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 verti-cal 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.