Michelle F. Heller

Changes in postural sway as a consequence of wearing a military backpack.

Military personnel are often required to carry all of their personal supplies and equipment for long distances during both training and combat situations, creating many biomechanical and postural challenges for these individuals. In addition to other problems such as generalized fatigue and the development of stress fractures, significant external loads may also affect a soldiers postural sway. The purpose of this study was to assess changes in postural sway as a consequence of wearing a military backpack in females. Forty-three female subjects between the ages of 18 and 25 volunteered to participate. There were two conditions: unloaded and while wearing an 18.1 kg military backpack. Each subject stood with two feet on a force platform for 30s under both conditions while center of pressure (COP) data were collected. COP path length increased 64%, medial-lateral excursion increased 131%, anterior-posterior excursion increased 54%, and COP area increased 229% with addition of the backpack (p<0.0001 for all of these measures). These data show that wearing 18.1 kg of external weight in a military backpack increases the postural sway of females, which may in turn increase the likelihood of falls and injury.

Effects of Mobile Technology Use on Walking

Objective: The goal of this study was to evaluate the efficacy of combining cognitive and kinematic measurements to study the effects of mobile technology use on walking. Background: It has previously been shown that being distracted by a cell phone, or other mobile technology, can have a negative impact on activities such as crossing a street and may also alter gait patterns. While the negative effects of cell phone use on driving have been extensively studied, research into the distracted pedestrian is lacking. Method: Twelve adults walked down an office corridor without using a cell phone (BASELINE) and while performing a secondary cognitive task under two conditions. The secondary task involved answering simple multiplication problems through either text messaging (TEXT) or while talking on the phone (VOICE). Participants’ gait patterns were measured using a GAITRite gait pad LEGSys wearable wireless sensors. Results: In the TEXT condition, participants walked more slowly and had shorter strides. There was no significant difference between the VOICE and BASELINE condition. Participants answered more multiplication problems per trial in the VOICE condition as compared to the TEXT condition. Excluding typos, error rates for the multiplication problems were not significantly different between the TEXT and VOICE conditions. Conclusion: This study demonstrated that the effect of reading and responding to text messages on gait was able to be detected utilizing methods that do not require strictly sterile laboratory settings. This serves as a proof of concept for researchers to bring the study and evaluation of distracted walking into the naturalistic environments in which it actually occurs. Application: This proof of concept will serve as a roadmap towards moving the study of gait and distraction from simple observational studies in naturalistic environments to specific quantitative analysis of people performing real world tasks in real world settings.

Accidental falls involving medical implant re-operation

Implantation of medical devices is becoming more prevalent, and as a result, a greater number of patients who fall accidentally are expected to have a medical implant. The Nationwide Inpatient Sample (NIS) was used to evaluate hospital admissions following accidental falls involving re-operation of existing medical implants (hip, knee, spine, and fracture fixation) from 1990 to 2005. From 1990 to 2005, hospitalisations due to accidental falls on level surfaces increased by 306%, and hospitalisations due to falls from stairs increased by 310%. Falls involving orthopaedic revision surgery (re-operation) are relatively rare, but the incidence has increased by approximately 35%. Hospital stays after falls on level surfaces involving re-operation were 1.0 day (median) longer and cost 50% (median) more than those that did not involve re-operation in 2005. After staircase falls, hospital stays for patients undergoing re-operations were 2.0 days (median) longer and cost 108% (median) more. The greater hospital costs and hospital stay for patients needing re-operations indicate that additional medical treatment was required.

Biomechanical, Perceptual, and Cognitive Factors Involved in Maintaining Postural Control While Standing or Walking on Non-Moving and Moving Surfaces: A Literature Review

Postural control has been defined as “regulating the body’s position in space for the dual purposes of stability and orientation.” How the body achieves postural control depends, in part, on the environment. A person navigating a non-moving surface (e.g. hallway, stairway, or step ladder) will process information and will employ different strategies to maintain postural control than someone who is standing or walking on a moving surface (e.g., forklifts, personal transportation systems, escalators, and moving walkways). In both environments, sensory, cognitive, and motor control systems contribute to postural control. The musculoskeletal system uses muscle activation and joint positioning to control the body’s alignment and muscle tone. The biomechanics of postural control rely on information that the musculoskeletal system receives from sensory systems including the vestibular system, which is generally implicated in behaviors requiring balance control, as well as the somatosensory and visual systems. Furthermore, sensory information from these and other systems can be enhanced by cognitive processes, such as attention. The ability to maintain postural control while standing or walking is critical in preventing falls on both non-moving and moving surfaces. This review focuses on moving surfaces and includes a discussion of the biomechanical, perceptual, and cognitive factors responsible for postural control.Copyright

Biomechanical, Perceptual, and Cognitive Factors Involved in Balance Recovery Following Unexpected Perturbations: A Literature Review

For an individual standing or walking on a moving or non-moving surface, perturbations can result in postural instability and sudden loss of balance. When unexpected perturbations occur, specific mechanisms involving the sensory, cognitive, and motor systems activate in order to regain postural control. For example, specific muscle synergies can result in compensatory limb movements (e.g. stepping or reaching towards a fixed object) that are prevalent mechanical responses to sudden loss of balance and play a crucial role in preventing falls. These movements require the interaction of multiple sensory systems including the visual, somatosensory, and vestibular systems. If sensory information is unavailable or incomplete, there may be a greater reliance on cognitive processes such as memory and attention in order to execute a balance-recovering mechanical response; however, if cognitive processes are tasked, compensatory responses may be negatively affected. The ability to recover from sudden loss of balance is critical in preventing falls on both non-moving and moving surfaces. This review includes a discussion of the biomechanical, perceptual, and cognitive factors responsible for the control of balance recovery on moving surfaces.Copyright

Injury Biomechanics: Evaluating the Evidence to Determine Causation

Biomechanical engineering is a field that encompasses a wide variety of applications including the development and evaluation of medical devices, research regarding sports and sporting equipment, and investigations of how individuals are injured and how those injuries could be prevented. Understanding human tolerance, injury mechanisms, and the facts regarding a given scenario allows the biomechanical engineer to use these data to determine how an individual was injured. As the field of biomechanics is becoming more broadly understood, the biomechanical engineer is being called upon more frequently to contribute to forensic analyses. According to Merriam-Webster, the definition of forensic is as follows: “relating to or dealing with the application of scientific knowledge to legal problems.” For a biomechanical engineer, an increasingly reasonable option is to pursue a career in forensic analysis, where his/her knowledge and skills are employed to help attorneys, judges, juries, and other participants in legal proceedings understand technical concepts key to understanding the case at hand.Copyright

HEAD MOTION IN THE CORONAL PLANE DURING LOW-SPEED LATERAL IMPACT COLLISIONS

INTRODUCTION Although numerous studies have been done on frontal and rear impact collisions and the resulting occupant kinematics, relatively few have considered the effects of lateral impacts on occupant kinematics. Understanding the kinematics of the head during lateral impacts can assist in determining how the passive response of the human body relate to one another when presented with such a stimulus. This information is invaluable in the design of motor vehicle safety systems, amusement park rides, and other situations where an unexpected lateral impact may occur.