Sara E. Wilson

Trunk posture and spinal stability.

OBJECTIVE The influence of trunk posture on musculoskeletal stability of the spine was investigated. DESIGN A biomechanical model was developed to evaluate the influence of posture on spinal stability. Model performance was assessed by comparing predicted muscle recruitment patterns with measured EMG activity from the trunk muscles during static lifting exertions. METHOD An inverted double-pendulum model of the spine controlled by 12 muscle equivalents of the trunk was implemented to determine spinal load and stability. Model input included trunk posture and lifted mass, output included muscle recruitment patterns necessary to achieve stability of the spine and spinal load. EMG activity recorded from the trunk muscles of 10 subjects were recorded during static exertions in various trunk flexion and asymmetric postures to compare with model output. Stable spinal load was examined as a function of trunk flexion and asymmetry during the lifting exertions. RESULTS Antagonistic co-contraction was necessary to achieve spinal stability, particularly in upright postures. Stable spinal load was increased in asymmetric postures as a result of antagonistic muscle recruitment, suggesting greater neuromuscular control is necessary to maintain stability in asymmetric lifting postures. As trunk flexion angle increased, stability improved but spinal load was greater. CONCLUSIONS Results illustrate that muscle recruitment patterns are more accurately explained by stability than by equilibrium alone. Spinal stability is influenced by posture. Specifically, control of spinal stability is reduced in asymmetric postures associated with low-back disorder risk. RELEVANCE Traditional assessment of low-back disorder risk have focussed on spinal loading. Results illustrate that postural risk factors for low-back pain may be partially attributable to stability considerations.

Influence of fatigue in neuromuscular control of spinal stability

Lifting-induced fatigue may influence neuromuscular control of spinal stability. Stability is primarily controlled by muscle recruitment, active muscle stiffness, and reflex response. Fatigue has been observed to affect each of these neuromuscular parameters and may therefore affect spinal stability. A biomechanical model of spinal stability was implemented to evaluate the effects of fatigue on spinal stability. The model included a 6-degree-of-freedom representation of the spine controlled by 12 deformable muscles from which muscle recruitment was determined to simultaneously achieve equilibrium and stability. Fatigue-induced reduction in active muscle stiffness necessitated increased antagonistic cocontraction to maintain stability resulting in increased spinal compression with fatigue. Fatigue induced reduction in force-generating capacity limited the feasible set of muscle recruitment patterns, thereby restricting the estimated stability of the spine. Electromyographic and trunk kinematics from 21 healthy participants were recorded during sudden-load trials in fatigued and unfatigued states. Empirical data supported the model predictions, demonstrating increased antagonistic cocontraction during fatigued exertions. Results suggest that biomechanical factors including spinal load and stability should be considered when performing ergonomic assessments of fatiguing lifting tasks. Potential applications of this research include a biomechanical tool for the design of administrative ergonomic controls in manual materials handling industries.

Reposition Sense of Lumbar Curvature with Flexed and Asymmetric Lifting Postures

Study Design. Reposition sense of lumbar curvature was assessed as a function of trunk flexion, trunk asymmetry, and target lumbar curvature using a repeated-measures design and an active-active proprioception paradigm. Objective. The objectives of the research were to measure the ability of the subjects to sense and control the lumbar curvature in different lifting postures and to see if error in the lumbar curvature would increase in high-risk postures. Summary of Background Data. The risk of low back disorders (LBDs) is related to trunk posture, with greater risk reported in flexed and asymmetric trunk positions. Spinal posture, including trunk position and lumbar lordosis, influences spinal stability. Hence, the ability to accurately sense and control spinal curvature may be an important factor in the control of LBD risk. Methods. Eleven subjects were trained to assume specified lumbar curvatures using visual feedback. The ability of the subjects to reproduce this curvature without feedback was then assessed. This procedure was repeated for different trunk postures, including flexion and asymmetry, and with different target lumbar curvatures. Results. These measurements demonstrated reposition error was increased in flexed trunk positions but was unchanged with trunk asymmetry. This increase in reposition error with flexion was diminished when the target posture and lumbar curvature were highly flexed and kyphotic. Conclusions. This research suggests that it may be difficult to control spinal curvature in flexed positions, leading to an increased risk of injury. For jobs in which flexed working postures are unavoidable, therefore, it is important to minimize potentially unstable events such as slipping or shifting loads to avoid injury.

The Importance of Formative Assessment in Science and Engineering Ethics Education: Some Evidence and Practical Advice

Recent research in ethics education shows a potentially problematic variation in content, curricular materials, and instruction. While ethics instruction is now widespread, studies have identified significant variation in both the goals and methods of ethics education, leaving researchers to conclude that many approaches may be inappropriately paired with goals that are unachievable. This paper speaks to these concerns by demonstrating the importance of aligning classroom-based assessments to clear ethical learning objectives in order to help students and instructors track their progress toward meeting those objectives. Two studies at two different universities demonstrate the usefulness of classroom-based, formative assessments for improving the quality of students’ case responses in computational modeling and research ethics.

Lumbar position sense with extreme lumbar angle

Tasks involving flexed torso postures have a high incidence of low back injuries. Changes in the ability to sense and adequately control low back motion may play a role in these injuries. Previous studies examining position sense errors of the lumbar spine with torso flexion found significant increases in error with flexion. However, there has been little research on the effect of lumbar angle. In this study, the aim of the study was to examine how position sense errors would change with torso flexion as a function of the target lumbar angle. Fifteen healthy volunteers were asked to assume three different lumbar angles (maximum, minimum and mid-range) at three different torso flexion angles. A reposition sense protocol was used to determine a subjects ability to reproduce the target lumbar angles. Reposition sense error was found to increase 69% with increased torso flexion for mid-range target curvatures. With increasing torso flexion, the increase in reposition sense errors suggests a reduction in sensation and control in the lumbar spine that may increase risk of injury. However, the reposition error was smaller at high torso flexion angles in the extreme target curvatures. Higher sensory feedback at extreme lumbar angles would be important in preventing over-extension or over-flexion. These results suggest that proprioceptive elements in structures engaged at limits (such as the ligaments and facet joints), may provide a role in sensing position at extreme lumbar angles. Sensory elements in the muscles crossing the joint may also provide increased feedback at the edges of the range of motion.

Novice lifters exhibit a more kyphotic lifting posture than experienced lifters in straight-leg lifting.

As torso flexion and repetitive lifting are known risk factors for low back pain and injury, it is important to investigate lifting techniques that might reduce injury during repetitive lifting. By normalizing lumbar posture to a subjects range of motion (ROM), as a function of torso flexion, this research examined when subjects approached their range of motion limits during dynamic lifting tasks. For this study, it was hypothesized that experienced lifters would maintain a more neutral lumbar angle relative to their range of motion, while novice lifters would approach the limits of their lumbar ROM during the extension phase of a straight-leg lift. The results show a statistically significant difference in lifting patterns for these two groups supporting this hypothesis. The novice group maintained a much more kyphotic lumbar angle for both the flexion (74% of the lumbar angle ROM) and extension phases (86% of the lumbar angle ROM) of the lifting cycle, while the experienced group retained a more neutral curvature throughout the entire lifting cycle (37% of lumbar angle ROM in flexion and 48% of lumbar angle ROM in extension). By approaching the limits of their range of motion, the novice lifters could be at greater risk of injury by placing greater loads on the supporting soft tissues of the spine. Future research should examine whether training subjects to assume more neutral postures during lifting could indeed lower injury risks.

SEEKING A SOLUTION OF THE PIONEER ANOMALY

The 1972 and 1973 launched Pioneer 10 and 11 were the first missions to explore the outer solar system. They achieved stunning breakthroughs in deep-space exploration. But around 1980 an unmodeled force of \sim 8 \times 10^{-8} cm/s^2, directed approximately towards the Sun, appeared in the tracking data. It later was unambiguously verified as not being an artifact. The origin remains unknown (although radiant heat remains a likely cause). Increasing effort has gone into understanding this anomaly. We review the situation and describe programs to resolve the issue.

Neuromotor Effects of Whole Body Horizontal Vibration

Low back disorders are very common affecting up to 80% of the population in their lifetime [1]. Whole body vibration (WBV) exposure has long been identified as an important risk factor for low back disorders in industrial workers [2]. A potential mechanism has been proposed by which vibration may lead to injury. Namely, vibration-induced losses in proprioception may lead to inappropriate stabilization and poor dynamic control of the lumbar spine [3]. Increases in proprioceptive errors and in delays in neuormotor response have been demonstrated with 5 Hz, vertical seatpan vibration [3]. While vertical vibration exposure is a common occupational exposure, in some cases, such as off road vehicles and construction vehicles horizontal (fore-aft) vibration may dominate [4]. In this study, the objective was to investigate how the whole body, horizontal, seatpan vibration affects muscle response and to compare these results with the previously studied whole body vertical vibration.Copyright

Immediate Effect of Lumbar Mobilization on Activity of Erector Spinae and Lumbar Multifidus Muscles

Objective: The purpose of this study was to investigate the effect of grade IV lumbar mobilization on the activity/contraction of erector spinae (ES) and lumbar multifidus (LM) muscles in healthy people. Methods: A randomized, repeated‐measures design was used. Sixteen healthy subjects attended 3 testing sessions with a different intervention in each session (no intervention, grade IV central lumbar mobilization at L4, and placebo/light touch). Lying in a prone position, subjects lifted a light weight with their right arm while ultrasound images of LM and surface electromyography signals of ES were captured before and immediately after application of the intervention in the session. The contraction of LM was calculated from US images, and the root mean square was calculated from the electromyography signals of ES and used as outcome measures. Results: A significant difference was found in LM contraction between the placebo and mobilization intervention (difference = 0.04, P = .02). There was no difference for the root mean square of electromyography signals between the interventions. Conclusion: The significant difference in LM contraction was small and may not have clinical significance. Lumbar mobilization did not change the activity of ES in healthy people. Future studies with larger samples are needed to confirm our findings and to investigate the effect of mobilization on back muscles in people with low back pain.

Prevalence of Low Back Pain among Nursing Students Compared to Physical Therapy, and Engineering Students in the United States

The study aimed to determine the prevalence of low back pain (LBP) among nursing students at various recall time points and compare the rates with physiotherapy (PT) and engineering students. Data were collected from 214 undergraduate and graduate students using a prevalence questionnaire via REDCap. LBP prevalence rates were found to be high at all recall time points in all the three disciplines. Nursing students had similar 12-month, 30-day and 7-day LBP prevalence rates as the PT students while the engineering students had the lowest prevalence rates at all the time points. Students from all three disciplines attributed the majority of their LBP to prolonged sitting. In addition, lifting patients and sports activities were also listed as other major causes for their LBP. Lack of awareness of correct sitting posture (p<.01) and Body Mass Index (BMI) (p<.01) were the significant predictors of LBP among students. These results suggest that prevalence of LBP is high among professional students and LBP was more prevalent among the nursing and PT students.