Background: One treatment of Muscle trigger points (MTrPs) is deep dry needling (DN) with the purpose of obtaining local twitch responses (LTRs), which are highly effective in releasing MTrPs. In DN procedures the mechanisms associated with LTRs and the LTR intensities required for optimal clinical results are poorly understood, especially in relation to range of motion after intervention. Therefore, evaluating the intensity of LTRs is relevant for implementing DN in different clinical settings, such as in patients with muscular or neurological dysfunctions. One way to assess muscle contractions and LTRs is through ultrasound video analysis.