The hypoalgesic effect of transcutaneous electrical nerve stimulation (TENS) at 
2 different frequencies was assessed under double-blind conditions using a 
standardised form of the submaximum effort tourniquet technique. For the purpose 
of pain induction, 32 healthy naive female subjects attended on 2 occasions, the 
first during which baseline data were obtained and the second during which the 
women were randomly allocated to 1 of 4 groups: Control, Placebo, TENS-1 (110 
Hz) or TENS-2 (4 Hz). In the treatment groups, 2 hydrogel electrodes were 
positioned over Erb's point and lateral to C6 and C7 vertebral spines. A TENS 
machine was applied for 10 min before the cuff was inflated and remained on for 
the duration of the pain procedure (12 min). Pain was measured using visual 
analogue scales (VAS) and the McGill Pain Questionnaire (MPQ) to assess 'current 
pain intensity' and 'worst pain experienced', respectively. Analysis of VAS 
scores showed significant differences between groups (ANOVA, P = 0.02), with the 
TENS-2 group showing a greater hypoalgesic effect than the other groups. 
One-factor ANOVA showed no significant differences in MPQ scores between groups. 
The results of this study have provided evidence of the hypoalgesic effects of 
TENS upon experimental ischaemic pain which were found to be frequency specific 
with the lower frequency used here (4 Hz) demonstrating the only significant 
effect.