High Spinal Loads Research Articles

Low occurrence of MRI spinal changes in elite climbing athletes; a cross-sectional study

ObjectivesTo examine the occurrence of magnetic resonance imaging (MRI) changes in the thoracolumbar spine among elite climbing athletes.MethodsAll climbers of the Swedish national sport climbing team (n = 8), and individuals having trained for selection to the national team (n = 11), were prospectively included. A control group, matched in age and sex, were recruited. All participants underwent a thoracolumbar MRI (1.5 T, T1- and T2-weighted imaging), evaluated according to Pfirrmann classification, modified Endplate defect score, Modic changes, apophyseal injuries and spondylolisthesis. Pfirrmann ≥ 3, Endplate defect score ≥ 2 and Modic ≥ 1 was defined as degenerative findings.ResultsFifteen individuals, 8 women, participated in both the climbing group (mean age 23.1, SD 3.2 years) and the control group respectively (mean age 24.3, SD 1.5 years). In the climbing group, 6.1% of the thoracic and 10.6% of the lumbar intervertebral discs showed signs of degeneration according to Pfirrmann. One disc with a grade above 3 was present. Modic changes in the thoracic/lumbar spine were prevalent in 1.7%/1.3% of the vertebrae. Degenerative endplate changes according to the Endplate defect score were found in 8.9% and 6.6% of the thoracic and lumbar spinal segments of the climbing group, respectively. Two apophyseal injuries were found, while no participants displayed signs of spondylolisthesis. There was no difference in point-prevalence of radiographic spinal changes between climbers and controls (0.07 < p < 1.0).ConclusionIn this small cross-sectional study, only a low proportion of elite climbers displayed changes of the spinal endplates or intervertebral discs, as opposed to other sports with high spinal loads. Most observed abnormalities were low grade degenerative changes and did not differ statistically compared to controls.

Trunk muscle forces and spinal loads during heavy deadlift: Effects of personalization, muscle wrapping, muscle lever arm, and lumbopelvic rhythm.

Heavy deadlift is used as a physical fitness screening tool in the U.S. Army. Despite the relevance of such a screening tool to military tasks performed by Service Members, the biomechanical impact of heavy deadlift and its risk of low-back injury remain unknown. A kinematics-driven musculoskeletal model of spine was implemented to investigate biomechanics of the lower back in a volunteer (23 years old, height of 1.82 m, and body mass of 98.8kg) during a 68 kg deadlift. In search of protective mechanisms, effects of model personalization and variations in trunk musculature and lumbopelvic rhythm were also investigated. The net moment, compression and shear forces at the L5-S1 reached peaks of 684 Nm, 17.2 and 4.2kN, respectively. Geometrical personalization and changes in lumbopelvic rhythm had the least effects on predictions while increases in muscle moment arms (40%) had the largest effects that caused, respectively, 32% and 36% decrease in the maximum compressive and shearing forces. Initiating wrapping of back muscles at farther distances from the spine had opposing effects on spinal loads; peak compression at the L5-S1 decreased by 12% whereas shear increased by 19%. Despite mechanisms considered, spinal loads during heavy deadlift exceed the existing evidence concerning the threshold of injury for spinal segments, suggesting the vulnerability to injury. Chronic exposure to such high-spinal loads may lead to (micro) fractures, degeneration, pathoanatomical changes and finally low-back pain.

Trunk muscle forces and spinal loads in persons with unilateral transfemoral amputation during sit-to-stand and stand-to-sit activities

BackgroundAlterations and asymmetries in trunk motions during activities of daily living, involving lower extremities, are suggested to cause higher spinal loads in persons with unilateral lower limb amputation. Given the repetitive nature of most activities of daily living, knowledge of the amount of increase in spinal loads is important for designing interventions aimed at prevention of secondary low back pain due to potential fatigue failure of spinal tissues. The objective of this study was to determine differences in trunk muscle forces and spinal loads between persons with and without lower limb amputation when performing sit-to-stand and stand-to-sit tasks. MethodsKinematics of the pelvis and thorax, obtained from ten males with unilateral transfemoral lower limb amputation and 10 male uninjured controls when performing sit-to-stand and stand-to-sit activities, were used within a non-linear finite element model of the spine to estimate trunk muscle forces and resultant spinal loads. FindingsThe peak compression force, medio-lateral (only during stand-to-sit), and antero-posterior shear forces were respectively 348 N, 269 N, and 217 N larger in person with vs. without amputation. Persons with amputation also experienced on average 171 N and 53 N larger mean compression force and medio-lateral shear force, respectively. InterpretationWhile spinal loads were larger in persons with amputation, these loads were generally smaller than the reported threshold for spinal tissue injury. However, a rather small increase in spinal loads during common activities of daily living like walking, sit-to-stand, and stand-to-sit may nevertheless impose a significant risk of fatigue failure for spinal tissues due to the repetitive nature of these activities.

An integrated model to improve ergonomic and economic performance in order picking by rotating pallets

This paper studies manual order picking activities in a warehouse where items are stored on pallets in two rows one above the other. Items stored on the pallets may be heavy, and manually picking the items may require excessive bending and stretching, which results in high spinal loads on the order picker associated with high injury risks. For this scenario that can frequently be observed in practice, this paper proposes an integrated model that supports the planning of order picking operations and pallet rotations taking account both of the time required for completing a set of orders as well as the spinal load on the order picker and the consequent injury risks. The results of a numerical experiment indicate that selectively rotating pallets may both reduce order picking time as well as the load on the order picker, leading to a quicker and less risky order picking process. The model proposed in this paper supports the decision of which pallet to rotate (and which not to rotate) against the company's cost objectives and its endeavor for worker well-being.

Low back pain in German elite hockey players

Introduction: Back pain (BP) and especially low back pain (LBP) is a frequent health problem in the general population, in sports and also in field hockey resulting in enormous costs for the health care system. Detailed data on prevalence of LBP in German sportsmen and women is rare. From a biomechanical perspective movements in field hockey are characterized by forward flexion and rotation of the trunk. The forward flexed posture must be maintained during most of the duration of a game or training session causing high spinal loads. This might be related with the development of pain in the lower back. The study aimed to determine the prevalence of LBP in German elite field hockey players to clarify associations between hockey-specific posture and pain generation.

Methods for Avoiding or Reducing High Spinal Loads in Everyday Life

Background: High loads on an anterior spinal implant can cause an implant to subside into the vertebral body. This alteration may endanger the clinical output of the treatment and can result in back pain. The aim of this paper is to show the possibilities for avoiding or reducing high spinal loads in daily life. Methods: The loads on a telemeterized vertebral body replacement were measured in 5 patients for a variety of different activities. The effects of the ways an exercise was performed on implant loads were evaluated. Results: Following a physiotherapist’s instructions reduced implant loads by approximately 60% when changing from one body position to another or when performing physiotherapeutic exercises. Supporting the upper body with one hand can reduce loads by approximately 30% when washing the face in front of a washing basin. Leaning against a backrest in a sitting position reduced implant loads by an average of 38%. If possible, weight should be carried in a backpack or spilt bilaterally and evenly between both hands. Generally, any weight should be held close to the body. Conclusions: Patients should follow their physiotherapists’ instructions. Spinal loads are generally reduced by reducing the lever arm of the upper body’s center of mass relative to the lumbar spine and by supporting the upper body, for example, with the hands.

Activities of Everyday Life with High Spinal Loads

Activities with high spinal loads should be avoided by patients with back problems. Awareness about these activities and knowledge of the associated loads are important for the proper design and pre-clinical testing of spinal implants. The loads on an instrumented vertebral body replacement have been telemetrically measured for approximately 1000 combinations of activities and parameters in 5 patients over a period up to 65 months postoperatively. A database containing, among others, extreme values for load components in more than 13,500 datasets was searched for 10 activities that cause the highest resultant force, bending moment, torsional moment, or shear force in an anatomical direction. The following activities caused high resultant forces: lifting a weight from the ground, forward elevation of straight arms with a weight in hands, moving a weight laterally in front of the body with hanging arms, changing the body position, staircase walking, tying shoes, and upper body flexion. All activities have in common that the center of mass of the upper body was moved anteriorly. Forces up to 1650 N were measured for these activities of daily life. However, there was a large intra- and inter-individual variation in the implant loads for the various activities depending on how exercises were performed. Measured shear forces were usually higher in the posterior direction than in the anterior direction. Activities with high resultant forces usually caused high values of other load components.

Body posture and backpack loading: an upright magnetic resonance imaging study of the adult lumbar spine

Axial loading of the spine while supine, simulating upright posture, decreases intervertebral disc (IVD) height and lumbar length and increases lumbar lordosis. The purpose of this study is to measure the adult lumbar spine's response to upright posture and a backpack load using upright magnetic resonance imaging (MRI). We hypothesize that higher spinal loads, while upright and with a backpack, will compress lumbar length and IVD height as well as decrease lumbar lordosis. Six volunteers (45 ± 6 years) underwent 0.6 T MRI scans of the lumbar spine while supine, upright, and upright with a 10 % body weight (BW) backpack. Main outcomes were IVD height, lumbar spinal length (distance between anterior-superior corners of L1 and S1), and lumbar lordosis (Cobb angle between the superior endplates of L1 and S1). The 10 % BW load significantly compressed the L4-L5 and L5-S1 IVDs relative to supine (p < 0.05). The upright and upright plus 10 % BW backpack conditions significantly compressed the anterior height of L5-S1 relative to supine (p < 0.05), but did not significantly change the lumbar length or lumbar lordosis. The L4-L5 and L5-S1 IVDs compress, particularly anteriorly, when transitioning from supine to upright position with a 10 % BW backpack. This study is the first radiographic analysis to describe the adult lumbar spine wearing common backpack loads. The novel upright MRI protocol described allows for functional, in vivo, loaded measurements of the spine that enables the study of spinal biomechanics and therapeutic interventions.

Lifting up and laying down a weight causes high spinal loads

Lifting up weights from a cupboard or table and putting them back are activities of daily living. Patients with spinal problems want to know whether they should avoid these activities. However, little is known about the spinal forces during these activities and about the effect of level height.Loads on a telemeterized vertebral body replacement were measured in 5 patients. The effect of level height when lifting or setting down weights of 0.01, 1.5 and 3.0kg in a standing posture were investigated. Furthermore, these weights were lifted and set down with a stretched arm while sitting at a table. No instructions were given on how to perform the task.For these activities, forces as high as 5 times the value for standing alone were measured. In 2 patients, implant loads decreased with increasing level height. In the other patients the effect of level height was small. Lifting a weight from a table with a stretched arm while sitting led to a strong increase of the maximum implant force. Setting down the weight usually caused a slightly higher maximum implant force than lifting it.Forces on a vertebral body replacement during lifting and setting down a weight varied strongly when no precise instructions were given on how to perform the activity. Thus, the measured forces are representative for such activities performed in daily life. This, however, led to wide variations in measured data. Compared to the value for standing, 5 times higher forces were measured for lifting and setting down of weights. This suggests that these activities should be avoided by patients who have spinal problems.

Measured loads on a vertebral body replacement during sitting

Sitting is frequently assumed to cause high spinal loads because people with sedentary work often suffer from low back pain. It is assumed that the posture while sitting, as well as several seat parameters, also affects the spinal loads. To measure the loads on a spinal implant for different upper body inclinations, backrest declinations, seat heights, types of seat, and arm positions. Loads on a vertebral body replacement during sitting were measured in five patients with telemeterized implants. The telemeterized vertebral body replacement measures all six load components. Itwas implanted into five patients suffering from compression fractures of a lumbar vertebral body. Loads were measured when the patients were sitting on a stool and inclining their upper body between 15° flexion and 10° extension in steps of 5°; on a chair with an adjustable backrest that allowed declination angles between 108° and 180°; on an office chair while the seat height was varied between 40 and 60 cm in steps of 5 cm; and successively on seven different types of seats. The effect of the arm position was also studied. The resultant implant force was increased on the average by 48% for 15° flexion and decreased by 19% for 10° extension of the trunk. When sitting on a chair with an adjustable backrest, the loads decreased with an increasing backrest declination angle. The seat height had in most cases only a minor effect on implant loads. In comparison to sitting on a stool, the loads were reduced when sitting on a bench (7%) or a stool with a padded wedge (9%), a knee stool (19%), a chair (35%), and an office chair (41%). Sitting on a physiotherapy ball increased the loads by 7%. Placing the hands on the thighs reduced the implant loads on the average by 19% in comparison to arms hanging on the sides. Spinal loads can be reduced by leaning against the backrest, placing the arms on the armrest or the thighs, and by decreasing the flexion angle of the upper body.

Quantitative assessment of trunk muscle coactivation in sub-maximal isometric exertion tasks

This study empirically quantified the antagonistic moment induced by antagonistic trunk muscles as well as the sum of antagonistic forces during isometric exertion tasks: flexion/extension, lateral bending left/right, and twisting clockwise/counter-clockwise. Twelve male subjects performed isometric voluntary exertions gradually increasing to maximum efforts. EMG signals from 10 trunk muscles and exertion forces were collected and muscle forces and moments were predicted from an EMG-assisted model. Antagonistic moments were assessed at 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90% MVE. Antagonistic coactivation was dependent on the magnitude and direction of the exertion moment ( p<0.05). The magnitude of the antagonistic moment was high during twisting exertions of about 40% of the exertion moment, 24% during flexion, 23% during lateral bending, and 10% during extension. The sum of antagonist forces showed almost the same result with the antagonistic moment. Spinal load was also high during twisting exertions and antagonistic muscles accounted for about 23% of the total compression force. From these results, it can be concluded that high coactivation is required to stabilize the spinal region during twisting exertions and this results in high spinal loads. Relevance to industry This study investigated the coactivation levels according to the different directions and magnitudes of exertions. Results from this study will be useful for diagnostic, preventive, and rehabilitative purposes in the analysis of manual materials handling tasks.

Placement control: a nontraditional risk factor for occupational low back pain

Purpose of study: As more complex work tasks become more common in the occupational environment, new unexplored factors containing both physical and mental stressors may place workers at risk for low back pain. One such factor is placement control—how specific the box must be placed within a targeted destination. The objective of this study was to investigate the impact of the load placement control on the biomechanical responses of the lumbar spine.Methods used: Sixty subjects (30 males and 30 females) lifted boxes (weighing 6.8 and 11.4 kg) from a conveyor (sagittally symmetric) and placed them at an asymmetric destination (90 degrees clockwise and 90 degrees counterclockwise). Subjects were required to deliver the loads under two conditions: 1) general placement within the vicinity of a destination target, and 2) precise placement on a target. Individual characteristics, such as gender and personality, were evaluated as potential modifiers of the impact of placement control. An electromyograph assisted biomechanical model evaluated the three-dimensional spinal loads and trunk moments.of findings: Individuals responded to controlled placement by producing faster motions with more awkward postures, increased their muscle coactivity and higher spinal loads. The precise placement task resulted in increases in spinal loads of 160 N of lateral shear, 80 N of anteroposterior shear and 700 N of compression above and beyond the general placement task. Controlled placement was more detrimental to females than males (5% to 10% more). The impact of placement control was also influenced by certain personality traits (3% to 17%).Relationship between findings and existing knowledge: This study has identified a previously unreported risk factor for occupational risk. By requiring workers to precisely position loads, a spine loading cost is incurred as a result of musculoskeletal system compensations such as coactivity and postural adjustments.Overall significance of findings: With the proliferations of more repetitive yet precise materials handling (as in semiautomated product distribution), such factors as precision placement that tax multiple components of the musculoskeletal system may play an important role in occupational risk.Disclosures: No disclosures.Conflict of interest: Kermit Davis, PhD, grant research support: International Society for Biomechanics Dissertation Grant.

A comprehensive analysis of low-back disorder risk and spinal loading during the transferring and repositioning of patients using different techniques

Although patient handlers suffer from low-back injuries at an alarming rate worldwide, there has been limited research quantifying the risk for the specific tasks performed by the patient handlers. The current study used both a comprehensive evaluation system (low-back disorder risk model) and theoretical model (biomechanical spinal loading model) to evaluate risk of LBD of 17 participants (12 experienced and five inexperienced) performing several patient handling tasks. Eight of the participants were female and nine were male. Several patient transfers were evaluated as well as repositioning of the patient in bed; these were performed with one and two people. The patient transfers were between bed and wheelchair (fixed and removable arms) and between commode chair and hospital chair. A ‘standard’ patient (a 50 kg co-operative female; nonweight bearing but had use of upper body) was used in all patient handling tasks. Overall, patient handling was found to be an extremely hazardous job that had substantial risk of causing a low-back injury whether with one or two patient handlers. The greatest risk was associated with the one-person transferring techniques with the actual task being performed having a limited effect. The repositioning techniques were found to have significant risk of LBD associated with them with the single hook method having the highest LBD risk and spinal loads that exceeded the tolerance limits (worst patient handling job). The twoperson draw sheet repositioning technique had the lowest LBD risk and spinal loads but still had relatively high spinal loads and LBD risk. Thus, even the safest of tasks (of the tasks evaluated in this study) had significant risk. Additionally, the current study represented a ‘best’ case scenario since the patient was relatively light and co-operative. Thus, patient handling in real situations such as in a nursing home, would be expected to be worse. Therefore, to have an impact on LBD, it is necessary to provide mechanical lift assist devices.

A video-based method for evaluation of low-back load in long-cycle jobs

A method for evaluation of the physical load on the lumbar spine in industrial work is presented. It is suitable for identification of high spinal loads and their time duration. The method is based on biomechanical analysis of video-recordings. It takes into account the posture of the body as such, as well as the possible occurrence of external load and support. Compression of the L5-S1 intervertebral disc and strain on the lumbodorsal fascia is determined at 5-s intervals in each work task.

The Relationship of Torque, Velocity, and Power with Constant Resistive Load During Sagittal Trunk Movement

Strength and fitness studies have been used to determine the predictability of back pain episodes. Tests have demonstrated that isometric strength displays little prognostic value in the development of low-back pain. Static isometric tests have achieved widespread usage due to the simplicity and safety of protocols, the readily available technology, and the low administrative costs. Dynamic lifting models have, however, predicted significantly higher spinal loads than those derived from static models. The objectives of this study were twofold: to investigate the relationship of the torque, velocity, and power to the resistive load during trunk flexion and extension, and to develop predictive models for these relationships for the subject's performance of the 10th, 50th, and 90th percentile distribution. The results of the study found that the flexion/extension torque had a positive linear correlation with the set resistance; the velocity displayed a negative linear correlation, while power had a quadratic relationship with the resistance.