## 4 Discussion
[10] and [PERSON] and [PERSON] [11] argued that they observed a slightly higher percentage of hip contribution (32.14 \(\pm\) 8.68% and 28%) than ankle contribution (26.44 \(\pm\) 4.85% and 23%) to the total positive work. In contrast, the present study found that the ankle joint contributed to \(\sim\)36% of the total positive work, which is higher than that of the hip joint (\(\sim\)17%) in both CMJ and CMRJ1. The discrepancy between the current investigation and the previous literature is likely because the arm swing was restricted, where participants performed all jumps with an upright trunk position. That said, vertical jumps with arm swing have been shown to induce greater trunk extension from forward inclination and exhibit greater angular velocity during hip joint extension in the propulsive phase, ultimately increasing the positive hip contribution [12; 37]. Regarding the variables between jumps, the results partially support our second hypothesis, where significantly higher negative hip and knee joint work (\(p\leq 0.035\), \(g\leq 0.62\)) were observed in CMJ compared to CMRJ1 (Figure 3). It seems participants utilized different jump strategies during the CMJ via slightly deeper CM depth (\(p\leq 0.304\), \(g\leq 0.32\)) and significantly longer TTTO (\(p\leq 0.027\), \(g\leq 0.62\)) to maximize their jump heights. It has previously been suggested that initiating the propulsive phase from different knee flexion angles (i.e., different CM depth) would generate significantly different positive kinetic variables [38]. In further support of this, this study found significantly higher positive work in hip joint in the CMJ (\(p\leq 0.029\), \(g\leq 0.54\)) during both sessions. Noting that although some of the joint work or strategy-based metrics were significantly different between CMJ and CMRJ1, jump height and individual joint contribution to the total work were not (\(p\geq 0.115\), \(g\leq 0.37\)), and the knee joint still acted as the primary contributor across both jumps. Thus, when arm swing was inhibited during our methods, participants consistently adopted knee and hip dominant strategies to attenuate the negative work while adopting knee and ankle dominant strategies to generate the positive work (see Figure 2). When comparing the DJ and CMRJ2, our results aligned with the previous studies [13; 15; 23], where the knee joint contributed the biggest amount of total negative and positive work, followed by the ankle and hip joints during both tests, as shown in Figure 2. However, authors in two studies argued that the biggest contributor to the total work was the ankle joint (45% to 51%), followed by the knee (30% to 37%) and hip (11% to 20%) joints [14; 17]. A possible reason is that participants in this study were physically active students who lacked extensive jump training experience, while the previous two investigations recruited male handball players [14] and male jumpers [17] who were likely to be more familiar with fast SSC-based plyometrics. Additionally, the GCT values measured in the DJ and CMRJ2 were longer than 0.25 s, making it hard to suggest that fast SSC mechanics were truly evident. Therefore, it is unlikely that participants with minimal jump-specific training employed the same jump strategies or joint dominance as those who are more familiar with the task [16], which likely explains why contradictions appeared between our findings and the previous literature. In terms of the variables between jump types, significantly higher negative knee work was observed in CMRJ2 by \(\sim\)0.54 J/kg (\(p=0.005\), \(g\leq 0.71\)) in session 1 and \(\sim\)0.54 J/kg(\(p=0.005\), \(g\leq 0.64\)) in session 2 (Figure 4). This might be because the actual drop heights differed between the two jumps, where the DJ had a fixed drop height of 0.30 m, and the CMRJ2 utilized the jump height in CMRJ1 as the drop height, which occasionally exceeded 0.30 m. [PERSON] et al.