From Stoop to Squat: A Comprehensive Analysis of Lumbar Loading Among Different Lifting Styles

Michael von Arx, Melanie Liechti, Lukas Connolly, Christian Bangerter, Stefan Schmid

Research output: Contribution to journalArticlepeer-review

34 Citations (Scopus)

Abstract

Lifting up objects from the floor has been identified as a risk factor for low back pain,
whereby a flexed spine during lifting is often associated with producing higher loads in the
lumbar spine. Even though recent biomechanical studies challenge these assumptions,
conclusive evidence is still lacking. This study therefore aimed at comparing lumbar loads
among different lifting styles using a comprehensive state-of-the-art motion capture-driven
musculoskeletal modeling approach. Thirty healthy pain-free individuals were enrolled in
this study and asked to repetitively lift a 15 kg-box by applying 1) a freestyle, 2) a squat and
3) a stoop lifting technique. Whole-body kinematics were recorded using a 16-camera
optical motion capture system and used to drive a full-body musculoskeletal model
including a detailed thoracolumbar spine. Continuous as well as peak compressive,
anterior-posterior shear and total loads (resultant load vector of the compressive and
shear load vectors) were calculated based on a static optimization approach and
expressed as factor body weight (BW). In addition, lumbar lordosis angles and total
lifting time were calculated. All parameters were compared among the lifting styles using a
repeated measures design. For each lifting style, loads increased towards the caudal end
of the lumbar spine. For all lumbar segments, stoop lifting showed significantly lower
compressive and total loads (−0.3 to −1.0BW) when compared to freestyle and squat
lifting. Stoop lifting produced higher shear loads (+0.1 to +0.8BW) in the segments T12/L1
to L4/L5, but lower loads in L5/S1 (−0.2 to −0.4BW). Peak compressive and total loads
during squat lifting occurred approximately 30% earlier in the lifting cycle compared to
stoop lifting. Stoop lifting showed larger lumbar lordosis range of motion (35.9 ± 10.1°) than
freestyle (24.2 ± 7.3°) and squat (25.1 ± 8.2°) lifting. Lifting time differed significantly with
freestyle being executed the fastest (4.6 ± 0.7 s), followed by squat (4.9 ± 0.7 s) and stoop
(5.9 ± 1.1 s). Stoop lifting produced lower total and compressive lumbar loads than squat
lifting. Shear loads were generally higher during stoop lifting, except for the L5/S1 segment,
where anterior shear loads were higher during squat lifting. Lifting time was identified as
another important factor, considering that slower speeds seem to result in lower loads.
Original languageEnglish
Article number769117
Number of pages13
JournalFrontiers in Bioengineering and Biotechnology
Volume9
DOIs
Publication statusPublished - 4 Nov 2021
Externally publishedYes

Bibliographical note

Funding Information:
The financial support of the University of Rome Research Committee and of the Italian National Research Council (CNR) is gratefully acknowledged. We also thank the INTAS committee for a travelling grant between Lisbon and Minsk (INTAS 93-1399) and the Italian-Portuguese exchange programme for the years 1998-1999 jointly administered by the CNR and the JNICT.

Publisher Copyright:
© Copyright © 2021 von Arx, Liechti, Connolly, Bangerter, Meier and Schmid.

Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.

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