Biomechanical Evaluation of Lumbar Extensor Fatigue Effects on the Postural Control System

Falls from heights are the fourth leading cause of occupational injury and fatality in the United States. In particular, construction workers such as roofers are often exposed to high risk environments. Recent research has reported that a leading cause of falls among workers is a loss of balance. Therefore, in moving towards reducing the number of occupational falls, further investigation of balance and factors that influence postural control is necessary. The effect of neuromuscular fatigue has been addressed by many investigators; however, few studies have examined the effect of localized fatigue in muscles not located in the lower extremities. Because low back fatigue is so prevalent during manual labor, this investigation determined to study the effects of lumbar extensor fatigue on balance. Chapter 1 includes a complete review of current literature addressing the effects of muscular fatigue on measures of balance. Chapter 2 details an initial investigation of lumbar extensor fatigue on center of pressure (COP) based measures of postural sway and examines the effect of fatiguing rate. Chapter 3 examines the effects of different levels of lumbar extensor fatigue and expands on the previous investigation by examining center of mass (COM) movement and incorporating additional measures of postural control. The results of these investigations indicate that lumbar extensor fatigue affects both COP and COM measures of postural sway, and might also lead to an increased reliance on feedforward postural control mechanisms. These findings contribute to understanding of effects of fatigue on balance and may aid the future design of interventions aimed at fall prevention.