Chip Wade

Impact on balance while walking in occupational footwear

Hazards and challenges present in the workplace pose a number of potential balance risks for injuries and illness. Purpose: The purpose of the study was to examine the differences in balance while walking for extended durations with different types of occupational footwear. Methods: Participants were tested for balance prior to walking session (Pre) and then again every 30 minutes until the 240th minute in three types of occupational footwear; work boots, tactical boots and low top shoes. Sway velocity and root-mean-square sway in the anterior-posterior and medial-lateral directions were evaluated using a 3 × 9 repeated measures analysis of variance to identify any existing differences within exposure time and footwear types. Results: Significant differences in postural sway were found over time in medial-lateral sway and between footwear in anterior-posterior and medial-lateral sway. Significant differences were found between the work boots, tactical boots and low top shoes, with the low top shoes exhibiting an increased postural sway. Conclusion: The changes in balance over time may be attributed to the workload placed on the individual resulting from the extended durations of walking/standing. Use of low top shoes resulted in a relatively greater balance decrement. The work boots and tactical boots despite having a greater mass, resulted in less of a balance decrement, which may be attributed to their elevated boot shaft height.

Joint kinetics and muscle activity while walking on ballast.

Objective: This study examined the impact of two common sizes of ballast on gait biomechanics. The terrain was designed to simulate a railroad work setting to investigate the variation in gait kinetics and muscle activation while walking. Background: Research and epidemiology suggest a potential link between walking surface characteristics and injury. However, few studies have investigated the impact of ballast surfaces, which is a surface of interest in the railroad and construction industries, on gait dynamics. Method: For this study, 20 healthy adult men walked along three distinct pathways (no ballast [NB], walking ballast [WB], and mainline ballast [MB]). WB and MB consisted of rock with an average size of 0.75 to 1 in. and 1.25 to 1.5 in., respectively. Full-body motion, ground reaction forces, and electromyographic (EMG) signals from lower extremity muscles were collected, and three dimensional joint moments were calculated. Parameters of interest were moment trajectories and ranges, EMG activity, and temporal gait measures. Results: Joint-specific differences indicate significant variations between surface conditions. Joint moment ranges were generally smaller for MB and WB compared with NB. EMG activity, in particular, co-contraction levels, was found to be significantly greater on ballast compared with NB. Temporal gait parameters were significantly different for MB than for either WB or NB. Conclusion: Walking on ballast increases muscle activation to control the moments of the lower extremity joints. Application: The results suggest that ballast has an effect on muscles and joints; thus, the findings provide insight to improve and develop new work practices and methods for injury prevention.

Physiological responses to simulated stair climbing in professional firefighters wearing rubber and leather boots

No studies have considered whether a firefighter’s boots are a factor influencing physiological responses. The purpose of this study was to examine physiological responses to a fire simulation activity (stair climb) in professional firefighters wearing rubber boots (RB) and leather boots (LB). Twelve professional firefighters participated in two counterbalanced simulated firefighter stair climb (SFSC) sessions, one wearing RB and the other wearing LB. Heart rate, oxygen uptake (VO2), expiratory ventilation (VE), blood lactate (BLa), salivary cortisol (SCORT), and leg strength were assessed prior to and following a SFSC. LB elicited significantly greater SCORT values and knee flexion time to peak torque. Furthermore, RB revealed significantly greater ankle dorsiflexion peak torque after SFSC. BLa was positively related to knee flexion peak torque after SFSC in the RB. Firefighters when wearing the RB may be more effective at resisting fatigue and increase more force production.

The influence of occupational footwear on dynamic balance perturbations

Occupational footwear is designed for safety and have been shown to impact balance, especially in occupational environments, where the human body is subjected to destabilizing forces by both internal and external perturbations. Purpose: The purpose of the study was to analyze the effects of three industry standard occupational footwear on balance performance during external perturbations. Methods: Thirty-one healthy male adults (age: 21.2 ± 1.4 years; height: 179 ± 9.4 cm; mass: 82.6 ± 15.4 kg) with no history of neuro-musculoskeletal abnormalities participated in this study. The experimental procedure followed a repeated measures design; all participants were tested for balance with barefoot (BF), and three occupational footwear presented in a randomized order: low top shoe (LT), tactical boot (TB) and work boot (WB) on the same day separated by 10-minute washout rest periods. Balance was assessed by Motor Control Test (MCT) on the NeuroCom Equitest with synced electromyography (EMG) recordings from right lower extremity muscles. Postural response latencies, EMG mean, peak, %maximal voluntary contraction and time-to-peak muscle activity were analyzed using a one-way RM ANOVA individually for backward and forward perturbations (p = 0.05) and followed by pairwise comparisons with a Bonferroni correction. Results: Postural response latencies were significantly faster with barefoot. Although no differences existed for response latencies between LT, TB and WB, the TB demonstrated significantly lower muscle activity during balance perturbations. Conclusion: Under acute conditions, even though postural response latencies were faster in barefoot condition, use of tactical boot had normal response latencies and also demonstrated significantly lower muscle activity, suggesting the need for only minimal requirement of muscular effort to maintain balance when exposed to external perturbations.

Balance and exposure to an elevated sloped surface

Fall injuries and fatalities exceed 50 billion dollars annually. One half of fatal falls are from pitched roof settings. Falls from elevation in an occupational setting have been documented to be a significant issue in todays workforce. The purpose of this study was to investigate the influence of exposure to inclined surfaces on flat surface balance at varying heights above the ground. Thirty participants, 10 male college students (inexperienced), 10 female college students (inexperienced) and 10 male roofers (experienced) between age 19 and 50 years participated in this study. Participants walked for 20 min on an elevated roof segment (9-14 feet above ground level) and a ground level roof segment (0-5 feet above ground level) on separate days. Results indicated a significant difference for all groups in sway velocity over time at both levels (elevated and ground) and from eyes open to eyes closed conditions at both levels (p<0.05). Statistical analysis revealed that roofers had significantly less increase in sway velocity, post exposure than that of the inexperienced group (p<0.05). These findings provide practical information to employers and employees during the construction of structures that employ a pitched roof design. The implication of these findings include the knowledge that an individual is less stable directly after performing roofing tasks on a pitched roof setting, and should be afforded ample time to recover before moving into activities that would place them at a higher risk of injury from falls.

Walking on ballast impacts balance

Railroad workers often perform daily work activities on irregular surfaces, specifically on ballast rock. Previous research and injury epidemiology have suggested a relationship between working on irregular surfaces and postural instability. The purpose of this study was to examine the impact of walking on ballast for an extended duration on standing balance. A total of 16 healthy adult males walked on a 7.62 m × 4.57 m (25 ft × 15 ft) walking surface of no ballast (NB) or covered with ballast (B) of an average rock size of about 1 inch for 4 h. Balance was evaluated using dynamic posturography with the NeuroCom® Equitest System™ prior to experiencing the NB or B surface and again every 30 min during the 4 h of ballast exposure. Dependent variables were the sway velocity and root-mean-square (RMS) sway components in the medial–lateral and anterior–posterior directions. Repeated measures ANOVA revealed statistically significant differences in RMS and sway velocity between ballast surface conditions and across exposure times. Overall, the ballast surface condition induced greater sway in all of the dynamic posturography conditions. Walking on irregular surfaces for extended durations has a deleterious effect on balance compared to walking on a surface without ballast. These findings of changes in balance during ballast exposure suggest that working on an irregular surface may impact postural control. Practitioner Summary: Epidemiology and scientific literature indicate a conceivable connection between walking surface characteristics and injury. These potential links are particularly evident in the railroad industry given the ballast surfaces widely encountered. The current findings provide data in which to enhance current work practices focusing on postural instability.

Slip initiation in alternative and slip-resistant footwear

Slips occur as a result of failure of normal locomotion. The purpose of this study is to analyze the impact of alternative footwear (Crocs™, flip-flops) and an industry standard low-top slip-resistant shoe (SRS) under multiple gait trials (normal dry, unexpected slip, alert slip and expected slip) on lower extremity joint kinematics, kinetics and muscle activity. Eighteen healthy male participants (age: 22.28 ± 2.2 years; height: 177.66 ± 6.9 cm; mass: 79.27 ± 7.6 kg) completed the study. Kinematic, kinetic and muscle activity variables were analyzed using a 3(footwear) × 4(gait trials) repeated-measures analysis of variance at p = 0.05. Greater plantar flexion angles, lower ground reaction forces and greater muscle activity were seen on slip trials with the alternative footwear. During slip events, SRS closely resembled normal dry biomechanics, suggesting it to be a safer footwear choice compared with alternative footwear.

Impact of alternative footwear on human balance

Alternative footwear are those that are most commonly used for casual or recreational purposes, over the course of the day. The purpose of this study was to examine the effects of three forms of alternative footwear (thong style flip-flops, clog style Crocs®, and Vibram Five-Fingers®) on balance with a low-intensity workload. Eighteen healthy male adults (age: 22.9 ± 2.88 years; height: 179 ± 6.0 cm; mass: 81.3 ± 8.8 kg) participated in this study. Balance performance along with electromyographic (EMG) measures was assessed with sensory organization test (SOT) and motor control test on the Neurocom Equitest, while donning alternative footwear, prior to and after a one-mile walk at a self-selected pace. Sway velocities and root-mean-square sway, SOT equilibrium scores, postural response latencies, and EMG measures from lower leg muscles were analysed using a 3 × 2 (footwear × time) repeated-measures ANOVA. Results from balance variables revealed a significant main effect difference for footwear in the eyes closed and eyes open sway-referenced vision conditions and a significant main effect difference for time in the eyes open, eyes open sway-referenced vision, and eyes open sway-referenced platform conditions. Pairwise comparisons revealed MIN demonstrating significantly greater balance performance in the pretest condition and the post-test demonstrating significantly lower balance performance. Greater balance performance from MIN could be attributed to the barefoot design suggesting an increase in somatosensory feedback from the plantar surface, particularly during absent or conflicting visual feedback. The lower balance performance seen in post-test could be attributed to the one-mile walk, suggesting that even a transient physiological workload could be sufficient to cause balance decrements in alternative footwear.

Measurement Performance of a Computer Assisted Vertebral Motion Analysis System.

Background Segmental instability of the lumbar spine is a significant cost within the US health care system; however current thresholds for indication of radiographic instability are not well defined. Purpose To determine the performance measurements of sagittal lumbar intervertebral measurements using computerassisted measurements of the lumbar spine using motion sequences from a video-fluoroscopic technique. Study design Sensitivity, specificity, predictive values, prevalence, and test-retest reliability evaluation of digitized manual versus computer-assisted measurements of the lumbar spine. Patient sample A total of 2239 intervertebral levels from 509 symptomatic patients, and 287 intervertebral levels from 73 asymptomatic participants were retrospectively evaluated. Outcome measures Specificity, sensitivity, negative predictive value (NPV), diagnostic accuracy, and prevalence between the two measurement techniques; Measurements of Coefficient of repeatability (CR), limits of agreement (LOA), intraclass correlation coefficient (ICC; type 3,1), and standard error of measurement for both measurement techniques. Methods Asymptomatic individuals and symptomatic patients were all evaluated using both the Vertebral Motion Analysis (VMA) system and fluoroscopic flexion extension static radiographs (FE). The analysis was compared to known thresholds of 15% intervertebral translation (IVT, equivalent to 5.3mm assuming a 35mm vertebral body depth) and 25° intervertebral rotation (IVR). Results The VMA measurements demonstrated greater specificity, % change in sensitivity, NPV, prevalence, and reliability compared with FE for radiographic evidence of instability. Specificity was 99.4% and 99.1% in the VMA compared to 98.3% and 98.2% in the FE for IVR and IVT, respectively. Sensitivity in this study was 41.2% and 44.6% greater in the VMA compared to the FE for IVR and IVT, respectively. NPV was 91% and 88% in the VMA compared to 62% and 66% in the FE for IVR and IVT, respectively. Prevalence was 12.3% and 11.9% for the VMA compared to 6.1% and 5.4% for the FE in IVR and IVT, respectively. Intra-observer IVR and IVT had a CR of 2.49 and 2.62, respectively. Inter-observer IVR and IVT had a CR of 1.99 and 2.81, respectively. Intra-subject (test/retest) CR were 2.49 and 3.11 for IVR and IVT, respectively. Conclusions The VMA system showed greater measurement performance in the detection of radiographic instability compared with FE radiographs.

Review of walking hazards for railroad workers

This is a review of walking tasks in the railroad environment, and the injuries that result from slips, trips, falls, or other acute or even non-traumatic exposures. The lack of federal regulations for railroad walkways has led several states to develop and enforce their own regulations. Support from the research literature for such regulations has come from biomechanical studies of the effects of walking on railroad ballast, which will be reviewed.