Article Title



LE Smith
H Singh


Lauren Elizabeth Smith, Harshvardhan Singh. University of Alabama at Birmingham, Birmingham, AL.

BACKGROUND: Achievement of an optimal stretch shortening cycle (SSC) potentiation lends to greater sport performance. During jump test, a quick countermovement-initiated jump (CMJ) or drop jump (DJ), which is a jump preceded by a drop off from a height, is compared to a jump where a static squat is held for 2-3 seconds before the jump occurs (SJ). It is unknown which potentiation of specific lower extremity joint lends greatest to enhanced jump height (JHt) in children. Such information can yield insight into joint-specific rehabilitation to improve JHt as well as increased accuracy in clinical decision making for risk and return to sport assessment. Thus, we examined the relationship between JHt potentiation and lower extremity joint-specific potentiation using a) extensor moment and b) propulsive power. METHODS: A rigid body model with 36 reflective markers and floor-embedded force plates was used to collect jump data in typically developing children (N=20; age = 8-14 years). Participants performed 3 trials of CMJ and DJ after familiarization. JHt from each trial was calculated from the greater trochanter marker data. JHt and joint-specific propulsive power potentiation and extensor moment as the ration of a) CMJ/SJ and b) DJ/SJ at the hip, knee, and ankle. All the moments and powers were normalized for body weight for analyses. RESULTS: Positive relationships between CMJ/SJ JHt and a) CMJ/SJ hip moment (r = 0.548; p = 0.012), and b) CMJ/SJ hip power (r = 0.547; p = 0.013) were noted. Positive relationship between DJ/SJ JHt and CMJ/SJ hip power (r = 0.525; p = 0.021) was found. No other relationships were noted. CONCLUSIONS: Greater potentiation of power and moment at the hip is associated with an enhanced JHt performance for different types of jump such as CMJ and DJ. Our data shows that the hip joint during different types of jumps has greater significance than that of knee or ankle. Whether increased contribution of hip potentiation toward enhanced jump performance occurs due to its greater involvement for balance and trunk control in prepubescent children remains to be examined.

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