Effects of Eccentric Pre-loading on Concentric Vertical Jump Performance in Young Female Athletes

Purpose: This study examined changes in vertical jump performance with progressively greater eccentric pre-loading in relation to growth and development in young female athletes. Methods: Twenty young female athletes ranging from 9 to 17 years old performed the following vertical jumps in random order: static jumps (SJs), counter-movement jumps (CMJs), and drop jumps (DJs) from drop heights of 20, 30, and 40 cm (DJ20, DJ30, and DJ40, respectively). Measurements included peak force (PF), peak rate of force development (RFD), peak power (PP), eccentric impulse (ECC), and concentric impulse (CON). Measurements of growth included age, maturity offset, height, body mass, fat-free mass, and thigh muscle cross-sectional area (CSA). Results: PF increased from the SJ-DJ20 (P ≤ 0.009), then plateaued from DJ20-DJ40 (P = 1.000). RFD remained the same from SJ-CMJ (P = 1.000), increased from CMJ-DJ20 (P < 0.001), and plateaued from DJ20-DJ40 (P = 0.874). PP increased from the SJ-CMJ (P < 0.001), then plateaued from the CMJ-DJ40 (P ≥ 0.486). CON remained the same across all vertical jumps (P = 1.000), while ECC increased from the SJ-DJ40 (P ≤ 0.038). Jump height (JH) increased from the SJ-CMJ (P < 0.001), decreased from CMJ-DJ20 (P < 0.001), and plateaued from DJ20-DJ40 (P = 1.000). The change in PP from the SJ-CMJ (ΔCMJ-SJ) was related to all measurements of growth except CSA (r = 0.558–0.815). Conclusion: Young females produced greater power during the CMJ than SJ, but equivalent power from the CMJ-DJ40, despite increases in ECC. Additionally, ΔCMJ-SJ was not related to CSA, which suggests other underlying mechanisms affect stretch–shortening cycle utilization in young female athletes.