•The cervical spine compensates for operative loss of ROM in ACDF patients.•TDR-C patients have greater improvement in total cervical ROM than ACDF patients.•TDR-C maintains a better physiologic ...distribution of ROM than ACDF.
This study was a retrospective radiographic evaluation of patients after cervical total disc replacement (TDR-C) or anterior cervical discectomy and fusion (ACDF) for one-level cervical disc disease. Our objective was to evaluate (1) total cervical (C1–C7) range of motion (ROM) during dynamic imaging, and (2) relative contribution to total cervical ROM from operative and adjacent levels. Radiographic review of 64 patients who underwent TDR-C (n = 30) or ACDF (n = 34) for one-level cervical disc disease. ROM measurements were performed independently using a vertebral motion analysis system to evaluate total cervical ROM and relative contribution to total ROM from each level (C1–C7) preoperatively and at 12-month follow-up. At follow-up, TDR-C patients had significantly greater improvement in total cervical ROM (+5.67°, 1.15 mm) than ACDF patients (−0.96°, 0.12 mm) (P = 0.001). In TDR-C patients, relative contributions to total cervical ROM from operative and adjacent caudal and cranial levels were statistically equivalent to baseline values. ACDF patients had a significantly reduced contribution to total cervical ROM from the operative level (−22.5%, P < 0.001) and significantly elevated contributions from the adjacent caudal level (+16.5%–21.3%, P < 0.001) and from the adjacent first (20.6% vs. 34.6%, P < 0.001), second (22.9% vs. 30.4%, P < 0.001), and third cranial levels (17.5% vs. 25.6%, P < 0.001). The cervical spine compensates for loss of ROM at the operative level in ACDF patients. However, total cervical ROM increases with TDR-C and maintains physiologic distribution of ROM throughout the cervical spine at 12-month follow-up, potentially reducing the risk for adjacent segment breakdown.
Background: Postural strategies such as ankle, hip, or combined ankle-hip strategies are used to maintain optimal postural stability, which can be influenced by the footwear type and physiological ...workload. Purpose: This paper reports previously unreported postural strategy scores during the six conditions of the sensory organization test (SOT). Methods: Fourteen healthy males (age: 23.6 ± 1.2 years; height: 181 ± 5.3 cm; mass: 89.2 ± 14.6 kg) were tested for postural strategy adopted during SOT in three types of occupational footwear (steel-toed work boot, tactical work boot, low-top work shoe) every 30 min during a 4-h simulated occupational workload. Postural strategy scores were analyzed using repeated measures analysis of variance at 0.05 alpha level. Results: Significant differences among postural strategy scores were only evident between SOT conditions, and but not between footwear type or the workload. Conclusions: Findings indicate that occupational footwear and occupational workload did not cause a significant change in reliance on postural strategies. The significant changes in postural strategy scores were due to the availability of accurate and/or conflicting sensory feedback during SOT conditions. In SOT conditions where all three types of sensory feedback was available, the ankle strategy was predominantly adopted, while more reliance on hip strategy occurred in conditions with absent or conflicting sensory feedback.
While design modifications present on work boots improve safety, they may not always provide optimal human performance during work tasks. Understanding the impact of these different design features ...on biomechanical and physiological postural control and locomotion variables can aid in better design modifications that can provide a safe and efficient human performance. This brief review focuses on a series of studies conducted by the current research team, that have tested three different work boots (SB: high-top steel-toed work boots; TB: high-top tactical work boots; SR: low-top slip-resistant work boots). The series of studies included testing of these work boots or combinations of them under acute and chronic simulated occupational workloads, assessing biomechanical variable such as postural stability, gait, slips, and muscle activity, as well as physiological variables such as heart rate, energy expenditure, oxygen consumption, and pain perception. The impact of each of the work boots and their design feature on postural control and locomotion are summarized from these studies’ previously published literature. Finally, work boot design suggestions for optimal human performance are provided for better work boot selection, modification, and design.
Performing cognitive tasks and muscular fatigue have been shown to increase muscle activity of the lower extremity during quiet standing. A common intervention to reduce muscular fatigue is to ...provide a softer shoe-surface interface. However, little is known regarding how muscle activity is affected by softer shoe-surface interfaces during static standing. The purpose of this study was to assess lower extremity muscular activity during erect standing on three different standing surfaces, before and after an acute workload and during cognitive tasks.
Surface electromyography was collected on ankle dorsiflexors and plantarflexors, and knee flexors and extensors of fifteen male participants. Dependent electromyography variables of mean, peak, root mean square, and cocontraction index were calculated and analyzed with a 2 × 2 × 3 within-subject repeated measures analysis of variance.
Pre-workload muscle activity did not differ between surfaces and cognitive task conditions. However, greater muscle activity during post-workload balance assessment was found, specifically during the cognitive task. Cognitive task errors did not differ between surface and workload.
The cognitive task after workload increased lower extremity muscular activity compared to quite standing, irrespective of the surface condition, suggesting an increased demand was placed on the postural control system as the result of both fatigue and cognitive task.
Maintaining postural stability is crucial, especially in hazardous occupational environments. The purpose of the study was to assess the role of three occupational footwear (low top shoe (LT); ...tactical work boot (TB) and steel-toed work boot (WB)) on postural stability when exposed to an occupational workload (4-h) involving standing/walking using the sensory organization test (SOT) equilibrium (EQ) scores and comparing current results with previously published postural sway variables from the same study. Fourteen male adults were tested on three separate days wearing a randomized occupational footwear, at the beginning (pre) and every 30 min of the 4-h workload until 240th min. SOT EQ scores were analyzed using a 3 × 9 repeated measures analysis of variance at an alpha level of 0.05. Significant differences between footwear was found in eyes open (p = 0.03) and eyes closed (p = 0.001) conditions. Pairwise comparisons revealed that LT had significantly lower postural stability compared to TB and WB. No other significant differences were found between footwear and over time. Significant differences between footwear can be attributed to design characteristics of footwear. Lack of significant differences over time suggests that, even though the average EQ scores decreased during the workload implying less postural stability, SOT EQ scores alone may not be sufficient to detect postural stability changes over the 4-h workload.
Fatal and non-fatal falls from elevation have been documented to be a significant issue. Historically, roofing work has been ranked among the highest in incidents of falls. Recent literature has ...indicated that exposure to inclined surfaces (roof) has a detrimental effect on postural stability. The purpose of this preliminary study was to determine if postural instability was found to increase following extended exposure to an inclined surface. Twenty-three participants were pre/post tested under four postural stability conditions while varying duration exposure (0.0–2.0
h) to an inclined surface. Dependent variable postural sway measures were calculated from center of pressure data derived from a portable force plate. The results indicate significant differences between pre and post-exposure measures. Specifically, the results imply that an individual is less stable directly after performing tasks on an inclined surface. These findings contribute to the literature and serve as a basis for further research into work rest cycles for those individuals who routinely work on inclined surfaces.
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.
Background: Performing cognitive tasks and muscular fatigue have been shown to increase muscle activity of the lower extremity during quiet standing. A common intervention to reduce muscular fatigue ...is to provide a softer shoe-surface interface. However, little is known regarding how muscle activity is affected by softer shoe-surface interfaces during static standing. The purpose of this study was to assess lower extremity muscular activity during erect standing on three different standing surfaces, before and after an acute workload and during cognitive tasks. Methods: Surface electromyography was collected on ankle dorsiflexors and plantarflexors, and knee flexors and extensors of fifteen male participants. Dependent electromyography variables of mean, peak, root mean square, and cocontraction index were calculated and analyzed with a $2{\times}2{\times}3$ within-subject repeated measures analysis of variance. Results: Pre-workload muscle activity did not differ between surfaces and cognitive task conditions. However, greater muscle activity during post-workload balance assessment was found, specifically during the cognitive task. Cognitive task errors did not differ between surface and workload. Conclusions: The cognitive task after workload increased lower extremity muscular activity compared to quite standing, irrespective of the surface condition, suggesting an increased demand was placed on the postural control system as the result of both fatigue and cognitive task.
Decrements to postural control manifest as an increase in muscle activity, indicating continuous attempts to maintain body equilibrium and postural stability. Extrinsic factors such as footwear, and ...intrinsic factors such as muscle fatigue, can affect postural stability. The purpose of this study was to analyze the impact of two types of military footwear and a military-type load-carrying task on lower extremity muscle activity during various postural stability tasks. Sixteen males’ (age: 26.63 ± 3.93 years; mass: 87 ± 12.4 kg; height: 178.04 ± 6.2 cm) muscle activity from knee flexors, extensors, ankle dorsiflexors, and plantar flexors were measured using electromyography in standard (STD) and minimalist (MIN) military footwear, before (PRE) and after (POST) a simulated workload during sensory organization and motor control tests on the Neurocom EquitestTM. Mean muscle activity was analyzed using 2 (footwear) × 2 (time) repeated measures ANOVA with an alpha level of 0.05. Results revealed a requirement of significantly greater muscle activity in POST and STD. MIN demonstrated lesser balance decrements POST workload, which could be attributed to its design characteristics. Results will help in suggesting footwear design characteristics to minimize muscular exertion while eliciting better postural control, and to prevent postural instability due to overexertion in military personnel.
PDF
