Tabriz University of Medical Sciences, Tabriz, Iran. The participants were randomly allocated into experimental (n, 15) and control (n, 15) groups. The experimental group was treated with the MPMS technique, while the control group received PRT. The participants took part in 3 treatment sessions, as well as a follow-up session 1 week after the third session. During each session, the second physiotherapist, who was blind to the pretreatment information, applied the appropriate technique. The visual analogue scale (VAS), pressure pain threshold (PPT), and bilateral active range of cervical lateral flexion were recorded to assess the effects of treatment. The first physiotherapist, who was blind to the treatment approach for the participants, recorded the outcomes before treatment, during the first session, after treatment (third session), and in the follow-up. Results: A total of 30 participants were included in the data analysis. In the follow-up, intergroup changes indicated a significant increase in PPT (P = 0.000), a significant decrease in VAS scores (P = 0.002), and a significant increase in the right lateral flexion (P= 0.012) in the experimental group. Left lateral flexion also increased in this group, although it was not statistically significant (P = 0.254). At the end of the study, there were no significant differences between the groups (P > 0.05). Conclusions: According to the results, both MPMS and PRT were effective techniques in immediate pain relief of upper-trapezius MTrPs. Therefore, MPMS may be used as a new technique in the treatment of MTrPs چکیده

The immediate effect of multiple mechanical impulses on electromyography and pressure pain threshold of lumbar latent trigger points: an experimental study.

BackgroundMyofascial pain is a common syndrome, which has not been studied extensively in the low back. Despite a variety of manual and instrument assisted interventions available, little work has targeted the possible effects of fast mechanical impulses on myofascial trigger points (MTrPs) on its sensitivity and electrical activity. The purpose of this experimental study was to quantify the immediate effect of one session of mechanical impulses to lumbar latent MTrPs and to normal muscle tissue with pressure pain threshold (PPT) and surface electromyography (sEMG) as outcome measures.MethodsDuring the autumn of 2009, in 41 asymptomatic subjects between 17-40 years of age the lumbar musculature was searched for a latent MTrP by a trained clinician. Using 3 disposable pre-gelled electrodes bilaterally, sEMG was recorded continuously from muscle containing either latent or no MTrP. Both the trigger point group and control group received the intervention and were blinded to group allocation. The immediate effects of mechanical impulses were assessed by sEMG and PPT before and after intervention using Wilcoxon matched-pairs signed-ranks test, Mann–Whitney U test and paired t-tests.ResultsThe PPT increased significantly across both groups (p < 0.01) after intervention. The proportionate increase (14.6 %) was comparable in both MTrP and control groups. The electrical activity on the MTrP side was not significantly higher in the MTrP group compared to the contralateral side. The decrease of resting electrical activity after intervention was significant in the MTrP group on the side of the latent MTrP (P = 0.001) as well as the contralateral side (p=0.022), and not significant in the control group on either side (p=0.33 and p=0.93).ConclusionIn this study, the immediate effect of one session of mechanical impulses was associated with a significant increase in PPT for both groups and a significant decrease in the resting electrical activity of the lumbar muscles only in the MTrP group. It is unknown if these effects have clinical significance.

Bilateral Sensory Effects of Unilateral Passive Accessory Mobilization in Patients With Thumb Carpometacarpal Osteoarthritis

ObjectiveThe purpose of this study was to investigate changes in pressure sensitivity and pinch grip force in the nonsymptomatic side in patients with thumb carpometacarpal (CMC) osteoarthritis (OA) after the application of a unilateral passive accessory mobilization to the symptomatic hand. MethodsSecondary analysis of data from a randomized trial with concealed allocation, blinded assessor, and intention-to-treat analysis was performed. Twenty-eight patients (72% females), with unilateral CMC OA and mean age ± SD of 82 ± 6 years, met all the inclusion criteria and agreed to participate. The experimental group received passive accessory mobilization to the CMC OA, and the control group received a nontherapeutic dose of intermittent ultrasound on the affected side for 4 sessions over 2 weeks. Outcome measures including pressure pain thresholds (PPTs) at the lateral epicondyle, thumb CMC joint, tubercle of the scaphoid bone, and the unciform apophysis of the hamate bone and tip and tripod pinch and grip strength of the contralateral/unaffected hand were assessed at baseline as well as 1 and 2 weeks after treatment by an assessor blinded to the group allocation. A repeated measures analysis of variance was used to determine changes in PPT and pinch and grip strength. ResultsNo important baseline differences were observed between groups. At the end of the follow-up period, the experimental group exhibited a significant increase in PPT at the CMC joint as compared with the control group 0.6 kg/cm2 (95% confidence interval, 0.3-1.0; F3.0 = 4.89; P = .009). Although PPT changes in the experimental group were higher than the control group at the remaining sites, differences did not reach statistically significance. Similarly, tip, tripod pinch, and grip strength remained unchanged after the intervention. ConclusionThis secondary analysis found that the application of a unilateral passive accessory mobilization targeted to the symptomatic CMC joint induced an increase of PPT levels 2 weeks after treatment; however, differences were small and likely of limited clinical value. No contralateral motor effects were observed. Future studies including larger sample sizes are needed to examine the effects of joint mobilization on motor and sensory effects.

A prospective open label pilot study to investigate whether quantitative sensory testing correlates with the effectiveness of diagnostic dorsal root ganglion block in patients with unilateral lumbar radiculopathy

Lumbar radicular pain is defined as neuropathic pain in the area supplied by the affected nerve root, which may be treated by targeting the dorsal root ganglion (DRG). Central sensitization can occur following peripheral nerve injury, via autosensitization of nociceptive receptors and ectopic firing of DRG cells.1 We hypothesize that central nociceptive processing may be modulated by DRG blockade with local anaesthetic and steroid. This study used quantitative sensory testing (QST) to investigate changes in peripheral and central sensitization in patients undergoing therapeutic DRG block for radicular low back pain. Fifteen patients were recruited for the study, after approval of the local research ethics committee, to undergo DRG blockade with local anaesthetic and steroid (inclusion criteria: unilateral lumbar radicular pain with concordant disc herniation confined to the spinal canal on magnetic resonance imaging). This was performed by a single operator with fluoroscopic guidance, using 1ml 0.25% bupivacaine and 20mg methylprednisolone per level. QST measurements were taken one week before and after their procedure; mechanical pressure pain threshold (PPT) was measured using manual pressure algometry, and diffuse noxious inhibitory control (DNIC) was measured by recording changes in PPT in response to experimental arm pain. A visual analogue scale (VAS) was used to measure pain intensity. There was a significant increase in PPT after DRG blockade (painful side p<0.0005 versus non-painful side p<0.004). A diminished DNIC response was seen prior to DRG blockade, increasing after the procedure (p<0.0001); this suggests ‘normalisation’ of pressure pain modulation. Pain intensity scores improved after DRG blockade (7.45 +/- 1.9 versus 2.28 +/- 0.26). This pilot data indicates that DRG blockade with local anaesthetic and steroid may have effects on peripheral and central sensitization. Potential mechanisms include modulation of afferent fibre nociceptive input on central nociceptive processing. (1. Schwartzman RJ, Arch Neurol, 2001.)

Effects of Carrier Frequency of Interferential Current on Pressure Pain Threshold and Sensory Comfort in Humans

ObjectiveTo assess the effect of carrier frequency of interferential current (IFC) on pressure pain threshold (PPT) and sensory comfort in healthy subjects. DesignA double-blind randomized trial. SettingUniversity research laboratory. ParticipantsHealthy subjects (N=150). InterventionsApplication of the IFC for 20 minutes and measures of PPT collected in the regions of the nondominant hand and forearm. Main Outcomes MeasuresWe measured PPT and comfort at frequencies of 1kHz, 2kHz, 4kHz, 8kHz, and 10kHz. ResultsThere was a significant increase in PPT in the 1-kHz group when compared with the 8-kHz and 10-kHz groups. There was a greater discomfort in the 1-kHz and 2-kHz groups. ConclusionsIFC with a carrier frequency of 1kHz promotes a higher hypoalgesic response during and after stimulation than IFC with carrier frequencies of 8kHz and 10kHz. Carrier frequencies of 1kHz and 2kHz are perceived as more uncomfortable than carrier frequencies of 4kHz, 8kHz, and 10kHz.

An investigation into the potential hypoalgesic effects of different amplitudes of PA mobilisations on the lumbar spine as measured by pressure pain thresholds (PPT)

Mobilisation of the spine is a common technique used in clinical practice. Studies have shown that mobilisation to the spine can decrease pain. The optimum treatment dose for achieving this has not so far been investigated. Previous studies that demonstrate the pain relieving effects of mobilisations have used large amplitude of oscillations. The importance of amplitude on pain relief has not been established. The current study aims to: a) Investigate the importance of amplitude as part of the treatment dose. b) To explore the extent of any pain reliving effects seen following mobilisations. The study employed a randomised, single blind, within-subjects repeated measure design. Thirty asymptomatic subjects participated. The subjects completed three experimental conditions on three separate occasions. The conditions were: large amplitude of oscillations (forces between 50 and 200 N), small amplitude of oscillations (150 N–200 N) and quasi-static (maintained at 200 N). Each condition involved a 3x1 minute central PA mobilisation at a frequency of 1.5 Hz on the lumbar spine. Pressure pain thresholds (PPT) were measured immediately before and after each intervention at 4 different sites. The sites were chosen to determine the extent of the hypoalgesic response. Results demonstrated a significant increase in PPT following lumbar mobilisations ( p = 0.013) at all measured sites. However, no significant difference was found between amplitude conditions ( p = 0.864). This study suggests that in asymptomatic subjects a systemic hypoalgesic response is caused by lumbar mobilisation regardless of amplitude.

Segmental and plurisegmental modulation of pressure pain thresholds during static muscle contractions in healthy individuals

The purpose of this study was to assess possible segmental (uni- and/or bilateral) and plurisegmental changes in pressure pain thresholds (PPTs) during static muscle contractions. Twenty-four healthy subjects (12 female, 12 male) performed a standardised isometric contraction with the dominant m. quadriceps femoris (MQF) and m. infraspinatus (MI), respectively. PPTs were assessed using pressure algometry at the contracting muscle, at the contralateral (resting) muscle and at a distant resting muscle (MI during contraction of MQF and vice versa). The PPT assessments were performed before, during and 30 min. following each contraction. The contractions were held until exhaustion or for a maximum of 10 PPT assessments/muscle. During contraction of MQF PPTs increased compared to baseline at the middle ( p<0.001) and the end ( p<0.001) of the contraction period at all assessed sites alike. During contraction of MI PPTs increased compared to baseline at the middle ( p<0.001) and the end ( p<0.007) of the contraction period at all sites. The increase was more pronounced at the contracting muscle compared to the contralateral ( p<0.002; p<0.01) and the distant ( p<0.002; p<0.002) site. No statistically significant difference was seen in PPTs between the latter two. Following the contractions PPTs returned to baseline. Submaximal isometric contraction of MQF and MI gave rise to a statistically significant increase in PPTs at the contracting muscle, the resting homologous contralateral muscle and at the distant resting muscle indicating that generalised pain inhibitory mechanisms were activated. Contraction of MI, but not of MQF, gave rise to an additional activation of unilateral segmental antinociceptive effects.

Pressure pain thresholds in volunteers and herniorrhaphy patients

Pressure algometry is a method to estimate pressure pain sensitivity in tissues. The aim of the present study was to evaluate the reproducibility of pressure pain thresholds (PPT) in the abdominal integument and to evaluate the use of pressure algometry as a measure of wound tenderness following surgery. PPT was determined in 20 healthy volunteers on two separate examinations, and in 14 patients at the incisional site before and following inguinal herniotomy. In volunteers, PPT was higher for men than for women, and no difference was observed between the first and second day of examination. In surgical patients a significant decrease in PPT was observed following operation. Morphine 0.07 mg/kg caused a slight but significant increase in PPT. Pressure algometry may be useful to study nociceptive mechanisms and the dynamics of wound pain in surgical patients.

Pressure-pain threshold in human temporal region. Evaluation of a new pressure algometer

A hand-held pressure algometer with a pressure sensitive strain gauge at the tip was used to measure the pressure-pain threshold (PPT) in the temporal region of healthy volunteers. Various sizes of circular tips and various application rates were tested before selecting an area of 0.5 cm 2 and a constant application rate of 0.68 N · sec -1 for future use. A highly significant correlation was found between PPT values obtained from the two sides (of the head) ( P < 0.001) and between PPT values obtained with a 3-week interval ( P < 0.001). In a series of 50 immediate consecutive measurements in the same individual, the mean PPT was 171 kP a (N = 6, 2 S.D. 24%). The mean relative change in PPT after a 3-week interval was 0 ± 51% (N = 11, 2 S.D.). In the course of 5 repeated determinations at weekly intervals there was a significant increase in PPT (ANOVA, P < 0.05). Subcutaneous lignocaine significantly elevated PPT compared to placebo. Due to the high inter-individual variation, determinations of PPT for group comparisons should include rather large population samples, whereas in paired studies, the intra-individual variation allows the investigation of much smaller groups (10–20 subjects). It is our experience that the pressure algometer is easy to operate in the hands of a skilled laboratory assistant.