Adaptations in human neuromuscular function following prolonged unweighting: Neurological and skeletal muscle properties and countermeasure efficacy

Date of Award


Degree Type


Degree Name

Doctor of Philosophy (PhD)


Exercise Science


Lori L. Ploutz-Snyder


Neuromuscular, Unweighting, Skeletal muscle, Disuse

Subject Categories

Medicine and Health Sciences


The purposes of these experiments were to determine the adaptations in plantarflexor muscle and neural function following prolonged periods of unweighting in human subjects, and evaluate the efficacy of two different types of interventions (applied ischemia [ISC] and motor imagery [MI] at mitigating the disuse-induced dysfunction. A total of eighteen subjects completed the experiments. Twice before and immediately following 4-weeks of unilateral lower limb suspension (ULLS; experimental disuse model) we utilized a combination of voluntary and electrically stimulated muscle contractions coupled with measurements of electromyography, muscle force and magnetic resonance imaging to gain insight into the electrophysiological function of the plantarflexor muscles and the motorneurons that innervates it, along with assessments of muscle morphology, and force-frequency and force-speed characteristics.

Within this dissertation the results from the aforementioned experiments are presented. Chapter III assesses the reliability of the utilized tests to evaluate in vivo neuromuscular function, while chapters IV and V present the findings on unweighting-induced alterations in skeletal muscle and neurological function along with the efficacy of the respective countermeasures.

Additionally, in fulfillment of degree requirements, this dissertation contains a science education component. This study investigated the role of personal relevance on learning and memory, and is presented in Chapter VII.


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