Falls from heights are a major concern in the occupational setting, and are often the result of a loss of balance. Lumbar extensor fatigue (LEF) increases postural sway which has been associated with degradations in balance. Study one focuses on the effects of fatiguing time and fatigue level on the duration of these increases in postural sway. Measures of postural sway were collected before fatigue and at 3 minute intervals for 30 minutes following fatigue. LEF had a significant effect on postural sway immediately following fatigue but this effect had only minor dependence on fatigue condition. During the 30 minutes following fatigue, the effects of fatiguing time and fatigue level became more apparent. Longer fatiguing time and higher fatigue levels resulted in significantly greater prolonged effects. While it is important to understand the immediate effect of LEF on sway, this study has demonstrated that the prolonged effect of such fatigue should be considered when addressing falls from heights. Study two attempts to explain the increases in postural sway associated with LEF. The ankle plays a major role in upright standing and degradations in proprioception could contribute to increases in sway, thus the effect of LEF on ankle proprioception was studied. Additionally, the effect of circumferential ankle pressure (CAP) on ankle proprioception was assessed to evaluate it as a potential intervention to improve proprioception. Results showed that both LEF and CAP impaired proprioception. These results may help to explain observed increases in postural sway subsequent to LEF. / Master of Science