The aim of this study is to analyse the effects of inclined stop-step training on kinematic variables as well as performance metrics in diagonal high spike at volleyball. Fourteen young male volleyball players were gathered, and a nine-week specialized training program was applied to an experimental group while the control group continued to undergo traditional training, using an experimental research design. We assessed changes in jump height, ball velocity, spike accuracy, and joint kinematics using high-speed motion analysis and statistical comparisons. The data showed that players in the experimental group improved jump height (p = 0.002), ball contact height (p = 0.003), ball velocity (p = 0.032), and spike accuracy (p = 0.028) compared to players in the control group. The results validated that changing stop-step mechanics improves force application, energy transfer, and spike execution. However, the results also indicated that some upper-body kinematic variables, including shoulder and elbow joint angles, did not exhibit remarkable improvement in performance, implying that some other upper-body coordination drills might be implemented for improving spiking mechanics. Data-driven biomechanical training interventions are evidently of utmost importance to physical training, and this article may be useful for sports scientists and volleyball coaches seeking novel insights into the mechanics of competitive play. Future studies need to investigate the long-term changes, inter-participant differences in biomechanics, and the involvement of EMG for improving volleyball training even more.