BACKGROUND & OBJECTIVE
To the authors knowledge, in vivo studies on the mechanical properties of nerves in humans have never been confirmed. Nerves have the ability to elongate when submitted to a load. Shear wave elastography can infer information regarding this elongation/stiffness reliably. However, it is unclear how neural stiffness changes by performing neurodynamic techniques. This study aimed to determine, in vivo, the immediate effects on stiffness of the sciatic nerve after applying tension in the slump position using shear wave elastography. The authors hypothesized this would induce an immediate decrease of the sciatic nerve stiffness of healthy subjects.
Fourteen participants without disorders of the lower limb or back were included. Pre and post tests were performed in prone using a dynamometer with maximal passive ankle dorsiflexion ROM determined. Then shear wave velocity of the sciatic nerve and the ankle torque-angle were assessed. Next, the slump test was performed to the experimental limb, while the control limb stayed relaxed. The knee was passively extended, and the ankle was maximally dorsiflexed, until the point of stretching discomfort. This position was statically maintained for 3 minutes. Immediately after the slump protocol, subjects were re-positioned in prone for post testing.
During all the tests, only a 1.5% ± 1.1%, 2.0% ± 0.9%, and 2.8% ± 1.3% muscle activation was observed for the semitendinosus, medial gastrocnemius, and tibialis anterior muscles, respectively. In respect to the sciatic shear wave velocity, no effects