## 4 Discussion  
In this strength diagnosis, the EC and C phases of the resistance exercises BP and MP were compared. According to our data, the eccentric muscle action effectively contributed to enhancing peak RVD, peak RFD, power output (mean and peak), and 1 RM in BP, increasing acceleration without improving peak velocity during the concentric phase. In contrast, the pre-stretch preceding the concentric movement did not improve kinetic and kinematic performance in the MP. The positive effects observed in kinetic and kinematic variables in BP-EC are consistent with the results of other studies in which SSC and load effects were detected in strength, velocity, and power output during jump performance [10; 21]. Similar effects were noted in upper limb resistance exercises [11]. In this study, average velocity, average and peak force, and average and peak power output were significantly increased for the SSC bench throws compared to the concentric bench throws. The highest mean power output was produced at the 30% (563 W) and 45% (560 W) loads during the SSC bench throws [11]. However, mean power output was higher in this study compared to our results (~560 w vs. ~365 w, respectively). Probably, the type of exercise was a key factor in noticing these differences in power output [11]. This could be interpreted as upper limbs showing explosive movement characteristics similar to those of the lower limbs after a SSC (jumps). However, the different kinetic and kinematic response to MP observed here indicates a need for further studies designed to address the SSC in other traditional resistance exercises of the upper limbs. Figure 2: Movement velocity and power output data recorded in the military press (MP) and bench press (BP) tests. (**A**) Peak velocity. (**B**) Peak power output up to peak velocity. (**C**) Mean power output up to peak velocity. (**D**) Mean power output up to braking phase. Abbreviations: C = concentric; EC = eccentric–concentric. + Significantly different to BP-C, MP-EC, MP-C (\(p\leq 0.01\)). Y Significantly different to MP-EC, MP-C (\(p<0.001\)). Data are presented as mean of all loads lifted during the isinertial strength test. The trend of recent studies has been to examine the kinetic and kinematic behavior, including a pause between the eccentric and concentric phases, in order to minimize the contribution of the rebound effect [8; 9]. This would allow for more reproducible, consistent measurements during isoinertial strength tests [7]. However, we consider it is best to carry out the isoinertial strength test with or without countermovement depending on the specific movement patterns evaluated. A prolonged pause between eccentric and concentric muscle actions is not an usual resistance training practice, and it could diminish the ecological validity of the measures [22], especially if reliability is only minimally affected between EC vs. C phases. To our knowledge, this is the first study to examine RVD behavior in traditional resistance exercises under isoinertial strength test conditions comparing the EC vs. C phases. RVD is considered an important performance indicator [16; 17] for motor patterns or sport modalities in which body mass and/or the mass of an object need to be quickly displaced [18]. The presence of the SSC gave rise to a greater RVD in the BP but not in the MP. The behavior of acceleration up to peak velocity is critical to interpret the role of the RVD in resistance exercises. Certainly, peak velocity is a relevant factor reflecting performance in resistance exercises [18]. In our study, peak velocity was similar in all four exercise sequences examined, a finding in line with the results of a prior study [11], in which no peak velocity differences between EC vs. C actions were found. As an explanation for  
Figure 3: Acceleration data in the military press (MP) and bench press (BP) tests. (**A**) Peak acceleration. (**B**) Portion of the concentric phase (%) at which peak acceleration was detected.