Vibratory stimulation increase the electro-cutaneous sensory detection and pain thresholds in women but not in men
© Dahlin et al; licensee BioMed Central Ltd. 2006
Received: 13 December 2005
Accepted: 23 May 2006
Published: 23 May 2006
Vibratory stimulation is a potential method for the treatment of pain.
The effect of vibration on the forearm on detection (DT) and pain thresholds (PT) induced by electro-cutaneous stimulation were investigated in healthy male and female volunteers.
Women have lower baseline detection and pain thresholds as compared to men. Furthermore, women but not men report increased detection and pain thresholds after vibratory stimulation.
Our findings indicate the potential usefulness of vibratory stimulation for pain treatment, and that gender differences should be considered in future evaluation of the method.
Vibratory stimulation is one of several non-pharmacological techniques used to reduce pain. The effects of vibration on pain has been reported in both clinical [1–8] and experimental [9–16] settings. Activation of the mechanical transient receptors is likely to be important (for review see ), but contribution of other more slowly adapting receptors can not be excluded . Vibration activates both superficial and deeply located receptors [11, 18, 19]. The subsequent afferent activity in myelinated sensory axons may interact with nociceptive processing at several levels of the nervous system, including the spinal cord. One of the effects is a long lasting elevation of the pain threshold (PT) [9, 14–16].
A number of experimental, clinical and epidemiological studies have shown that men and women experience pain differently; for review see ref. [20, 21]. In healthy volunteers, women often report lower thresholds and tolerance to painful stimuli compared to men [21–24]. It has been suggested the gender differences are related partly to the mode of painful stimulation and pain induction method (frequency, duration, size and location) , the manner of presentation [20, 24], but also to gender-related physiological differences [20, 21, 23, 25, 26]. In experimentally induced pain, women seem to be more sensitive to painful mechanical pressure, electrical stimulation and ischemic pain compared to men [22–24, 27]. There are yet no reports on possible gender-related threshold responses to vibration stimulation.
The aim of the present study was to evaluate the effect of vibratory stimulation on electro-cutaneous detection threshold and pain threshold levels in healthy volunteers taking also the possible influence of gender into account.
The experimental subjects were healthy student volunteers recruited from the physiotherapy programme at the Karolinska Institute. They were informed of the purpose and non-invasive experimental procedures before the experiments commenced and that they could leave at any time. The study was approved by the Ethic Committee of the Karolinska Hospital (dnr. 01-169).
Assessment of detection and pain thresholds
The threshold assessment procedure includes non-invasive electrocutaneous stimulation of the skin of the thumb and forefinger of one hand by pressing the electrodes of the electrical stimulation unit. When reaching the respective threshold level the subjects release there fingers from the electrodes. The detection threshold (DT) was defined as the first pricking sensation and the pain threshold (PT) when the pricking sensation was altered to the first sensation of pain.
The threshold values at the respective levels were automatically recorded immediately when the fingers were released from the electrodes, but in that moment not shown to the subjects making them blind to the ongoing assessments.
The threshold assessment unit is controlled by a microprocessor (PainMatcher®, Cefar Medical AB, Sweden). The generated current is distributed with a monophasic rectangular pulse of 15 mA and 10 Hz. The output intensity increases by gradually widening the pulse duration in steps of 4 μs to a maximum of 396 μs, i.e. in a total of 99 steps directly related to the output. The maximum electrical charge per pulse is 5.9 μC. The contact surface area, and hence the resulting current density, is ensured by a certain load of minimum finger pressure against the electrodes. Loads between 0 and 13 kΩ secured the output of 15 mA. The numerical cut-off range is 0–99.
Both electrical DTs and PTs were recorded on four occasions separated by 10 minutes: before, during and after vibration stimulation.
The vibratory stimulation (Vitamed, Germany) was applied with a rectangular probe of 13 × 20 cm to the dorsal aspect of the forearm, covering the dermatomes C5-8, with 3000 Hz, and a constant and moderate pressure for 20 minutes. The therapist was well-known to the experimental subjects.
The mean value and standard deviation (SD) were calculated for age. The threshold assessments were regarded as subjective estimations and the produced threshold data as ordinal data, here presented as the median and range (minimum to maximum) for the numerical units of the PainMatcher (PM) values [28, 29].
The proportions of subjects with increased, unchanged, and decreased threshold values on the second occasion were calculated. The hypotheses of no change in threshold assessments between before and after vibration were analyzed by the non-parametric sign test. Mann Whitney U-test was used to analyse gender differences. A p-value less than 0.05 was regarded as significant.
Assessed levels of detection and pain thresholds in response to vibratory stimulation to one forearm. Descriptive data, showing Pain matcher values as median value and range (min to max, numerical cut-off 0–99).
10 minutes after
Women, n = 29
men, n = 27
Women, n = 29
men, n = 27
women, n = 29
men, n = 27
women, n = 27
men, n = 24
3 (1 to 8)
5 (1 to 9)
4 (1 to 8)
5 (2 to 8)
4 (2 to 9)
5 (1 to 9)
4 (2 to 7)
5 (2 to 8)
12 (5 to 24)
15 (5 to 71)
16 (6 to 30)
17 (7 to 99)
15 (7 to 24)
18 (7 to 93)
12 (6 to 27)
19 (8 to 93)
Previous studies have shown that in order to get optimal pain relief, the best site to apply the vibration probe is either in the area of pain or in dermatomes no more than two segmental levels from the pain [1, 3, 10, 30], or in the same dermatome on the contralateral side , or in a trigger point outside the painful area using moderate pressure . Vibration distal to the site of threshold measurement also seems to be more effective, at least during the stimulation . Furthermore, findings in a previous report indicate that a larger size of the stimulus probe results in more pain relief . In this study, the vibration was applied across up to four dermatomes, proximal to and in the same arm as the test stimulus, and the vibratory probe was relatively large (13 × 20 cm) with the aim to cover a reasonably large area. The 20 minutes used as standard application duration in this study is within the time interval used in previous studies, and was shown to be the shortest duration to elicit maximal pain relief for the most patients in a group with myalgia , but the most efficient application time for various pain states seems to be unknown. It could be that a longer application time than 20 minutes would have been more effective. Another factor which could be of importance is cyclic variation in thresholds to pain stimulations linked to the menstrual cycle . We did not include this variable in the present study.
Effects of vibratory stimulation
The finding of this study that vibration may increase the threshold for experimentally induced pain is in accordance with earlier findings [10, 15, 16]. It is unclear how afferent signals elicited by vibration interfere with central transmission of nociceptive stimuli even though there are indications of mechanisms that include purinergic mechanisms [33, 34], lowering of spinal substance P , but not, however, ligands to naloxone sensitive μ-opioid receptors [36, 37].
Clinically, the effect of vibration stimulation in patients with different pain states varies between studies. Some demonstrated a pain lowering effect [1, 3, 10, 30] whereas others were unable to show a statistically significant effect [38, 39].
The reason why women tend to have lower thresholds to some types of sensory stimulation including painful stimuli is obscure. The sensitivity to vibration as such does not appear to be different between men and women , indicating that differences in the intensity of the afferent signal was not the cause.
Another possibility is gender related differences in temporal summation. Temporal summation of painful stimuli has previously been shown to be larger in women [41, 42], see however . Whether this is also true for non-painful stimulation does not seem to be known. It could be that longer vibration duration in men would have cancelled out the observed threshold differences between men and women.
Even though gender related differences in pain perception have been reported [24, 27], the gender differences appear to be rather small. The differences have been attributed to experimental, social, psychological and physiological factors, including the experimental setup and mode of stimulation, attention, emotional reactions including anxiety, willingness to report pain and gender of experiment assistant, and to catstrophizing [13, 20, 23, 44]. Some of the complexity of the issue is also illustrated by the finding that repetitive mechanical painful stimuli were rated equal for the first stimulus, but higher in women than in men for the fifth and tenth stimulus, respectively , indicating central mechanisms. Also in line with this, less habituation in women than in men was found after intramuscular glutamate injections , and greater temporal summation following repetitive noxious stimulation .
The main results of the present study are firstly that women have lower baseline DTs and PTs to electrical stimulation than men, and secondly that women, but not men, respond with an increase of the DTs and PTs immediately after vibration stimulation. Even though vibration had a statistically significant effect in women, further studies are needed to investigate the effect in a clinical context.
This work was supported by grants from Karolinska Institutes foundation and Cefar Medical Inc.
- Ottoson D, Ekblom A, Hansson P: Vibratory stimulation for the relief of pain of dental origin. Pain. 1981, 10: 37-45. 10.1016/0304-3959(81)90043-9.View ArticlePubMed
- Ekblom A, Hansson P: Extrasegmental transcutaneous electrical nerve stimulation and mechanical vibratory stimulation as compared to placebo for the relief of acute oro-facial pain. Pain. 1985, 23: 223-229. 10.1016/0304-3959(85)90100-9.View ArticlePubMed
- Hansson P, Ekblom A: Influence of stimulus frequency and probe size on vibration-induced alleviation of acute orofacial pain. Appl Neurophysiol. 1986, 49: 155-165.PubMed
- Lundeberg TC: Vibratory stimulation for the alleviation of chronic pain. Acta Physiol Scand Suppl. 1983, 523: 1-51.PubMed
- Lundeberg T: Long-term results of vibratory stimulation as a pain relieving measure for chronic pain. Pain. 1984, 20: 13-23. 10.1016/0304-3959(84)90807-8.View ArticlePubMed
- Lundeberg T: The pain suppressive effect of vibratory stimulation and transcutaneous electrical nerve stimulation (TENS) as compared to aspirin. Brain Res. 1984, 294: 201-209. 10.1016/0006-8993(84)91031-X.View ArticlePubMed
- Lundeberg T, Abrahamsson P, Bondesson L, Haker E: Vibratory stimulation compared to placebo in alleviation of pain. Scand J Rehabil Med. 1987, 19: 153-158.PubMed
- Roy EA, Hollins M, Maixner W: Reduction of TMD pain by high-frequency vibration: a spatial and temporal analysis. Pain. 2003, 101: 267-274. 10.1016/S0304-3959(02)00332-9.View ArticlePubMed
- Lundeberg T, Abrahamsson P, Bondesson L, Haker E: Effect of vibratory stimulation on experimental and clinical pain. Scand J Rehabil Med. 1988, 20: 149-159.PubMed
- Yarnitsky D, Kunin M, Brik R, Sprecher E: Vibration reduces thermal pain in adjacent dermatomes. Pain. 1997, 69: 75-77. 10.1016/S0304-3959(96)03250-2.View ArticlePubMed
- Weerakkody NS, Percival P, Hickey MW, Morgan DL, Gregory JE, Canny BJ, Proske U: Effects of local pressure and vibration on muscle pain from eccentric exercise and hypertonic saline. Pain. 2003, 105: 425-435. 10.1016/S0304-3959(03)00257-4.View ArticlePubMed
- Hollins M, Roy EA, Crane SA: Vibratory antinociception: effects of vibration amplitude and frequency. J Pain. 2003, 4: 381-391. 10.1016/S1526-5900(03)00714-4.View ArticlePubMed
- Longe SE, Wise R, Bantick S, Lloyd D, Johansen-Berg H, McGlone F, Tracey I: Counter-stimulatory effects on pain perception and processing are significantly altered by attention: an fMRI study. Neuroreport. 2001, 12: 2021-2025. 10.1097/00001756-200107030-00047.View ArticlePubMed
- Pantaleo T, Duranti R, Bellini F: Effects of vibratory stimulation on muscular pain threshold and blink response in human subjects. Pain. 1986, 24: 239-250. 10.1016/0304-3959(86)90046-1.View ArticlePubMed
- Zoppi M, Voegelin MR, Signorini M, Zamponi A: Pain threshold changes by skin vibratory stimulation in healthy subjects. Acta Physiol Scand. 1991, 143: 439-443.View ArticlePubMed
- Kakigi R, Shibasaki H: Mechanisms of pain relief by vibration and movement. J Neurol Neurosurg Psychiatry. 1992, 55: 282-286.PubMed CentralView ArticlePubMed
- Willis WD, Coggeshall RE: Sensory mechanisms of the spinal cord. 2004, New York, Kluwer academic/Plenum publishers, 1 and 2: 3rd
- Hagbarth KE, Eklund G: Motor effects of muscle vibration in spasticity, rigidity and cerebellar disorders. Electroencephalogr Clin Neurophysiol. 1968, 25: 407-
- Ferrington DG, Nail BS, Rowe M: Human tactile detection thresholds: modification by inputs from specific tactile receptor classes. J Physiol. 1977, 272: 415-433.PubMed CentralView ArticlePubMed
- Berkley KJ: Sex differences in pain. Behav Brain Sci. 1997, 20: 371-80; discussion 435-513. 10.1017/S0140525X97221485.PubMed
- Rollman GB, Lautenbacher S: Sex differences in musculoskeletal pain. Clin J Pain. 2001, 17: 20-24. 10.1097/00002508-200103000-00004.View ArticlePubMed
- Lautenbacher S, Rollman GB: Sex differences in responsiveness to painful and non-painful stimuli are dependent upon the stimulation method. Pain. 1993, 53: 255-264. 10.1016/0304-3959(93)90221-A.View ArticlePubMed
- Fillingim RB, Maixner W: Gender differences in the responses to noxious stimuli. Pain Forum. 1995, 4: 209-221.View Article
- Riley JL, Robinson ME, Wise EA, Myers CD, Fillingim RB: Sex differences in the perception of noxious experimental stimuli: a meta-analysis. Pain. 1998, 74: 181-187. 10.1016/S0304-3959(97)00199-1.View ArticlePubMed
- Craft RM, Mogil JS, Aloisi AM: Sex differences in pain and analgesia: the role of gonadal hormones. Eur J Pain. 2004, 8: 397-411. 10.1016/j.ejpain.2004.01.003.View ArticlePubMed
- Ge HY, Madeleine P, Arendt-Nielsen L: Gender differences in pain modulation evoked by repeated injections of glutamate into the human trapezius muscle. Pain. 2005, 113: 134-140. 10.1016/j.pain.2004.09.041.View ArticlePubMed
- Wise EA, Price DD, Myers CD, Heft MW, Robinson ME: Gender role expectations of pain: relationship to experimental pain perception. Pain. 2002, 96: 335-342. 10.1016/S0304-3959(01)00473-0.PubMed CentralView ArticlePubMed
- Svensson E: Concordance between ratings using different scales for the same variable. Stat Med. 2000, 19: 3483-3496. 10.1002/1097-0258(20001230)19:24<3483::AID-SIM786>3.0.CO;2-A.View ArticlePubMed
- Lund I, Lundeberg T, Sandberg L, Budh CN, Kowalski J, Svensson E: Lack of interchangeability between visual analogue and verbal rating pain scales: a cross sectional description of pain etiology groups. BMC Med Res Methodol. 2005, 5: 31-10.1186/1471-2288-5-31.PubMed CentralView ArticlePubMed
- Lundeberg T: Vibratory stimulation for the alleviation of pain. Am J Chin Med. 1984, 12: 60-70. 10.1142/S0192415X84000076.View ArticlePubMed
- Sherer CL, Clelland JA, O'Sullivan P, Doleys DM, Canan B: The effect of two sites of high frequency vibration on cutaneous pain threshold. Pain. 1986, 25: 133-138. 10.1016/0304-3959(86)90015-1.View ArticlePubMed
- Riley JL, Robinson ME, Wise EA, Price DD: A meta-analytic review of pain perception across the menstrual cycle. Pain. 1999, 81: 225-235. 10.1016/S0304-3959(98)00258-9.View ArticlePubMed
- De Koninck Y, Henry JL: Peripheral vibration causes an adenosine-mediated postsynaptic inhibitory potential in dorsal horn neurons of the cat spinal cord. Neuroscience. 1992, 50: 435-443. 10.1016/0306-4522(92)90435-5.View ArticlePubMed
- De Koninck Y, Salter MW, Henry JL: Substance P released endogenously by high-intensity sensory stimulation potentiates purinergic inhibition of nociceptive dorsal horn neurons induced by peripheral vibration. Neurosci Lett. 1994, 176: 128-132. 10.1016/0304-3940(94)90887-7.View ArticlePubMed
- Guieu R, Tardy-Gervet MF, Giraud P: Substance P-like immunoreactivity and analgesic effects of vibratory stimulation on patients suffering from chronic pain. Can J Neurol Sci. 1993, 20: 138-141.PubMed
- Lundeberg T: Naloxone does not reverse the pain-reducing effect of vibratory stimulation. Acta Anaesthesiol Scand. 1985, 29: 212-216.View ArticlePubMed
- Guieu R, Tardy-Gervet MF, Giraud P: Met-enkephalin and beta-endorphin are not involved in the analgesic action of transcutaneous vibratory stimulation. Pain. 1992, 48: 83-88. 10.1016/0304-3959(92)90134-W.View ArticlePubMed
- Watanabe I, Svensson P, Arendt-Nielsen L: Influence of segmental and extra-segmental conditioning, stimuli on cortical potentials evoked by painful electrical stimulation. Somatosens Mot Res. 1999, 16: 243-250. 10.1080/08990229970492.View ArticlePubMed
- Taylor AG, Galper DI, Taylor P, Rice LW, Andersen W, Irvin W, Wang XQ, Harrell FEJ: Effects of adjunctive Swedish massage and vibration therapy on short-term postoperative outcomes: a randomized, controlled trial. J Altern Complement Med. 2003, 9: 77-89. 10.1089/107555303321222964.View ArticlePubMed
- Liou JT, Lui PW, Lo YL, Liou L, Wang SS, Yuan HB, Chan KH, Lee TY: Normative data of quantitative thermal and vibratory thresholds in normal subjects in Taiwan: gender and age effect. Zhonghua Yi Xue Za Zhi (Taipei). 1999, 62: 431-437.
- Sarlani E, Greenspan JD: Gender differences in temporal summation of mechanically evoked pain. Pain. 2002, 97: 163-169. 10.1016/S0304-3959(02)00015-5.View ArticlePubMed
- Sarlani E, Grace EG, Reynolds MA, Greenspan JD: Sex differences in temporal summation of pain and aftersensations following repetitive noxious mechanical stimulation. Pain. 2004, 109: 115-123. 10.1016/j.pain.2004.01.019.View ArticlePubMed
- Nie H, Arendt-Nielsen L, Andersen H, Graven-Nielsen T: Temporal summation of pain evoked by mechanical stimulation in deep and superficial tissue. J Pain. 2005, 6: 348-355. 10.1016/j.jpain.2005.01.352.View ArticlePubMed
- Levine FM, De Simone LL: The effects of experimenter gender on pain report in male and female subjects. Pain. 1991, 44: 69-72. 10.1016/0304-3959(91)90149-R.View ArticlePubMed
- The pre-publication history for this paper can be accessed here:http://www.biomedcentral.com/1472-6882/6/20/prepub
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.