Gait Posture

Background:A plurality of fatal falls to lower levels involve ladders. After a slip/misstep on a ladder, climbers use their upper and lower limbs to reestablish contact with the ladder.Research question:This study investigates the impact of upper body strength, hand placement and foot placement on fall severity after a ladder climbing perturbation.Methods:Participants performed upper body strength tests (breakaway and grip strength) and climbed a vertical, fixed ladder while a misstep perturbation was applied under the foot. After the perturbation, three hand placement and two foot placement responses were generally observed. Common hand placement responses included the hand moving two rungs, one rung, or did not move to a different rung. Foot placement responses included at least one foot or no feet reestablished contact with the ladder rung(s). Fall severity was quantified by the peak harness force observed after the perturbation.Results:Increased strength, reestablishing at least one foot on the ladder, and ascending (compared with descending) the ladder was associated with a reduction in fall severity. An interaction effect indicated that the impact of hand placement was altered by climbing direction. Moving the hand one rung during ascent and moving the hand two rungs during descent was associated with an increased fall severity. Cases where the hand decoupled from the ladder was associated with higher fall severity. Upper body strength assessed using a portable grip dynamometer was sufficient to predict fall severity.Discussion:This study confirms the multifactor role of upper body strength, hand placement and foot placement in preventing falls from ladders. Furthermore, a portable dynamometer shows potential to screen for high-risk individuals. Results of this investigation may guide targeted interventions to prevent falls from ladders.20182020-02-01T00:00:00ZP20 GM109040/GM/NIGMS NIH HHS/United StatesR21 OH010038/OH/NIOSH CDC HHS/United States30439684PMC6380680717

Factors Contributing to Ladder Falls and Broader Impacts on Safety and Biomechanics

Ladder falls cause disabling injury and death in the workplace and at home. Numerous scenarios lead to ladder falls given the variation in ladder types and how they are used. Of the potential factors influencing ladder fall risk under these different scenarios, many have yet to be investigated. This dissertation used a multifaceted approach to determine ladder fall risk factors. Specifically, this dissertation tested younger and older adults, designed occupational and domestic based ladder experiments, and investigated factors that precede and follow a ladder falling event. Aim 1 of this dissertation identified individual factors associated with safe and effective domestic ladder use among older adults. Balance measured with clinical assessments was a primary predictor of safe and effective ladder use. Aim 2 of this dissertation determined individual, environmental and biomechanical factors that aid in arresting a falling event from a ladder. Ascending climbs, males, greater upper body strength, higher hand placement during recovery and reestablishing at least one foot back onto the ladder during recovery were associated with reduced ladder fall severity (i.e. better recovery). Surprisingly, glove condition was not found to contribute to ladder fall severity. Hand-rung forces were correlated with the severity of the falling event and not an individual’s ability to generate force, suggesting that these forces are dependent on the circumstances of the perturbation. Findings from this dissertation may guide fall interventions (e.g. screenings, improvements in safety standards, perturbation response training, ladder re-design). Therefore, this work is expected to have impact on the safety field by reducing ladder fall injuries. Furthermore, this work contributes new knowledge to the biomechanics of ladder use and fall recovery. As part of a larger strategy to improve safety for all populations, increased diversity is needed in the Science, Technology, Engineering, and Mathematics (STEM) fields. Aim 3 of this dissertation utilized biomechanics as a link to develop a student-interest based pedagogy to improve engagement of underrepresented groups in the STEM fields. This work found lectures tailored to student interests to increase student engagement. Long-term effects from this work can increase diversity in the STEM fields including safety

Development of a methodology for integrated performance analyses of anti-vibration gloves for controlling the hand-transmitted vibration

Hand-transmitted vibration (HTV) arising from hand-held power tools has been associated with an array of disorders of the hand-arm system, collectively referred to as the hand-arm vibration syndrome (HAVS). The risk of HAVS among hand-held power tools operators has been related to the nature of HTV exposure and the mechanical coupling of the hand with a tool handle, which is neglected in the current standardized exposure assessment method (ISO 5349, 2001). Anti-vibration (AV) gloves are considered as convenient and effective means to reduce exposure to HTV. The effectiveness of AV gloves is, invariably, assessed on the basis of the handle vibration transmitted to the palm of the hand. The method does not consider the vibration responses of the fingers, which differ significantly from that of the palm. The AV gloves adversely influence the manual dexterity and grip strength of the operators, which are considered as primary factors discouraging the usage of AV gloves. The current standardized method, however, does not consider the loss of dexterity and grip strength caused by wearing these gloves. This thesis proposes a methodology for evaluating the integrated performance of AV gloves, considering the distributed vibration transmission to the palm and fingers through gloves, manual dexterity and grip strength. In order to establish the methodology, independent experiments were designed to quantify each performance measure. Three series of experiments were designed to evaluate vibration responses distributed over the palm and fingers, manual dexterity and grip strength performance of gloves. Each experiment design involved ten different gloves and 15 adult male subjects. Viscoelastic properties of vibration isolation materials used in the AV gloves were also characterized under a constant preload. In the first series, the fine fingers and hand dexterity were investigated using the Two-Hand Turing & Placing Minnesota and ASTM F2010 methods. Subsequently, the handle vibration transmitted to the palm and mid phalanges of the index and middle fingers of the glove hand were measured along the three translational axes using the palm and fingers’ adapters, respectively. In the final series, the influence of AV gloves on the operator’s grip strength were investigated via direct as well as indirect methods. A flexible thin-film hand sensor was designed and verified for direct measurement of the contact force developed at the rigid as well as flexible hand-handle, and hand-glove interfaces. The activities of four different forearm muscles were also measured via surface electromyography (EMG) under different hand grip forces imposed by the gloved hand. The correlations among the individual performance measures of AV gloves and the material properties were analyzed via Pearson’s correlation coefficient, which provided essential knowledge on the roles of design factors and the design guidance. A relationship among the hand grip, push and contact forces imposed on flexible hand-handle was developed via multiple linear regression analysis. The individual measures of AV gloves were also analyzed via two-factor repeated analyses of variance (ANOVA) and multivariate analysis of variance (MANOVA) to evaluate significance of different independent variables such as glove type, test method, frequency range, and hand grip force. The glove type yielded significant effect on all the measures (p<0.05). Post-Hoc tests were subsequently conducted via Bonferroni and Tukey HSD (honest significant difference) test for discriminating difference among the gloves. The combination of extensor carpi radialis longus (ECR) and flexor carpi radialis (FCR) muscles activities revealed highest sensitivity to discriminate among gloves and could serve as an effective indirect measure of the grip strength performance. Increasing the glove thickness resulted in improved vibration isolation by the glove but reduced manual dexterity and enhanced muscles activities. Strong correlation was observed between the material stiffness and wh-weighted palm vibration transmissibility in the high frequency range (r>0.90), while a weak correlation was evident between the manual dexterity and the wp-weighted fingers’ vibration transmissibility. Strong positive correlations were observed among the palm vibration isolation, material properties and material thickness in the 25-1250 Hz frequency range. The results also revealed conflicting glove design requirements imposed by the individual measures. A methodology based on analytical hierarchy process (AHP) is proposed to identify weightings for the conflicting performance measures for the given work condition, classified in accordance with the frequency ranges of predominant vibration (low and high), as defined in ISO-10819 (2013) together with assembly/disassembly tasks. An integrated performance index is identified and applied to rank five different AV gloves with known individual performance measures for identifying the most desirable glove