IMMEDIATE ANALGESIC EFFECT OF 4KHZ AMFS INTERFERENTIAL CURRENT ON CHRONIC LOW BACK PAIN

ABSTRACT Objective: To analyze the immediate effect of amplitude modulation frequencies (AMFs) of 4kHz interferential current (IFC) on chronic low back pain (CLBP). Method: This is a randomized controlled clinical trial. Sixty-three subjects with CLBP were recruited. The subjects were randomized into 3 groups: the placebo group (PG, n=21) and 2 intervention groups (IG), IG4kHz/2Hz (n=21) and IG4kHz/100Hz (n=21). All groups were submitted to a single session of 30 minutes. Pain was evaluated using a numerical rating scale (NRS), the McGill Pain Questionnaire (MPQ), and pressure algometry. Flexibility was evaluated using the Modified Schober Test (MST), the Sit-and-Reach Test (SRT), the Fingertip-to-Floor Test (FTF), and the Passive Straight-Leg Raise Test (PSLR). Results: Comparing IG4kHz/100Hz with PG, we found a significant difference (p<0.05) in NRS in the total and in the MPQ categories, whereas in the comparison between IG4kHz/2Hz and PG, we found a significant difference only in the sensory and evaluative categories of MPQ. Regarding the flexibility tests, we observed a significant difference of both IG4kHz/100Hz and IG4kHz/2Hz in comparison to PG in MST and PSLR, and of IG4kHz/2Hz in comparison to PG in SRT. The 4kHz IFC was effective in immediately reducing CLBP and, consequently, in increasing the flexibility of the lumbar spine and lower limbs. Conclusion: Conclusion: There was a greater number of significant positive outcomes when the 100Hz AMF was adopted. Level of Evidence I; High quality randomized clinical trial with or without statistically significant differences, but with narrow confidence intervals.