Modifying bowling kinematics in cricket pace bowlers with exercise-based injury prevention: A cluster-randomised controlled trial

OBJECTIVES

Undesirable bowling kinematics can increase the risk of low back injury. This study investigated if an exercise-based injury prevention program (IPP) could modify bowling kinematics in community-level adolescent pace bowlers.

DESIGN

Cluster-randomised controlled trial.

METHODS

Pace bowlers from eight cricket organisations were cluster-randomised into an intervention or control group. At baseline and follow-up sessions biomechanical bowling data were collected. Between sessions, the intervention group completed an eight-week IPP while the control continued their normal cricket activity. Treatment effects (95% CI) were estimated with linear mixed models.

RESULTS

There were significant treatment effects favouring the intervention group for shoulder counter-rotation (-3.8°; -7.2° to -0.3°) and lateral trunk flexion relative to the pelvis (-2.2°; -4.0° to -0.5°). Shoulder counter-rotation also increased in the control group by 2.2° (Cohen's d=0.22). There were no effects of the intervention on: lateral trunk flexion at front foot contact (FFC) (1.2°; -2.5° to 4.8°), lateral trunk flexion at ball release (BR) (-0.5°; -3.0° to 2.0°), pelvis rotation at FFC (0.9°; -4.0° to 2.2°), pelvis rotation at BR (-1.1°; -5.7° to 3.6°), front hip angle at FFC (1.6°; -3.6° to 6.7°), front hip angle at BR (-1.6°; -5.0° to 1.9°), front knee angle at FFC (-1.1°; -4.5° to 2.3°), front knee angle at BR (1.7°; -5.6° to 9.1°), or ball velocity (1.1kmh^-1; -7.5kmh^-1 to 9.7kmh^-1).

CONCLUSIONS

The IPP maintained shoulder counter-rotation and lateral trunk flexion relative to the pelvis in the intervention group and this could attenuate injury risk. No treatment effects were observed for lower-limb kinematics.

The influence of age on quality of life after upper body burn

BACKGROUND

In Spain, the number of aged persons is increasing. By the year 2066, it is expected that 34.6% of the Spanish population will be over 65 years of age. Elderly people present a higher burning risk owing in part to impaired balance and decreased physical strength, lower cognitive abilities, or socioeconomic context.

OBJECTIVE

Burns to the upper body body are common and affect both emotional state and physical function, thus leading to reduced quality of life (QoL). Our objective was to determine the influence of age on the QoL of patients who experienced burns to the upper body, with burns with 2 years.

METHODS

This is an observational study with a sample of 58 patients with burns only on the upper body. Patients were divided into two groups: 29 patients of age over 65 years and 29 patients under 65 years; all of them attended the Vall d'Hebron Burn Center, Barcelona, between 2011 and 2014. From the original sample, 45 patients had survived by the time the information was gathered. The QoL of these individuals was evaluated with the Spanish version of the Burn Specific Health Scale. Demographic data (sex, age, total burn surface area [TBSA], burn mechanism, pathological history, length of hospital stay, and rehabilitation duration) were collected. Statistical analysis included parametric and nonparametric tests as appropriate with R3.3.3.

RESULTS

There were no differences between groups regarding the mechanism of burn, TBSA, length of hospital stay, and the domains of QoL test. High blood pressure, diabetes, and other comorbidities were significantly more common in the elderly group than in the younger group. Eleven patients died in the elderly group and two in the younger group (p=0.012).

CONCLUSION

As opposed to what could be expected, in this study, there were no significant differences between surviving patients in both age groups in terms of perceived QoL. Nevertheless, mortality after a burn in the upper side of the body was significantly higher in elderly people than in younger people. The present study results do not support the use of different rehabilitation approaches in elderly patients.

Musculoskeletal Demands in Violin and Viola Playing: A Literature Review

BACKGROUND/AIMS

Research in music medicine has reported incidence rates of musculoskeletal disorders of approx. 70% in instrumental musicians. String players have the highest risk, with rates of performance-related musculoskeletal disorders (PRMDs) of 65% to 88%. Playing the violin or viola requires complex neuromusculoskeletal skills, and the high frequency of repetitive movements, dynamic and static muscle load, awkward postures, poor technique, and practice time are factors causing musculoskeletal strain. In ergonomic terms, these disorders can be categorized based on extrinsic and intrinsic loads. Identification of intrinsic loads, such as muscle utilization and joint motion, is necessary to understand factors influencing musculoskeletal disorders associated with violin playing. The aim of this study was to review the literature on musculoskeletal demands in violin and viola playing.

METHODS

A literature search was conducted in the PubMed, COCHRANE, and CINAHL electronic databases from 1999 to 2015 using the search terms violin, viola, high strings, movement, posture, and synonyms. A manual search of Medical Problems of Performing Artists was also conducted. Additional references were identified by searching the citations and reference lists of all identified relevant studies.

RESULTS

The results suggest that an asymmetric playing posture, the associated muscle activity, and joint mobility may contribute to musculoskeletal problems in violin and viola players. Evidence suggests an increased load of intrinsic factors in violin/viola performance.

CONCLUSION

The identification of intrinsic loads in violin and viola playing may facilitate the development of prevention strategies and interventions.

Supervisor and Organizational Factors Associated with Supervisor Support of Job Accommodations for Low Back Injured Workers

Purpose Temporary job accommodations contribute to the prevention of chronic work disability due to low back pain (LBP) through the facilitation of early return to work; yet, workplace dimensions of job accommodation are poorly understood. The objective of this study was to determine supervisor and organizational factors associated with supervisors' support for temporary job accommodations for LBP injured workers. Methods Supervisors were recruited from 19 workplaces in the USA and Canada and completed an online survey regarding job accommodation practices and potential associated factors with respect to a case vignette of a worker with LBP. Multivariable linear regression was used to identify the most parsimonious set of factors associated with supervisors' support for accommodations. Results A total of 804 supervisors participated with 796 eligible for inclusion in the analysis. The final set of factors explained 21 % of the variance in supervisors' support for temporary job accommodations. Considerate leadership style (β = 0.261; 95 % CI 0.212, 0.310), workplace disability management policies and practices (β = 0.243; 95 % CI 0.188, 0.298), and supervisor autonomy for designing and providing workplace accommodations (β = 0.156; 95 % CI 0.071, 0.241) had the largest effect on supervisor support for accommodations. Conclusion Factors predicting supervisors' likelihood to accommodate LBP injured workers include use of considerate leadership style, workplace disability management policies and practices, and supervisor autonomy. Workplace interventions targeting these factors should be developed and evaluated for their ability to improve work disability prevention outcomes.

Reported load carriage injuries of the Australian army soldier

INTRODUCTION

Many injuries experienced by soldiers can be attributed to the occupational loads they are required to carry.

PURPOSE

The aim of this study was to determine whether contemporary military load carriage is a source of injuries to Australian Regular Army soldiers and to profile these injuries.

METHODS

The Australian Defence Force 'Occupational Health, Safety and Compensation Analysis and Reporting' database was searched to identify all reported injuries sustained during load carriage events. Key search terms were employed and narrative description fields were interrogated to increase data accuracy.

RESULTS

A total of 1,954 injury records were extracted from the database. Of these, 404 injuries were attributed to load carriage. The majority of these load carriage injuries involved either the lower limb or back, with bones and joints accounting for the most frequently reported body structures to be injured. Field activities were the leading activities being performed at the time that load carriage injuries occurred, and muscular stress was identified as the mechanism of injury for over half of reported load carriage injuries.

CONCLUSION

This study suggests that load carriage is a substantial source of injury risk to Australian Army soldiers. Physical training may fail to adequately prepare soldiers for load carriage tasks during field training exercises.

Differences in lumbopelvic control and occupational behaviours in female nurses with and without a recent history of low back pain due to back injury

Low back pain is highly prevalent in nurses. This study aimed to determine which physical fitness, physical activity (PA) and biomechanical characteristics most clearly distinguish between nurses with [recently injured (RInj)] and without [not recently injured (NRInj)] a recent back injury. Twenty-seven (8 RInj, 19 NRInj) female nurses completed questionnaires (pain, work, PA), physical fitness, biomechanical and low back discomfort measures, and wore an accelerometer for one work shift. Relative to NRInj nurses, RInj nurses exhibited reduced lumbopelvic control (41.4% more displayed a moderate loss of frontal plane position), less active occupational behaviours (less moderate PA; less patient lifts performed alone; more sitting and less standing time) and more than two times higher low back discomfort scores. Despite no physical fitness differences, the lumbopelvic control, occupational behaviours and discomfort measures differed between nurses with and without recent back injuries. It is unclear whether poor lumbopelvic control is causal or adaptive in RInj nurses and may require further investigation. Practitioner Summary: It is unclear which personal modifiable factors are most clearly associated with low back pain in nurses. Lumbopelvic control was the only performance-based measure to distinguish between nurses with and without recent back injuries. Future research may investigate whether reduced lumbopelvic control is causal or adaptive in recently injured nurses.

The assessment of material handling strategies in dealing with sudden loading: the effects of load handling position on trunk biomechanics

Back injury caused by sudden loading is a significant risk among workers that perform manual handling tasks. The present study investigated the effects of load handling position on trunk biomechanics (flexion angle, L5/S1 joint moment and compression force) during sudden loading. Eleven subjects were exposed to a 6.8 kg sudden loading while standing upright, facing forward and holding load at three different vertical heights in the sagittal plane or 45° left to the sagittal plane (created by arm rotation). Results showed that the increase of load holding height significantly elevated the peak L5/S1 joint compression force and reduced the magnitude of trunk flexion. Further, experiencing sudden loading from an asymmetric direction resulted in significantly smaller peak L5/S1 joint compression force, trunk flexion angle and L5/S1 joint moment than a symmetric posture. These findings suggest that handling loads in a lower position could work as a protective strategy during sudden loading.

Reduction of spinal loads through adjustable interventions at the origin and destination of palletizing tasks

OBJECTIVE

This article evaluates the effectiveness of two interventions: a self-leveling pallet carousel designed to position the loads vertically and horizontally at origin, and an adjustable cart designed to raise loads vertically at destination to reduce spine loads.

BACKGROUND

Low back disorders among workers in manual material handling industries are very prevalent and have been linked to manual palletizing operations. Evidence into the effectiveness of ergonomic interventions is limited, with no research that investigates interventions with adjustable load location.

METHOD

Thirteen males experienced in manual material handling participated in simulated order selecting tasks where spine loads were quantified for each intervention condition: carousel to traditional cart, pallet to traditional cart, pallet to adjustable cart, and carousel to adjustable cart.

RESULTS

The results showed that combining both devices results in reduction in spine compression (61%), anterior-posterior shear (72%), and lateral shear (63%) compared to traditional palletizing conditions. Individually, the carousel was responsible for the greatest reductions, but the lowest values were typically achieved by combining the adjustable cart and carousel.

CONCLUSION

The combination of the interventions (self-leveling carousel and adjustable cart) was most effective in reducing the spine loads when compared to the traditional pallet-cart condition. The individual interventions also reduced the loads compared to the traditional condition.

APPLICATION

With de-palletizing/palletizing tasks being a major source of low back injuries, the combination of self-leveling carousel and adjustable cart has been found to be effective in reducing the peak spine loading as compared to traditional pallet on floor and nonadjustable flat cart conditions.

Injury and lumbar reposition sense in cricket pace bowlers in neutral and pace bowling specific body positions

BACKGROUND AND CONTEXT

The cricket pace bowling action consists of a complex sequence of forceful actions, involving practiced, particular movements of the lumbar spine. The nature and repetition of the pace bowling action is known to be associated with a high incidence of low back injuries.

PURPOSE

This study aimed to establish whether lumbar proprioception (as measured by joint position sense) in the neutral lumbar spine position as well as lumbar positions corresponding to those at front foot placement and ball release positions of the cricket pace bowling action were related to previous injury and injury sustained during the cricket season under review. Injuries specifically sustained during the bowling action and those specific to the low back were explicitly investigated.

STUDY SETTING

Longitudinal study with participants tested at the start and monitored over the duration of a cricket season.

PARTICIPANT SAMPLE

Seventeen male cricket pace bowlers between the ages of 18 and 26 years participated in this study.

OUTCOME MEASURES

Physiological outcome measures were used. Lumbar position sense was established using electrogoniometry.

METHODS

Lumbar reposition error was measured in three positions (neutral lumbar spine, front foot placement, and ball release bowling positions). In each position, lumbar orientation was determined in the sagittal (flexion-extension) and coronal (left-right lateral flexion) planes. Wilcoxon matched-pairs ranks and Kruskal-Wallis tests were used to establish the relationship between variables.

RESULTS

Reposition error was associated with general injuries sustained in the past and during the cricket season under review, low back injuries, as well as injuries sustained during the bowling action (p<.05).

CONCLUSION

Lumbar position sense, as a measure of proprioception, was related to injury in general, injuries sustained during the bowling action, and, especially, low back injury sustained in the past. Low back injury prevention methods are particularly needed because of the high load nature of the pace bowling action. If the proprioception of the lumbar spine is improved in pace bowlers, their risk of lumbar injury can potentially be reduced.

The ratio of thoracic to lumbar compression force is posture dependent

Despite the evidence suggesting that between 8% and 55% of manual labourers experience thoracic pain, research on spinal loading during occupational tasks has been almost invariably limited to the lumbar spine. In this study, we determined the ratio of thoracic to lumbar compression force and the relative risk of injury to each region in various postures. Compressive forces on the spine were calculated based on previously reported thoracic and lumbar intradiscal pressures and disc cross-sectional areas. Flexion postures were associated with an approximate doubling in lumbar compression force but only small increases (or even decreases) in thoracic compression. The ratio of thoracic to lumbar compression was above the tolerance ratio (i.e. the ratio of thoracic to lumbar compressive strength) during upright postures and below the tolerance ratio during flexion postures, indicating that upright postures may pose a greater relative risk of injury to the thoracic spine than to the lumbar spine. Practitioner summary: Previously reported thoracic and lumbar in vivo disc pressures during various postures were compared. The ratio of thoracic and lumbar compression increased during upright postures and decreased in flexed postures, indicating that upright postures may pose a greater risk of injury to the thoracic spine than to the lumbar spine.

[Aiming at the chest, but hitting the back]

Gunshot injuries in the back may suggest the unjustified use of firearms. A wound in the back inflicted by a firearm should not automatically imply that the shooter aimed at the back. A previous study demonstrated that it is possible for men to turn their trunk faster than it takes for a shooter to fire or throw a hand-operated weapon. With a high speed motion camera the authors were able to demonstrate that it is also possible for women to turn their trunk fast enough, so that a shot in the back could have been aimed at the front of the body. This conclusion is also likely to apply to hand-operated or thrown weapons, since the velocity of their projectiles is considerably lower than that of firearms.

Risk assessment of patient handling with ambulance stretcher systems (ramp/(winch), easi-loader, tail-lift) using biomechanical failure criteria

The research aims to carry out a detailed analysis of the loads applied by the ambulance workers when loading/unloading ambulance stretchers. The forces required of the ambulance workers for each system are measured using a load cell in a force handle arrangement. The process of loading and unloading is video recorded for all the systems to register the posture of the ambulance workers in different stages of the process. The postures and forces exerted by the ambulance workers are analyzed using biomechanical assessment software to examine if the work loads at any stage of the process are harmful. Kinetic analysis of each stretcher loading system is performed. Comparison of the kinetic analysis and measurements shows very close agreement for most of the cases. The force analysis results are evaluated against derived failure criteria. The evaluation is extended to a biomechanical failure analysis of the ambulance worker's lower back using 3DSSPP software developed at the Centre for Ergonomics at the University of Michigan. The critical tasks of each ambulance worker during the loading and unloading operations for each system are identified. Design recommendations are made to reduce the forces exerted based on loading requirements from the kinetic analysis.

Forces and pressures beneath the saddle during mounting from the ground and from a raised mounting platform

The objective was to use an electronic pressure mat to measure and compare forces and pressures of the saddle on a horse's back when riders mounted from the ground and with the aid of a mounting platform. Ten riders mounted a horse three times each from the ground and from a 35 cm high mounting platform in random order. Total force (summation of forces over all 256 sensors) was measured and compared at specific points on the force-time curve. Total force was usually highest as the rider's right leg was swinging upwards and was correlated with rider mass. When normalized to rider mass, total force and peak pressure were significantly higher when mounting from the ground than from a raised platform (P<0.05). The area of highest pressure was on the right side of the withers in 97% of mounting efforts, confirming the importance of the withers in stabilizing the saddle during mounting.

Movement-based feedback may reduce spinal moments in male workers during lift and lowering tasks

BACKGROUND AND PURPOSE

To assess if lifting performance can be modified and spine stresses reduced in workers who perform repetitive material-handling jobs in a warehouse environment via a novel real-time, movement-based feedback training protocol.

METHOD

A pre-test/post-test group study design was used with a control group. Data were collected in a warehouse setting and analysed in a university setting. A convenience sample of 22 male warehouse employees was divided equally, based on height and weight, and assigned to either an experimental group or a control group. The experimental group received real-time, performance-based auditory feedback from their calculated moments during lifting or lowering using an electromagnetic tracking system. The electromagnetic tracking system was used to measure the side-bending, flexion and rotation moments during six lifts under four different conditions. A series of repeated-measures analyses of variance (ANOVA) (one between (Group); one within (Time)) was performed on the average maximum moments from six lifting or lowering cycles for all three directions: side-bending, flexion and rotation.

RESULTS

There were significant group x time interactions for the side-bending moment (p < 0.05) and the flexion moment (p < 0.05) but not the rotation moment (p > 0.05). Lower moments were found in the experimental group, which received the training and feedback, compared to the control group.

CONCLUSIONS

Real-time, auditory feedback combined with coaching during lifting or lowering tasks may be effective in the short term (six weeks) in reducing the average maximum side-bending and flexion moments in warehouse workers. Further research is needed to determine the long-term effects of this training protocol on low back injury rates.

Analysis of squat and stoop dynamic liftings: muscle forces and internal spinal loads

Despite the well-recognized role of lifting in back injuries, the relative biomechanical merits of squat versus stoop lifting remain controversial. In vivo kinematics measurements and model studies are combined to estimate trunk muscle forces and internal spinal loads under dynamic squat and stoop lifts with and without load in hands. Measurements were performed on healthy subjects to collect segmental rotations during lifts needed as input data in subsequent model studies. The model accounted for nonlinear properties of the ligamentous spine, wrapping of thoracic extensor muscles to take curved paths in flexion and trunk dynamic characteristics (inertia and damping) while subject to measured kinematics and gravity/external loads. A dynamic kinematics-driven approach was employed accounting for the spinal synergy by simultaneous consideration of passive structures and muscle forces under given posture and loads. Results satisfied kinematics and dynamic equilibrium conditions at all levels and directions. Net moments, muscle forces at different levels, passive (muscle or ligamentous) forces and internal compression/shear forces were larger in stoop lifts than in squat ones. These were due to significantly larger thorax, lumbar and pelvis rotations in stoop lifts. For the relatively slow lifting tasks performed in this study with the lowering and lifting phases each lasting approximately 2 s, the effect of inertia and damping was not, in general, important. Moreover, posterior shift in the position of the external load in stoop lift reaching the same lever arm with respect to the S1 as that in squat lift did not influence the conclusion of this study on the merits of squat lifts over stoop ones. Results, for the tasks considered, advocate squat lifting over stoop lifting as the technique of choice in reducing net moments, muscle forces and internal spinal loads (i.e., moment, compression and shear force).

In vivolumbar erector spinae oxygenation and blood volume measurements in healthy men during seated whole-body vibration

Exposure to whole-body vibration is implicated as one of the occupational risk factors for lower back disorders; however, its influence on the lumbar muscle physiology is still poorly understood. The objective of this study was to investigate the effects of backrest support and hand grip contractions on lumbar muscle oxygenation and blood volume responses during seated whole-body vibration using continuous dual-wave near-infrared spectroscopy. Thirteen healthy men were exposed to frequencies of 3, 4.5 and 6 Hz on a vibration simulator, in randomized order on separate days. Each day the duration of the protocol was 30 min. During the fifth minute of vibration 'with' and 'without' backrest support, participants performed maximal rhythmic hand grip contractions for 1 min. In general, erector spinae oxygenation and blood volume showed a trend to decrease with vibration exposure compared to the control condition. However, these responses were not influenced by the change in vibration frequency (P > 0.05). Sitting without backrest resulted in a greater decrease in oxygenation (by 27%, P = 0.02) and blood volume (by 11%, P = 0.05) than with backrest, implying a deficiency in oxygen supply owing to the sitting posture. Compared to the vibration-only condition, hand grip work decreased both oxygenation (by 22%, P = 0.003) and blood volume responses (by 13%, P = 0.04), suggesting that postural load due to prolonged sitting combined with physical activity during vibration might further burden paraspinal muscles. The influence of adipose tissue thickness of the lumbar muscle on optically derived oxygenation and blood volume changes was inconclusive.

Changes in spine loading patterns throughout the workday as a function of experience, lift frequency, and personality

BACKGROUND CONTEXT

Psychosocial stressors have been associated with low back pain reporting. However, response to psychosocial risk factors may be dependent on the individual's personality type that, in turn, can affect muscle recruitment and spine loading. This study explores how personality might be associated with spine loading during repetitive lifting performed throughout an entire work shift.

PURPOSE

Assess spine loading as a function of an individual's personality type during repetitive, long-term exposure to a materials handling tasks.

STUDY DESIGN

Laboratory experiment where experienced and inexperienced participants performed repetitive, asymmetric lifts at various load and lift frequency levels throughout a series of 8-hour exposure periods. Spine loads were monitored throughout the work period.

PATIENT SAMPLE

Twelve novice and 12 experienced materials handlers who were asymptomatic for back pain.

OUTCOME MEASURES

Spine compression, anterior-posterior (A/P) shear, and lateral shear at the L5-S1 level.

METHODS

Participants were categorized into personality types based upon the Myers-Briggs personality type indicator. An electromyography-assisted biomechanical model was used to assess spine compression, A/P shear, and lateral shear throughout the exposure period.

RESULTS

The results indicate that intuitors had higher shear spinal loading regardless of moment exposure, lift frequency, and time through the work period, compared with the sensor personality type. In addition, higher spine compressive and shear forces occurred in the perceiver personality compared with the judgers' personality trait, regardless of moment and, often, lift frequency. Novice lifters typically experienced greater spine loading.

CONCLUSIONS

The results suggest that when there exists a personality-job environment mismatch, spinal loading increases via an increase in antagonistic co-contraction. The trends suggest that inherent personality characteristics may play a role in one's motor control strategies when performing a repetitive lifting task.

Overuse injuries in equestrian athletes

Some 30 million Americans are involved in equestrian sports. Although there is significant literature regarding catastrophic injury, there is very little literature that addresses overuse injury and its effect on rider and horse. As the horse and rider function as a unit, overuse injuries to the rider can affect the horse's training and responsiveness. Sports physicians treating riders should understand correct posture in the saddle and its alteration by muscular imbalance and injury. This review discusses common equestrian events, and common overuse injuries in recreational and competitive riders.

High-repetition cyclic loading is a risk factor for a lumbar disorder

Epidemiological data suggest that prolonged exposure to cyclic lumbar flexion elicits a chronic neuromuscular disorder and disability in workers. This study provides a physiological and biomechanical assessment of various repetitions of cyclic lumbar flexion sessions as a risk factor for development of an acute neuromuscular disorder. An in vivo feline model was subjected to 10 minutes of cyclic (0.25-HZ) loading, followed by a 10-minute rest period, repeated three times in one experimental group, six times in a second group, and nine times in the third group, followed by rest for 7 hours. Displacement of the lumbar viscoelastic tissue and reflex electromyographic (EMG) activity from the lumbar multifidus muscle were monitored. Creep developed and accumulated during each load/rest period and partially recovered during the subsequent rest. Loading periods were characterized by a decrease in reflex EMG activity with superimposed spasms. In the 7-hour recovery period, initial hyperexcitability was present in all groups, whereas only the six- and nine-repetition groups displayed significant delayed hyperexcitability, indicating the presence of acute inflammation. The mathematical model developed fit the data reasonably well, as the R2 values were generally near 0.90. It was concluded that the resulting delayed muscular hyperexcitability constitutes an acute neuromuscular disorder associated with exposure to many repetitions of cyclic lumbar flexion. The acute disorder can become chronic if not allowed sufficient rest to resolve itself. Workers engaged in cyclic lumbar flexion (e.g., loading/unloading, assembly workers) should avoid long-term exposure in order to prevent the development of a chronic neuromuscular condition known as cumulative trauma disorder.

Delayed trunk muscle reflex responses increase the risk of low back injuries

STUDY DESIGN

Prospective observational study with a 2- to 3-year follow-up.

OBJECTIVES

To determine whether delayed muscle reflex response to sudden trunk loading is a result of or a risk factor for sustaining a low back injury (LBI).

SUMMARY OF BACKGROUND DATA

Differences in motor control have been identified in individuals with chronic low back pain and in athletes with a history of LBI when compared with controls. However, it is not known whether these changes are a risk for or a result of LBI.

METHODS

Muscle reflex latencies in response to a quick force release in trunk flexion, extension, and lateral bending were measured in 303 college athletes. Information was also obtained regarding their personal data, athletic experience, and history of LBI. The data were entered into a binary logistic regression model to identify the predictors of future LBI. RESULTS.: A total of 292 athletes were used for the final analysis (148 females and 144 males). During the follow-up period, 31 (11%) athletes sustained an LBI. The regression model, consisting of history of LBI, body weight, and the latency of muscles shutting off during flexion and lateral bending load releases, predicted correctly 74% of LBI outcomes. The odds of sustaining LBI increased 2.8-fold when a history of LBI was present and increased by 3% with each millisecond of abdominal muscle shut-off latency. On average, this latency was 14 milliseconds longer for athletes who sustained LBI in comparison to athletes who did not sustain LBI (77 [36] vs. 63 [31]). There were no significant changes in any of the muscle response latencies on retest following the injury.

CONCLUSIONS

The delayed muscle reflex response significantly increases the odds of sustaining an LBI. These delayed latencies appear to be a preexisting risk factor and not the effect of an LBI.

Electromyography as a measure of peak and cumulative workload in intermediate care and its relationship to musculoskeletal injury: an exploratory ergonomic study

Injury rates in Intermediate Care (IC) facilities are high and the factors related to these injuries are unclear. The objectives of this exploratory sub-study, which is part of a large multi-faceted study in 8 IC facilities are to: (1) evaluate EMG measured over a full-shift in the back and shoulders of 32 care aides (CAs) as an indicator of peak and cumulative workload (n = 4 x 8 facilities); investigate the relationship between EMG measures and injury indicators; and explore the relationship between EMG measures and other workload measurements. Lumbar EMG was converted to predicted cumulative spinal compression and ranged in CAs from 11.7 to 22.8 MNs with a mean of 16.4 MNs. Average compression was significantly different during different periods of the day (p < 0.001) with highest compression during pre-breakfast when CAs assist most with activities of daily living. Significant differences were found in average compression between low and high injury facilities for 3 of 5 periods of the day (p < 0.010). Peak compressions exceeding 3400 N occurred for very little of the workday (e.g. 11.25s during the 75 min period pre-breakfast). Peak neck/shoulder muscle activity is low (99% APDF ranged from 8.33% to 28% MVC). Peak and cumulative spinal compression were significantly correlated with lost-time and musculoskeletal injury rates as well as with total tasks observed in the CAs (p < 0.01). Perceived exertion was only correlated with peak compressions (p < 0.01). Facilities with low injury rates provided significantly more CAs (p < 0.01) to meet resident needs, and subsequently CAs performed fewer tasks, resulting in less peak and cumulative spinal loading over the day.

Predicting return to work after low back injury using the Psychosocial Risk for Occupational Disability Instrument: a validation study

INTRODUCTION

This paper reports on the predictive validity of a Psychosocial Risk for Occupational Disability Scale in the workers' compensation environment using a paper and pencil version of a previously validated multimethod instrument on a new, subacute sample of workers with low back pain.

METHODS

A cohort longitudinal study design with a randomly selected cohort off work for 4-6 weeks was applied. The questionnaire was completed by 111 eligible workers at 4-6 weeks following injury. Return to work status data at three months was obtained from 100 workers. Sixty-four workers had returned to work (RTW) and 36 had not (NRTW).

RESULTS

Stepwise backward elimination resulted in a model with these predictors: Expectations of Recovery, SF-36 Vitality, SF-36 Mental Health, and Waddell Symptoms. The correct classification of RTW/NRTW was 79%, with sensitivity (NRTW) of 61% and specificity (RTW) of 89%. The area under the ROC curve was 84%.

CONCLUSIONS

New evidence for predictive validity for the Psychosocial Risk-for-Disability Instrument was provided.

IMPLICATIONS

The instrument can be useful and practical for prediction of return to work outcomes in the subacute stage after low back injury in the workers' compensation context.

Factor structure of the pain disability index in workers compensation claimants with low back injuries

OBJECTIVE

To examine the factor structure of a telephone-administered Pain Disability Index (PDI) and the effects of race and sex on the PDI.

DESIGN

Computer-assisted telephone interviews of a cohort with occupational low back injuries.

SETTING

General community.

PARTICIPANTS

Missouri workers compensation claimants (N=1329) with low back injuries.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

PDI, levels of pain severity, Social Security Disability Insurance status, and the Fear-Avoidance Behavior Questionnaire.

RESULTS

Results for the total sample and by race/sex group indicated support for a 2-factor model of the PDI corresponding to voluntary activities (eg, social, occupational, recreational) and obligatory activities (eg, activities of daily living, eating, sleeping). Additional psychometric analyses of the voluntary and obligatory subscales indicated adequate reliability and construct validity overall and in each of the race/sex groups. African Americans reported more pain-related disability on both subscales than whites. Women reported more disability on the voluntary subscale than men.

CONCLUSIONS

The results support use of the PDI as a bidimensional measure of pain-related disability, with strong psychometric properties. They also support its administration by telephone.

Load spatial pathway and spine loading: how does lift origin and destination influence low back response?

While heavy lifting has been identified as an important risk factor for low back disorders, little is known about workplace spatial layout - the relative positions of shelves and the impact of this on spine loads. The objective of the current study was to investigate how the relative positions of the load origin and destination impact three-dimensional spine loads. Seven females and seven males lifted an 11.4 kg box from an origin shelf to a destination shelf, each defined by height (elbow, knee and shoulder level) and asymmetry (60 degrees clockwise, sagittally symmetric, 60 degrees counter-clockwise) while their spine loading was assessed by an electromyographic-assisted model. The results indicated that the starting and destination heights and starting task asymmetry all had significant impact on spine compression (with an increase of between 400 and 1900 N when compared to the most neutral position) and lateral shear (with a 100 to 150 N increase) while the destination height impacted the anterior - posterior shear forces (with up to 400 N increase). The results of the current study emphasize the importance of proper workplace spatial layout, specifically the importance of specifying starting position of the load relative to the destination. Adjustment of the starting position will impact the three-dimensional spine loads while the destination height and asymmetry influence the shear forces. Furthermore, the influence of the specific pathway (origin relative to destination) indicates there may be a potential preparatory muscle response leading to the loads on the spine. Thus, the pathway of the box plays an important role in the spine responses during lifting, in that longer and non-neutral pathways increase spine loads - indicating the importance of the relative position of the origin and destination shelf.

Transfer of the horizontal patient: the effect of a friction reducing assistive device on low back mechanics

Recognizing that the transfer of bedridden patients is associated with a high rate of low back injuries, various devices have been developed to assist with sparing the patient handlers. The purpose of this study was to quantify the friction-reducing ability of three different 'sliding' patient transfer devices together with the subsequent consequences on the low back loads of people performing the transfers. Coefficients of friction of the devices were determined by 'transferring' a standard object and a 'patient' over several surfaces common to a hospital setting. Then three participants performed controlled transfers with the various devices. Electromyography to measure muscle activation levels together with external forces and kinematic positional data were collected during push, pull and twist transfers. Spine loads were estimated with a three-dimensional biomechanical static link-segment model of the human body. Simply sliding a patient on a cotton sheet (control condition) produced a coefficient of friction of 0.45. The assistive devices substantially reduced friction by well over one-half (coefficients of 0.18 - 0.21). However, when using the devices the subjects adopted a variety of postures and techniques, such that there were no consistent influences on trunk inclination, low back compression or muscle activation profiles. Direct measurement of reduced friction between the bed and the patient with a friction-reducing device together with measurement of the back loads when actually transferring a patient formed a proof of principle. Specifically, while the device lowers friction, the transfer technique adopted by the lifter must be proper to reduce low back loading and any subsequent risks of back troubles associated with patient transfers. The direction of hand forces and torso position remains important.

Back strength and flexibility of EMS providers in practicing prehospital providers

In the execution of prehospital care duties, an EMS provider may be required to carry equipment and patients over long distances or over multiple flights of stairs at any time of the day. At a minimum, a prehospital provider must have sufficient lower back strength and hamstring flexibility to prevent musculoskeletal injury while lifting. This study administered fitness assessments related to the occupational activities of the prehospital provider with the purpose of describing the incidence of occupational back injury and percentage of providers with known risk factors for back injury. Ninety subjects were tested during a regional EMS conference. Men were significantly taller and heavier than women and had significantly less hamstring flexibility. Body Mass Index was 30.7 +/- 7.2 in men and 28 +/- 5.7 in women. However, no significant differences were noted in an extension test of back strength. When surveyed, 47.8% of subjects reported a back injury in the previous 6 months but only 39.1% of these injuries were sustained while performing EMS duties. While only 13% of these injuries resulted in missed work, 52.2% reported their injury interfered with their daily activities. In spite of the physical nature of the profession, EMS providers in our sample were significantly overweight according to their Body Mass Index and may lack sufficient back strength and flexibilityfor safe execution of their duties. This group of professionals may be at risk for occupational injury and should be targeted for interventions to improve strength and flexibility.

An ergonomics intervention program to prevent worker injuries in a metal autoparts factory

An ergonomics intervention program (EIP) was conducted with male employees working in the pressing and storage sections of a metal autoparts factory in Samut Prakan Province, Thailand. The objectives of this study were to assess the causes of injuries in the pressing and storage sections of that factory, and to improve working conditions by reducing worker injuries from accidents and low back muscular discomfort, using an EIR The study design used a participatory research approach which was quasi-experimental with pretest-posttest evaluations, with a non-equivalent control group. A total of 172 male participants working in Building A were the target group for assessing causes of injury. A retrospective study of official accident information, and questionnaires for general information, health and muscular discomfort, injury frequency rate (IFR), injury severity rate (ISR), medical expenses, and EIP design. Two groups of employees volunteered for the study on muscular back discomfort. The first group of 35 persons volunteered to participate in the EIP (EIP group), and the second 17 persons from Building B did not (non-EIP group). The EIP was composed of 4 major categories: (1) engineering improvement, (2) change in personal protective equipment, (3) environmental improvement, (4) administrative intervention, training, and health education. Low back muscular discomfort was measured through questionnaires on subjective feelings of muscular discomfort, and by surface electromyography (sEMG). Muscle activities were measured by sEMG of the left and right erector spinae and multifidus muscles, and evaluated by multivariate test for dependent samples (paired observation), and multivariate test for two independent samples. After EIP, IFR decreased 65.46%, ISR decreased 41.02%, and medical expenses decreased 42.79%. The low back muscular loads of the EIP group were significantly reduced, with a 95% confidence level (p < 0.05) while those of the non-EIP group were not. Subjective feelings of muscular discomfort, determined by Wilcoxon Signed Ranks test, showed that after applying the EIP to the EIP group, the mean scores for general bodily discomfort and low back muscular discomfort in the EIP group had significantly reduced, while those of the non-EIP group increased, (p < 0.05).

Physical limitations and musculoskeletal complaints associated with work in unusual or restricted postures: a literature review

INTRODUCTION

The vast majority of ergonomics research has addressed the demands of work in standing or sitting postures, and understandably so. However, many workers (e.g., underground miners, aircraft baggage handlers, plumbers, agricultural workers, mechanics, and others) are often required to adopt postures such as kneeling, stooping, squatting, or lying down for significant periods of the workday.

METHOD

A literature search was performed using the ISI Web of Science database (for years 1980-2004). Articles retrieved from this search were evaluated in terms of relevance to assessing physical capabilities of workers in these postures and/or the musculoskeletal epidemiology associated with these postures.

RESULTS

Work in unusual and restricted postures was associated with significantly higher rates of musculoskeletal complaints compared to workers not adopting these postures in epidemiology studies (Odds Ratios ranging from 1.13 to 13). Some studies suggested a dose-response relationship, with longer exposures leading to increased musculoskeletal complaints. Physical strength and psychophysical lifting capacity vary significantly as unusual or restricted postures are adopted, with lower lifting capacities evident in the kneeling, squatting, and lying positions.

CONCLUSIONS

Workers who adopt unusual or restricted postures appear to be at higher risk of musculoskeletal complaints and often exhibit reduced strength and lifting capacity. Research needs in this area include improved exposure assessment tools, studies of intervention effectiveness, adaptations of the body in response of work in unusual postures, and elucidation of relevant injury pathways.

IMPACT ON INDUSTRY

Workers who adopt unusual or restricted postures in their work often experience higher musculoskeletal injury rates. If awkward postures cannot be eliminated in the workplace, jobs should be designed in accordance with the reduced strength and lifting capabilities observed in these postures.

Autonomic Nervous System Function Among Individuals With Acute Musculoskeletal Injury

OBJECTIVE

To determine differences in peripheral and cardiovascular autonomic function between individuals with acute musculoskeletal injury (<1 week) and healthy controls.

METHODS

Autonomic cardiovascular modulation, baroreceptor sensitivity, skin conductance, and peripheral skin temperature were obtained in 6 subjects with acute musculoskeletal injury and 6 age- and sex-matched controls. Power spectral analysis was performed on both beat-to-beat R-R intervals and continuous systolic blood pressure (SBP) peaks. Baroreceptor sensitivity was derived using both heart rate and blood pressure spectral analysis components.

RESULTS

The SD of R-R intervals was significantly different for the acute injury group relative to controls (49.8 +/- 10.5 vs 76.8 +/- 12.7 ms; P < .01). Continuous SBP peaks and skin conductance (sympathetic vasomotor and sudomotor indices, respectively) were significantly higher (59.6 +/- 6.7 vs 23.8 +/- 6.4 mm Hg2 /Hz, and 3.87 +/- 1.04 vs 2.19 +/- 0.3 mhos; P < .01, respectively) and baroreceptor sensitivity lower (0.97 +/- 0.07 vs 1.10 +/- 0.08 mm Hg; P < .02) in the acute injury group compared with controls. Regression analysis revealed a significant relationship between skin conductance and continuous SBP peaks (r = 0.75; P < .01).

CONCLUSIONS

These findings suggest that interaction between cutaneous and vasomotor sympathetic neurons in response to acute musculoskeletal injury, reflected as increased afferent input from sensitized nociceptors and other sensory neurons, results in alterations in autonomic function.

Workplace design guidelines for asymptomatic vs. low-back-injured workers

While numerous efforts have attempted to provide quantitative guidelines for the prevention of initial low back disorders during material handling tasks, none have appeared in the literature that address the issue of recurrent low back disorders due to materials handling when returning to the workplace. A study comparing the spine loads of low back pain patients and asymptomatic controls was conducted. Subjects lifted weights varying from 4.5-11.4 kg at four vertical heights, two horizontal distances and five task asymmetries collectively representing common industrial lifting situations. Spine loading was calculated using a validated EMG-assisted biomechanical model. Spine loads observed during lifting tasks were compared to spine tolerance values believed to initiate low back injuries. In addition, the percentage of patients successfully performing the lift was noted and used as an indication of the willingness of the subject to perform the task. These evaluations are summarized in a series of three lifting guidelines indicating safe, medium risk and high risk lifting tasks for low back patients as well as asymptomatic workers. It is believed that adherence to these guidelines can minimize the risk of recurrent low back disorders due to occupational lifting.

Return to work following whiplash and back injury: a review and evaluation

The purpose of this study is to review the reported return-to-work rates following whiplash and back-injury. The return-to-work rates for the 71 relevant studies that were reviewed varied from 29% to 100% with a median of 67%. The results suggest considerable residual return-to-work potential for persons with whiplash and back injury. Return-to-work rates were substantially higher for motor vehicle (96%) compared to work-related (71%) studies and also considerably higher for whiplash (95%) compared to back injuries (65%). It is suggested that these indices may form potential benchmarks for personal injury claims outcomes. The purpose of this paper is to analyse the published rates of return to work following whiplash and back injury. This criterion of return to work is not without limitations or controversy and Pfingsten, Hildebrandt Leibing, Franz and Saur (1997) noted: "... a high variability exists in data on return-to-work. Results often range from either no return to a very high return rate, with an approximate average of 68% following multimodal treatment procedures...".

Core stability measures as risk factors for lower extremity injury in athletes

INTRODUCTION/PURPOSE

Decreased lumbo-pelvic (or core) stability has been suggested to contribute to the etiology of lower extremity injuries, particularly in females. This prospective study compares core stability measures between genders and between athletes who reported an injury during their season versus those who did not. Finally, we looked for one or a combination of these strength measures that could be used to identify athletes at risk for lower extremity injury.

METHODS

Before their season, 80 female (mean age = 19.1 +/- 1.37 yr, mean weight 65.1 +/- 10.0 kg) and 60 male (mean age = 19.0 +/- 0.90 yr, mean weight 78.8 +/- 13.3 kg) intercollegiate basketball and track athletes were studied. Hip abduction and external rotation strength, abdominal muscle function, and back extensor and quadratus lumborum endurance was tested for each athlete.

RESULTS

Males produced greater hip abduction (males = 32.6 +/- 7.3%BW, females = 29.2 +/- 6.1%BW), hip external rotation (males = 21.6 +/- 4.3%BW, females = 18.4 +/- 4.1%BW), and quadratus lumborum measures (males = 84.3 +/- 32.5 s, females = 58.9 +/- 26.0 s). Athletes who did not sustain an injury were significantly stronger in hip abduction (males = 31.6 +/- 7.1%BW, females = 28.6 +/- 5.5%BW) and external rotation (males = 20.6 +/- 4.2%BW, females = 17.9 +/- 4.4%BW). Logistic regression analysis revealed that hip external rotation strength was the only useful predictor of injury status (OR = 0.86, 95% CI = 0.77, 0.097).

CONCLUSION

Core stability has an important role in injury prevention. Future study may reveal that differences in postural stability partially explain the gender bias among female athletes.

Return to play after lumbar spine conditions and surgeries

Low back pain in athletes can result from a wide variety of conditions. A detailed history and physical examination supplemented by appropriate imaging studies can lead to an accurate diagnosis. The majority of cases will be self-limiting and resolve within 6 weeks regardless of treatment, but it is important to be able to identify conditions that require specific treatment. The decision of when an athlete can return to active competition is determined by the specific condition, associated symptoms, and treatment provided. Most athletes can return to full unrestricted play after sufficient resolution of pain and restoration of range of motion. Athletes undergoing spinal fusion are typically restricted from full-contact sports.

Is the trunk movement more perturbed after an asymmetric than after a symmetric perturbation during lifting?

Low back injury is associated with sudden movements and loading. Trunk motion after sudden loading depends on the stability of the spine prior to loading and on the trunk muscle activity in response to the loading. Both factors are not axis-symmetric. Therefore, it was hypothesized that the effects on trunk dynamics would be larger after an asymmetric than after a symmetric perturbation. Ten subjects lifted a crate in which, prior to lifting, a mass was displaced to the front or to the side without the subjects being aware of this. Crate and subject movements, crate reaction forces and muscle activity were recorded. From this, the stability prior to the perturbation was estimated, and the trunk angular kinematics and moments at the lumbo-sacral joint were calculated. Both perturbations only minimally affected the trunk kinematics, although the stability of the spine prior to the lifting movement was higher in the sagittal plane than in the frontal plane. In both conditions the stability appeared to be sufficient to absorb the applied perturbation.

Soldier load carriage: historical, physiological, biomechanical, and medical aspects

This study reviews historical and biomedical aspects of soldier load carriage. Before the 18th century, foot soldiers seldom carried more than 15 kg while on the march, but loads have progressively risen since then. This load increase is presumably due to the weight of weapons and equipment that incorporate new technologies to increase protection, firepower, communications, and mobility. Research shows that locating the load center of mass as close as possible to the body center of mass results in the lowest energy cost and tends to keep the body in an upright position similar to unloaded walking. Loads carried on other parts of the body result in higher energy expenditures: each kilogram added to the foot increases energy expenditure 7% to 10%; each kilogram added to the thigh increases energy expenditure 4%. Hip belts on rucksacks should be used whenever possible as they reduce pressure on the shoulders and increase comfort. Low or mid-back load placement might be preferable on uneven terrain but high load placement may be best for even terrain. In some tactical situations, combat load carts can be used, and these can considerably reduce energy expenditure and improve performance. Physical training that includes aerobic exercise, resistance training targeted at specific muscle groups, and regular road marching can considerably improve road marching speed and efficiency. The energy cost of walking with backpack loads increases progressively with increases in weight carried, body mass, walking speed, or grade; type of terrain also influences energy cost. Predictive equations have been developed, but these may not be accurate for prolonged load carriage. Common injuries associated with prolonged load carriage include foot blisters, stress fractures, back strains, metatarsalgia, rucksack palsy, and knee pain. Load carriage can be facilitated by lightening loads, improving load distribution, optimizing load-carriage equipment, and taking preventive action to reduce the incidence of injury.

Back injuries and pain in adolescents attending a ski high school

This study compared overuse injuries, small abnormalities, and pain alone in different types of skiing and activity levels. Subjects were 45 ski high school athletes aged 15-19 years. We found the back and knees significantly more prone to activity-related injuries and pain than other body regions. Thirty subjects (67%) had low back pain on the first examination, and 17 had pain caused by overuse of the back. This was more frequent among active, young competitive boys in the cross-country skiing group, with mature height less than 99%, than among noncompetitive boys in the same group or among the alpine skiers. Neck pain was reported only by girls. Eight subjects had low back pain related to small abnormalities. The subjects were given counseling about training and physiotherapy. The 1-year follow-up found a significant reduction in back pain due to overuse injuries (from 17 to 3 subjects) and indistinct neck pain (from 10 to 2) but no reduction in pain in those with small abnormalities in the low back. Low back pain was common in young athletes, particularly in cross-country skiers. Excessively rapid progression of training and faulty technique increased back pain complaints from 36% when entering the school to 67% at the first examination. A proper evaluation and treatment of overuse injuries and accurate counseling of training types, volume, and progression reduced the low back pain problems to 29% of subjects 1 year later in spite of a maintained high activity level. A minimum entrance requirement to conditioning seems mandatory for students attending a ski high school.

Dynamic stiffness and damping of human intervertebral disc using axial oscillatory displacement under a free mass system

The aim of this study was to analyse the dynamic response of the human intervertebral disc to vibration in a physiologically relevant frequency spectrum. Eight lumbar intervertebral discs were harvested. After preparation, each sample was subjected to a pre-loading and then dynamic compression (from 5 to 30 Hz). The dynamic compression was applied using an experimental set-up comprising a free weight loading from above and a driving oscillatory displacement from below (closest to the in vivo loading). A viscoelastic model enabled the calculation of stiffness and damping from the transfer function. From 5 Hz to 30 Hz the stiffness values are between 0.19 and 3.66 (MN/m) and the damping values between 32 and 2094 (Ns/m). The mean resonant frequency was found at 8.7 Hz. These dynamic characteristics of the intervertebral disc could be used in a three-dimensional finite elements model of the human body to study its response to vibration in the driving position.

Partitioning the contributing role of biomechanical, psychosocial, and individual risk factors in the development of spine loads

BACKGROUND CONTEXT

The role of biomechanical workplace factors in spine loading has been well documented. However, our understanding of the role of psychosocial and individual factors in producing spine loads is poorly understood. Even less is understood about the relative contribution of these factors with respect to kinematic, kinetic and muscle activity responses, as well as spine loading.

PURPOSE

To explore the relative contribution of biomechanical and psychosocial workplace factors and individual characteristics on the biomechanical responses and spine loading.

STUDY DESIGN/SETTING

The contribution of various levels of workplace factors to spine loading was monitored under laboratory conditions.

PATIENT SAMPLE

Sixty (30 male and 30 female) college-age individuals who were asymptomatic to low back pain.

OUTCOME MEASURES

Trunk kinematics and kinetics, muscle activity and the three-dimensional spinal loads.

METHODS

The subjects performed lifting tasks while being exposed to varying levels of biomechanical (lift rate, load weight and task asymmetry) and psychosocial (social support and mental concentration) workplace factors as well as an unexplored (load placement) workplace factor.

RESULTS

The workplace job demands that had the largest contribution were load placement (4% to 30%) and load weight (15% to 55%). Mental concentration and social environment had a relatively small contribution to the spinal loads (up to 0.2%). Anthropometry played a large role in the shears (about 12% to 58%) but a relatively minor role in the compressive forces (about 3%).

CONCLUSIONS

Under the given experimental conditions, load weight is the most important factor when controlling compression forces associated with lifting, but other factors, such as individual characteristics, significantly contribute to the shear loads. Thus, one must account for the weight lifted and the anthropometric dimensions when designing the workplace. For the first time, the relative contribution of workplace job demands and individual factors in the development of spine loading have been identified.

Backpacks in children

Back pain and deformity are common in adolescents. There has been extensive discussion in the lay literature as to the potential for back pain and spinal deformity with backpack use. The scientific literature on this subject is sparse but is increasing. Epidemiologic studies have identified risk factors associated with back pain in adolescents and daily use of a heavy backpack may be important. A book bag weighing more than 15% to 20% of a child's weight is associated with back pain, and improper use of the backpack can result in changes of posture and gait. There is no evidence that structural spinal deformity can result from backpack use. Children who experience back pain are at increased risk of having back pain as adults. The economic impact may be significant, because back pain is a major cause of disability in adults. The current authors review the available scientific literature and comments on this public health issue.

Trunk extension effort in patients with chronic low back dysfunction

STUDY DESIGN

Single-session measurement was performed.

OBJECTIVE

To measure trunk extension strength and assess trunk extension effort in patients with chronic low back dysfunction using a novel test protocol and the DEC parameter.

SUMMARY OF BACKGROUND DATA

In normal subjects, the DEC parameter effectively and reproducibly differentiates between maximal effort and feigned weakness of the trunk extensors, but its applicability to patients with chronic low back dysfunction has not yet been explored.

METHODS

Isokinetic trunk extension strength was measured in 44 patients with chronic low back dysfunction (22 women and 22 men) who were not involved in litigation process. Tests were conducted using a range of motion of 20 degrees, angular velocities of 10 degrees and 40 degrees per second, and an isometric preactivation force of 50 N. The average strength at these velocities served for calculation of the DEC score, which is the difference between the eccentric and concentric strength ratios at these velocities.

RESULTS

The strength scores resembled the characteristic physiologic moment-angular velocity relation, and were much reduced, as compared with the scores of normal subjects. The DEC scores for 39 patients (89%) were less than the cutoff value, which in normal subjects differentiates maximal effort (below cutoff) from feigned weakness (above cutoff) at tolerance limits of 99%. This figure was slightly lower (84%) at a corresponding 95% level. A principal finding in the false-positive cases was a particularly low concentric strength at 40 degrees per second.

CONCLUSIONS

This study indicates that under the current protocol, the large majority of patients perform at a maximal level of effort.

Interaction of physical and mental work

The objective of the research was to determine the effect of mental load on the physical capacity of an individual. An experiment involving 9 combinations of lifting tasks, 1 lowering task, and 3 treadmill tasks was conducted. Heart rate was measured and maximum acceptable weight of lift was determined using the psychophysical method. A simple multiplication task was used as the mental load. The output variables were determined with and without the mental task. The results indicate that the individual's physical capacity decreased with the mental task while lifting from floor to knuckle and shoulder to reach lifting heights.

Neuromuscular function in athletes following recovery from a recent acute low back injury

STUDY DESIGN

Observational case control design.

OBJECTIVES

To examine muscle response to sudden trunk loading in athletes with and without a recent history of acute low back injury (LBI).

BACKGROUND

Impaired neuromuscular function is associated with chronic low back pain. This study examined whether such impairment persists after recovery from an acute LBI.

METHODS AND MEASURES

Seventeen athletes who had a recent history of acute LBI and 17 matched healthy controls were tested. At the time of testing (mean = 56 days postinjury, range = 7-120 days postinjury), all athletes were symptom free and had returned to regular competition. Subjects performed isometric exertions in trunk flexion, extension, and left and right lateral bending against a trunk restraining cable. Upon reaching the target isometric force, the cable was released to impose sudden loading on the lumbar spine. Surface EMG signals from 12 major trunk muscles were recorded. The shut-off and switch-on latencies and number of muscles responding to sudden loading were compared between the 2 groups.

RESULTS

In all 4 testing directions, the athletes with a recent history of acute LBI shut off significantly fewer muscles and did so with delayed latency. On average, the injured subjects shut off 4.0 out of 6.0 (SD = 1.3) muscles compared to 4.6 out of 6.0 (SD = 1.3) muscles in the control group. The average muscle shut-off latency was 71 (SD = 31) milliseconds for the injured and 50 (SD = 21) milliseconds for the control subjects. No differences were found in number or latency of muscles switching on.

CONCLUSIONS

These objective measures of neuromuscular function indicated an altered muscle response pattern to sudden trunk loading in athletes following their clinical recovery from a recent acute LBI.

[Generators of walking movements in humans: spinal mechanisms of their activation]

The paper is focused on spinal generation of walking movements in patients afflicted with loss of supraspinal control consequent to back trauma. The author cites literature on methods of initiation of walking movements with pharmacological and proprioceptive stimulation. On his own experimental investigations with epidural electrical stimulation of the spinal marrow dorsal surface he proves existence of walking generators in the human. There is evidence that the walking pattern in extensors is formed through amplitude modulation of monosynaptic reflexes, whereas in flexors it is established through switching of the reflex paths from the monosynaptic reflex to the polysynaptic neuron network. Investigations of the functional deafferentation of lower extremities showed that walking movements as a result of epidural stimulation are intraspinal by origin and adjusted by way of peripheral feedback. A hypothetical sequence of activation of walking generators through the propriospinal system of dorsolateral and ventrilateral funiculi has been put forward.

Sensory-motor control of the lower back: implications for rehabilitation

Although low back pain (LBP) is a widespread and disabling health problem, there is a lack of evidence based medicine with respect to its treatment and rehabilitation. A major reason for this is the poor understanding of the underlying mechanisms of the LBP syndromes. In an attempt to fill this gap, the present review article provides an overview of the sensory-motor control aspects of trunk stabilization and postural control of the trunk, and how they may relate to the evolution of LBP. In particular, the anatomy and physiology of the sensory-motor control mechanisms of the trunk muscles that contribute to general and segmental stability of the lumbar spine will be elucidated. Furthermore, a brief overview of current theories of postural control will be provided with respect to spinal stabilization. Finally, a concept of the pathophysiological changes within the sensory-motor control mechanisms of the lumbar spine in the presence of muscle injury and pain will be presented. The impact of pain and muscle injury on the muscular support for the lumbar motion segment will be discussed along with the deficits in neuromuscular control in LBP patients with decreased segmental lumbar stability.

A randomized controlled trial to prevent patient lift and transfer injuries of health care workers

STUDY DESIGN

Randomized controlled trial (RCT).

OBJECTIVES

To compare the effectiveness of training and equipment to reduce musculoskeletal injuries, increase comfort, and reduce physical demands on staff performing patient lifts and transfers at a large acute care hospital.

SUMMARY OF BACKGROUND DATA

Back injury to nursing staff during patient handling tasks is a major issue in health care. The value of mechanical assistive devices in reducing injuries to these workers is unclear.

METHODS

This three-armed RCT consisted of a "control arm," a "safe lifting" arm, and a "no strenuous lifting" arm. A medical, surgical, and rehabilitation ward were each randomly assigned to each arm. Both intervention arms received intensive training in back care, patient assessment, and handling techniques. Hence, the "safe lifting" arm used improved patient handling techniques using manual equipment, whereas the "no strenuous lifting" arm aimed to eliminate manual patient handling through use of additional mechanical and other assistive equipment.

RESULTS

Frequency of manual patient handling tasks was significantly decreased on the "no strenuous lifting" arm. Self-perceived work fatigue, back and shoulder pain, safety, and frequency and intensity of physical discomfort associated with patient handling tasks were improved on both intervention arms, but staff on the mechanical equipment arm showed greater improvements. Musculoskeletal injury rates were not significantly altered.

CONCLUSIONS

The "no strenuous lifting" program, which combined training with assured availability of mechanical and other assistive patient handling equipment, most effectively improved comfort with patient handling, decreased staff fatigue, and decreased physical demands. The fact that injury rates were not statistically significantly reduced may reflect the less sensitive nature of this indicator compared with the subjective indicators.