Scholarly Works, Industrial and Systems Engineering

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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.
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.
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.
Healthy older adults have insufficient hip range of motion and plantar flexor strength to walk like healthy young adults
Anderson, Dennis E.; Madigan, Michael L. (Elsevier, 2014-01-10)
Limited plantar flexor strength and hip extension range of motion (ROM) in older adults are believed to underlie common age-related differences in gait. However, no studies of age-related differences in gait have quantified the percentage of strength and ROM used during gait. We examined peak hip angles, hip torques and plantar flexor torques, and corresponding estimates of functional capacity utilized (FCU), which we define as the percentage of available strength or joint ROM used, in 10 young and 10 older healthy adults walking under self-selected and controlled (slow and fast) conditions. Older adults walked with about 30% smaller hip extension angle, 28% larger hip flexion angle, 34% more hip extensor torque in the slow condition, and 12% less plantar flexor torque in the fast condition than young adults. Older adults had higher FCU than young adults for hip flexion angle (47% vs. 34%) and hip extensor torque (48% vs. 27%). FCUs for plantar flexor torque (both age groups) and hip extension angle (older adults in all conditions; young adults in self-selected gait) were not significantly <100%, and were higher than for other measures examined. Older adults lacked sufficient hip extension ROM to walk with a hip extension angle as large as that of young adults. Similarly, in the fast gait condition older adults lacked the strength to match the plantar flexor torque produced by young adults. This supports the hypothesis that hip extension ROM and plantar flexor strength are limiting factors in gait and contribute to age-related differences in gait.
Age Differences in the Required Coefficient of Friction During Level Walking Do Not Exist When Experimentally-Controlling Speed and Step Length
Anderson, Dennis E.; Franck, Christopher T.; Madigan, Michael L. (Human Kinetics, 2014-06-30)
The effects of gait speed and step length on the required coefficient of friction (COF) confound the investigation of age-related differences in required COF. The goals of this study were to investigate whether age differences in required COF during self-selected gait persist when experimentally-controlling speed and step length, and to determine the independent effects of speed and step length on required COF. Ten young and 10 older healthy adults performed gait trials under five gait conditions: self-selected, slow and fast speeds without controlling step length, and slow and fast speeds while controlling step length. During self-selected gait, older adults walked with shorter step lengths and exhibited a lower required COF. Older adults also exhibited a lower required COF when walking at a controlled speed without controlling step length. When both age groups walked with the same speed and step length, no age difference in required COF was found. Thus, speed and step length can have a large influence on studies investigating age-related differences in required COF. It was also found that speed and step length have independent and opposite effects on required COF, with step length having a strong positive effect on required COF, and speed having a weaker negative effect.
Executive Function and Measures of Fall Risk Among People With Obesity
Wu, Xuefang; Nussbaum, Maury A.; Madigan, Michael L. (Sage, 2016-05-11)
This study investigated the relationship between obesity and executive function, and between executive function and fall risk (as estimated from select gait parameters). Of the 39 young adults (age = 21.3±2.6 years) recruited from the local university population via email announcement, 19 were in the obese group (based upon BMI and body fat percentage) and 20 were in the nonobese comparison group. Executive function was assessed using standardized tests including the Stroop test for selective attention; Trail Making test for divided attention, visuomotor tracking, and cognitive flexibility; the Verbal Fluency test for semantic memory; and the Digit-span test for working memory. Participants performed singleand dual-task walking (walking while talking) to evaluate fall risk during gait as measured by minimum toe clearance, required coefficient of friction, stance time, and stance-time variability. The obese group had lower scores for selective attention, semantic memory, and working memory. All participants had gait changes suggestive of a higher fall risk, for example, lower minimum toe clearance, longer stance time, and increased stance variability, during dual-task walking compared with single-task walking, and executive function scores (selective attention) were associated with gait (stance-time variability) during dual-task walking. Results indicate obesity was negatively associated with executive function among young adults and could increase fall risk.
Improvement in trunk kinematics after treadmill-based reactive balance training among older adults is strongly associated with trunk kinematics before training
Aviles, Jessica; Wright, David L.; Allin, Leigh J.; Alexander, Neil B.; Madigan, Michael L. (Elsevier, 2020-11-09)
Reactive balance training (RBT) is an emerging fall prevention exercise intervention for older adults. To better understand factors that influence improvements after RBT, the goal of this study was to identify key factors that strongly associate with training-induced improvements in reactive balance. This study is a secondary analysis of data from a prior study. Twenty-eight residents of senior housing facilities participated, including 14 RBT participants and 14 Tai Chi participants (controls). Before and one week after training, participants completed balance and mobility tests and a reactive balance test. Reactive balance was operationalized as the maximum trunk angle in response to standardized trip-like perturbations on a treadmill. Bivariate (Pearson) correlation was used to identify participant characteristics before RBT and measures of performance during RBT that associated with training-induced changes in maximum trunk angle. Maximum trunk angle before reactive balance training exhibited the strongest association with training-induced changes in maximum trunk angle among RBT participants (r2 = 0.84; p < .001), but not among Tai Chi participants (r2 = 0.17; p = .138). Measures of performance during RBT, based upon perturbation speed, also associated with RBT-induced improvements in maximum trunk angle. These results help clarify the characteristics of individuals who can benefit from RBT, and support the use of treadmill perturbation speed as a surrogate measure of training-induced improvements in trunk kinematics.
Effects of Manual Material Handling Workload on Measures of Fall Risk
Allin, Leigh J.; Madigan, Michael L. (Taylor & Francis, 2020-12-15)
OCCUPATIONAL APPLICATIONS: We found, contrary to expectations, that performing a fatiguing simulated heavy manual material handling (MMH) task did not adversely affect the risk of trip-induced falls when compared to a less-fatiguing light MMH task. However, when considering these MMH tasks together rather than in comparison, our results provide evidence for adverse effects of fatigue on both gait and the ability to recover balance after tripping. The current results provide additional evidence that physical fatigue increases fall risk, start to clarify the mechanisms by which this increase occurs, and can help in developing and evaluating fall prevention strategies targeting these mechanisms.
Potential Implementation of Reactive Balance Training within Continuing Care Retirement Communities
Aviles, Jessica; Porter, Gwenndolyn C.; Estabrooks, Paul A.; Alexander, Neil B.; Madigan, Michael L. (Lippincott Williams & Wilkins, 2020-03-15)
Purpose: The purpose of the study was to evaluate the feasibility of implementing reactive balance training (RBT) in continuing care retirement communities, as a part of typical practice in these facilities. Methods: RBT, a task-specific exercise program, consisted of repeatedly exposing participants to trip-like perturbations on a modified treadmill to improve reactive balance, and subsequently reduce fall risk. Semi-structured interviews were conducted with retirement community residents (RBT participants) and administrators, to assess the organizational context, perceptions of evidence for falls prevention, and facilitation strategies that could improve the likelihood of implementing RBT as a falls-prevention program. Results: Contextual factors such as leadership support, culture of change, evaluation capabilities, and receptivity to RBT among administrators and health leaders at the participating retirement communities could facilitate future implementation. The cost associated with RBT (e.g. equipment and personnel), resident recruitment, and accessibility of RBT for many residents were identified as primary barriers related to the intervention. Participants perceived observable health benefits after completing RBT, had increased awareness toward tripping, and greater confidence with respect to mobility. Across interviewees potential barriers for implementation regarding facilitation revolved around the compatibility and customizability for different participant capabilities that would need to be considered before adopting RBT. Conclusion: RBT could fill a need in retirement communities and the findings provide areas of context, characteristics of the intervention, and facilitation approaches that could improve uptake.
Comparison of Treadmill Trip-Like Training Versus Tai Chi to Improve Reactive Balance Among Independent Older Adult Residents of Senior Housing: A Pilot Controlled Trial
Aviles, Jessica; Allin, Leigh J.; Alexander, Neil B.; Van Mullekom, Jennifer; Nussbaum, Maury A.; Madigan, Michael L. (Oxford University Press, 2018-12-21)
Background: There is growing interest in using perturbation-based balance training to improve the reactive response to common perturbations (eg, tripping and slipping). The goal of this study was to compare the efficacy of treadmill-based reactive balance training versus Tai Chi performed at, and among independent residents of, older adult senior housing. Methods: Thirty-five residents from five senior housing facilities were allocated to either treadmill-based reactive balance training or Tai Chi training. Both interventions were performed three times per week for 4 weeks, with each session lasting approximately 30 minutes. A battery of balance tests was performed at baseline, and again 1 week, 1 month, 3 months, and 6 months post-training. The battery included six standard clinical tests of balance and mobility, and a test of reactive balance performance. Results: At baseline, no significant between-group differences were found for any balance tests. After training, reactive balance training participants had better reactive balance than Tai Chi participants. Maximum trunk angle was 13.5 smaller among reactive balance training participants 1 week after training (p =. 01), and a reactive balance rating was 24%-31% higher among reactive balance training participants 1 week to 6 months after training (p <. 03). Clinical tests showed minimal differences between groups at any time point after training. Conclusion: Trip-like reactive balance training performed at senior housing facilities resulted in better rapid balance responses compared with Tai Chi training.
A Reactive Balance Rating Method That Correlates With Kinematics After Trip-like Perturbations on a Treadmill and Fall Risk Among Residents of Older Adult Congregate Housing
Madigan, Michael L.; Aviles, Jessica; Allin, Leigh J.; Nussbaum, Maury A.; Alexander, Neil B. (Oxford University Press, 2018-04-16)
Background: A growing number of studies are using modified treadmills to train reactive balance after trip-like perturbations that require multiple steps to recover balance. The goal of this study was thus to develop and validate a low-tech reactive balance rating method in the context of trip-like treadmill perturbations to facilitate the implementation of this training outside the research setting. Methods: Thirty-five residents of five senior congregate housing facilities participated in the study. Participants completed a series of reactive balance tests on a modified treadmill from which the reactive balance rating was determined, along with a battery of standard clinical balance and mobility tests that predict fall risk. We investigated the strength of correlation between the reactive balance rating and reactive balance kinematics. We compared the strength of correlation between the reactive balance rating and clinical tests predictive of fall risk with the strength of correlation between reactive balance kinematics and the same clinical tests. We also compared the reactive balance rating between participants predicted to be at a high or low risk of falling. Results: The reactive balance rating was correlated with reactive balance kinematics (Spearman's rho squared = .04-.30), exhibited stronger correlations with clinical tests than most kinematic measures (Spearman's rho squared = .00-.23), and was 42%-60% lower among participants predicted to be at a high risk for falling. Conclusion: The reactive balance rating method may provide a low-tech, valid measure of reactive balance kinematics, and an indicator of fall risk, after trip-like postural perturbations.
Relative Strength at the Hip, Knee, and Ankle Is Lower Among Younger and Older Females Who Are Obese
Koushyar, Hoda; Nussbaum, Maury A.; Davy, Kevin P.; Madigan, Michael L. (Lippincott Williams & Wilkins, 2016-03-22)
Background and Purpose: The mobility of individuals who are obese can be limited compared with their healthy weight counterparts. Lower limb strength has been associated with mobility, and reduced strength may contribute to mobility limitation among individuals who are obese. However, our understanding of the effects of obesity on lower limb strength is limited. The purpose of this study was to investigate the effects of obesity and age on extension and flexion strength at the hip, knee, and ankle. Methods: Using a cross-sectional design, 10 younger (18-30 years) healthy weight (body mass index = 18-24.9 kg/m2), 10 younger obese (body mass index >30 kg/m2), 10 older (65-80 years) healthy weight, and 10 older obese female participants performed isokinetic maximum voluntary contractions in ankle plantar flexion (PF), ankle dorsiflexion (DF), knee extension (KE), knee flexion (KF), hip extension (HE), and hip flexion (HF). Results and Discussion: Absolute strength among obese participants was 29% higher in DF (P =.002), 27% higher in KE (P =.004), and 23% higher in HF (P =.001), compared with healthy weight participants. Strength relative to body mass among obese participants was 31% lower in PF (P <.001), 14% lower in DF (P =.042), 16% lower in KE (P =.015), 27% lower in KF (P <.001), 29% lower in HE (P <.001), and 19% lower in HF (P =.001). Conclusions: Obese females exhibited lower relative strength at the ankle and hip, similar to the lower relative strength exhibited at the knee. Obese females also exhibited higher absolute strength, but only for 3 of 6 lower limb exertions investigated. This lack of uniformity across the 6 exertions is likely due to the still unclear underlying biomechanical mechanism responsible for these strength differences, which may also be influenced by aging. The effects of obesity on lower limb strength were also generally consistent between the 2 age groups investigated.
Fall impacts from standing show equivalence between experts in stage combat landing strategy and naive participants after training
Lee, Youngjae; Srinivasan, Divya; Rawlings, Cara; Madigan, Michael (IOS Press, 2022-11-11)
BACKGROUND: Slips, trips, and falls are the second leading cause of non-fatal injuries in workplace in the United States. A stage combat landing strategy is used in the theatre arts to reduce the risk of fall-induced injury, and may be a viable approach among some working populations. OBJECTIVE: The goal of this study was to compare fall impact characteristics between experts in stage combat landing strategy and naïve participants after four training sessions of stage combat landing strategy training. METHODS: Forward and backward falls from standing were induced by releasing participants from static leans. Participants fell onto a foam mat, and impact force was measured using force platforms under the mat. A statistical equivalence test was used to determine if impact characteristics between groups were similar. RESULTS: Results indicated equivalence between groups in peak impact force during backward but not forward falls. Equivalence between groups in impact time suggested a mechanism by which equivalence in peak impact force as achieve. CONCLUSIONS: Four training sessions was sufficient for naïve participants to exhibit fall impact characteristics similar to experts in an anecdotally-effective landing strategy, and support further study. To our knowledge, this was the first study to investigate training for a landing strategy involving stepping after losses of balance from standing.
Assessing the role of ankle and hip joint proprioceptive information in balance recovery using vibratory stimulation
Asghari, Mehran; Elali, Karam; Sullivan, Alexis; LaFleur, Bonnie; Madigan, Michael L.; Toosizadeh, Nima (Cell Press, 2024-02-11)
Background: Previous work suggests that proprioceptive information from ankle and hip are crucial in maintaining balance during upright standing; however, the contribution of these proprioceptive information during stepping balance recovery in not clear. The goal of the current study was to assess the role of ankle and hip proprioceptive information on balance recovery performance by manipulating type 1a afferent in muscle spindles using vibratory stimulation. Methods: Twenty healthy young participants were recruited (age = 22.2 ± 2.7 years) and were randomly assigned to balance recovery sessions with either ankle or hip stimulation. Trip-like perturbations were imposed using a modified treadmill setup with a protecting harness. Vibratory stimulation was imposed bilaterally on ankle and hip muscles to expose participants to three condition of no-vibration, 40Hz vibration, and 80Hz vibration. Kinematics of the trunk and lower-extremities were measured using wearable sensors to characterize balance recovery performance. Outcomes were response time, recovery step length, trunk angle during toe-off and heel-strike of recovery stepping, and required time for full recovery. Findings: Ankle vibratory stimulation elicited main effects on reaction time and recovery step length (p < 0.002); reaction time and recovery step length increased by 23.0% and 21.2%, respectively, on average across the conditions. Hip vibratory stimulation elicited significant increase in the full recovery time (p = 0.019), with 55.3% increase on average across the conditions. Interpretation: Current findings provided evidence that vibratory stimulation can affect the balance recovery performance, causing a delayed recovery initiation and an impaired balance refinement after the recovery stepping when applied to ankle and hip muscles, respectively.

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