Author(s): MARTÍN-RUIZ, J., RUIZ-SANCHIS, L., TAMARIT-GRANCHA, I., GALLEGO-CERVERÓ, C., GARCÍA-SOTTILE, E., AGUILAR-PRIMA, A., ROS-ROS, C., Institution: CATHOLIC UNIVERSITY OF VALENCIA SAN VICENTE MÁRTIR, Country: SPAIN, Abstract-ID: 182

INTRODUCTION:
Vertical jump tests are widely used to monitor neuromuscular performance and stretch–shortening cycle (SSC) function in sport. However, field-derived drop jump metrics such as contact time and reactive strength index (RSI) may show substantial within-athlete variability, complicating interpretation and athlete profiling. This study aimed to describe jump performance in university athletes using SJ, CMJ, ABK and drop jump outcomes, to compare men and women, and to evaluate between-trial reliability and multivariate performance profiles. By combining traditional jump heights with SSC-related indices, we sought to provide evidence for practical monitoring while highlighting measurement constraints typical of field testing.
METHODS:
A cross-sectional observational study was conducted in 29 university athletes (8 women, 21 men). Anthropometrics (stature, body mass, segment lengths) and vertical jump performance were assessed using squat jump (SJ), countermovement jump (CMJ), Abalakov jump (ABK) and drop jump (DJ), with three trials per condition. From DJ trials, contact time, flight time and reactive strength index (RSI = flight/contact) were derived, together with an elastic index ((CMJ−SJ)/SJ). Between-trial reliability was quantified using ICC(3,1). Sex comparisons used Welch’s t-test or Wilcoxon rank-sum depending on distributional assumptions, reporting effect sizes (Cohen’s d or rank-biserial r) and FDR adjustment. Principal component analysis (PCA) on z-scored variables and k-means clustering were applied to identify jump-performance profiles. Normality was screened using Shapiro–Wilk tests within sex groups; test selection followed this rule. Effect sizes were interpreted using conventional thresholds, and significance was set at α=0.05.
RESULTS:
No missing data were observed for the main outcomes. DJ reliability was poor for contact time (ICC(3,1) ≈ −0.01) and RSI (≈ 0.00), and moderate for flight time (≈ 0.49), indicating high within-athlete variability for reactive metrics in this testing context. In sex comparisons, ABK height differed markedly (Welch’s t-test p ≈ 0.00016, Cohen’s d ≈ 1.75; FDR-adjusted p ≈ 0.00080). CMJ was significant before correction (p ≈ 0.024, d ≈ 1.04) but did not remain significant after FDR (p_FDR ≈ 0.059). SJ height, mean RSI and elastic index showed no meaningful sex differences. PCA and clustering separated two groups, one characterized by larger SSC gain (CMJ−SJ) and higher elastic index, and another more heterogeneous profile.
CONCLUSION:
Multivariate jump profiling distinguished performance patterns; however, the very low reliability of DJ-based RSI and contact time limits their use for athlete classification or monitoring small changes unless testing and technique control are improved. The clearest sex-related difference emerged in ABK performance, suggesting a relevant contribution of coordination/arm swing to maximal jump height in this sample.