DISCUSSION
According to the results presented, TENS and IFC produced significant effects in relation to pain intensity reduction, disability improvement and reduction in medication consumption. These results did not occur in the control group. Although 13 patients (8.66%) did not finish the study, this small number of losses was not enough to influence the significant results of this clinical trial.
It is difficult to achieve complete masking of patients in physiotherapy investigations, since there are differences between visual sensory and alternative treatments.28 We chose not to apply switched-off electrical equipment to the control group in this study, given that all three groups investigated received guidance relating to ergonomic spinal care.
Some previous studies observed the effects of TENS in relation to IFC in situations of experimentally induced pain.29-36 Johnson et al.29 and Cramp et al.30 did not find significant differences in pain intensity among healthy people subjected to both types of electric current. Similar results were found by Johnson and Tabasam33 and Cheing and Hui-Chan,35 with IFC showing a slight advantage over TENS in some ways. Although these previous results were not similar to those of the present study, it was not possible to make direct comparisons between the previous and present results because of the different methodologies used in the research.
To investigate TENS in low back pain patients, Melzack et al.7 carried out a randomized clinical trial comparing its effects with the effects from massage, in cases of chronic or acute low back pain. From the McGill Pain Questionnaire (MPQ), the TENS group was found to present a reduction in PRI of 69.5%, a reduction in PPI of 80.8%, a range of movement improvement and a reduction in pain intensity (VAS) of 84%. The effectiveness of the interventions, as determined by the patients’ percentage improvement, was 38% in the massage group and 85% in the TENS group. There was no statistically significant difference between the groups.
Marchand et al.9 randomized 48 patients with chronic low back pain into three groups (TENS, placebo and control). Comparing TENS and placebo, they found a 43% reduction in pain intensity in the TENS group and 17% in the placebo group. However, the methodology of their study can be criticized because it included patients with different diseases, such as ankylosing