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

There are 3 different groups receiving one of each treatment: 1. Percutaneous Electrical Stimulation (PES group). Subjects in the PES Group received the PES thecnique in the perineurium of the sciatic nerve. Specifically, this intervention consisted in the application of an asymmetric biphasic rectangular current of 150 microseconds and 10 Hz using a specifically developed medically certified device (Physio Invasive, Enraf Nonius, Prim, SPAIN). The subject lay prone with his feet outside the table. The sciatic nerve was located at 50% of the distance between the greater trochanter and interlinear articular knee by ultrasound machine (cross-section) (Logiq, GE Healthcare, USA) and then, a needle (0.30mm x 0.40mm) was inserted, perpendicular to the surface of the skin, until the perineurium of sciatic nerve. Prior to inserting a needle, the underlying skin was cleaned with isopropyl alcohol. The intensity of the current was necessary to cause an exacerbated muscle contraction, according to the Valera and Minaya protocol´s: once-off 1.5 mins session, current was applied every 4 times cycle for 20 s. The intervention will be performed in the department of Physicaltherapy in the University of Seville by a sports physiotherapist with an experience of more than 5 years. 2. Passive Stretching Technique. Subjects in the Stretching group received passive stretching of the hamstring muscles in their dominant leg. While lying supine, a researcher who was blinded to SLR test measures would passively position the subject into the SLR position (hip in flexion, knee in extension, and ankle in neutral) without pain/discomfort to the point where resistance to movement was first noted. This position was then maintained for 20 seconds and repeated further 4 times. During the 20 second stretches, the therapist monitored the subjects to ensure they did not make any compensation that could modify the stretching position. Each subject had a total of 1.5 minutes of stretching on their lower extremity. 3. Neurodynamic Sliding Technique. Subjects in the Neurodynamic group received sciatic neurodynamic sliders, performed in supine. The objective of the technique is to produce a sliding movement of neural (sciatic) structures relative to their adjacent tissues . Sliders involve the application of movement/stress to the nervous system proximally while releasing movement/stress distally and then reversing the sequence. Recent research has shown that sliders actually result in greater excursion than simply stretching the nerve. Subjects were supine with their neck and thoracic spine supported in a forward flexed position. Concurrent hip and knee flexion were alternated dynamically with concurrent hip and knee extension. The therapist alternated the combination of movement depending on the tissue resistance level. This combination of movements was performed for 1.5 minutes on their dominant lower extremity.