A biomechanical approach to prevent falls in ergonomic settings

Introduction: Fall-related injuries are exceptionally prevalent in occupational settings. While endangering the workers’ health, falls cause poor productivity and increased economic burden in the workplace. Hence, identifying these threats and training workers to achieve proper postural control is crucial. Purpose: Study 1: To investigate the ankle joint kinematics in unexpected and expected trip responses during single-tasking (ST), dual-tasking (DT), and triple-tasking (TT), before and after a physically fatiguing exercise. Study 2: To investigate the impact of virtual heights, DT, and training on static postural stability and cognitive processing. Methods: Study 1: Twenty collegiate volunteers (10 males and females, one left leg dominant, age 20.35 plus-minus 1.04 years, height 174.83 plus-minus 9.03 cm, mass 73.88 plus-minus 15.55 kg) were recruited. Ankle joint kinematics were recorded while treadmill walking during normal gait (NG), unexpected trip (UT), and expected trip (ET) perturbations with DT and physical fatigue. Study 2: Twenty-eight collegiate volunteers (14 males and females; all right leg dominant; age 20.48 plus-minus 1.26 years; height 172.67 plus-minus 6.66 cm; mass 69.52 plus-minus 13.78 kg; body mass index 23.32 plus-minus 3.54 kg/m2) were recruited. They were exposed to different virtual environments (VEs) over three days with and without DT. Postural sway parameters, lower extremity muscle activity, heart rate, and subjective anxiety parameters were collected. Results: Study 1: Greater maximum ankle angles were observed during UT compared to NG, MDT compared to ST, and TT compared to ST, while greater minimum ankle angles were observed during ET compared to NG and during post-fatigue compared to pre-fatigue. Study 2: Greater postural decrements and poor cognitive processing were observed in high altitudes and DT. Discussion & conclusions: Study 1: Trip recovery responses are different between during DT, TT, and fatigue. Study 2: Static postural stability deteriorates at higher virtual altitudes and with DT, while it improves with a two-day training. Virtual height exposure reduces cognitive performance. Importance: The findings of these studies will provide insights into the biomechanics of falls in ergonomic settings and aid in designing functional and convenient fall prevention programs

Effects of Slips and Trips on Resultant Lumbar Kinematics, Lumbar Muscle Activity and Low-Back Loads

Slips, trips, and falls (STFs) represent one of the leading causes of occupational injuries and fatalities. In particular, many prior reports have linked STFs with the onset of low-back disorders, which, depending on the severity of the incident, can leave the worker physically limited both in the workplace and at home. In contrast, the incidence and outcomes of loads acting on the low back due to a slip and trip that does not lead to a fall (i.e., slip/trip without fall: STWF) remain only marginally investigated to date. To address this research deficit, this quantitative study was designed to explore selected physiological outcomes of STWFs. In terms of methodology, participants completed several walking trials during which two unexpected perturbations involving a slip and trip were introduced (a harness prevented a fall). A biomechanical model developed using the AnyBody modeling software yielded trunk kinematics and muscle geometry. These outputs - along with the electromyography of fourteen lumbar flexor and extensor muscles - were employed as input data for our 3D, dynamic, EMG-based lumbar spine model. Results of (a) lumbar kinematics (range of the motion of the trunk relative to the pelvis), (b) lumbar muscle activity, (c) lumbosacral reaction forces, and (d) moments all indicated more than a two-fold increase during the slip and trip trials compared to normal walking. Specifically, reported values for the slip trial were (a) 45°, (b) 0.694, (c) 2939 N, and (d) 52 Nm; Reported values for the trip trial were (a) 42°, (b) 0.691, (c) 2898 N, and (d) 50 Nm; and the analogous figures for normal walking were (a) 19°,(b) 0.195, (c) 1174 N, and (d) 16 Nm. Findings from this study can be used to develop interventions to avoid such incidents; for example, to determine specific training parameters (e.g., frequency, duration, and intensity) to optimize a developed intervention’s effectiveness. Such approaches may lead to the control of specific mechanisms involved with lowback disorders consequent to a slip or trip, and potentially reduce the risk for slip- and trip-related injuries

Impact of Total Knee Arthroplasty on Dynamic Fall Response

abstract: Falls are the leading cause of fatal and non-fatal injuries in the older adult population with more than 27,000 fall related deaths reported every year[1]. Adults suffering from lower extremity arthritis have more than twice the likelihood of experiencing multiple falls resulting in increased fall-related injuries compared to healthy adults. People with lower extremity end-stage osteoarthritis(KOA), experience a number of fall risk factors such as knee instability, poor mobility, and knee pain/stiffness. At end-stage knee OA, the space between the bones in the joint of the knee is significantly reduced, resulting in bone to bone frictional wearing causing bone deformation. In addition, an impaired stepping response during a postural perturbation is seen in people with OA related knee instability. The most common treatment for end-stage knee osteoarthritis is a surgical procedure called, total knee replacement (TKR). It is known that TKR significantly reduces pain, knee stiffness, and restores musculoskeletal functions such as range of motion. Despite studies concluding that knee OA increases fall-risk, it remains unknown if standard treatments, such as TKR, can effectively decrease fall-risk. Analyzing the compensatory step response during a fall is a significant indicator of whether a fall or a recovery will occur in the event of a postural disturbance and is key to determining fall risk among people. Studies have shown reduced trunk stability and step length, as well as increased trunk velocities, correspond to an impaired compensatory step. This study looks at these populations to determine whether TKR significantly enhances compensatory stepping response by analyzing trunk velocities and flexions among other kinematic/kinetic variable analysis during treadmill induced perturbations and clinical assessments.Dissertation/ThesisMasters Thesis Biomedical Engineering 201

An analysis of human gait under slippery conditions using OpenSim\u27s musculoskeletal simulations

Computational simulations of gait under abnormal conditions provide insights into the actions of muscles, its relationships with external reaction forces and motions of the body during slips, trips, and falls - the leading causes of occupational injuries worldwide. OpenSimTM, an open-source motion simulation software, was utilized to construct musculoskeletal structures and create dynamic simulations of body movements. Gaits of eighteen subjects were studied to extract experimentally difficult-to-obtained variables under slippery conditions. The joint angles and moments of hip, knee, ankle and the forces of four prime muscle groups were analyzed for body corrective movements during slip events. Besides, the connections between one\u27s perception of the surrounding environment and their postural alterations to prevent falls are also discussed. Hence, this study provides a better understanding on the joint angles, moments and muscle forces of human body, evaluates the movement deviations, and contributes to the development of predictive injury thresholds during slip events

The Slippery Slope Between Falling And Recovering: An Examination Of Sensory And Somatic Factors Influencing Recovery After A Slip

Background: Slips and falls account for large rates of injury and mortality in multiple populations. During an unexpected slip, sensory mechanisms are responsible for signaling the slip to the central nervous system, and a series of corrective responses is generated to arrest the slip and prevent a fall. While previous research has examined the corrective responses elicited, the answer of how these systems break down during a fall remains elusive. Purpose: To examine differences in postural control (slip detection), lower extremity corrective responses (slip recovery), and cortical control of the slip recovery response between individuals who fall and those who recover. Methods: One hundred participants were recruited for this study (50 males & 50 females). Participant’s gait kinematics and kinetics were collected during normal gait (NG) and an unexpected slip (US). The slip was classified as a fall or recovery, and by slip severity. Once classified, postural control, reaction times, corrective moments, and cortical contribution were examined between groups using ANOVAs and independent t-tests. Additionally, prediction equations for slip outcome, and slip severity were created using a binary logistic regression model. Slip Detection Results: Postural sway when the proprioceptive (OR = 0.02, CI: 0.01-1.34) and vestibular (OR = 0.60, CI: 0.26-1.39) systems are stressed were negatively associated with odds of falling. While postural sway when the visual system was stressed (OR = 3.18, CI: 0.887-11.445) was positively associated with odds of falling. Slip Recovery Results: Increased time to peak hip extension (OR = 1.006, CI: 1.00-1.01) and ankle dorsiflexion (OR = 1.005, CI: 1.00-1.01) moments increased the odds of falling. While the average ankle moment was negatively associated with falling (OR = 0.001, CI: 0.001-0.005). Cortical Contribution Results: Spectral power in the Piper frequency band was increased in US trials compared to NG. Further, fallers exhibited an increase in cortical activity compared to those who recovered. Conclusions: Rapid lower extremity corrective responses appear critical in arresting the slip and preventing a fall, and the temporal nature of this response may depend on slip detection and subsequent response selection. Moreover, our results suggest that more severe slips may require increased activation of higher centers of the motor cortex

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

Evaluating the Effects of Ankle-Foot-Orthoses, Functional Electrical Stimulators, and Trip-specific Training on Fall Outcomes in Individuals with Stroke

abstract: This dissertation aimed to evaluate the effectiveness and drawbacks of promising fall prevention strategies in individuals with stroke by rigorously analyzing the biomechanics of laboratory falls and compensatory movements required to prevent a fall. Ankle-foot-orthoses (AFOs) and functional electrical stimulators (FESs) are commonly prescribed to treat foot drop. Despite well-established positive impacts of AFOs and FES devices on balance and gait, AFO and FES users fall at a high rate. In chapter 2 (as a preliminary study), solely mechanical impacts of a semi-rigid AFO on the compensatory stepping response of young healthy individuals following trip-like treadmill perturbations were evaluated. It was found that a semi-rigid AFO on the stepping leg diminished the propulsive impulse of the compensatory step which led to decreased trunk movement control, shorter step length, and reduced center of mass (COM) stability. These results highlight the critical role of plantarflexors in generating an effective compensatory stepping response. In chapter 3, the underlying biomechanical mechanisms leading to high fall risk in long-term AFO and FES users with chronic stroke were studied. It was found that AFO and FES users fall more than Non-users because they have a more impaired lower limb that is not fully addressed by AFO/FES, therefore leading to a more impaired compensatory stepping response characterized by increased inability to generate a compensatory step with paretic leg and decreased trunk movement control. An ideal future AFO that provides dorsiflexion assistance during the swing phase and plantarflexion assistance during the push-off phase of gait is suggested to enhance the compensatory stepping response and reduce more falls. In chapter 4, the effects of a single-session trip-specific training on the compensatory stepping response of individuals with stroke were evaluated. Trunk movement control was improved after a single session of training suggesting that this type of training is a viable option to enhance compensatory stepping response and reduce falls in individuals with stroke. Finally, a future powered AFO with plantarflexion assistance complemented by a trip-specific training program is suggested to enhance the compensatory stepping response and decrease falls in individuals with stroke.Dissertation/ThesisDoctoral Dissertation Mechanical Engineering 201

An Evaluation of the Relationship Between Core Endurance and Lower Extremity Strength, and the Ability to Recover After Perturbation

Previous research suggests core strength training improves anticipatory postural adjustments, reducing one’s risk of a fall, and stronger core muscles lead to faster reaction times. This study investigated whether core endurance and lower extremity strength relate to the time one needs to stabilize after being perturbed. An evaluation of ten participants while warming up determined each participant’s transition speed between walking and running. While each participant walked at his/her transition speed, the belts were stopped randomly at an acceleration rate of 2.7 m∙s-2 and ground reaction forces were recorded during balance recovery. Additionally, each participant completed a series of core endurance and lower extremity strength assessments, revealing a significant relationship only between hip extension and time to stability in the medial/lateral direction (r = .784, p = .012). Results contrasted expectations but match recent leanings in literature, suggesting isolated strength measures fail adequately to predict time to stability