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Tuning materials properties by various stimuli remains at the forefront of research because it can generate novel phenomena and enhance functionality of future electronic devices. Of particular interest are transition metal oxides (TMO) whose transport properties can be tuned by an applied electric field. For example, a reversible resistive switching induced by an electric bias was previously demonstrated in 5d [1] and 4d [2] TMOs with potential applications in resistive and magnetic random access memories (Re-RAM and MRAM). The switching was tentatively attributed to electric-field driven lattice distortions. Here we study the resistive switching in single crystals of 3d TMO La₂NiO₄ and use an ultra-high precision capacitive displacement gauge to probe the distortions. We observe a clear correlation between the displacement gauge signal and sample resistance. Our results provide unequivocal evidence that the resistive switching is related to structural distortions induced by electric fields. [1] C. Wang et al. Phys. Rev. B 92, 115136 (2015); H. Seinige et al. ibid 94, 214434 (2016). [2] S. Shen et al. http://meetings.aps.org/link/BAPS.2017.MAR.E43.11