G.D. Baxter

Delayed onset muscle soreness: effect of an ischaemic block upon mechanical allodynia in humans.

&NA; The current study, for which ethical approval was obtained, was designed to assess the extent to which the tenderness or mechanical allodynia observed in delayed onset muscle soreness (DOMS) might be mediated by large diameter myelinated nerve fibres. Healthy human volunteers were recruited and randomly allocated to one of three groups: Normal‐Control, Ischaemic‐Control, and Test‐DOMS (total n=21; n=7 in each group). In the Normal‐Control group, subjects attended on a single occasion for assessment of mechanical pain threshold (MPT) at standardized sites over the biceps brachii using a pressure algometer for a period of 20 min. In both remaining groups, ischaemia was induced in subjects non‐dominant upper limbs by elevation of the limb, followed by application of a sphygmomanometer cuff at a pressure of 250 mmHg. Throughout the period of the block (20–40 min), sharp/blunt sensation was assessed at regular intervals. MPT was assessed upon inflation of the cuff and reassessed at 10 min intervals until deflation. In the two ischaemic block groups, current level of pain was also monitored using a computerized visual analogue scale (VAS) at the beginning and end of the procedure. Subjects in the Test‐DOMS group attended 48 h prior to ischaemic block for induction of DOMS using a standardized regime of eccentric exercise, but thereafter were treated in exactly the same manner as the Ischaemic‐Control group. Results showed a significant (P<0.05; ANOVA) increase in MPT in the Test‐DOMS group by the 20 min point, corresponding to a ‘normalization’ of MPT; loss of the ability to distinguish between sharp/blunt sensation accompanied such changes. Parallel increases in reported pain were seen in both groups undergoing ischaemic block, indicating that the procedure did not alter nociception. While not definitive, these results suggest that altered processing of activity in large diameter (myelinated) afferents might underlie the mechanical allodynia observed in DOMS; thus, this is an area which warrants further investigation.

Lack of effect of pulsed low-intensity infrared (820 nm) laser irradiation on nerve conduction in the human superficial radial nerve

To investigate the effect of pulsed low‐intensity laser irradiation on nerve conduction in the human superficial radial nerve and on temperature in the skin overlying the nerve.

The lack of hypoalgesic efficacy of H-wave therapy on experimental ischaemic pain

&NA; The hypoalgesic effect of H‐wave therapy (HWT) at various frequencies (2–60 Hz) was assessed using a standardised form of the submaximal effort tourniquet technique (SETT). Healthy human volunteers (n = 112; 56 men, 56 women) were required to attend on two occasions; on the first, baseline pain scores were obtained and on the second, 48 h later, subjects were randomly assigned to control, placebo or 1 of 5 H‐wave treatment conditions. In the treatment groups 2 self‐adhesive electrodes were attached to the ipsilateral Erbs point and just lateral to the spinous processes of C6/C7. H‐wave stimulation commenced 10 min prior to pain induction and continued throughout the 12‐min duration of the technique. In the placebo group electrodes were attached as normal but leads were connected to a dummy power output. Analysis of variance of the differences in visual analogue scale and McGill Pain Questionnaire scores showed no significant differences in the treatment groups compared to placebo or controls. These results do not provide convincing evidence for any hypoalgesic effects of HWT at the frequency parameters stated on the experimental model of pain used.

Effect of acupuncture upon experimentally induced ischemic pain: a sham-controlled single-blind study.

OBJECTIVEnTo investigate the hypoalgesic effect of true and sham acupuncture upon experimentally induced ischemic pain.nnnDESIGNnHuman volunteers (n = 60) were required to attend two sessions for pain induction using a submaximal effort tourniquet technique; on the first occasion, baseline pain scores were recorded and on the second, 48 hours later, subjects were randomly allocated to one of five groups: Control, Treatment Groups 1 or 2, or Placebo Groups 1 or 2.nnnSUBJECTSnHealthy human volunteers.nnnINTERVENTIONnIn all the Treatment and Placebo Groups, subjects received some form of needle acupuncture 15 minutes before, and 5 minutes during, the pain induction procedure on the second day. Treatment Group 1 received acupuncture on acupuncture points situated distal to the tourniquet, whereas Treatment Group 2 received acupuncture on acupuncture points situated proximal to the tourniquet. In Placebo Groups 1 and 2, subjects received sham acupuncture either on nonacupuncture points (Placebo Group 1) or on acupuncture points (Placebo Group 2) using (standardized) minimal levels of stimulation. A licensed acupuncturist who was not involved in data collection and analyses carried out all treatments.nnnOUTCOME MEASURESnPain was assessed using a computerized visual analog scale (VAS) and a McGill Pain Questionnaire (MPQ).nnnRESULTSnAnalysis of VAS scores using ANOVA revealed no significant differences between groups (e.g., VAS sum of differences data (mean +/- SEM): Treatment Group 1: 90+/-47, Treatment Group 2: 187+/-56, Placebo Group 1: 152+/-40, Placebo Group 2: 121+/-42, CONTROLS: 46+/-24, p>0.05). Analysis of MPQ percentage difference scores using one-way ANOVA revealed some isolated effects in the subjective descriptors and the Pain Rating Index, both for Treatment Group 2 and Placebo Group 2, proving them superior to any of the other groups.nnnCONCLUSIONnThe results of the study provide no convincing evidence for a superior hypoalgesic effect of acupuncture compared with sham procedures on this model of experimental pain.