All Faculty Deposits

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The "All Faculty Deposits" collection contains works deposited by faculty and appointed delegates from the Elements (EFARs) system. For help with Elements, see Frequently Asked Questions on the Provost's website. In general, items can only be deposited if the item is a scholarly article that is covered by Virginia Tech's open access policy, or the item is openly licensed or in the public domain, or the item is permitted to be posted online under the journal/publisher policy, or the depositor owns the copyright. See Right to Deposit on the VTechWorks Help page. If you have questions email us at vtechworks@vt.edu.

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A Fast Transient Response Distributed Power Supply With Dynamic Output Switching for Power Side-Channel Attack Mitigation
Liu, Xingye; Ampadu, Paul (IEEE, 2024-09)
We present a distributed power supply and explore its load transient response and power side-channel security improvements. Typically, countermeasures against power side-channel attacks (PSCAs) are based on specialized dc/dc converters, resulting in large power and area overheads and they are difficult to scale. Moreover, due to limited output voltage range and load regulation, it is not feasible to directly distribute these converters in multicore applications. Targeting those issues, our proposed converter is designed to provide multiple fast-responding voltages and use shared circuits to mitigate PSCAs. The proposed three-output dc/dc converter can deliver 0.33-0.92 V with up to 1 A to each load. Comparing with state-of-the-art power management works, our converter has 2× load step response speed and 4× reference voltage tracking speed. Furthermore, the converter requires 9× less inductance and 3× less output capacitance. In terms of PSCA mitigation, this converter reduces the correlation between input power trace and encryption load current by 107×, which is 3× better than the best standalone work, and it only induces 1.7% area overhead and 2.5% power overhead. The proposed work also increases minimum traces to disclose (MTDs) by 1250×. Considering all the above, our work could be a great candidate to be employed in future multicore systems supplying varying voltages and resisting side-channel attacks. It is the first work bridging the gap between on-chip power management and side-channel security.
Got Followership? Rethinking Leadership from the Other Side
Kaufman, Eric K. (2025-03-04)
90-second presentation for Virginia Tech's 2025 Faculty Nutshell Talks.
Comparing National Institute of Health Funding for Cancer Survivorship: A Spotlight on Breast and Gynecologic Cancers
White, Payden; Greer, Heather; Armbruster, Shannon (Lippincott, Williams & Wilkins, 2025)
Objective: To evaluate the distribution of National Institutes of Health (NIH) funding for breast and gynecologic cancer survivorship research in relation to survivor populations. Methods: A retrospective cohort study was conducted on NIH-funded grants for breast and gynecologic cancer survivorship from fiscal years (FY) 2017–2021 using an existing dataset from the NIH Office of Cancer Survivorship. Grant characteristics, including funding amount, study design, and research focus, were extracted from NIH Reporter and ClinicalTrials.gov. Total funding and per-survivor funding were calculated using prevalence data from the Surveillance, Epidemiology, and End Results (SEER) program. Descriptive statistics were applied to compare funding disparities between breast and gynecologic cancer survivorship research. Results: Among 160 NIH-funded grants on cancer survivorship, 144 (90%) focused on breast cancer, and 16 (10%) on gynecologic cancers. Breast cancer survivorship research received significantly more funding ($188.35 million) compared to gynecologic cancer survivorship research ($15.41 million). Per-survivor funding was also higher for breast cancer ($9.69 per survivor) than for gynecologic cancers ($2.15 per survivor). Most survivorship studies were interventional (60%), with randomized controlled trials as the predominant design. The primary study focus was on late and long-term effects of cancer treatment (53%), followed by health promotion (21%) and care delivery (16%). Conclusion: NIH funding for gynecologic cancer survivorship research is significantly lower than that for breast cancer, even when accounting for survivor prevalence. The findings highlight the need for equitable resource allocation to ensure comprehensive survivorship support for gynecologic cancer survivors. Increased funding and research efforts are necessary to address the unique challenges faced by this population and to optimize long-term outcomes.
Encounters with Foreign Lands: developing a sensuous empirical approach to reading depth
Rosier, Shaun (2025-03-28)
The Cardiovascular Effects of Interleukin-6 Inhibition in Patients with Severe Coronavirus-19 Infection
Binder, Michael S.; Timmerman, Clinton; Marof, Biwar; Wu, Yingxing; Bankole, Adegbenga; Heletz, Ido (SAGE Publishing, 2025-04-02)
Objective: The coronavirus disease 2019 (COVID-19) pandemic illustrated the relationship between cardiac arrhythmias and pro-inflammatory states. Pro-inflammatory cytokines, including interleukin-6 (IL-6), have significant effects on cardiac conduction. Atrial or ventricular arrhythmias occurring while infected results in a doubling of mortality. Tocilizumab, a monoclonal antibody that blocks the IL-6 receptor, is associated with improved mortality and is believed to be related to immune modulation of the COVID-19–related hyperinflammatory state. Methods: A single-center retrospective review of all patients with severe COVID-19, defined as admission to an intensive care unit or requirement of respiratory or circulatory support, from March 2020 through March 2022, was conducted. Patients who received or did not receive tocilizumab were grouped into the treatment and control groups, respectively. Results: Four hundred seventy-three patients were reviewed and 400 met the criteria for inclusion in our study. There were 305 patients (age, 63 ± 13 years, 58% male) in the control group and 95 (age, 57 ± 15 years, 51% male) in the treatment group. In-hospital mortality was greatly reduced with tocilizumab compared with controls (44.2% vs 85.9%, p < 0.001) and new-onset atrial fibrillation (AF) showed a statistically significant reduction (17.8% vs 29.5%, p = 0.019). New-onset wall motion abnormalities, potentially related to myocarditis or acute coronary syndrome, also trended toward significance with tocilizumab (7.7% vs 15.7%, p = 0.10). Deep vein thrombosis, pulmonary embolism, stroke, and sustained ventricular arrhythmias did not meet statistical significance. Conclusion: As expected, tocilizumab did show significant improvement in mortality. Tocilizumab also showed a significant reduction of new-onset AF. Other cardiac structural endpoints did not reach statistical significance.
The review sentiment garden: Blossoming loss aversion and diminishing sensitivity across time and crisis
Sharma, Abhinav; Shin, Seunghun; Nicolau, Juan Luis; Park, Sangwon (Elsevier, 2025-08)
Adopting an approach grounded in prospect theory, this article tests the principles of loss aversion and diminishing marginal sensitivity in hotel review sentiment. While prospect theory has been extensively tested in other areas, its application to review sentiment is novel, thereby extending our understanding of how hotel guests perceive and evaluate their service experiences. Simultaneously, this study examines whether the predictions of prospect theory hold to the same extent in post-Covid-19 reviews as they do in pre-Covid-19 reviews. The analysis is conducted on a sample of 416,756 reviews from 375 hotels in 14 European cities posted between 2000 and 2022. The findings show that a significant level of loss aversion and diminishing sensitivity characterizes reviews from both the pre-pandemic as well as post-pandemic periods. However, the effect of loss aversion becomes even more accentuated after Covid-19, with a gradual return to pre-pandemic levels.
Use of wearable sensors for continuous field monitoring of upper arm and trunk postures among construction workers
Porta, Micaela; Casu, Giulia; Lim, Sol; Nussbaum, Maury A.; Pau, Massimiliano (Taylor & Francis, 2025-02-28)
Construction is considered amongst the highest risk sectors for the development of work-related musculoskeletal disorders (MSDs) considering the large number of unfavourable environmental and task-specific factors typical in this sector. Thus, it is important to have quantitative tools to support the assessment of the exposure to physical MSD risk factors. We employed wearable inertial sensors (ISs) to perform a real-world characterisation of static postures and repetitive movements involving the trunk and upper arms (UA), among 15 workers during 2 hours of their regular shifts. IS data were processed according to ISO 11226 and EN 1005-4 standards. We found that workers spent ∼25% of the monitored time in static trunk flexion >20% and more than 50% of the time with UA elevations >20°. The ability to assess working postures for prolonged periods may represent a useful tool for different stakeholders involved in the protection of construction worker health.
Cognitive workload assessment during VR forklift training
Zahabi, Saman Jamshid Nezhad; Islam, Md Shafiqul; Kim, Sunwook; Lau, Nathan; Nussbaum, Maury A.; Lim, Sol (Elsevier, 2025-05)
Virtual Reality (VR)-based training offers a safe and engaging environment for training forklift operators. Given the complexity of forklift operation, monitoring the cognitive workload of novice operators in these virtual settings is essential for optimizing the training process. This study investigated cognitive workload variation during a VR-based training for forklift operators due to varying levels of task difficulty and repeated training. Twenty novice participants completed two sessions in a VR simulator with each session including three forklift driving lessons at three difficulty levels. Perceived workload (NASA-TLX) and normalized encephalographic (EEG) activity were employed to assess cognitive workload. Five of the six NASA-TLX subscales and EEG activity in three distinct frequency bands (theta, alpha and beta) all significantly increased with increasing task difficulty. However, we did not observe significant changes in cognitive workload as measured by EEG in the second training session, highlighting a potential limitation in using EEG to track workload variations across days. Perceived workload and EEG measures showed moderate, positive correlations. Our results highlight the potential of EEG for real-time monitoring of workload during VR-based forklift training, particularly in differentiating tasks of varying difficulty. While more research is needed to confirm measurement consistency across sessions, this capability could facilitate worker monitoring to deliver timely alerts or assistance when workload levels exceed optimal thresholds.
Perspectives of Mining Personnel on Adopting Occupational Exoskeletons: Comparisons Between a Developed and a Developing Country
Akinwande, Feyisayo; Kim, Sunwook; Ojelade, Aanuoluwapo; Muslim, Khoirul; Iridiastadi, Hardianto; Nasarwanji, Mahiyar; Kim, Jeong Ho; Nussbaum, Maury A. (Springer, 2025-03-01)
Occupational exoskeletons (EXOs) have received growing attention as a new ergonomic intervention to reduce physical demands in various industries (e.g., manufacturing, logistics, construction, and agriculture). However, their potential use in mining has not yet been reported. Survey data (n = 135) were obtained from mining workers in the United States (US) and Indonesia (ID). Qualitative and frequency analyses were used to summarize and compare respondents’ perceived barriers, benefits, and promoters to EXO use and adoption. Beta regression analyses were also used to examine whether the perceived likelihood to use arm-support EXOs or back-support EXOs differed between the countries and was affected by demographic or job characteristics, or by perceptions regarding EXOs. Both US and ID respondents reported potential benefits of EXOs for physically demanding tasks such as lifting and overhead work, and they shared concerns about adaptation, uncertainty or lack of knowledge, confined spaces, device weight, potential failure or damage, and costs. However, some key differences also emerged: US respondents were more likely to consider using arm-support EXOs and back-support EXOs, despite expressing concerns about their use; ID respondents, although they reported more existing health and safety hazards, appeared more hesitant about adopting EXOs, possibly due to these additional hazards. These results demonstrate that miners appear to have an interest in EXOs but also emphasize the need to ensure task compatibility, comfort, and affordability to ensure the safe and effective adoption of EXO technology in mining in both developed and developing countries.
Exploring Student Perceptions of Capstone Design Outcomes
Lutz, Ben; Paretti, Marie C. (Tempus Publications, 2017)
Capstone design courses are pivotal in engineering curricula, and understanding and assessing the resultant learning is critical to both researchers and practitioners. While current scholarship does provide tools for such assessments, most are based on outcomes derived through research with faculty, administrators, and various industry stakeholders. As a result, students' self-reported learning gains have been largely overlooked. Addressing this gap, this paper presents a qualitative thematic analysis that explores student perceptions of capstone learning. Drawingon50semi-structured interviewswith 31 students from three different institutions, we describe four emergent themes: (1) Engineering Design Skills; (2) Teamwork and Communication; (3) Self-directed Learning Skills; and (4) Development of an Engineering Identity. These themes are generally consistent with current outcomes identified from other sources, but students' discussions also highlight areas of personal development that move beyond acquisition of technical and professional skills. That is, students' perceptions of their own learning in capstone reflect not only those outcomes currently desired by various stakeholders and accreditation bodies, but also outcomes that might be more subtle and less tangible than those demonstrated via traditional assessment approaches. Thus, we argue that in order to more meaningfully support student growth, both technical and professional, capstone faculty should incorporate opportunities to actively promote and provide evidence for the kinds of critical reflection that students engage in throughout the course.
Risk factors for vulvar dysplasia recurrence in patients from southwestern Virginia and surrounding states: A retrospective cohort study
Greer, Heather O.; Metz, Kallie; Locklear, Tonja M.; Armbruster, Shannon D. (Springer, 2025)
Objective. To determine whether distance to a tertiary care center is an independent risk factor for recurrence of VIN 2/3 or invasive vulvar cancer. Methods. A retrospective chart review included individuals with VIN 2/3 from southwest Virginia and surrounding states treated at a single institution. The patients were treated from 1/1/2010 to 12/31/2020. Medical records were reviewed for demographics, risks factors, distance to care determined by a geographic information system (GIS) software, treatment modality, and recurrent disease. Results. We identified 251 patients. Most patients were Caucasian (92%) and had history of tobacco use (current [49%] and former [27.5%] tobacco users). Patients traveled an average of 20 miles for care (range: 0.3-113.9 miles). Most commonly, VIN 2/3 was treated with excision (n=136), excision and ablation (n=59), or ablation alone (n=31). The average lesion size was 20 mm (range: 2, 100 mm). Thirty-five percent of patients (n=88) developed recurrent VIN 2/3, on average, 9.6 months (range: 0.1, 7.8 years) following treatment. Recurrences were associated with increased body mass index (p=0.049), immunocompromised status (p=0.039), steroid use (p=0.024), and positive margins (p=0.0003). No subsequent diagnoses of cancer were made. Logistic regression showed that margin status was the only field impacting recurrence (p=0.0075; OR=2.63, 95% CI: 1.30-5.35). Distance to care was not related to recurrence risk (p>0.05). Conclusions. Our findings confirm known risk factors for current disease, while indicating that distance to care does not impact their recurrence. Further research is merited to investigate other recurrence risk factors that were not included in our model.
Ticam2 ablation facilitates monocyte exhaustion recovery after sepsis
Caldwell, Blake A.; Ie, Susanti; Lucas, Amy; Li, Liwu (Nature Portfolio, 2025-01-15)
Sepsis is a leading cause of death worldwide, with most patient mortality stemming from lingering immunosuppression in sepsis survivors. This is due in part to immune dysfunction resulting from monocyte exhaustion, a phenotype of reduced antigen presentation, altered CD14/CD16 inflammatory subtypes, and disrupted cytokine production. Whereas previous research demonstrated improved sepsis survival in Ticam2-/- mice, the contribution of TICAM2 to long-term exhaustion memory remained unknown. Using a cecal slurry injection sepsis model, we monitored the establishment and recovery of monocyte exhaustion in Ticam2-/- mice. After one week of recovery, we profiled bone marrow and splenic reservoir monocytes in Ticam2-/- mice and found that, in contrast to the persistent exhaustion observed in wild-type monocytes, Ticam2-/- monocytes largely resembled healthy controls. To determine the impact of TICAM2 ablation on innate epigenetic memory in sepsis, we measured genome-wide DNA methylation in bone marrow monocytes and found that Ticam2-/- cells exhibit a unique profile of altered methylation at CEBPE binding sites and regulatory features for key immune genes such as Dmkn and Btg1. Bearing human translational relevance, a case study of time course blood samples collected from a sepsis patient presenting with SIRS and a positive qSOFA revealed a similar effect in human monocytes, which steadily transition into an exhausted memory characterized by a CD38high; CX3CR1low; HLA-DRlow state within four days of hospital admittance. Together, our data reveal the chronic preservation of monocyte exhaustion, partially controlled by TICAM2.
Pulmonary metastatic melanoma: current state of diagnostic imaging and treatments
Zhang, Kermit S.; Pelleg, Tomer; Campbell, Sabrina; Rubio, Catalina; Loschner, Anthony Lukas; Ie, Susanti (Future Medicine, 2021-07-09)
Melanoma is the deadliest form of skin cancer with an estimated incidence of over 160,000 cases annually and about 41,000 melanoma-related deaths per year worldwide. Malignant melanoma (MM) primarily occurs in the skin but has been described in other organs. Although the respiratory system is generally afflicted by tumors such as lung cancer, it is also rarely affected by primary MM. The estimated incidence of pulmonary MM of the lung accounts for 0.01% of all primary lung tumors. The current understanding of pulmonary MM of the lung pathophysiology and its management are not well established. We aim to survey current clinical modalities with a focus on diagnostic imaging and therapeutic intervention to guide providers in the management of patients with a high index of suspicion.
Passive arm-support and back-support exoskeletons have distinct phase-dependent effects on physical demands during cart pushing and pulling: An exploratory study
Park, Hanjun; Noll, Alex; Kim, Sunwook; Nussbaum, Maury A. (Elsevier, 2025-03-20)
Arm-support exoskeletons (ASEs) and back-support exoskeletons (BSEs) can be effective in reducing physical demands during various occupational tasks, yet evidence of their effects in pushing and pulling tasks remains limited. We examined the effects of using a passive ASE and a BSE on task completion time, shoulder and trunk kinematics, and muscle activity in the shoulder and back while pushing and pulling a moderately loaded (100 kg) cart. Forty volunteers (24 M and 16 F) completed the study. Using the BSE substantially reduced thoracic and lumbar erector spinae muscle activity for males, especially during the initial and ending phases of pushing (by up to ∼31.4 %) and pulling (by up to ∼25.4 %) compared to the No Device (ND) condition. In contrast, using the ASE showed no significant benefits, with females experiencing an increase in anterior deltoid muscle activity (by up to ∼46.3 %) compared to ND. Findings from this study help to understand the effects of BSEs and ASEs in pushing and pulling tasks and support the development of more versatile exoskeletons.
Gait variability predicts post-fatigue obstacle course performance among military cadets: An exploratory study
Ulman, Sophia; Srinivasan, Divya; Nussbaum, Maury A. (Elsevier, 2025-03-12)
We explored the extent to which pre-fatigue gait variability during load carriage is associated with the ability of an individual to perform an obstacle course post-fatigue. Twenty-four military cadets were monitored during treadmill gait and completed an obstacle course before and after a full-body fatigue protocol. Gait variability measures were determined from spatiotemporal stride characteristics, joint angle trajectories, and inter-joint coordination. These measures were then used in multiple linear regression models to predict three measures of post-fatigue performance (i.e., hurdle completion time, maximum jump height, and maximum jump distance). Measures of joint kinematic variability predicted 73–89% of the variance in post-fatigue performance. Specifically, the significant predictors were sagittal plane variability of 1) hip angle and hip-knee coordination during swing phase; and 2) knee-ankle coordination during both stance and swing phase. Measures of joint kinematic variability obtained from gait thus appear relevant for predicting individual differences in adapting to fatigue, and such measures could aid in predicting post-fatigue performance in diverse dynamic tasks.
Understanding the drivers of and barriers to adopting passive back- and arm-support exoskeletons in construction: Results from interviews and short-term field testing
Ashtiani, Mohamad Behjati; Morris, Wallace; Ojelade, Aanuoluwapo; Kim, Sunwook; Akinwande, Feyisayo; Barr, Alan; Harris-Adamson, Carisa; Akanmu, Abiola; Nussbaum, Maury A. (Elsevier, 2025-05)
Construction workers experience high rates of work-related musculoskeletal disorders (WMSDs), particularly affecting the back and shoulders. Exoskeletons (EXOs), including arm-support (ASEs) and back-support (BSEs) devices, have clear potential as ergonomic interventions for reducing WMSD risks, yet the specific benefits and limitations in the construction industry remain largely unclear. We aimed to identify drivers and barriers to adopting EXOs in construction, which was done using a two-phase approach: an interview study involving 24 construction stakeholders, followed by a field study with 22 construction workers. Participants in the interview study had hands-on experiences with diverse EXOs, then provided feedback on initial impressions, perceived barriers, and potential benefits of EXO use. Interview recordings were analyzed for sentiment, systematically categorizing responses as positive, neutral, and negative. During the field study, workers wore EXOs while performing their job tasks for up to 1 h, then completed structured exit surveys that assessed usability, comfort, safety, and overall satisfaction. We found a generally positive view of EXO technology in construction, with stakeholders open to adoption for enhancing productivity and reducing physical demands. However, usability, safety, and social acceptance concerns indicated a need for design improvements focused on comfort and compatibility. Notably, safety concerns expressed by interviewees contrasted with positive field study responses, suggesting that the input obtained can vary between assessment conditions. Future research should include longitudinal studies to track shifts in perception and assess diverse designs. These findings highlight the need for refined EXOs to meet construction demands and support broader industry adoption.
Estimating dynamic external hand forces during overhead work with and without an exoskeleton: Evaluating an approach using electromyography signals and random forest regression
Ashtiani, Mohamad Behjati; Ojelade, Aanuoluwapo; Kim, Sunwook; Nussbaum, Maury A. (Elsevier, 2025-05)
We developed a model to estimate hand contact forces during dynamic overhead tasks completed with and without passive arm-support exoskeletons (ASEs). One approach to assessing ASE effectiveness is evaluating shoulder joint forces through inverse dynamics, which requires data on both external kinetics and body kinematics. However, obtaining the former (e.g., hand contact forces) is challenging. To address this, our model estimates these forces using electromyographic (EMG) signals. For model development, we used data from a study in which participants completed dynamic overhead task simulations under various conditions, both with and without three ASEs. A random forest regression was used to map EMG signals to time series of hand contact force, considering task conditions and biological sex. Overall, the model produced reasonable force estimations, with errors generally consistent across conditions and regardless of ASE use. However, the model tended to underestimate peak forces, especially for upward vs. forward exertions and among males vs. females. Overall, the proposed model has the potential to support musculoskeletal modeling for assessing the effect of ASE use on workers. We provide several suggestions for improving future model performance.
Learning to Teach Engineering Capstone Design: An Analysis of Faculty Members' Experiences
Paretti, Marie C.; Murzi, Homero; Lutz, Benjamin; Menon, Maya; Schibelius, Lisa (Tempus Publications, 2024)
The credentials required to teach engineering at the university level vary widely around the world. In the U.S., though many universities ask for a statement of teaching philosophy as part of job applications, U.S. faculty members are rarely, if ever, required to have any form of pedagogical training or credentials, and little is known about how many, to what extent, or with what frequency engineering faculty members engage in such faculty development around teaching and pedagogy. This study draws on interview data from a larger project examining capstone teaching, asking three questions: (1) What do faculty members need to learn to teach the capstone course? (2) How do they gain this learning? and (3) How does learning vary based on engineering discipline? Analysis revealed seven learning foci and three sources of learning and examined the relationships between them. Findings suggest that beyond general strategies for course design, assessment, active learning, and student motivation, capstone faculty members need to develop teaching practices such as structuring and mentoring teams, and such learning needs to be grounded in current industry practices. Given the central role of capstone courses in preparing students for engineering practice, departments and programs may need to think more intentionally about how they prepare new faculty members for the capstone teaching role, including explicit support for professional development.
Effects of exercise-induced low back pain on intrinsic trunk stiffness and paraspinal muscle reflexes
Miller, Emily M.; Bazrgari, Babak; Nussbaum, Maury A.; Madigan, Michael L. (Elsevier, 2012-11-23)
The purpose of this study was to (1) compare trunk neuromuscular behavior between individuals with no history of low back pain (LBP) and individuals who experience exercise-induced LBP (eiLBP) when pain free, and (2) investigate changes in trunk neuromuscular behavior with eiLBP. Seventeen young adult males participated including eight reporting recurrent, acute eiLBP and nine control participants reporting no history of LBP. Intrinsic trunk stiffness and paraspinal muscle reflex delay were determined in both groups using sudden trunk flexion position perturbations 1-2 days following exercise when the eiLBP participants were experiencing an episode of LBP (termed post-exercise) and 4-5 days following exercise when eiLBP had subsided (termed post-recovery). Post-recovery, when the eiLBP group was experiencing minimal LBP, trunk stiffness was 26% higher in the eiLBP group compared to the control group (p=0.033) and reflex delay was not different (p=0.969) between groups. Trunk stiffness did not change (p=0.826) within the eiLBP group from post-exercise to post-recovery, but decreased 22% within the control group (p=0.002). Reflex delay decreased 11% within the eiLBP group from post-exercise to post-recovery (p=0.013), and increased 15% within the control group (p=0.006). Although the neuromuscular mechanisms associated with eiLBP and chronic LBP may differ, these results suggest that previously-reported differences in trunk neuromuscular behavior between individuals with chronic LBP and healthy controls reflect a combination of inherent differences in neuromuscular behavior between these individuals as well as changes in neuromuscular behavior elicited by pain.
Effects of Age-Related Differences in Femoral Loading and Bone Mineral Density on Strains in the Proximal Femur During Controlled Walking
Anderson, Dennis E.; Madigan, Michael L. (Human Kinetics, 2012-11-21)
Maintenance of healthy bone mineral density (BMD) is important for preventing fractures in older adults. Strains experienced by bone in vivo stimulate remodeling processes, which can increase or decrease BMD. However, there has been little study of age differences in bone strains. This study examined the relative contributions of age-related differences in femoral loading and BMD to age-related differences in femoral strains during walking using gait analysis, static optimization, and finite element modeling. Strains in older adult models were similar or larger than in young adult models. Reduced BMD increased strains in a fairly uniform manner, whereas older adult loading increased strains in early stance but decreased strains in late stance. Peak ground reaction forces, hip joint contact forces, and hip flexor forces were lower in older adults in late stance phase, and this helped older adults maintain strains similar to those of young adults despite lower BMD. Because walking likely represents a "baseline" level of stimulus for bone remodeling processes, increased strains during walking in older adults might indicate the extent of age-related impairment in bone remodeling processes. Such a measure might be clinically useful if it could be accurately determined with age-appropriate patient-specific loading, geometry, and BMD.

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