Research

Abstract

In the human body, fatigue at the muscular level is characterized by a reduction in the force generating capacity of a muscle. This fatigue often results in alterations in motor performance during various tasks. These alterations from fatigue have been attributed to an elevated risk of musculoskeletal injury.
Alterations in normal gait patterns have been observed in response to general fatigue. However, inducing general fatigue can be limiting as it restricts the ability to determine the limiting factor of fatigue-induced changes. Muscular fatigue may also alter activation patterns by shifting the activation from fatigues to less fatigued muscles in order for the body to perform a task. Other observed alterations include greater activation in other lower extremity joints that are less fatigued.

The purpose of this study is to compare the effects of lower extremity joint fatigue on kinematics during walking and running. By examining the effect of localized fatigue of the ankle and knee joints during locomotion a greater understanding of the alterations made by the body will be gained which may then be used in preventing the risk of musculoskeletal injury as a result of fatigue in the future.

Equipment/Software Used

• AMTI Force Treadmill
• 16 Channel Delsys EMG System
• Cybex Isokinetic Dynamometer
• VICON Motion Capture System
• Nexus
• Visual 3D

Author

Dr. Clark Dickin
Director of Biomechanics Laboratory and Associate Professor of Exercise Science

Abstract

Claims of whole body vibration (WBV) have ranged from increasing power, strength, speed, flexibility, bone density, circulation and even balance. However, the findings in all of these areas have been equivocal at best. In the majority of studies, often as a limitation of the vibration platform, the frequency of vibration has ranged between 25-40Hz. It has been posited that the vibration causes the muscle spindle to increase its sensitivity and become primed for easier activation in future muscular contractions. To the area of posture and balance this could potentially result in faster activation of the somatosensory system in response to postural sway. In the current study we are assessing the impact of both frequency and amplitude of WBV on postural control in altered and unaltered sensory environments in healthy younger adults.

Equipment/Software Used

• NeuroCom SMART Balance Master
• Pneumex Pneu-Vib Pro Vibration Platform

Author

Dr. Clark Dickin
Director of Biomechanics Laboratory and Associate Professor of Exercise Science

Background

While stress fractures impact both military and non-military persons, there are several unique aspects to the problem in the military context. One of the primary differences is in the physical activities and demands on the recreational and competitive runners versus military personnel. In addition to typical exposures to running for fitness and recreation, military personnel must routinely engage in physical activities such as running and marching while carrying additional loads. The load that soldiers are expected to carry has increased substantially, from WWI and WWII to the current conflicts in Afghanistan and Iraq. While, the effects of load carriage on the biomechanical aspects of gait have been examined by several researchers, there is still much that is unknown in terms of how these additional loads influence the risk of overuse injuries such as tibial stress fractures.

Purpose

The purpose of this research is to determine the effects of load carriage and fatigue on mechanical variables associated with increased risk of tibial stress fractures. It is hypothesized that an increase in load carried will result in changes in gait mechanics leading to increased stresses, strains, and strain rates in the tibia. It is also hypothesized that fatigue will result in changes in gait mechanics and muscular activity leading to increased stresses, strains, and strain rates in the tibia.

Specific aims

The specific aims of this research are to determine the effect of increased load carriage and fatigue on gait mechanics during a walking protocol and to determine the effect of increased load carriage and fatigue on the resulting stress/strain profile in tibia.

Study design

In order to determine the effects of load carriage and fatigue on mechanical variables associated with increased risk of tibial stress fractures, traditional kinematic and kinetic analyses derived from motion capture and force plate data will be combined with subject-specific finite element models of the tibia utilizing customized musculoskeletal modeling software.

Significance

The immediate significance of this research to the Armed Forces is the ability to quantify the effects of load carriage and fatigue, in situations similar to those encountered by military personnel, on the mechanical loading of the tibia. It is this mechanical loading and the stresses and strains it causes in the bone that ultimately leads to injury. The results of this study can then be used to evaluate the relative changes in bone loading parameters and thus the potential risk of tibial stress fracture due to these conditions.

Equipment/Software Used

• AMTI Force Treadmill
• 16 Channel Del-Sys EMG System
• Cluster Marker Set
• VICON Motion Capture System
• ParvoMedics metabolic cart
• Vertec
• CT scan (at Ball Memorial Hospital)
• LifeMOD
• Mimics 12.3
• MSC/Marc

Author

Henry Wang
Associate Professor of Exercise Science