Doctor of Philosophy

dissertationRailroad workers experience a unique exposure to walking on ballast and uneven ground walking is a possible risk factor for knee osteoarthritis. However, the effect of ballast on workers is still not clear, especially for mechanical joint loads. Published research on walking on ballast principally examines temporal gait parameters and joint kinematics. The aim of this research is to investigate the change of knee contact force (KCF) during walking on ballast as surface condition, surface configuration, and uphill or downhill limbs by using an new OpenSim model. There are two significant contributions of this research. First, a new OpenSim gait model with robust knee structures was developed, which included patella structures, a six degrees of freedom knee joint, and four main knee ligaments. Second, KCF was investigated when walking on ballast. Temporal gait parameters were found to be different between uphill and downhill limbs. A trend was observed that the second peak KCF decreased in ballast conditions compared with no ballast. The timing of the first peak KCF was different among no ballast, main ballast and walking ballast. Knee muscle cocontraction was higher in walking ballast compared with no ballast in both peak KCFs. Knee muscle cocontraction was also higher for the uphill limb than the downhill limb. Lateral collateral ligament force was larger and medial collateral ligament force was smaller for the downhill limb compared with the uphill limb in both peak KCFs. The effect of surface configuration was significant for some ligament bundles, including iv anterior cruciate ligament and medial collateral ligament in the first peak KCF, and lateral collateral ligament in the second peak KCF. There are two additional findings in this research. First, the ankle kinematics was found to be sensitive to toe marker placement error and muscle forces responded the residual variance of joint kinematics in various degrees based on the muscle function. Second, a method to combine ground reaction data from different trials was described, which can successfully simulate the gait cycle and obtain the results of joint moments and muscle forces in a certain acceptable range

Biomechanics and energetics of walking on uneven terrain

Walking on uneven terrain is more energetically costly than walking on smooth ground, but the biomechanical factors that contribute to this increase are unknown. To identify possible factors, we constructed an uneven terrain treadmill that allowed us to record biomechanical, electromyographic and metabolic energetics data from human subjects. We hypothesized that walking on uneven terrain would increase step width and length variability, joint mechanical work and muscle co-activation compared with walking on smooth terrain. We tested healthy subjects (N=11) walking at 1.0 m s−1, and found that, when walking on uneven terrain with up to 2.5 cm variation, subjects decreased their step length by 4% and did not significantly change their step width, while both step length and width variability increased significantly (22 and 36%, respectively; P<0.05). Uneven terrain walking caused a 28 and 62% increase in positive knee and hip work, respectively, and a 26% greater magnitude of negative knee work (0.0106, 0.1078 and 0.0425 J kg−1, respectively; P<0.05). Mean muscle activity increased in seven muscles in the lower leg and thigh (P<0.05). These changes caused overall net metabolic energy expenditure to increase by 0.73 W kg−1 (28%; P<0.0001). Much of that increase could be explained by the increased mechanical work observed at the knee and hip. Greater muscle co-activation could also contribute to increased energetic cost but to unknown degree. The findings provide insight into how lower limb muscles are used differently for natural terrain compared with laboratory conditions

Biomechanics and Energetics of Bipedal Locomotion on Uneven Terrain.

Humans navigate uneven terrain in their everyday lives. From trails, grass, and uneven sidewalks, we constantly adapt to various surfaces in our environment. Past research has shown that walking on natural terrain, compared to walking on smooth flat surfaces, results in increased energy expenditure during locomotion. However, the biomechanical adaptations responsible for this energetic increase are unclear, since locomotion research is often conducted either on short walkways or in an outdoor setting, thus limiting data collections. To further our understanding of human locomotion on uneven terrain, I focused on quantifying the biomechanical and energetic changes due to increased terrain variability during walking and running. First, this thesis presents modifications to a regular exercise treadmill to allow for attachment of a separate uneven surface. Using this treadmill, I collected kinetic, kinematic, electromyographic, and energy expenditure data during continuous human walking and running. I showed that humans walking at 1.0m/s on an uneven surface, with a 2.5cm height variability, increased energy expenditure by 0.73W/kg (approx. 28%) compared to walking on smooth terrain. Greater energy expenditure was primarily caused by increased positive work at the hip and knee, with minor contributions from increased muscle activity and step parameter adaptations. I then showed that running at 2.3m/s on the same surface resulted in an energetic increase of 0.48W/kg (approx. 5%) compared to running on even terrain. In contrast to walking, humans compensated for uneven terrain during running by reducing positive work produced by the ankle and adapting a more crouched leg posture. The similar absolute increases in energetic cost between walking and running implied that much of this increase is likely due to surface height variability and changes in mechanical work. Finally, this work presents analytical and simulated analyses for the rimless wheel and simplest walker models. These analyses explored the relationship between gait dynamics, energy input strategies, surface unevenness and the energetic cost of walking. Together, these studies advance our understanding of the relationship between mechanics and energetics of human walking on uneven surfaces and could potentially lead to more robust and energetically efficient legged robots, prostheses and more effective clinical rehabilitation interventions.PhDKinesiology and Mechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111616/1/voloshis_1.pd

Doctor of Philosophy

dissertationMarching while carrying a backpack load is the most common activity in the army so being able to endure such a task is required of all military personnel. It is a predictable source of common injuries. Lower limb injuries in particular are caused not only by the extra load but also by the type of surface on which the soldier marches. The objective of this study was thus to expand on the current knowledge of the biomechanical effects of loads by investigating lower limb gait parameters on a sand surface while carrying a military backpack. Twenty healthy male participants were recruited from among students at the University of Utah who fit the current U. S. military recruitment criteria. The independent variables controlled were the surface type (i.e. hard and sand), slope (i.e. flat and slant), backpack type (i.e. no load, MOLLE, and ALICE), and marching speed (i.e. self-selected and 4 km/h). Data acquisition was performed using 16 NaturalPoint cameras, AMASS software, and 4 force plates. Over all, it was observed that a decrease in cadence, a decrease in stride length, and an increase in double support time occurred as load was added. In terms of the effects of slope, an increase in double support time and a decrease in stride width were found to occur on the slanted surface as compared to the flat surface. As for the effects of surface type, a decrease in cadence, double support time, and stride length was observed on the sand surface as compared to the hard surface. There was also found to be a general iv increase in ankle dorsiflexion/plantarflexion, knee flexion/extension, and hip abduction/adduction RoM (Range of Motion) angle on the sand surface as compared to the hard surface. On the whole, walking on a sand surface thus increased M/L GRF, increased vertical impact force, decreased vertical thrust force, and increased knee abduction/adduction moment. No difference was detected between the MOLLE and ALICE backpacks in terms of resulting cadence, double support time, and stride length. However, a statistically significant increase in stride width was observed with the MOLLE as compared to the ALICE pack. The MOLLE also influenced a statistically significant increase in hip abduction/adduction RoM angle as compared to the ALICE. The ALICE backpack in turn resulted in increased hip A/A moment and higher braking/propulsive forces. Although all of these differences were statistically significant, they are not substantial enough to be considered practically meaningful. From the findings of this research, it is recommended that military training and general operations be minimized in sand environments in order to reduce the injury potentials discussed above. In unforeseen or unavoidable cases where exposure to such terrain is prolonged, reducing overall load thus needs to be considered to reduce injury potential

Indicators of Anticipated Walking Surface Transitions for Powered Prosthetic Control

abstract: Human locomotion is an essential function that enables individuals to lead healthy, independent lives. One important feature of natural walking is the capacity to transition across varying surfaces, enabling an individual to traverse complex terrains while maintaining balance. There has been extensive work regarding improving prostheses' performance in changing walking conditions, but there is still a need to address the transition from rigid to compliant or dynamic surfaces, such as the transition from pavement to long grass or soft sand. This research aims to investigate the mechanisms involved such transitions and identify potential indicators of the anticipated change that can be applied to the control of a powered ankle prosthetic to reduce falls and improve stability in lower-limb amputees in a wider range of walking environments. A series of human subject experiments were conducted using the Variable Stiffness Treadmill (VST) to control walking surface compliance while gait kinematics and muscular activation data were collected from three healthy, nondisabled subjects. Specifically, the kinematics and electromyography (EMG) profiles of the gait cycles immediately preceding and following an expected change in surface compliance were compared to that of normal, rigid surface walking. While the results do not indicate statistical differences in the EMG profiles between the two modes of walking, the muscle activation appears to be qualitatively different from inspection of the data. Additionally, there were promising statistically significant changes in joint angles, especially in observed increases in hip flexion during the swing phases both before and during an expected change in surface. Decreases in ankle flexion immediately before heel strike on the perturbed leg were also observed to occur simultaneously with decreases in tibialis anterior (TA) muscle activation, which encourages additional research investigating potential changes in EMG profiles. Ultimately, more work should be done to make strong conclusions about potential indicators of walking surface transitions, but this research demonstrates the potential of EMG and kinematic data to be used in the control of a powered ankle prosthetic.Dissertation/ThesisMasters Thesis Mechanical Engineering 201

Effects of Running on Sand vs. Stable Ground on Kinetics and Muscle Activities in Individuals With Over-Pronated Feet

Background: In terms of physiological and biomechanical characteristics, over-pronation of the feet has been associated with distinct muscle recruitment patterns and ground reaction forces during running. Objective: The aim of this study was to evaluate the effects of running on sand vs. stable ground on ground-reaction-forces (GRFs) and electromyographic (EMG) activity of lower limb muscles in individuals with over-pronated feet (OPF) compared with healthy controls. Methods: Thirty-three OPF individuals and 33 controls ran at preferred speed and in randomized-order over level-ground and sand. A force-plate was embedded in an 18-m runway to collect GRFs. Muscle activities were recorded using an EMG-system. Data were adjusted for surface-related differences in running speed. Results: Running on sand resulted in lower speed compared with stable ground running (p < 0.001; d = 0.83). Results demonstrated that running on sand produced higher tibialis anterior activity (p = 0.024; d = 0.28). Also, findings indicated larger loading rates (p = 0.004; d = 0.72) and greater vastus medialis (p < 0.001; d = 0.89) and rectus femoris (p = 0.001; d = 0.61) activities in OPF individuals. Controls but not OPF showed significantly lower gluteus-medius activity (p = 0.022; d = 0.63) when running on sand. Conclusion: Running on sand resulted in lower running speed and higher tibialis anterior activity during the loading phase. This may indicate alterations in neuromuscular demands in the distal part of the lower limbs when running on sand. In OPF individuals, higher loading rates together with greater quadriceps activity may constitute a proximal compensatory mechanism for distal surface instability

Impacts on Balance When Walking in Occupational Footwear

Hazards and challenges present in the workplace pose a number of potential risks for injuries and illness. Nearly 3.1 million nonfatal workplace injuries and illness were reported in 2010 (BLS, 2010). The probability of falls has been related to balance decrements. Further, an important point of distinction is 45% of all falls have been attributed to inappropriate footwear (Menant et al. 2008) Previous studies have shown decrements in balance as a result of different footwear (Menant et al. 2008) and after an increased workload over a specific period of time (Yaggie & McGregor, 2002; Gribble & Hertel, 2004). Occupational footwear is often designed for safety and may fail to provide appropriate foot biomechanics. As such the functionality of occupational footwear may impact balance characteristics over time. The purpose of the study is to examine the differences in balance in while wearing different types of occupational footwear for extended durations. Fourteen healthy male adults (aged 23.6±1.2 years; height of 181±5.3 cm; weight of 89.2±14.6 kg), with no history of orthopedic, musculoskeletal, cardiovascular, neurological and vestibular abnormalities participated in this study. The experimental session included an extended duration of walking (4hours) with balance measured at 30min intervals (Pre, 30, 60, 90, 120, 150, 180, 210 & 240min). The standing balance protocol assessment was done on the six conditions of the Neurocom Equitest SOT (EO, EC, EOSRV, EOSRP, ECSRP and EOSRVP). The values of the dependent sway variables were derived from the Center of Pressure (CoP) movement. The average sway velocity (VEL) and the root-mean-square (RMS) of the CoP were used to characterize the postural sway in the anterior-posterior (APVEL & APRMS) and the medio-lateral (MLVEL & MLRMS) directions during the 60-second testing period. Participants were randomly assigned 3 different types of occupational footwear: Work Boots (WB) (mass 0.39±0.06 kg), Tactical Boots (TB) (mass 0.53±0.08 kg) and Low Top Boots (LT) (mass 0.89±0.05 kg) with a minimum of 72 hours of rest between conditions. Balance dependent variables were evaluated using a 3 x 9 (Footwear [WB v. TB v. LT]) x (Extended duration of walking intervals [Pre, 30, 60, 90, 120, 150, 180, 210 & 240] RMANOVA and independently for the six SOT balance conditions (EO, EC, EOSRV, EOSRP, ECSRP and EOSRVP) to identify any existing differences within the exposure time as well as the footwear types. Significant differences were found over time in the EO, EC, EOSRV & EOSRP for MLRMS and between footwear in the EC for APRMS and MLRMS and EOSRP for MLRMS. These results indicate a decrement in balance performance over time but the differences were limited to MLRMS. The decline in balance may be attributed to fatigue resulting from an extended duration of walking/standing. Significant differences were found between the WB, TB and LT, where the LT had a higher postural sway RMS. The use of LT resulted in a relatively greater balance decrement, especially when vision was absent and with conflicting somatosensory input. The WB and TB despite having a greater mass, had less balance decrement, which can be related to their elevated boot shaft height. Results from this data suggest that the high boot shaft supports the ankle, resulting in decreased fatigue, and thus better balance

Biomechanics Of Slips In Alternative Footwear

Injuries in the workplace pose a significant burden to the health of human beings as well as financial or economic losses to occupational organizations. Slips, trips and an induced loss of balance have been identified as the major causative factor for workplace injuries involving falls (Courtney et al, 2001; Redfern et al, 2001). The bureau of labor statistics reported 15% of a total of 4,693 workplace fatalities and a total of 299,090 cases of non-fatal workplace injuries that were due to slips, trips and falls (BLS, 2011). The purpose of the study was to analyze the biomechanics of human locomotion under normal dry flooring conditions and under slippery flooring conditions with three commonly used alternative casual footwear [thong style flip-flops (ff), crocs with clogs (cc) and slip resistant low-top shoe (lt)]. The study will follow a within-subjects repeated measures design with each participant exposed to all three footwear using a counter balanced design. Eighteen healthy male participants with no orthopedic, cardiovascular or neurological abnormalities completed the study. Participants were required to come in for three testing sessions separated by at least 24 hours of rest interval and an initial familiarization day. On each testing day, participants were provided with an alternative footwear based on a counterbalanced selection and were tested for maximal voluntary contraction for lower extremity muscles and were exposed to a series of walking trails that included a normal dry surface non slip gait trial (ns); unexpected slip (us), alert slip (as) and expected slip (es). A 3 x 4 [3 (ff, cc, lt) x 4 (ns, us, as, es)] within-subjects repeated measures anova was used to analyze the dependent slip parameters (heel slip distance and mean heel slip velocity), kinematic and kinetic gait variables (mean and peak vertical ground reaction forces and lower extremity joint angles) and muscle activity (mean, peak and % maximal voluntary contraction in lower extremity muscles). Significant interactions between the footwear and gait trials were found for the slip parameters, gait parameters and muscle activity variables (p\u3c0.05). Significant interactions were folloup with post-hoc multiple comparisons using a Sidak Bonferroni correction. Based on the results from the study the alternative footwear (cc & ff) had greater slip parameters, reduced ground reaction forces and a plantar flexed foot position at heel strike compared to the lt. The us and as had greater incidence of slips than ng and es and moreover with the a priori knowledge of the slippery flooring conditions (es), the individuals were able to modify the gait kinematic and kinetic parameters rather than lower extremity muscle activity to reduce the potential for a slip. Overall, the most hazardous slips were seen with alternative footwear and during the unexpected slips folloby the alert slips. The lt had lower incidence of slips and maintained a normal gait pattern during all gait trial conditions and demonstrates to be the choice of footwear for maneuvering slippery flooring conditions that exist in both occupational and public places

Saf Sci

Residential roofers have the highest rate of falls in the construction sector with injuries and fatalities costing billions of dollars annually. The sloped roof surface is the most predominant component within the residential roof work environment. Postural stability on a sloped work environment is not well studied. Calculating inclination angles (IAs) using the lateral ankle marker could be a quality measure to determine how cross-slope roof walking will influence stability. Will cross-slope roof-walking effect anterior-posterior (AP) and medial-lateral (ML) IAs in adult males? Eleven adult males participated in two testing sessions-level and cross-slope roof gait session on a 6/12 pitched roof segment. Changes in AP and ML IAs between conditions were compared at: heel strike (HS) and toe off (TO). Legs were analyzed separately due to the cross-slope walking. The left foot was 'higher' on the sloped roof and the right was 'lower.' Significant increases (p 64 0.006) in IAs were observed due to the sloped roof in all conditions except the AP 'lower' leg (p = 0.136). Increases in IA suggest a decrease in postural stability as the body will result in greater sway compared to a natural posture. Increases in AP IAs may cause slipping in the anterior or posterior direction as the normal force will decrease during HS and TO. In the ML direction, fall risk is increased and more stress is placed on the hip abductors in order to reduce falling. Thus traversing a sloped roof surface reduces stability of healthy workers and escalates injury/fall risk factors.CC999999/ImCDC/Intramural CDC HHSUnited States/2021-09-21T00:00:00Z34552309PMC84551541036

Climbing and Walking Robots

With the advancement of technology, new exciting approaches enable us to render mobile robotic systems more versatile, robust and cost-efficient. Some researchers combine climbing and walking techniques with a modular approach, a reconfigurable approach, or a swarm approach to realize novel prototypes as flexible mobile robotic platforms featuring all necessary locomotion capabilities. The purpose of this book is to provide an overview of the latest wide-range achievements in climbing and walking robotic technology to researchers, scientists, and engineers throughout the world. Different aspects including control simulation, locomotion realization, methodology, and system integration are presented from the scientific and from the technical point of view. This book consists of two main parts, one dealing with walking robots, the second with climbing robots. The content is also grouped by theoretical research and applicative realization. Every chapter offers a considerable amount of interesting and useful information