Study protocol title: a prospective cohort study of low back pain

BACKGROUND: Few prospective cohort studies of workplace low back pain (LBP) with quantified job physical exposure have been performed. There are few prospective epidemiological studies for LBP occupational risk factors and reported data generally have few adjustments for many personal and psychosocial factors. METHODS/DESIGN: A multi-center prospective cohort study has been incepted to quantify risk factors for LBP and potentially develop improved methods for designing and analyzing jobs. Due to the subjectivity of LBP, six measures of LBP are captured: 1) any LBP, 2) LBP ≥ 5/10 pain rating, 3) LBP with medication use, 4) LBP with healthcare provider visits, 5) LBP necessitating modified work duties and 6) LBP with lost work time. Workers have thus far been enrolled from 30 different employment settings in 4 diverse US states and performed widely varying work. At baseline, workers undergo laptop-administered questionnaires, structured interviews, and two standardized physical examinations to ascertain demographics, medical history, psychosocial factors, hobbies and physical activities, and current musculoskeletal disorders. All workers’ jobs are individually measured for physical factors and are videotaped. Workers are followed monthly for the development of low back pain. Changes in jobs necessitate re-measure and re-videotaping of job physical factors. The lifetime cumulative incidence of low back pain will also include those with a past history of low back pain. Incident cases will exclude prevalent cases at baseline. Statistical methods planned include survival analyses and logistic regression. DISCUSSION: Data analysis of a prospective cohort study of low back pain is underway and has successfully enrolled over 800 workers to date

Tracking decrement as a result of grip holding endurance

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Ladder Climbing: a Dynamic Biomechanical Model and Ergonomic Analysis (Slip, Fall, Overexertion, Heights).

Accidents from slips, falls and overexertion during climbing activities frequently result in injuries. Little research, however, has been performed in this area. A dynamic biomechanical model of the ladder climbing activity was developed. The inputs are: (1) subject joint locations, (2) h and and foot separation, (3) anthropometry, and (4) rung forces. The outputs are: (1) joint moments and (2) compressive and shear forces at the L5/S1. Ten male subjects were tested under combinations of rung separation, ladder slant, climbing speed and climbing direction. The joint moments estimated by the model were validated using principles of internal consistency. The estimated back forces were validated through a comparison of the torso muscle IEMG activity to the model-predicted torso muscle forces. The validation study also generated safety and biomechanical design guidelines relating to the affect of task, equipment and user parameters on h and and foot forces, h and torque, and h and and foot separation. The validation results indicate that the biomechanical model may be used to predict joint moments during the climbing activity. The model appears to significantly underpredict the compressive and shear forces at the L5/S1 level. This may be due to the highly dynamic and asymmetric nature of the climbing activity and the tendency for body stability and support requirements to generate antagonist torso muscle activity and drive the torso muscles to contract at higher levels than predicted by the optimization model. Under the conditions studied there does not appear to be a significant slip hazard for people with no previous musculoskeletal problems, artificial joints or other pathology. Under field conditions there may be a potential for climber grip strength to be exceeded, and foot-slip potential to exist during the use of vertical ladders. There is also the potential for localized muscle fatigue at the elbow, hip and ankle during long climbs. The relatively high measured torso IEMG activity suggests that a ladder climbing activity may generate considerable compressive and shear force at the L5/S1 disc.Ph.D.Industrial engineeringUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/161210/1/8702688.pd

An ergonomic analysis of the ladder climbing activity

Injuries from slips, falls and overexertion during ladder climbing activities are common in both occupational and non-occupational environments. Little is known, however, about the task, equipment, and user parameters which may cause these injuries. In order to evaluate the hazards associated with ladder climbing, ten male subjects were tested under combinations of ladder rung separation, ladder slant, climbing speed, and climbing direction.Hand and foot forces, hand torques, torso muscle EMGs and hand and foot locations on the ladder rungs were recorded. A biomechanical model was developed which allowed the evaluation of dynamic joint moments and back forces. Study results include safety and biomechanical design guidelines relating to the effect of the task, equipment, and user parameters on climbing safety.Under the conditions studied there does not appear to be a significant slip hazard for people with reasonable strength and mobility. There may be a potential for climber grip strength to be exceeded under some field conditions and foot slip is possible during the use of vertical ladders. There is also the potential for localized fatigue in muscles acting at the elbow, hip and ankle joints during long climbs. The relatively high measured torso muscle IEMG suggests that certain ladder climbing activities may generate considerable back forces.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28475/1/0000267.pd

Gait Characteristics Associated with Trip-Induced Falls on Level and Sloped Irregular Surfaces

Same level falls continue to contribute to an alarming number of slip/trip/fall injuries in the mining workforce. The objective of this study was to investigate how walking on different surface types and transverse slopes influences gait parameters that may be associated with a trip event. Gait analysis was performed for ten subjects on two orientations (level and sloped) on smooth, hard surface (control) and irregular (gravel, larger rocks) surfaces. Walking on irregular surfaces significantly increased toe clearance compared to walking on the smooth surface. There was a significant (p < 0.05) decrease in cadence (steps/min), stride length (m), and speed (m/s) from control to gravel to larger rocks. Significant changes in external rotation and increased knee flexion while walking on irregular surfaces were observed. Toe and heel clearance requirements increased on irregular surfaces, which may provide an explanation for trip-induced falls; however, the gait alterations observed in the experienced workers used as subjects would likely improve stability and recovery from a trip

Gait Characteristics Associated with Trip-Induced Falls on Level and Sloped Irregular Surfaces

Same level falls continue to contribute to an alarming number of slip/trip/fall injuries in the mining workforce. The objective of this study was to investigate how walking on different surface types and transverse slopes influences gait parameters that may be associated with a trip event. Gait analysis was performed for ten subjects on two orientations (level and sloped) on smooth, hard surface (control) and irregular (gravel, larger rocks) surfaces. Walking on irregular surfaces significantly increased toe clearance compared to walking on the smooth surface. There was a significant (p &lt; 0.05) decrease in cadence (steps/min), stride length (m), and speed (m/s) from control to gravel to larger rocks. Significant changes in external rotation and increased knee flexion while walking on irregular surfaces were observed. Toe and heel clearance requirements increased on irregular surfaces, which may provide an explanation for trip-induced falls; however, the gait alterations observed in the experienced workers used as subjects would likely improve stability and recovery from a trip

The Effect of Lifting Speed on Cumulative and Peak Biomechanical Loading for Symmetric Lifting Tasks

Background: To determine the influence of lifting speed and type on peak and cumulative back compressive force (BCF) and shoulder moment (SM) loads during symmetric lifting. Another aim of the study was to compare static and dynamic lifting models. Methods: Ten male participants performed a floor-to-shoulder, floor-to-waist, and waist-to-shoulder lift at three different speeds [slow (0.34 m/s), medium (0.44 m/s), and fast (0.64 m/s)], and with two different loads [light (2.25 kg) and heavy (9 kg)]. Two-dimensional kinematics and kinetics were determined. A three-way repeated measures analysis of variance was used to calculate peak and cumulative loading of BCF and SM for light and heavy loads. Results: Peak BCF was significantly different between slow and fast lifting speeds (p < 0.001), with a mean difference of 20% between fast and slow lifts. The cumulative loading of BCF and SM was significantly different between fast and slow lifting speeds (p < 0.001), with mean differences ≥80%. Conclusion: Based on peak values, BCF is highest for fast speeds, but the BCF cumulative loading is highest for slow speeds, with the largest difference between fast and slow lifts. This may imply that a slow lifting speed is at least as hazardous as a fast lifting speed. It is important to consider the duration of lift when determining risks for back and shoulder injuries due to lifting and that peak values alone are likely not sufficient

Prediction of Peak Back Compressive Forces as a Function of Lifting Speed and Compressive Forces at Lift Origin and Destination - A Pilot Study

Objectives: To determine the feasibility of predicting static and dynamic peak back-compressive forces based on (1) static back compressive force values at the lift origin and destination and (2) lifting speed. Methods: Ten male subjects performed symmetric mid-sagittal floor-to-shoulder, floor-to-waist, and waist-to-shoulder lifts at three different speeds (slow, medium, and fast), and with two different loads (light and heavy). Two-dimensional kinematics and kinetics were captured. Linear regression analyses were used to develop prediction equations, the amount of predictability, and significance for static and dynamic peak back-compressive forces based on a static origin and destination average (SODA) back-compressive force. Results: Static and dynamic peak back-compressive forces were highly predicted by the SODA, with R2 values ranging from 0.830 to 0.947. Slopes were significantly different between slow and fast lifting speeds (p < 0.05) for the dynamic peak prediction equations. The slope of the regression line for static prediction was significantly greater than one with a significant positive intercept value. Conclusion: SODA under-predict both static and dynamic peak back-compressive force values. Peak values are highly predictable and could be readily determined using back-compressive force assessments at the origin and destination of a lifting task. This could be valuable for enhancing job design and analysis in the workplace and for large-scale studies where a full analysis of each lifting task is not feasible