Crossover effects of ultrasound-guided percutaneous neuromodulation on contralateral hamstring flexibility.

Background: Crossover effects refer to the responses of a non-exercised contralateral limb. There is evidence of this effect, as it relates to muscle fatigue, strength, and stretch, but not as it relates to neuromodulation.

Objectives: To compare the crossover effects of percutaneous neuromodulation (PNM) on hip range of motion (ROM), observed in a straight leg raise (SLR) test, in asymptomatic participants with bilateral reduced hamstring flexibility, versus the neurodynamic sciatic sliding technique, hamstring stretching and mechanical stimulation of the sciatic nerve using a needle (without electrical stimulation). To evaluate the tensiomyographic changes between the two lower limbs after these interventions.

Methods: 80 participants with bilateral reduced hamstring flexibility were randomized into four groups: Stretching, Neurodynamic, PNM, and Needle groups. All interventions were performed on the right limb. Each participant's leg was subjected to SLR testing and tensiomyography before and after the interventions.

Results: Each group improved their SLR values in the non-intervention limb compared to baseline values, but the PNM and Needle groups obtained higher values for the SLR test in the non-intervention limb compared with the Neurodynamic and Stretching groups. There were statistically significant differences for mean SLR measures between limbs pre- and post-intervention for all groups except the PNM group, suggesting crossover effects for PNM but not the other techniques studied. There were no differences in tensiomyographic assessments between groups or between sides, at baseline or upon completion of the study.

Conclusion: PNM produced benefits in the SLR test in the non-intervention limb and only 1.5 min was enough to obtain this effect. In addition, no technique interfered with muscle activation.