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

Abstract

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.

Influences of the Stretch-Shortening Cycle and Arm Swing on Vertical Jump Performance in Children and Adolescents

“…Ground reaction forces during all vertical jumps were collected using 2 force plates (PASCO PS-2142, PASCO Scientific, Roseville, CA) seated in a custom platform. To perform the SJ, subjects began with their feet in the middle of each force plate and their knees and hips flexed into a static squat position with a knee angle of 90° (11,12,24,25). From this position, subjects performed a maximal vertical jump without a countermovement.…”

“…The results of the present study extend previous findings by demonstrating that the CMJA exhibited less eccentric preloading than the CMJ during the counter-movement phase of the vertical jump in children and adolescents. Since previous studies have hypothesized that children have limited skeletal musculature to absorb and reapply large eccentric forces (1,12,21,29,39,40), using a vertical jump technique that minimizes ECC while maximizing power production may be optimal for vertical jump performance during growth and development.…”

“…Perhaps the most popular vertical jump test is the countermovement jump (CMJ), which involves a downward, eccentric movement followed by a maximal vertical jump. Other techniques, such as the static jump (SJ), which deliberately restricts the eccentric movement, have been studied to understand the stretchshortening cycle (SSC) contributions to vertical jump performance in children (1,12,17,21,25,39), although this has been debated (24). In fact, in young boys and girls, previous studies have shown that vertical jump performance is greater during the CMJ than the SJ because of increased use of the SSC, which augments force and power output during the concentric phase (1,12,17,21,25,39).…”

“…Previous studies comparing the SJ and CMJ in children have typically restricted the use of the arms by requiring subjects to keep their hands on their hips (1,12,17,21,25,39). However, several studies in adults have suggested that using an arm swing during the CMJ (CMJA) may increase vertical jump performance beyond the CMJ due to biomechanical augmentations during the eccentric and concentric phases (7,15,16,18,22,34,43).…”

Editorial

“…Kelly et al also show that higher ranked players display superior decision-making and perceptual-cognitive skills, reinforcing the need for a multidisciplinary approach to talent development [4]. For practitioners wanting to use jump training with young female athletes, Gillen et al examine a number of jump conditions to describe the influence of eccentric pre-loading on kinetic outcomes while also examining the influence of size and maturity [3].…”