## 1 Introduction  
Multiple hops and jumps, specifically triple (3-Hop) and quintuple hops (5-Hop), have been found to be valid and reliable tools for evaluating athletes' physical capabilities [1, 2, 3, 4, 5]. Moreover, these types of hop and stop tests are considered suitable for late-stage rehabilitation assessment and for improving athletic performance, such as sprinting, as their execution requires high neuromuscular demands, and in turn necessitates a significant tolerance for stretch load through cyclical expressions of unilateral propulsive and braking forces [6]. Four research groups [7, 8, 9, 10] have examined the relationship between 3-Hop distance and short (10-20 m) sprint performances (times and velocities), with some variability observed between these studies (\(r=0.33\) to \(-0.89\)). A very large negative correlation (\(r=-0.86\)) between 3-Hop distance and 20 m sprint time was reported in recreationallyengaged male sports athletes [8], and strong correlations (\(r=0.68\)) with 10-yard sprint time, again in a cohort of mixed sub-elite level male athletes [10]. [PERSON] et al. observed similarly high correlations (\(r=0.89\)) for sub-elite male sprinters with 10 m block starts [7]; however, a previous identical study found weak correlations (\(r=0.24\) to 0.33) in an elite group of male sprinters [9]. Due to this variation, [PERSON] et al. (2006) [9] suggested that horizontal jump measures might be more effective for predicting sprint performance in athletes participating in sports requiring a variety of sprint running expressions but may not be valid for competitive level sprinters. They also considered that multiple jump measures, such as force and power, might better represent the dynamics of sprint running compared to jump distance alone. Nevertheless, given the relationship between jump distance and sprint performance, it can be hypothesized that the strength qualities required for achieving greater hop distances may also confer benefits to sprinting ability. In addition to those investigating the relationship between 3-Hop tests and sprint performance, a 5-step jump test was reported to have very large negative correlations (\(r=-0.81\)) to 40 m sprint time [11] in a cohort of male sub-elite sports athletes. In the sprint training literature [6; 12] the 5-Hop test has been used extensively to determine readiness for competition and, therefore, is also worthy of further investigation to determine the relationship between 3-Hop and sprint performance, and additionally whether the 5-Hop test is a stronger predictor of sprint performance. Moreover, as [PERSON] et al. (2006) [9] suggested, it would be useful for a deterministic purpose, i.e., to quantify this relationship, to use kinetic measures (force or power) rather than just distance hopped. Reactive strength, the ability to efficiently couple eccentric-concentric contractions [the stretch-shorten cycle (SSC)] is a metric that has garnered considerable attention. It is thought to be a fundamental determinant of many athletic qualities [13] and has shown to be highly correlated with vertical leg-spring stiffness [14]. This strength quality is typically represented as a strength index (RSI), measured by the ratio between jump height and contact time in a drop jump [15] or by the ratio between jump height and time to take off (RSI\({}_{\text{mod}}\)) in the countermovement jump [16], or the ratio of flight time to ground contact time [17], and it is sometimes referred to as the reactive strength ratio [18; 19]. Given the principle of specificity, it may make sense to calculate the RSI parallel to the principal line of movement when explicitly calculating a horizontal reactive strength index (RSI\({}_{\text{hor}}\)) for sprinting performance. [PERSON] et al. (2021) [20] examined whether such a measure (the ratio between flight and contact time) was reliable using a 3-Hop test. The between-session coefficients of variation were less than 5.5%, and the intraclass correlation coefficients greater than 0.70 across hops. [PERSON] et al.