## 5 Conclusions  
The aim of this study was (1) to explore the main phases of the BP exercise considering barbell acceleration and power; (2) to describe the maximum and mean velocity and acceleration in principal phases and the maximum and mean mechanical power and mechanical work of the barbell at different load intensities; and (3) to analyse whether there are differences in kinematics and mechanical parameters depending on load intensities. Thus, we hypothesised that (1) the BP exercise would consist of four different phases considering barbell acceleration and power; (2) the mean/maximum velocity/acceleration/power would decrease as the load increases, while mechanical work would increase; and (3) there would be significant differences in kinematics and mechanical parameters depending on load intensities. The results confirm the first hypothesis, as the BP exercise was found to consist of four distinct phases defined by barbell acceleration and power. The second hypothesis was partially supported, as the mean and maximum velocity, acceleration and power decreased with increasing load, aligning with the hypothesis; however, mechanical work did not consistently increase across all intensities, particularly in the eccentric phase at intermediate and high loads. Finally, the third hypothesis was also confirmed, as significant differences were observed in kinematic and mechanical parameters across varying load intensities, except for mechanical work in specific load ranges, which showed no significant differences. Regarding the contributions and novelty of the present study, it represents a significant advancement in the biomechanical analysis of the bench press (BP) by introducing the characterisation of movement into four well-defined phases based on barbell acceleration. This approach surpasses previous methodologies, which typically focus on analysing the concentric and eccentric phases as a whole, offering a more detailed and nuanced description of the exercise dynamics. In this sense, the study identifies an initial descending acceleration phase (phase 1), an eccentric braking phase (phase 2), a concentric acceleration phase (phase 3) and a final ascending deceleration phase (phase 4), highlighting phases 2 and 3 as the key moments where active muscle action is most relevant, making them critical for performance and training adaptation. This analysis not only provides a deeper understanding of the motor patterns involved in BP but also allows for a more precise assessment of the muscular and mechanical contributions at each stage of the lift. From a methodological perspective, the use of the Xsens MVN Link system in this study represents a significant advancement. This system has proven to be a robust tool for the detailed analysis of movement phases, overcoming the limitations of traditional methods such as photogrammetry systems and linear transducers. By comprehensively characterising movement phases through high-resolution kinematic and mechanical parameters, this study establishes a foundation for future research, enabling greater precision in performance assessment and a deeper understanding of movement patterns. This approach facilitates detailed analyses of body segment and joint dynamics, as well as muscle electrical activity and muscular synergies. Furthermore, this methodology is not limited to the bench press but can also be extended to other strength exercises, contributing to the evolution of applied biomechanics in fitness. Conceptualization, M.R., K.G. and J.P.-G.; methodology, M.R. and J.M.F.-G.; formal analysis, J.C.-V. and A.P.G. ; investigation, M.R., A.P.G. and G.C.S. ; resources, J.M.F.-G. and G.C.S. ; writing--original draft preparation, J.M.F.-G. and M.R. ; writing--review and editing, M.R., J.P.-G., K.G. and F.G.-M.S.J. ; supervision, J.P.-G., K.G. and F.G.-M.S.J. All authors have read and agreed to the published version of the manuscript. This study was supported by the Spanish Ministry of Education, Culture and Sport through a collaboration grant awarded to JMFG.