Combined effects of transcutaneous electrical nerve stimulation and stretching

Abstract

Background: Transcutaneous Electrical Nerve Stimulation (TENS) has an influence on the pain inhibitory mechanism. TENS is believed to influence pain threshold levels via gate control theory, endogenous anesthesia theory, and local nerve block. Although TENS is reported to be effective when used in combination with other therapeutic exercises, the combined effects are still conflicted. Purpose: The purpose of this study is to clarify the effects of TENS in combination with stretching on pressure pain threshold (PPT), muscle hardness (MH) and range of motion (ROM) of straight leg raising (SLR) in healthy individuals. Methods: 11 healthy males (age 18–26 years old, height 168.8± 4.7 cm, weight 67.8± 13.7 kg) with no self-reported musculoskeletal disorders and neurological symptoms volunteered to participate in this study. An inclusive criterion is that the ROM of SLR is less than 70 degrees. Subjectswere randomly assigned and all participated in all of the three groups; stretching exercise (S group), TENS treatment followed by stretching (TS group), and simultaneously combined TENS and stretching (CTS group). Prior to experiment, subjects had a 10minute rested for all protocols. S group performed a stretching exercise and the exercise was done at 90% of maximum SLR range for 30 seconds followed by 30 second rest, and repeated 10 times for 10minutes. In the TS group, the stretching was done just after TENS (biphasic symmetry pulse, pulse width 200 s, frequency 100Hz, 80% of pain threshold) was applied over the medial hamstrings for 20minutes. The protocol for the CTS group was 20minutes of applied TENS, with the final 10minutes combined with the stretching exercise. Three evaluations were used for analysis; PPT, MH and range of SLR. The data were collected before TENS (T1), before stretching (T2), and for immediately after stretching and 10minutes post-stretching (T3 and T4 respectively). Results: TS and CTS groups showed significant difference inPPT,MHand rangeofSLRatT2,T3 andT4compared to T1 (p< 0.01). Regarding a comparison of S group (a difference between T2-3), and TS or CTS groups (a difference between T1-3), all PPT, MH and range of SLR in TS and CTS groups had a significant effect compared to S group (p< 0.01). Conclusion(s): These results support the use of TENS in combination with stretching, i.e. stretching after TENS or stretching during TENS, to reduce pain and increase muscle flexibility, and thus increase the joint range of motion. Since CTS group had the same effect with T S group, the TS protocol would be more time efficient while maintaining the effects of TENS. Implications: Further research is required to determine if TENS is beneficial to older and less physically able patients. For young physically unimpaired subjects the benefits are clear.