Understanding the limitations that are imposed by a disability is critical to ensure engineers develop designs that can be used by people with reduced function. Current literature lacks detail on this information for people with cervical spinal cord injuries. The purpose of this study was to investigate the reliability of a novel testing methodology to quantitatively assess the multi-directional upper limb strength of individuals in a seated position. Eleven non-disabled males and 10 males with a C4–C7 spinal cord injury completed isometric strength tests on parasagittal (XY) planes using a novel method. Multidirectional (XY) force measurements were taken at discrete points within the participant's reach envelope. Isometric force trends and analysis of the coefficients of variation were used to evaluate the novel methodology. The isometric force trends were consistent in showing a reduction in strength for people with higher injury levels. Analysis of the coefficient of variation showed that the methodology produces repeatable results with an average coefficient of variation of 18% and 19% for the right and left upper limbs, respectively. These results show that the novel testing methodology is a reliable way to gather quantitative multidirectional upper limb strength data for individuals in a seated position.