## 4 Discussion
[17] partly supported this explanation, as they observed an increase in the negative work in all three joints after landing from higher heights (from 0.30 to 1.20 m). Herein, landing from greater heights necessitates forceful eccentric muscle actions of the lower limb muscles to attenuate the larger inertial force impacted on the body [13; 14; 16; 17][PERSON] The significantly larger negative knee joint work in CMRJ2 suggested a potential increase in elastic strain energy stored in the tendons, which in turn may have contributed to a significantly larger positive knee joint work by -0.40 J/kg compared to DJ (\(p\leq 0.034\), \(g\leq 0.54\)) [10; 23][PERSON] This finding [PERSON] closely with [PERSON] and [PERSON] [16], who reported higher positive work in all three joints when landing from 0.60 m than from 0.40 m. No significant differences in jump height were observed between the DJ and CMRJ2 (\(p\geq 0.812\)), whilst the GCT was slightly longer in CMRJ2 than in DJ) by 0.03 s (\(p\leq 0.324\), \(g\leq-0.24\)). A large contribution of the ankle joint to the total positive work has been shown to be associated with a shorter GCT [13; 39]. Similarly, in our study, the ankle joint contributed to 43% of the total positive work in DJ, and this value was significantly lower in CMRJ2 (\(p\leq 0.048\), \(g\leq 0.53\)). These disparities in GCT and ankle joint contribution between DJ and CMRJ2 suggest that participants may have used their ankle joints differently due to variations in drop heights and eccentric loads between the two jump types. Thus, our second hypothesis was partially confirmed, where the CMRJ2 test largely mimics the characteristics of the DJ test and provides practitioners with similar joint work and joint contribution percentages. Differences in the jump strategies might result in variations in the joint work and joint contribution to the total work performed between the three jump tests. Concurrently focusing on more than two verbal cues during the CMRJ may add more challenge to participants than during the CMJ and DJ tests, and potentially may have been a greater learning effect for CMRJ compared to the other two tests. Furthermore, no familiarization session was involved in this study; instead, participants had only five minutes to familiarize themselves with the CMRJ in each session. Therefore, it seems plausible to suggest that as challenges increased (in the CMRJ), participants were likely to utilize a range of different jump strategies to achieve comparable movement outcomes to the CMJ and DJ tests. Given that only some metrics show significant differences across the three different jump types, and the contributions of the lower limb joints to total negative and positive work remained consistent between three jump actions (see Figure 2). Therefore, practitioners can confidently utilize the CMRJ as a viable alternative to CMJ and DJ tests, with the exception of the hip joint work and contributions that showed questionable reliability (CV \(\leq\) 20.95%). Some limitations of this study should be acknowledged. Firstly, the inverse dynamic method cannot determine individual muscle activity. For instance, if a relatively large positive knee joint work was found during jump actions, it is unknown whether this increase occurs due to the increased activity of the knee extensor or knee flexor muscles. Secondly, large SD values for the measured variables indicated the variability of foot stiffness and jump performance amongst the participants. In cases where participants exhibited weak foot stiffness, it was likely that kinetic energy had been lost as heat, leading to an underestimation of the calculated ankle joint work [23]. Consequently, this inter-subject variation indicated that the strategies at the ankle joint are abundant and more varied from trial to trial and ultimately result in different percentages of the ankle joint contributions to the total work performed compared to the previous literature [14; 17].