Lumbar Spine Loads Research Articles

The influence of hip extensor and lumbar spine extensor strength on lumbar spine loading during a squat lift

Weakness of the hip extensors and lumbar spine extensors has been proposed to contribute to greater demands on the lumbar spine during lifting. The purpose of the current study was to examine the associations among strength of the hip and lumbar spine extensors, lumbar spine extensor moments and lumbar paraspinal muscle activation during a squat lift task. Twenty-seven healthy females participated. Strength of the hip and lumbar spine extensors was measured using a dynamometer. Lumbar spine moments and lumbar paraspinal muscle activity were quantified during the concentric phase of the squat lifting task. There was a significant positive association between lumbar extensor strength and average lumbar extensor moment during lifting (r = 0.498, p = 0.008). Similarly, hip extensor strength was positively associated with the average lumbar extension moment (r = 0.382, p = 0.049). Hip extensor strength was negatively associated with activation of the lumbar paraspinal muscles during lifting (ρ = −0.382, p = 0.049). Stronger individuals are more likely to use their hip extensors and lumbar spine extensors to perform a squat lift task. In contrast, those with lower strength employ subtle biomechanical changes to reduce lumbar spine demand.

Walking Biomechanics and Spine Loading in Patients With Symptomatic Lumbar Spinal Stenosis.

Symptomatic lumbar spinal stenosis is a leading cause of pain and mobility limitation in older adults. It is clinically believed that patients with lumbar spinal stenosis adopt a flexed trunk posture or bend forward and alter their gait pattern to improve tolerance for walking. However, a biomechanical assessment of spine posture and motion during walking is broadly lacking in these patients. The purpose of this study was to evaluate lumbar spine and pelvic sagittal angles and lumbar spine compressive loads in standing and walking and to determine the effect of pain and neurogenic claudication symptoms in patients with symptomatic lumbar spinal stenosis. Seven participants with symptomatic lumbar spinal stenosis, aged 44–82, underwent a 3D opto-electronic motion analysis during standing and walking trials in asymptomatic and symptomatic states. Passive reflective marker clusters (four markers each) were attached to participants at T1, L1, and S2 levels of the spine, with additional reflective markers at other spinal levels, as well as the head, pelvis, and extremities. Whole-body motion data was collected during standing and walking trials in asymptomatic and symptomatic states. The results showed that the spine was slightly flexed during walking, but this was not affected by symptoms. Pelvic tilt was not different when symptoms were present, but suggests a possible effect of more forward tilt in both standing (p = 0.052) and walking (p = 0.075). Lumbar spine loading during symptomatic walking was increased by an average of 7% over asymptomatic walking (p = 0.001). Our results did not show increased spine flexion (adopting a trunk-flexed posture) and only indicate a trend for a small forward shift of the pelvis during both symptomatic walking and standing. This suggests that provocation of symptoms in these patients does not markedly affect their normal gait kinematics. The finding of increased spine loading with provocation of symptoms supports our hypothesis that spine loading plays a role in limiting walking function in patients with lumbar spinal stenosis, but additional work is needed to understand the biomechanical cause of this increase.

A physiological and biomechanical investigation of three passive upper-extremity exoskeletons during simulated overhead work

The objective of this study was to evaluate three passive upper-extremity exoskeletons relative to a control condition. Twelve subjects performed an hour-long, simulated occupational task in a laboratory setting. Independent measures of exoskeleton, exertion height (overhead, head height), time, and their interactions were assessed. Dependent measures included changes in tissue oxygenation (ΔTSI) in the anterior deltoid and middle trapezius, peak resultant lumbar spine loading, and subjective discomfort in various body regions. A statistically significant reduction in ΔTSI between exoskeleton and control was only observed in one instance. Additionally, neither increases in spinal loading nor increases in subjective discomfort ratings were observed for any of the exoskeletons. Ultimately, the exoskeletons offered little to no physiological benefit for the conditions tested. However, the experimental task was not highly fatiguing to the subjects, denoted by low ΔTSI values across conditions. Results may vary for tasks requiring constant arm elevation or higher force demands. Practitioner summary This study quantified the benefits of upper-extremity exoskeletons using NIRS, complementary to prior studies using EMG. The exoskeletons offered little to no physiological benefit for the conditions tested. However, the experimental task was not highly fatiguing, and results may vary for an experimental task with greater demand on the shoulders. Abbreviations: WMSD: work-related musculoskeletal disorder; EMG: electromyography; NIRS: near-infrared spectroscopy; NIR: near-infrared; Hb: haemoglobin; Mb: myoglobin; TSI: tissue saturation index; ATT: adipose tissue thickness

Axial Spondyloarthritis is associated with changes in lumbosacral loading during daily activities

BackgroundThere is currently little insight in lumbar spine loading during activities of daily living in patients with axial spondyloarthritis. Furthermore, it is unclear how inflammation or ankylosis-related mobility limitations in patients with axial spondyloarthritis affect lumbosacral loading, and if lumbar movement profiles have an effect on lumbosacral loading as well. Therefore, the aim of this study is to get more insight in the differences in peak and cumulative lumbosacral loading in patients with axial spondyloarthritis during activities of daily living. MethodsThree-dimensional motion analysis with integrative force-plates was used to calculate peak lumbosacral moment (peak loading) and lumbosacral moment impulse (cumulative loading), of 19 patients with axial spondyloarthritis and 23 healthy controls during forward bending, sit-to-stand and two lifting tasks (symmetric/asymmetric). We compared inflammatory (n = 7) and ankylosed (n = 12) patients with axial spondyloarthritis and controls. Patients were also classified into Flexion or Lordotic profile. FindingsBoth inflammatory and ankylosed patients generated significantly larger lumbosacral moment impulses than healthy controls in all movements, except during sit-to-stand, where the inflammatory group showed larger moment impulse than both other two groups. Patients with a Lordotic profile showed lowered peak lumbosacral moments and moment impulses compared to those with a Flexion profile. InterpretationBoth inflammatory and ankylosed patients experienced more cumulative loading depending on the activity. But our findings suggest that classification of patients into different movement profiles might be more interesting to clinically target specific loading adaptations related to pain and fear of movement.

The relationship of trunk kinematics and kinetics with lower limb pathology during gait in children with spastic cerebral palsy

BackgroundTrunk control during gait in children with cerebral palsy (CP) is known to be impaired. While differentiation of trunk movement between CP subtypes (unilateral/bilateral) has been examined, differentiation of lower lumbar spinal loading has not been considered. Furthermore, the relationship between lower lumbar loading and lower limb pathology has not been reported. Research QuestionHow do lower lumbar spinal kinetics differ during unilateral and bilateral CP gait and what is the relationship between trunk kinematics and L5/S1 kinetics with lower limb pathology? MethodsThree-dimensional thorax kinematics and L5/S1 kinetics were measured during gait with children divided into 3 groups (unilateral CP (n = 21), bilateral CP (n = 31) and typical development (TD) (n = 26)). Differences in thorax kinematics and reactive forces and moments at L5/S1 between groups were analysed using Statistical Parametric Mapping. Correlation coefficients were calculated between Gait Profile Score (GPS) and kinematic measures of the thorax and kinetics at L5/S1. ResultsAn increased ipsilateral bending moment was present for unilateral CP in the coronal plane (55–70% Gait Cycle (GC), p < 0.001), while children with bilateral CP demonstrated two distinct increased peaks during mid-stance (10–30 % GC, p < 0.001) and mid-swing (60–80% GC, p = 0.004) compared to TD. RMS and RoM thorax flexion, side flexion and L5/S1 lateral bend moment demonstrated significant moderate correlations with GPS. SignificanceThis study confirmed an increased involvement at the trunk and of lower lumbar spinal loading for children with bilateral CP compared to unilateral CP. It has been suggested that altered trunk movement in CP gait may be a combination of both a compensation for lower limb pathology and an underlying deficit. Our result of positive yet moderate correlations between GPS and trunk movement and lower spinal loading support this theory.

Development of a finite element biomechanical whole spine model for analyzing lumbar spine loads under caudocephalad acceleration

Background: Spine injury risk due to military conflict is an ongoing concern among defense organizations throughout the world. A better understanding of spine biomechanics could assist in developing protection devices to reduce injuries caused by caudocephalad acceleration (+Gz) in under-body blasts (UBB). Although some finite element (FE) human models have demonstrated reasonable lumbar spine biofidelity, they were either partial spine models or not validated for UBB-type loading modes at the lumbar functional spinal unit (FSU) level, thus limiting their ability to analyze UBB-associated occupant kinematics. Methods: An FE functional representation of the human spine with simplified geometry was developed to study the lumbar spine responses under +Gz loading. Fifty-seven load curves obtained from post mortem human subject experiments were used to optimize the model. Results: The model was cumulatively validated for compression, flexion, extension, and anterior-, posterior-, and lateral-shears of the lumbar spine and flexion and extension of the cervical spine. The thoracic spine was optimized for flexion and compression. The cumulative CORrelation and Analysis (CORA) rating for the lumbar spine was 0.766 and the cervical spine was 0.818; both surpassed the 0.7 objective goal. The model’s element size was confirmed as converged. Conclusions: An FE functional representation of the human spine was developed for +Gz lumbar load analysis. The lumbar and cervical spines were demonstrated to be quantitatively biofidelic to the FSU level for multi-directional loading and bending typically experienced in +Gz loading, filling the capability gap in current models.

Intersegmental kinematic analysis of lumbar spine by functional radiography between two subgroups of patients with chronic low back pain

IntroductionKinematic deficits such as fault in joint accessory motion is one of the most important contributing factors for developing the movement impairment in the lumbar spine. Functional radiography is accessible method for detecting the artherokinematic disorders. The aim of this study was to compare lumbar spine intersegmental motion between low back pain (LBP) subgroups of movement system impairment (MSI) model by functional radiography. Materials and methods20 subjects with chronic LBP in two subgroups of the MSI model (Rotation with Flexion and Rotation with Extension) participated in this study. Five x-rays were taken in different positions. Intersegmental linear translation and angular rotation of the lumbar segments were calculated. ResultsIn the Rotation with Extension subgroup, the translation and rotation values of the L3-4 segment from full to full position were significantly more than their values in the Rotation with Flexion subgroup ((mean difference = −1.69 (mm) P = 0.01), (mean difference = −3.80 (mm) P = 0.02) respectively). The translation of L2-3 segment from the neutral to the mid-flexion position was significantly greater in the Rotation with Flexion subgroup compared to the Rotation with Extension subgroup (mean difference = 1.12 (mm) P = 0.04). cumulative intersegmental angular rotation of all lumbar segments from mid to mid position was greater in the Rotation with Flexion subgroup compared to the Rotation with Extension subgroup (P = 0.03). ConclusionChanges in intersegmental translation and angular rotation of lumbar segments in subgroups of patients with LBP may be important contributing factors that induce direction specific lumbar spine loads and contribute to the development or persistence of LBP problems.

Lumbar spine loads are reduced for activities of daily living when using a braced arm-to-thigh technique.

To evaluate the effect of the braced arm-to-thigh technique (BATT) (versus self-selected techniques) on three-dimensional trunk kinematics and spinal loads for three common activities of daily living (ADLs) simulated in the laboratory: weeding (gardening), reaching for an object in a low cupboard, and car egress using thetwo-legs outtechnique. Ten young healthy males performed each task using a self-selected technique, and then using the BATT. The pulling action of weeding was simulated using a magnet placed on a steel plate. Cupboard and car egress tasks were simulated using custom apparatus representing the dimensions of a kitchen cabinet and a medium-sized Australian car, respectively. Three-dimensional trunk kinematics and L4/L5 spinal loads were estimated using the Lifting Full-Body OpenSim model and compared between techniques. Paired t-tests were used to compare peak values between methods (self-selected vs BATT). The BATT significantly reduced peak extension moments (13-51%), and both compression (27-45%) and shear forces (31-62%) at L4/L5, compared to self-selected techniques for all three tasks (p < 0.05). Lateral bending angles increased with the BATT for weeding and cupboard tasks, but these changes were expected as the BATT inherently introduces asymmetric trunk motion. The BATT substantially reduced L4/L5 extension moments, and L4/L5 compression and shear forces, compared to self-selected methods, for three ADLs, in a small cohort of ten young healthy males without prior history of back pain. These study findings can be used to inform safe procedures for these three ADLs, as the results are considered representative of a mature population.

Loading of the lumbar spine during transition from standing to sitting: effect of fusion versus motion preservation at L4–L5 and L5–S1

BACKGROUND CONTEXTTransition from standing to sitting significantly decreases lumbar lordosis with the greatest lordosis-loss occurring at L4–S1. Fusing L4–S1 eliminates motion and thus the proximal mobile segments maybe recruited during transition from standing to sitting to compensate for the loss of L4–S1 mobility. This may subject proximal segments to supra-physiologic flexion loading. PURPOSEAssess effects of instrumented fusion versus motion preservation at L4–L5 and L5–S1 on lumbar spine loads and proximal segment motions during transition from standing to sitting. STUDY DESIGNBiomechanical study using human thoracolumbar spine specimens. METHODSA novel laboratory model was used to simulate lumbosacral alignment changes caused by a person's transition from standing to sitting in eight T10-sacrum spine specimens. The sacrum was tilted in the sagittal plane while constraining anterior-posterior translation of T10. Continuous loading-data and segmental motion-data were collected over a range of sacral slope values, which represented transition from standing to different sitting postures. We compared different constructs involving fusions and motion preserving prostheses across L4–S1. RESULTSAfter L4–S1 fusion, the sacrum could not be tilted as far posteriorly compared to the intact spine for the same applied moment (p<.001). For the same reduction in sacral slope, L4–S1 fusion induced 2.9 times the flexion moment in the lumbar spine and required 2.4 times the flexion motion of the proximal segments as the intact condition (p<.001). Conversely, motion preservation at L4–S1 restored lumbar spine loads and proximal segment motions to intact specimen levels during transition from standing to sitting. CONCLUSIONSIn general, sitting requires lower lumbar segments to undergo flexion, thereby increasing load on the lumbar disks. L4–S1 fusion induced greater moments and increased flexion of proximal segments to attain a comparable seated posture. Motion preservation using a total joint replacement prosthesis at L4–S1 restored the lumbar spine loads and proximal segment motion to intact specimen levels during transition from standing to sitting. CLINICAL SIGNIFICANCEAfter L4–S1 fusion, increased proximal segment loading during sitting may cause discomfort in some patients and may lead to junctional breakdown over time. Preserving motion at L4–S1 may improve patient comfort and function during activities of daily living, and potentially decrease the need for adjacent level surgery.

Development of a multiscale model of the human lumbar spine for investigation of tissue loads in people with and without a transtibial amputation during sit-to-stand.

Quantification of lumbar spine load transfer is important for understanding low back pain, especially among persons with a lower limb amputation. Computational modeling provides a helpful solution for obtaining estimates of in vivo loads. A multiscale model was constructed by combining musculoskeletal and finite element (FE) models of the lumbar spine to determine tissue loading during daily activities. Three-dimensional kinematic and ground reaction force data were collected from participants with ([Formula: see text]) and without ([Formula: see text]) a unilateral transtibial amputation (TTA) during 5 sit-to-stand trials. We estimated tissue-level load transfer from the multiscale model by controlling the FE model with intervertebral kinematics and muscle forces predicted by the musculoskeletal model. Annulus fibrosis stress, intradiscal pressure (IDP), and facet contact forces were calculated using the FE model. Differences in whole-body kinematics, muscle forces, and tissue-level loads were found between participant groups. Notably, participants with TTA had greater axial rotation toward their intact limb ([Formula: see text]), greater abdominal muscle activity ([Formula: see text]), and greater overall tissue loading throughout sit-to-stand ([Formula: see text]) compared to able-bodied participants. Both normalized (to upright standing) and absolute estimates of L4-L5 IDP were close to in vivo values reported in the literature. The multiscale model can be used to estimate the distribution of loads within different lumbar spine tissue structures and can be adapted for use with different activities, populations, and spinal geometries.

An Enhanced Planar Linked Segment Model for Predicting Lumbar Spine Loads during Symmetric Lifting Tasks

The present technical note aimed at enriching the planar linked segment model originally proposed by Chaffin with the prediction of the moment arm and of the orientation of the line of action of the back extensor muscles during symmetric lifting tasks. The prediction equations proposed by van Dieen and de Looze for their single equivalent muscle model were used for such a purpose. Their prediction was based on the thorax-to-pelvis flexion angle as computed from 3D video-based motion capture. In order to make these prediction equations compliant with a two-dimensional analysis, the planar angle formed by the segment joining L5/S1 to the shoulder with the longitudinal axis of the pelvis was introduced. This newly computed planar trunk flexion angle was used to feed van Dieen and de Looze’s equations, comparing the results with the original model. A full-body Plug-in-Gait model relative to 10 subjects performing manual lifting activities using a stoop and a squat technique was used for model validation. A strong association was found between the proposed planar trunk flexion angle and that used by van Dieen and de Looze (r = 0.970). A strong association and a high level of agreement were found between the back extensor muscle moment arm (r = 0.965; bias &lt; 0.001 m; upper limit of agreement (LOA) = 0.002 m; lower LOA &lt; 0.001 m) and the orientation of the line of action (r = 0.970; bias = 2.8°; upper LOA = 5.3°; lower LOA = 0.2°) as computed using the two methods. For both the considered variables, the prediction error fell within the model sensitivity.

A numerical study to determine the effect of strengthening and weakening of the transversus abdominis muscle on lumbar spine loads

This work aimed to determine the influence of strengthening or weakening of the transversus abdominis (TrA) muscle on loads in the lumbar spine using musculoskeletal modelling methods. The input kinematic data of two positions (a standing position and a position during a sitting-down task) were angles in the elbow joint (0°;4°), shoulder joint (0°;3°), hip joint (0°;75°) and knee joint (0°;69°) as well as the torso tilt angle (0°;32°). It was shown that a change in the TrA physiological cross section area (PCSA) has a crucial impact on lumbar spine loads (2xTrA PCSA causes a reduction in the force in joint L5–S1 by 11% for a standing position and by 25% for a sitting-down position) and value of intra-abdominal pressure.

Submarining sensitivity across varied seat configurations in autonomous driving system environment

Objective Self-driving technology will bring novelty in vehicle interior design and allow for a wide variety of occupant seating choices. Thus, vehicle safety systems may be challenged to protect occupants over a wider range of potential postures. This study aims to investigate the effects of the seat cushion angle on submarining risk, lumbar spine loads and pelvis excursion for reclined occupants in frontal crashes. Methods Frontal crash finite element simulations were performed with two of the simplified Global Human Body Model Consortium (GHBMC) occupant models: the small female and the midsize male. Occupant restraints consisted of a frontal airbag, a seatback-integrated 3-point belt with a lap belt anchor pre-tensioner, and a retractor pre-tensioner with a force limiter. For each simulation, parameters including seat cushion angle (3°, 8°, 13°), seatback recline angle (0°, 10°, 20°, 30°), and knee bolster (KB) position relative to the occupant (baseline and no KB) were varied. A full-factorial simulation matrix was performed using the USNCAP 56 km/h frontal crash pulse. Occupant kinematics data were extracted from each simulation to investigate how changes in seat cushion angle, anthropometry, seatback angle, and KB position would affect submarining across all simulated cases. Results Overall, the F05-OS female model was more likely to submarine when compared to the male occupant model. The threshold for submarining was also affected by the seat cushion angle, seatback angle and KB distance. For the F05-OS model, increasing the seat cushion angle to 13° prevented submarining in the 10° seatback angle case, regardless of the KB position. Similarly, the 13° cushion angle prevented submarining for the M50-OS in the 30° seatback angle configuration but only in the presence of a KB. The results further show an increased lumbar flexion load with increased seat recline angle, as well as occupant-to-KB distance, although an opposite trend with the increased seat cushion angle. Conclusions Submarining may be a major challenge to overcome for reclined occupants in autonomous driving systems. This study shows that seat cushion angle plays a role in restraining occupants in recline scenarios, but it is not sufficient to prevent submarining without additional countermeasures.

One versus two-handed lifting and lowering: lumbar spine loads and recommended one-handed limits protecting the lower back

The objectives of this study were to quantify loads imposed upon the lumbar spine while lifting/lowering with one versus two hands and to create guidelines for one-handed lifting/lowering that are protective of the lower back. Thirty subjects (15 male, 15 female) performed one- and two-handed exertions in a laboratory, lifting from/lowering to 18 lift origins/destinations using medicine balls of varying masses. An electromyography-assisted model predicted peak spinal loads, which were related to tissue tolerance limits to create recommended weight limits. Compared to two-handed exertions, one-handed exertions resulted in decreased spinal compression and A/P shear loading (p < 0.001) but increased lateral shear (p < 0.001). Effects were likely driven by altered moment exposures attributable to altered torso kinematics. Differences between spinal loads for one- versus two-handed exertions were influenced by asymmetry (p < 0.001) and amplified at lower lift origin/destination heights, lower object masses and larger horizontal distances between the body and the load (p < 0.001). Practitioner summary: A biomechanical model was utilised to compare spinal loading for one versus two-handed lifting/lowering. Spinal loads in compression and A/P shear were reduced for one-handed relative to two-handed exertions. As current lifting guidelines cannot appropriately be applied to one-handed scenarios, one-handed weight limits protecting the lower back are presented herein. Abbreviations: LBD: low back disorder, EMG: electromyography, A/P: anterior/posterior, MVC: maximum voluntary contraction

Modified electromyography-assisted optimization approach for predicting lumbar spine loading while walking with backpack loads.

This study modified an electromyography-assisted optimization approach for predicting lumbar spine loading while walking with backpack loads. The modified-electromyography-assisted optimization approach eliminated the electromyography measurement at maximal voluntary contraction and adopted a linear electromyography-force relationship. Moreover, an optimal lower boundary condition for muscle gain was introduced to constrain the trunk muscle co-activation. Anthropometric information of 10 healthy young men as well as their kinematic, kinetic, and electromyography data obtained while walking with backpack loads were used as inputs in this study. A computational algorithm was used to find and analyse the sensitivity of the optimal lower boundary condition for achieving minimum deviation of the modified-electromyography-assisted optimization approach from the electromyography-assisted optimization approach for predicting lumbosacral joint compression force. Results validated that the modified-electromyography-assisted optimization approach (at optimal lower boundary condition of 0.92) predicted on average, a non-significant deviation in peak lumbosacral joint compression force of -18 N, a standard error of 9 N, and a root mean square difference in force profile of 73.8 N. The modified-electromyography-assisted optimization approach simplified the experimental process by eliminating the electromyography measurement at maximal voluntary contraction and provided comparable estimations for lumbosacral joint compression force that is also applicable to patients or individuals having difficulty in performing the maximal voluntary contraction activity.

Sensitivity of musculoskeletal model-based lumbar spinal loading estimates to type of kinematic input and passive stiffness properties

The study investigated the potential for obtaining more accurate spine joint reaction force (JRF) estimates from musculoskeletal models by incorporating dynamic stereo X-ray imaging (DSX)-based in vivo lumbar vertebral rotational and translational kinematics compared to generic, rhythm (RHY)-based kinematics, while also observing the influence of accompanying inputs: intervertebral segment stiffness and neutral state. A full-body OpenSim® musculoskeletal model, constructed by combining existing lower- and upper-body models, was driven based on one volunteer’s (female; age 25; 60.8 kg; 176 cm) anthropometrics and kinematics from a series of upright standing and straight-legged dynamic lifting tasks. The lumbar spine portion was modified in a step-wise manner to observe effects of: (1) RHY vs. DSX lumbar kinematics; (2) No disc (bushing) stiffness (NBS); generic, linear bushing stiffness (LBS); subject-specific nonlinear bushing stiffness (NLBS); (3) Upright standing (UP) vs. Supine (SUP) neutral state; (4) Weight lifted: 4.5 kg vs. 13.6 kg. L4L5 JRF from 24 model variations based on combinations of aforementioned parameters were compared. Rhythm-based kinematics without translational components tends to over-predict JRF (31% and 39% for compression and shear, respectively) compared to DSX-based kinematics. Additionally, differences due to accompanying passive stiffness and neutral state choice combinations were even larger (>50%), indicating heightened demand on the quality of these accompanying inputs. The study not only highlights model sensitivity to choices made regarding the three primary inputs—kinematics, passive stiffness and neutral state— separately, but also how interactions between these choices can result in significant variability in joint loading estimates.

Lumbar Spine Loading During Dressage Riding.

Lower back pain is prevalent in horse riders as a result of the absorption of repetitive and multiplanar propulsive forces from the horse. Global positioning system technology provides potential for in vivo measurement of planar loading during riding. To quantify the uniaxial loading at the lumbar and cervicothoracic spine during dressage elements. Repeated measures, randomized order. Equestrian arena. Patients (or Other Participants): Twenty-one female dressage riders. Each rider completed walk, rising trot, sitting trot, and canter trials in a randomized order. A global positioning system unit was placed within customized garments at C7 and L5, collecting triaxial accelerometry data at 100Hz. PlayerLoad based on the rate of change of acceleration and calculated in the anteroposterior (AP), mediolateral, and vertical planes during each trial. There was no significant main effect for global positioning system location in the AP (P = .76), mediolateral (P = .88), or vertical (P = .76) planes. There was a significant main effect for pace in all trials (P < .001), with successive elements eliciting significantly greater loading (P ≤ .03) in all planes in the order walk < rising trot < canter < sitting trot. There was a significant placement × element interaction only in the AP plane (P = .03) with AP loading greater at L5 during walk, rising trot, and canter trials, but greater at C7 during sitting trot. The significant main effect for dressage element was indicative of greater pace of the horse, with faster pace activities eliciting greater loading in all planes. In vivo measurement of spinal accelerometry has application in the objective measurement and subsequent management of lumbar load for riders.

A braced arm-to-thigh (BATT) lifting technique reduces lumbar spine loads in healthy and low back pain participants

Despite the common use of one-handed lifting techniques for activities of daily living, these techniques have received little attention in the biomechanics literature. The braced arm-to-thigh technique (BATT) is a one-handed lifting method in which the dominant hand picks up objects, while the free hand braces the trunk on the ipsilateral thigh. The aim of this study was to compare the BATT to two-handed or unsupported one-handed lifting techniques with loads of 2 and 10 kg, by evaluating trunk motion and spine loading at L4/L5. Twenty healthy participants (30–70 years old) matched in age and sex to 18 participants with low back pain were recruited to the study. A three-axis load cell secured to the distal anterior thigh measured the bracing forces applied by the hand. The OpenSim Lifting Full-Body model was used to estimate trunk kinematics and spinal loading at L4/L5. Linear mixed-effects models were developed to compare trunk angles and L4/L5 moments and forces between lifting techniques. Trunk flexion angles were significantly reduced for the BATT lift compared to one-handed and two-handed stoop lifts (9–20%). However, the BATT also increased asymmetric trunk kinematics and moments at L4/L5. The BATT produced significantly lower moments (28–38%), and compressive (25–32%) and antero-posterior shear (25–45%) forces at L4/L5, compared to unsupported lifting techniques. Bracing the hand on the thigh to support the trunk can substantially reduce low back loading during lifting tasks of 2 to 10 kg.

Spinal Loading During One and Two-Handed Lifting

Background: Lifting at work remains one of the most highly studied potential risk factors for low back disorders, but most of the studies that have been conducted on this topic focus on lifting scenarios in which two hands are used to lift the weight. Few investigations have examined one-handed lifting scenarios, as might be observed when lifting objects from industrial storage bins or stocking products onto shelves. Moreover, there remains a need to re-examine one versus two-handed lifting scenarios utilizing a more advanced and accurate biomechanical model than was used previously (Ferguson et al., 2002; Kingma and van Dieen, 2004; Marras and Davis, 1998). The objective of this study was to quantify biomechanical loads imposed upon the lumbar spine during one-handed lifting versus two-handed lifting, specifically in relation to any interaction effects present between the number of hands used to perform the lift and external lifting conditions like the lift origin or object weight. Methods: Thirty subjects (15 male, 15 female) were recruited for this laboratory study. In each experimental task, subjects lifted one of three medicine balls (of the same size/shape but differing in weight) with either one or two hands from the lift origin predefined by the study design to a common lift destination directly in front of the body. All one-handed exertions were performed with the dominant hand, and asymmetric conditions were tested on the dominant side of the body. Independent variables included lift origin height (ankle, knee, waist), lift origin asymmetry (0 degrees, 45 degrees, 90 degrees), load weight (2.7 kg, 7.3 kg, 11.4 kg), horizontal distance of the lift origin from the body (40 cm, 70 cm), and the number of hands used to perform the lift (one, two). An EMG-driven biomechanical spine model was implemented to evaluate lumbar spinal loads in compression, anterior/posterior (A/P) shear, and lateral shear (Dufour et al., 2013; Hwang et al., 2016a, 2016b). Results and Discussion: One-handed lifting resulted in 6% lower spinal compression and 16% lower A/P shear loads than two-handed lifting on average, but lateral shear was increased by 23% for one-handed lifting relative to two-handed lifting (p&lt;0.001). Consistent with Marras and Davis (1998), spinal compression increased with increased lift origin asymmetry in two-handed lifting but decreased with increased lift origin asymmetry in one-handed lifting (p&lt;0.001). The effects of using one versus two hands to perform the lift were generally amplified at lower lift origin heights, lower weights, and for the far reach distance. Effects were likely driven by differing moment exposures on the spine attributable to the weight of the torso. Conclusion: One-handed lifting resulted in lower peak spinal compression and peak A/P shear loads on the lumbar spine, so it may be preferred to two-handed lifting if the load to be lifted falls within the strength capabilities of the worker population. However, while this study shows benefits of one-handed lifting for the low back, these results should be placed in context with future studies aimed at assessing the impacts of one-handed lifting on the upper extremity. Acknowledgement: This study was funded, in part, by the Ohio Bureau of Workers’ Compensation.

EMG-based lumbosacral joint compression force prediction using a support vector machine

Electromyography-assisted optimization (EMGAO) approach is widely used to predict lumbar joint loads under various dynamic and static conditions. However, such approach uses numerous anthropometric, kinematic, kinetic, and electromyographic data in the computation process, and thus makes data collection and processing complicated. This study developed an electromyography-based support vector machine (EMGB_SVM) approach for predicting lumbar spine load during walking with backpack loads. The EMGB_SVM is simple and uses merely the electromyographic data. Anthropometric information of 10 healthy male adults as well as their kinematic, kinetic, and electromyographic data acquired during walking exercises with no-load and with various backpack loads (5%, 10%, 15%, and 20% of their body weight) were used as the inputs of a biomechanical model, which was then used for predicting the lumbosacral joint compression force. The efficacy of the EMGB_SVM was investigated by comparing the force profiles obtained using this model with those obtained using the current EMGAO approach. On average, the EMGB_SVM obtained deviations in the peak and minimum forces of −3.3% and 5.1%, respectively, and a root mean square difference in the force profile of 7.5%. The EMGB_SVM is a comparable estimator in terms of its slight bias, favourable consistency, and efficiency at predicting the lumbosacral joint compression force.