Variation in lifting kinematics related to individual intrinsic lumbar curvature: an investigation in healthy adults

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Abstract

Objective

Lifting postures are frequently implicated in back pain. We previously related responses to a static load with intrinsic spine shape, and here we investigate the role of lumbar spine shape in lifting kinematics.

Methods

Thirty healthy adults (18–65 years) performed freestyle, stoop and squat lifts with a weighted box (6–15 kg, self-selected) while being recorded by Vicon motion capture. Internal spine shape was characterised using statistical shape modelling (SSM) from standing mid-sagittal MRIs. Associations were investigated between spine shapes quantified by SSM and peak flexion angles.

Results

Two SSM modes described variations in overall lumbar curvature (mode 1 (M1), 55% variance) and the evenness of curvature distribution (mode 2 (M2), 12% variance). M1 was associated with greater peak pelvis (r=0.38, p=0.04) and smaller knee flexion (r=–0.40, p=0.03) angles; individuals with greater curviness preferred to lift with a stooped lifting posture. This was confirmed by analysis of those individuals with very curvy or very straight spines (|M1|>1 SD). There were no associations between peak flexion angles and mode scores in stoop or squat trials (p>0.05). Peak flexion angles were positively correlated between freestyle and squat trials but not between freestyle and stoop or squat and stoop, indicating that individuals adjusted knee flexion while maintaining their preferred range of lumbar flexion and that ‘squatters’ adapted better to different techniques than ‘stoopers’.

Conclusion

Spinal curvature affects preferred lifting styles, and individuals with curvier spines adapt more easily to different lifting techniques. Lifting tasks may need to be tailored to an individual’s lumbar spine shape.

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Most cited references 43

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Revised NIOSH equation for the design and evaluation of manual lifting tasks.

Robert L. Fine, A Garg, Colin T. Waters … (1993)

In 1985, the National Institute for Occupational Safety and Health (NIOSH) convened an ad hoc committee of experts who reviewed the current literature on lifting, recommend criteria for defining lifting capacity, and in 1991 developed a revised lifting equation. Subsequently, NIOSH developed the documentation for the equation and played a prominent role in recommending methods for interpreting the results of the equation. The 1991 equation reflects new findings and provides methods for evaluating asymmetrical lifting tasks, lifts of objects with less than optimal hand-container couplings, and also provides guidelines for a larger range of work durations and lifting frequencies than the 1981 equation. This paper provides the basis for selecting the three criteria (biomechanical, physiological, and psychophysical) that were used to define the 1991 equation, and describes the derivation of the individual components (Putz-Anderson and Waters 1991). The paper also describes the lifting index (LI), an index of relative physical stress, that can be used to identify hazardous lifting tasks. Although the 1991 equation has not been fully validated, the recommended weight limits derived from the revised equation are consistent with or lower than those generally reported in the literature. NIOSH believes that the revised 1991 lifting equation is more likely than the 1981 equation to protect most workers.

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Repeatability of gait data using a functional hip joint centre and a mean helical knee axis.

Thor Besier, Daina L Sturnieks, Jacque Alderson … (2003)

Repeatability of traditional kinematic and kinetic models is affected by the ability to accurately locate anatomical landmarks (ALs) to define joint centres and anatomical coordinate systems. Numerical methods that define joint centres and axes of rotation independent of ALs may also improve the repeatability of kinematic and kinetic data. The purpose of this paper was to compare the repeatability of gait data obtained from two models, one based on ALs (AL model), and the other incorporating a functional method to define hip joint centres and a mean helical axis to define knee joint flexion/extension axes (FUN model). A foot calibration rig was also developed to define the foot segment independent of ALs. The FUN model produced slightly more repeatable hip and knee joint kinematic and kinetic data than the AL model, with the advantage of not having to accurately locate ALs. Repeatability of the models was similar comparing within-tester sessions to between-tester sessions. The FUN model may also produce more repeatable data than the AL model in subject populations where location of ALs is difficult. The foot calibration rig employed in both the AL and FUN model provided an easy alternative to define the foot segment and obtain repeatable data, without accurately locating ALs on the foot.

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A follower load increases the load-carrying capacity of the lumbar spine in compression.

B Dunlap, Gloria Meade, B. Lee … (1999)

An experimental approach was used to test human cadaveric spine specimens. To assess the response of the whole lumbar spine to a compressive follower load whose path approximates the tangent to the curve of the lumbar spine. Compression on the lumbar spine is 1000 N for standing and walking and is higher during lifting. Ex vivo experiments show it buckles at 80-100 N. Differences between maximum ex vivo and in vivo loads have not been satisfactorily explained. A new experimental technique was developed for applying a compressive follower load of physiologic magnitudes up to 1200 N. The experimental technique applied loads that minimized the internal shear forces and bending moments, made the resultant internal force compressive, and caused the load path to approximate the tangent to the curve of the lumbar spine. A compressive vertical load applied in the neutral lordotic and forward-flexed postures caused large changes in lumbar lordosis at small load magnitudes. The specimen approached its extension or flexion limits at a vertical load of 100 N. In sharp contrast, the lumbar spine supported a load of up to 1200 N without damage or instability when the load path was tangent to the spinal curve. Until this study, an experimental technique for applying compressive loads of in vivo magnitudes to the whole lumbar spine was unavailable. The load-carrying capacity of the lumbar spine sharply increased under a compressive follower load, as long as the load path remained within a small range around the centers of rotation of the lumbar segments. The follower load path provides an explanation of how the whole lumbar spine can be lordotic and yet resist large compressive loads. This study may have implications for determining the role of trunk muscles in stabilizing the lumbar spine.

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Author and article information

Journal

Journal ID (nlm-ta): BMJ Open Sport Exerc Med

Journal ID (iso-abbrev): BMJ Open Sport Exerc Med

Journal ID (hwp): bmjosem

Journal ID (publisher-id): bmjosem

Title: BMJ Open Sport — Exercise Medicine

Publisher: BMJ Publishing Group (BMA House, Tavistock Square, London, WC1H 9JR )

ISSN (Electronic): 2055-7647

Publication date Collection: 2018

Publication date (Electronic): 15 July 2018

Volume: 4

Issue: 1

Electronic Location Identifier: e000374

Affiliations

[1 ] departmentArthritis and Musculoskeletal Medicine, School of Medicine, Medical Sciences and Nutrition , University of Aberdeen , Aberdeen, UK

[2 ] departmentBiophysics Research Group, College of Engineering, Mathematics and Physical Sciences , University of Exeter , Exeter, UK

[3 ] departmentSchool of Health Sciences , Robert Gordon University, Faculty of Health and Social Care , Aberdeen, UK

[4 ] departmentMedicines Monitoring Unit (MEMO), Division of Molecular & Clinical Medicine , School of Medicine, University of Dundee , Dundee, UK

Author notes

[Correspondence to ] Dr Richard M Aspden; r.aspden@ 123456abdn.ac.uk

Author information

Richard M Aspden http://orcid.org/0000-0002-0693-1194

Article

Publisher ID: bmjsem-2018-000374

DOI: 10.1136/bmjsem-2018-000374

PMC ID: 6059291

SO-VID: 39d5d057-dd1d-4115-81a1-9fcae601b3bc

License:

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/

History

Date accepted : 25 June 2018

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Keywords: lumbar spine,biomechanics,lifting,kinematic analysis,positional mri

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Keywords: lumbar spine, biomechanics, lifting, kinematic analysis, positional mri

Variation in lifting kinematics related to individual intrinsic lumbar curvature: an investigation in healthy adults

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Most cited references 43

Revised NIOSH equation for the design and evaluation of manual lifting tasks.

Repeatability of gait data using a functional hip joint centre and a mean helical knee axis.

A follower load increases the load-carrying capacity of the lumbar spine in compression.

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