Phuong T.M. Quach, Richard Preus, Bethany A. Moore, Gary Hunter, FACSM, Patricia Perez, Harshvardhan Singh. University of Alabama at Birmingham, Birmingham, AL.

BACKGROUND: Stretch shortening cycle (SSC) potentiation is critical for greater sports performance. During jump test, a quick countermovement-initiated jump (CMJ) or drop jump (DJ) (jump preceded by a drop off from a height) is compared with a jump where a static squat of 2-3 seconds is maintained before the jump occurs (SJ). It is unknown if scaling of jump height (JHt) with increasing level of SSC potentiation is achieved by differential lower extremity joint-specific strategy. Thus, we examined the relationships of JHt potentiation with lower extremity joint-specific potentiation of a) extensor moment and b) propulsive power. METHODS: We used a rigid body model, using 36 reflective markers, and floor-embedded force plates to collect jump data in typically developing children (n = 20; age = 8 - 14 years). After familiarization, participants performed 3 trials of 3 jump types: CMJ, SJ, and DJ. JHt was calculated from the greater trochanter marker data. JHt, and joint-specific extensor moment and propulsive power potentiation were calculated as the ratio of a) DJ/CMJ, b) CMJ/SJ, and c) DJ/SJ at the hip, knee, and ankle. Scaling relationship was examined via spearman correlation coefficients between increasing level of SSC potentiation conditions and a) JHt and b) joint-specific potentiation of extensor moment and propulsive power. RESULTS: Positive scaling of potentiation of JHt (r= 0.629; p < 0.001), hip moment (r = 0.437; p = 0.001) and hip power (r = 0.495; p < 0.001) and a negative scaling of potentiation of knee power (r = -0.276; p = 0.041) occurred. Scaled potentiated JHt was positively correlated with scaled hip moment (r = 0.502; p < 0.001) and hip power (r = 0.696; p < 0.001), and negatively correlated with scaled ankle moment (r = -0.293; p = 0.03), knee moment (r = -0.348; p = 0.009), and knee power (r = -0.340; p = 0.011). Negative correlation existed between CMJ/SJ knee power and hip power (r = -0.456; p = 0.05) while positive correlation was found between CMJ/SJ ankle power and knee power (r = 0.668; p = 0.002). Separate linear regression analysis showed that scaled hip moment and power were the only predictors of scaled potentiated JHt (r = 0.533-0.661; p < 0.001). CONCLUSIONS: Scaling of extensor moment and propulsive power of only the hip potentiation predicted scaled JHt enhancement.

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