All ETDs from UAB

Advisory Committee Chair

Harshvardhan Singh

Advisory Committee Members

Donald H Lein Jr

Gary R Hunter

Christopher P Hurt

William R Reed

Document Type

Dissertation

Date of Award

2021

Degree Name by School

Doctor of Philosophy (PhD) School of Health Professions

Abstract

The stretch-shortening cycle (SSC) is a well-known phenomenon to enhance an individual’s muscular performance, and it is an area of active focus of research scientists for decades. However, it is not known whether SSC potentiation is a joint-specific event and shows a joint-specific temporal behavior. It is also unclear if constraints of joint and movement specificity of SSC potentiation can be captured via isokinetic dynamometer. Therefore, the purposes of this dissertation were to examine joint specificity of SSC potentiation via isokinetic dynamometer and kinetic-kinematic analysis of jump test performance and investigate joint-specific temporal behavior of SSC potentiation. My first study examined the joint specificity of SSC potentiation by testing the knee extensors and plantar flexors separately under two conditions (with and without SSC) using isokinetic dynamometers at different movement velocities. It demonstrated that SSC is joint-specific and that ankle plantar flexors exhibited greater torque potentiation than knee extensors, independent of movement velocity. My second study assessed the joint specificity of SSC potentiation under three conditions of jump test performance (JTP) using motion capture and force plates system. Findings from this study showed that SSC is joint-specific during JTP and that, at the propulsive onset, the ankle joint extensor moment showed greater SSC potentiation than the hip and knee extensors. Finally, my third study aimed to further analyze the propulsive phase of JTP conditions to track the temporal change of the joint extensor moment potentiation over the peak propulsive phase, and whether enhanced JTP can be predicted by joint specific extensor moment potentiation. Novel findings from our last study provided preliminary evidence of time series SSC potentiation during JTP is joint-specific. Potentiation of extensor moment was highest immediately at the onset of peak propulsive phase and progressively decreased across the peak propulsive phase for all the lower extremity joints. Finally, our findings informed that hip extensor moment potentiation at the propulsion onset and the end of propulsive phase were the best predictors of JTP. Whether these joint specific and time specific SSC potentiation are related to or can be used as a biomechanical marker of task efficiency remains to be examined.

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