G. David Baxter

Gender differences in pressure pain threshold in healthy humans.

&NA; Aims of investigation: To quantify the magnitude of putative gender differences in experimental pressure pain threshold (PPT), and to establish the relevance of repeated measurements to any such differences. Methods: Two separate studies were undertaken. A pressure algometer was used in both studies to assess PPT in the first dorsal interosseous muscle. Force was increased at a rate of 5 N /s. In study 1, two measurements were taken from 240 healthy volunteers (120 males, 120 females; mean age 25 years) giving a power for statistical analysis of &bgr;=0.80 at &agr;=0.01. In study two, 30 subjects (15 males, 15 females mean age 28 years) were randomly selected from study one. Fourteen repeated PPT measurements were recorded at seven, 10 min intervals. Mean PPT data for gender groups, from both studies, were analysed using analysis of covariance with repeated measures, and age as the covariate. Results: The mean PPT for each of the two measurements in study one showed a difference between gender of 12.2 N (f=30.5 N, m=42.7 N) and 12.8 N (f=29.5 N, m=42.3 N), respectively, representing a difference of 28% with females exhibiting a lower threshold. In study two, the mean difference calculated from 14 PPT repeated measurements over a 1 h period was comparable to that in study one at 12.3 N (range 10.4–14.4 N) again females exhibited the lower threshold. The differences in mean PPT values between gender were found to be significant in both study one, at (P<0.0005, F=37.8, df=1) and study two (P=0.01, F=7.6, df=1). No significant differences were found in either study with repeated measurement (P=0.892 and P=0.280), or on the interaction of gender and repeated measurement after controlling for age (P=0.36 and P=0.62). Conclusion: Healthy females exhibited significantly lower mean PPTs in the first dorsal interosseous muscle than males, which was maintained for fourteen repeated measures within a 1 h period. This difference is likely to be above clinically relevant levels of change, and it has clear implications for the use of different gender subjects in laboratory based experimental designs utilising PPT as an outcome measure.

Exercise and chronic low back pain: what works?

&NA; The aim of this review was to investigate current evidence for the type and quality of exercise being offered to chronic low back pain (CLBP) patients, within randomised controlled trials (RCTs), and to assess how treatment outcomes are being measured. A two‐fold methodological approach was adopted: a methodological assessment identified RCTs of ‘medium’ or ‘high’ methodological quality. Exercise quality was subsequently assessed according to the predominant exercise used. Outcome measures were analysed based on current recommendations. Fifty‐four relevant RCTs were identified, of which 51 were scored for methodological quality. Sixteen RCTs involving 1730 patients qualified for inclusion in this review based upon their methodological quality, and chronicity of symptoms; exercise had a positive effect in all 16 trials. Twelve out of 16 programmes incorporated strengthening exercise, of which 10 maintained their positive results at follow‐up. Supervision and adequate compliance were common aspects of trials. A wide variety of outcome measures were used. Outcome measures did not adequately represent the guidelines for impairment, activity and participation, and impairment measures were over‐represented at the expense of others. Despite the variety offered, exercise has a positive effect on CLBP patients, and results are largely maintained at follow‐up. Strengthening is a common component of exercise programmes, however, the role of exercise co‐interventions must not be overlooked. More high quality trials are needed to accurately assess the role of supervision and follow‐up, together with the use of more appropriate outcome measures.

Sensory stimulation (TENS): effects of parameter manipulation on mechanical pain thresholds in healthy human subjects

&NA; Transcutaneous electrical nerve stimulation (TENS) is a popular form of electrostimulation. Despite an extensive research base, there remains no consensus regarding the parameter selection required to achieve maximal hypoalgesic effects. The aim of this double blind, sham‐controlled study was to investigate the relative hypoalgesic effects of different TENS parameters (frequency, intensity and stimulation site) upon experimentally induced mechanical pain. Two hundred and forty participants were recruited in order to provide statistical analysis with 80% power at &agr;=0.05. Subjects were randomised to one of the six TENS groups, a control, and a sham TENS group (n=30, 15 males, 15 females, per group). TENS groups differed in their combinations of stimulation; frequency (4 or 110 Hz), intensity (‘to tolerance’ or ‘strong but comfortable’) and stimulation site (segmental–over the distribution of the radial nerve or, extrasegmental–over acupuncture point ‘gall bladder 34’, or a combination of both segmental and extrasegmental). Pulse duration was fixed at 200 &mgr;s. Stimulation was delivered for 30 min and subjects were then monitored for a further 30 min. Mechanical pain threshold (MPT) was measured using a pressure algometer and taken from the first dorsal interosseous muscle of the dominant hand, ipsilateral to the stimulation site. MPT measures were taken, at baseline, and at 10‐min intervals for 60 min. Difference scores were analysed using repeated measures and one‐way ANOVA and relevant post hoc tests. Low frequency, high intensity, extrasegmental stimulation produced a rapid onset hypoalgesic effect, which increased during the stimulation period (P<0.0005 control and sham) and was sustained for 30 min post‐stimulation (P<0.0005control, P=0.024sham). Whilst high frequency, ‘strong but comfortable’ intensity, segmental stimulation produced comparable hypoalgesic levels during stimulation, this effect was not sustained post‐stimulation. Stimulation at a combination of the two sites did not produce any greater hypoalgesic effects. These results may have implications for the clinical use of sensory stimulation.

Monochromatic Infrared Irradiation (890 nm): Effect of a Multisource Array upon Conduction in the Human Median Nerve

OBJECTIVEnAntidromic conduction studies in the human median nerve were used to assess the neurophysiological effects of irradiation of the skin overlying the nerve using a novel treatment unit comprising a multisource monochromatic infrared diode array (Equilight, Denver, CO).nnnMATERIALS AND METHODSnHealthy human volunteers (n = 40) were recruited and randomly allocated to one of four groups: control, placebo, or one of two treatment groups (1.7 and 4.0 J/cm2). After baseline recordings of negative peak latency (NPL) were completed on the nondominant arm, subjects were treated according to group allocation. Recordings were subsequently repeated at 5-min intervals over a 45-min period.nnnRESULTSnAnalysis of negative peak latency difference scores (ANOVA) demonstrated significant differences in NPL between groups and over time (p < 0.05). While in the control and placebo groups NPL values remained relatively stable, in the two treatment groups such values decreased marginally, with the greatest effects observed in the 4.0 J/cm2 group (e.g., at 5 min, differences in NPL [mean +/- SEM]: control group, 0.02+/-0.03 msec; treatment group 2, 4 J/cm2, -0.07+/-0.03 msec). Similar significant differences were observed in skin temperature; correlation analysis indicated a weak (but expected) positive linear relationship between skin temperature and nerve conduction velocity (r = 0.125).nnnCONCLUSIONnThese results suggest that irradiation at the parameters and under the conditions used here produce a direct neurophysiological effect. The magnitude of such effects are in keeping with previous findings using single source arrays at higher radiant exposures or thermal effects of the treatment unit.

Complementary and alternative medicine and rheumatology nurses: A survey of current use and perceptions

A questionnaire-based survey of rheumatology nurses was undertaken to investigate the use, and perceptions, of the effectiveness of complementary and alternative medicines (CAM) in the management of patients with rheumatic diseases (RD). A total of 192 rheumatology nurses (response rate 76.2%) completed the questionnaire, which included sections on qualifications and clinical experience, perceptions of, training in, and use of CAM in the management of RD patients. CAM was provided by 8.3% of respondents, principally aromatherapy, massage and reflexology. Furthermore, over half of respondents (51.6%) provided advice to patients about CAM, primarily to patients with rheumatoid arthritis (RA). Perceptions of the benefits of CAM are overwhelmingly positive: 89.8% of respondents considered it to have a role in the NHS. Current barriers to wider use of CAM include budgetary constraints in the health service, limited availability of published evidence, and the current lack of a clear and adequate regulatory framework for its practice.