Assessment of nerve trunk mechanosensitivity using the upper limb neurodynamic test 1 (ULNT1) often includes measurement of the angle of occurrence in the range of pain onset (PO) and submaximal pain (SP). A measurement that better fits the idea of mechanosensitivity could be the angle between PO and SP (AbOS). This study investigated the intra- and intersession reliability of AbOS, PO, and SP during the ULNT1. Forty-four healthy volunteers underwent three ULNT1 to the point of PO and SP, twice in the first session and once in the second. AbOS, PO, and SP angles of occurrence reliability were examined using the Intraclass Correlation Coefficient (ICC 3,1) and Bland-Altman plots. The intra- and intersession ICC values for AbOS were 0.71 (95% CI: 0.47; 0.85) and 0.79 (95% CI: 0.60; 0.89), respectively. The intra- and intersession mean difference and 95% limits of agreement (±1.96 SD) in the Bland-Altman plots were 2.3° (-18.3°; 23.1°) and 2.8° (-14.7°; 20.4°), respectively. The intra- and intersession reliability of the AbOS during the ULNT1 in healthy individuals is high and higher than the reliability of PO and SP angles of occurrence. The AbOS could be a preferable variable in the assessment of neural mechanosensitivity.