Document Type


Date of Degree

Fall 2014

Degree Name

PhD (Doctor of Philosophy)

Degree In

Biomedical Engineering

First Advisor

Frey Law, Laura

First Committee Member

Grosland, Nicole

Second Committee Member

Fethke, Nathan

Third Committee Member

Wilder, David

Fourth Committee Member

Marler, Tim


Muscle fatigue is universally experienced in daily life, from recreational physical activity to the workplace. However, our ability to estimate fatigue is limited. Several attempts have been made to mathematically model the effects of fatigue, such as how long a muscle contraction may be sustained, known as `endurance time.' However, these simple models of endurance time are limited to static contractions when the body is not moving, but muscles are contracted. This research aims to advance a previously proposed analytical model of muscle fatigue to represent complex tasks such as with rest intervals and dynamic contractions. Multiple methodologies were employed to assemble data to examine the model prediction accuracy, including 1) compiling previously published data involving intermittent rest intervals (i.e., meta-analysis); 2) experimentally collecting data on intermittent fatigue for shoulder flexion as it is not well represented in the literature; and 3) experimentally collecting data on fatigue during a dynamic task for elbow flexion as dynamic tasks have been virtually ignored in fatigue literature. The results of these investigations indicate that a mathematical model of fatigue is reasonably accurate in predicting an average fatigue response across multiple subjects for both intermittent and dynamic tasks, but does not currently reflect the often wide variation in muscle fatigue development that is observed between individuals. Accordingly, this type of modeling approach may have value for general assessments of fatigue accumulation, but will need further development and modification to better represent individual characteristics.

Public Abstract

Fatigue is a part of everyone’s daily lives. Some days we feel tired, other days our muscles are sore and we cannot perform the activities we would like. Muscle fatigue is a constant aspect of everyday life for many industrial, mechanical, and office workers. While it is a part of our everyday lives and has been studied for over a century, there is still much to learn about the long and short term effects of localized muscle fatigue. In order to learn about these effects, there first must be an objective way of measuring its’ development. This dissertation attempts to improve on one such model to account for the variations and pauses that occur during the work day. The ability for the model to account for the rest muscles are given during these pause and breaks during a particular work task would allow researchers and ergonomist to objectively be able to assess muscle fatigue development and look at its potential health outcome effects. The first chapter outlines the increasing musculoskeletal disorder prevalence and what has already been examined. The next two chapter use published subject data as well as collect experimental data to determine the best rest multiplier parameter for each available joint segment. The final chapter explores whether these model improvements increase the accuracy for dynamic tasks ones might encounter in the workplace, while the last chapter sums up the model improvements.


publicabstract, Dynamic, Intermittent, Modeling, Muscle Fatigue


xii, 84 pages


Includes bibliographical references (pages 69-84).


Copyright 2014 John Maurice Looft