European Spine Journal

, Volume 16, Issue 5, pp 687–699 | Cite as

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

  • Babak Bazrgari
  • Aboulfazl Shirazi-AdlEmail author
  • Navid Arjmand
Original Article


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 ∼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).


Muscle force Finite element Dynamic Kinematics Lifting technique 


  1. 1.
    ABAQUS CAE [Computer Program] (2004) United States of America, ABAQUS, Inc. 2004Google Scholar
  2. 2.
    Adams MA, McNally DS, Chinn H, Dolan P (1994) Posture and the compressive strength of the lumbar spine. Clin Biomech 9:5–14Google Scholar
  3. 3.
    Anderson CK, Chaffin DB, Herrin GD, Matthews LS (1985) A biomechanical model of the lumbosacral joint during lifting activities. J Biomech 18:571–584PubMedGoogle Scholar
  4. 4.
    Andersson GB (1981) Epidemiologic aspects on low-back pain in industry. Spine 6:53–60PubMedGoogle Scholar
  5. 5.
    Arjmand N, Shirazi-Adl A (2005) Sensitivity of kinematics-based model predictions to optimization criteria in static lifting tasks. Med Eng Phys 28:504–514PubMedGoogle Scholar
  6. 6.
    Arjmand N, Shirazi-Adl A (2005) Biomechanics of changes in lumbar posture in static lifting. Spine 30:2637–2648PubMedGoogle Scholar
  7. 7.
    Arjmand N, Shirazi-Adl A (2005) Role of intra-abdominal pressure in the unloading and stabilization of the human spine during static lifting tasks. Eur Spine J 15:1265–1275PubMedGoogle Scholar
  8. 8.
    Arjmand N, Shirazi-Adl A (2006) Model and in vivo studies on human trunk load partitioning and stability in isometric forward flexions. J Biomech 39:510–521PubMedGoogle Scholar
  9. 9.
    Bendix T, Eid SE (1983) The distance between the load and the body with three bi-manual lifting techniques. Appl Ergon 14:185–192PubMedGoogle Scholar
  10. 10.
    Bogduk N, Macintosh JE, Pearcy MJ (1992) A universal model of the lumbar back muscles in the upright position. Spine 17:897–913PubMedGoogle Scholar
  11. 11.
    Bogduk N, Johnson G, Spalding D (1998) The morphology and biomechanics of latissimus dorsi. Clin Biomech 13:377–385Google Scholar
  12. 12.
    Burdorf A, Sorock G (1997) Positive and negative evidence of risk factors for back disorders. Scand J Work Environ Health 23:243–256PubMedGoogle Scholar
  13. 13.
    Buseck M, Schipplein OD, Andersson GB, Andriacchi TP (1988) Influence of dynamic factors and external loads on the moment at the lumbar spine in lifting. Spine 13:918–921PubMedGoogle Scholar
  14. 14.
    Cappozzo A, Catani F, Leardini A, Benedetti MG, Croce UD (1996) Position and orientation in space of bones during movement: experimental artefacts. Clin Biomech 11:90–100Google Scholar
  15. 15.
    Cholewicki J, McGill SM, Norman RW (1991) Lumbar spine loads during the lifting of extremely heavy weights. Med Sci Sports Exerc 23:1179–1186PubMedGoogle Scholar
  16. 16.
    Cholewicki J, McGill S (1996) Mechanical stability of the in vivo lumbar spine: implications for injury and chronic low back pain. Clin Biomech 11:1–15Google Scholar
  17. 17.
    Damkot DK, Pope MH, Lord J, Frymoyer JW (1984) The relationship between work history, work environment and low-back pain in men. Spine 9:395–399PubMedGoogle Scholar
  18. 18.
    Davis KG, Marras WS, Waters TR (1998) Evaluation of spinal loading during lowering and lifting. Clin Biomech 13:141–152Google Scholar
  19. 19.
    Davis J, Kaufman KR, Lieber RL (2003) Correlation between active and passive isometric force and intramuscular pressure in the isolated rabbit tibialis anterior muscle. J Biomech 36:505–512PubMedGoogle Scholar
  20. 20.
    Davis KG, Marras WS (2000) The effects of motion on trunk biomechanics. Clin Biomech 15:703–717Google Scholar
  21. 21.
    Davis JR, Mirka GA (2000) Transverse-contour modeling of trunk muscle-distributed forces and spinal loads during lifting and twisting. Spine 25:180–189PubMedGoogle Scholar
  22. 22.
    Delitto RS, Rose SJ, Apts DW (1987) Electromyographic analysis of two techniques for squat lifting. Phys Ther 67:1329–1334PubMedGoogle Scholar
  23. 23.
    van Dieen JH, Creemers M, Draisma I, Toussaint HM, Kingma I (1994) Repetitive lifting and spinal shrinkage, effects of age and lifting technique. Clin Biomech 9:367–374Google Scholar
  24. 24.
    van Dieen JH (1997) Are recruitment patterns of the trunk musculature compatible with a synergy based on the maximization of endurance? J Biomech 30:1095–1100PubMedGoogle Scholar
  25. 25.
    van Dieen JH, Hoozemans MJ, Toussaint HM (1999) Stoop or squat: a review of biomechanical studies on lifting technique. Clin Biomech 14:685–696Google Scholar
  26. 26.
    Dietrich M, Kedzior K, Zagrajek T (1991) A biomechanical model of the human spinal system. Inst Mech Eng Part [H] 205(1):19–26Google Scholar
  27. 27.
    Dolan P, Earley M, Adams MA (1994) Bending and compressive stresses acting on the lumbar spine during lifting activities. J Biomech 27:1237–1248PubMedGoogle Scholar
  28. 28.
    Dolan P, Kingma I, van Dieen J, de Looze MP, Toussaint HM, Baten CT, Adams MA (1999) Dynamic forces acting on the lumbar spine during manual handling. Can they be estimated using electromyographic techniques alone? Spine 24:698–703PubMedGoogle Scholar
  29. 29.
    Dvorak J, Panjabi MM, Chang DG, Theiler R, Grob D (1991) Functional radiographic diagnosis of the lumbar spine. Flexion–extension and lateral bending. Spine 16:562–571PubMedGoogle Scholar
  30. 30.
    El-Rich M, Shirazi-Adl A, Arjmand N (2004) Muscle activity, internal loads, and stability of the human spine in standing postures: combined model and in vivo studies. Spine 29:2633–2642PubMedGoogle Scholar
  31. 31.
    Esola MA, McClure PW, Fitzgerald GK, Siegler S (1996) Analysis of lumbar spine and hip motion during forward bending in subjects with and without a history of low back pain. Spine 21:71–78PubMedGoogle Scholar
  32. 32.
    Fathallah FA, Marras WS, Parnianpour M (1998) An assessment of complex spinal loads during dynamic lifting tasks. Spine 23:706–716PubMedGoogle Scholar
  33. 33.
    Ferguson S, Marras W (1997) A literature review of low back disorder surveillance measures and risk factors. Clin Biomech 12:211–226Google Scholar
  34. 34.
    Frobin W, Brinckmann P, Leivseth G, Biggemann M, Reikeras O (1996) Precision measurement of segmental motion from flexion–extension radiographs of the lumbar spine. Clin Biomech 11:457–465Google Scholar
  35. 35.
    Gardner-Morse M, Stokes IA, Laible JP (1995) Role of muscles in lumbar spine stability in maximum extension efforts. J Orthop Res 13:802–808PubMedGoogle Scholar
  36. 36.
    Gracovetsky S, Farfan HF, Lamy C (1981) The mechanism of the lumbar spine. Spine 6:249–262PubMedGoogle Scholar
  37. 37.
    Gracovetsky S (1988) The spinal engine. Springer, Berlin Heidelberg New YorkGoogle Scholar
  38. 38.
    Grag A, Herrin GD (1979) Stoop or squat. A biomechanical and metabolic evaluation. AIIE Trans 11:293–302Google Scholar
  39. 39.
    Granata KP, Marras WS (1995) The influence of trunk muscle coactivity on dynamic spinal loads. Spine 20:913–919PubMedGoogle Scholar
  40. 40.
    Granata KP, Marras WS (1995) An EMG-assisted model of trunk loading during free-dynamic lifting. J Biomech 28:1309–1317PubMedGoogle Scholar
  41. 41.
    Granata KP, Sanford AH (2000) Lumbar-pelvic coordination is influenced by lifting task parameters. Spine 25:1413–1418PubMedGoogle Scholar
  42. 42.
    Hagen KB, Hallen J, Harms-Ringdahl K (1993) Physiological and subjective responses to maximal repetitive lifting employing stoop and squat technique. Eur J Appl Physiol Occup Physiol 67:291–297PubMedGoogle Scholar
  43. 43.
    Hagen KB, Harms-Ringdahl K (1994) Ratings of perceived thigh and back exertion in forest workers during repetitive lifting using squat and stoop techniques. Spine 19:2511–2517PubMedGoogle Scholar
  44. 44.
    Haig AJ, Weismann G, Haugh LD, Pope M, Grobler LJ (1993) Prospective evidence for change in paraspinal muscle activity after herniated nucleus pulposus. Spine 18:926–930PubMedGoogle Scholar
  45. 45.
    Hart DL, Stobbe TJ, Jaraiedi M (1987) Effect of lumbar posture on lifting. Spine 12:138–145PubMedGoogle Scholar
  46. 46.
    Hilber HM, Hughes TJR, Taylor RL (1978) Collocation, dissipation and overshoot for time integration schemes in structural dynamics. Earthq Eng Struct Dyn 6:99–117Google Scholar
  47. 47.
    Holmes JA, Damaser MS, Lehman SL (1992) Erector spinae activation and movement dynamics about the lumbar spine in lordotic and kyphotic squat-lifting. Spine 17:327–334PubMedGoogle Scholar
  48. 48.
    Hsiang SM, Brogmus GE, Courtney TK (1997) Low back pain (LBP) and lifting technique—a review. Int J Ind Ergon 19:59–74Google Scholar
  49. 49.
    Hughes RE, Chaffin DB, Lavender SA, Andersson GB (1994) Evaluation of muscle force prediction models of the lumbar trunk using surface electromyography. J Orthop Res 12:689–698PubMedGoogle Scholar
  50. 50.
    Jorgensen MJ, Marras WS, Gupta P, Waters TR (2003) Effect of torso flexion on the lumbar torso extensor muscle sagittal plane moment arms. Spine J 3:363–369PubMedGoogle Scholar
  51. 51.
    Kasra M, Shirazi-Adl A, Drouin G (1992) Dynamics of human lumbar intervertebral joints. Experimental and finite-element investigations. Spine 17:93–102PubMedGoogle Scholar
  52. 52.
    Kingma I, Baten CT, Dolan P, Toussaint HM, van Dieen JH, de Looze MP, Adams MA (2001) Lumbar loading during lifting: a comparative study of three measurement techniques. J Electromyogr Kinesiol 11:337–345PubMedGoogle Scholar
  53. 53.
    Kuiper JI, Burdorf A, Verbeek JHAM, Frings-Dresen MHW, van der Beek AJ, Viikari-Juntura ERA (1999) Epidemiologic evidence on manual materials handling as a risk factor for back disorders: a systematic review. Int J Ind Ergon 24:389–404Google Scholar
  54. 54.
    Lariviere C, Gagnon D, Loisel P (2000) The comparison of trunk muscles EMG activation between subjects with and without chronic low back pain during flexion-extension and lateral bending tasks. J Electromyogr Kinesiol 10:79–91PubMedGoogle Scholar
  55. 55.
    Lariviere C, Gagnon D (1998) Comparison between two dynamic methods to estimate triaxial net reaction moments at the L5/S1 joint during lifting. Clin Biomech 13:36–47Google Scholar
  56. 56.
    Lee YH, Chiou WK, Chen WJ, Lee MY, Lin YH (1995) Predictive model of intersegmental mobility of lumbar spine in the sagittal plane from skin markers. Clin Biomech 10:413–420Google Scholar
  57. 57.
    Lindbeck L, Arborelius UP (1991) Inertial effects from single body segments in dynamic analysis of lifting. Ergonomics 34:421–433PubMedGoogle Scholar
  58. 58.
    de Looze MP, Kingma I, Thunnissen W, van Wijk MJ, Toussaint HM (1994) The evaluation of a practical biomechanical model estimating lumbar moments in occupational activities. Ergonomics 37:1495–1502PubMedGoogle Scholar
  59. 59.
    de Looze MP, Dolan P, Kingma I, Baten CTM (1998) Does an asymmetric straddle-legged lifting movement reduce the low-back load? Hum Mov Sci 17:243–259Google Scholar
  60. 60.
    Lundberg A (1996) On the use of bone and skin markers in kinematics research. Hum Mov Sci 15:411–422Google Scholar
  61. 61.
    Macintosh JE, Bogduk N, Gracovetsky S (1987) Biomechanics of the thoracolumbar fascia. Clin Biomech 2:78–83Google Scholar
  62. 62.
    Macintosh J, Bogduk N, Pearcy M (1993) The effects of flexion on the geometry and actions of the lumbar erector spinae. Spine 18:884–893PubMedGoogle Scholar
  63. 63.
    Markolf KL (1970) Stiffness and damping characteristics of thoracolumbar spine. In: Proceedings of workshop on bioengineering approaches to problems of the spine. Division of Research Grants, NIH, Bethesda, pp 87–143Google Scholar
  64. 64.
    McClure PW, Esola M, Schreier R, Siegler S (1997) Kinematic analysis of lumbar and hip motion while rising from a forward, flexed position in patients with and without a history of low back pain. Spine 22:552–558PubMedGoogle Scholar
  65. 65.
    McGill SM, Patt N, Norman RW (1988) Measurement of the trunk musculature of active males using CT scan radiography: implications for force and moment generating capacity about the L4/L5 joint. J Biomech 21:329–341PubMedGoogle Scholar
  66. 66.
    McGill SM (1997) The biomechanics of low back injury: implications on current practice in industry and the clinic. J Biomech 30:465–475PubMedGoogle Scholar
  67. 67.
    McGill SM, Yingling VR, Peach JP (1999) Three-dimensional kinematics and trunk muscle myoelectric activity in the elderly spine—a database compared to young people. Clin Biomech 14:389–395Google Scholar
  68. 68.
    McGill SM, Hughson RL, Parks K (2000) Changes in lumbar lordosis modify the role of the extensor muscles. Clin Biomech 15:777–780Google Scholar
  69. 69.
    McGill SM, Norman RW (1985) Dynamically and statically determined low back moments during lifting. J Biomech 18:877–885PubMedGoogle Scholar
  70. 70.
    McGill SM, Norman RW (1986) Partitioning of the L4-L5 dynamic moment into disc, ligamentous, and muscular components during lifting. Spine 11:666–678PubMedGoogle Scholar
  71. 71.
    Neumann P, Keller TS, Ekstrom L, Hansson T (1994) Effect of strain rate and bone mineral on the structural properties of the human anterior longitudinal ligament. Spine 19:205–211PubMedGoogle Scholar
  72. 72.
    Nussbaum MA, Chaffin DB (1996) Development and evaluation of a scalable and deformable geometric model of the human torso. Clin Biomech 11:25–34Google Scholar
  73. 73.
    Oxland TR, Lin RM, Panjabi MM (1992) Three-dimensional mechanical properties of the thoracolumbar junction. J Orthop Res 10:573–580PubMedGoogle Scholar
  74. 74.
    Paquet N, Malouin F, Richards CL (1994) Hip-spine movement interaction and muscle activation patterns during sagittal trunk movements in low back pain patients. Spine 19:596–603PubMedGoogle Scholar
  75. 75.
    Peach JP, Sutarno CG, McGill SM (1998) Three-dimensional kinematics and trunk muscle myoelectric activity in the young lumbar spine: a database. Arch Phys Med Rehabil 79:663–669PubMedGoogle Scholar
  76. 76.
    Pearcy M, Portek I, Shepherd J (1984) Three-dimensional x-ray analysis of normal movement in the lumbar spine. Spine 9:294–297PubMedGoogle Scholar
  77. 77.
    Pearsall DJ, Reid JG, Livingston LA (1996) Segmental inertial parameters of the human trunk as determined from computed tomography. Ann Biomed Eng 24:198–210PubMedGoogle Scholar
  78. 78.
    Pearsall DJ (1994) Segmental inertial properties of the human trunk as determined from computer tomography and magnetic resonance imagery. Dissertation, Queen’s University, KingstonGoogle Scholar
  79. 79.
    Plamondon A, Gagnon M, Maurais G (1988) Application of a stereoradiographic method for the study of intervertebral motion. Spine 13:1027–1132PubMedGoogle Scholar
  80. 80.
    Pop DG (2001)Analyse non linéaire par éléments finis du systém actif passif de la colonne vertébrale humaine. Dissertation, Génie mécanique, École Polytechnique, MontréalGoogle Scholar
  81. 81.
    Porter JL, Wilkinson A (1997) Lumbar-hip flexion motion. A comparative study between asymptomatic and chronic low back pain in 18- to 36-year-old men. Spine 22:1508–1514PubMedGoogle Scholar
  82. 82.
    Potvin JR, Norman RW, McGill SM (1991) Reduction in anterior shear forces on the L4/L5 disc by the lumbar musculature. Clin Biomech 6:88–96Google Scholar
  83. 83.
    Potvin JR, McGill SM, Norman RW (1991) Trunk muscle and lumbar ligament contributions to dynamic lifts with varying degrees of trunk flexion. Spine 16:1099–1107PubMedGoogle Scholar
  84. 84.
    Raikova RT, Prilutsky BI (2001) Sensitivity of predicted muscle forces to parameters of the optimization-based human leg model revealed by analytical and numerical analyses. J Biomech 34:1243–1255PubMedGoogle Scholar
  85. 85.
    Sadouk S (1998) Analyse mécanique par éléments finis du systéme actif passif de la colonne lombaire humaine. Dissertation, Génie mécanique, École Polytechnique, MontréalGoogle Scholar
  86. 86.
    Shirazi-Adl A (1989) Nonlinear finite element analysis of wrapping uniaxial elements. Comput Struct 32:119–123Google Scholar
  87. 87.
    Shirazi-Adl A (1994) Analysis of role of bone compliance on mechanics of a lumbar motion segment. J Biomech Eng 116:408–412PubMedGoogle Scholar
  88. 88.
    Shirazi-Adl A, Sadouk S, Parnianpour M, Pop D, El-Rich M (2002) Muscle force evaluation and the role of posture in human lumbar spine under compression. Eur Spine J 11:519–526PubMedGoogle Scholar
  89. 89.
    Shirazi-Adl A, El-Rich M, Pop DG, Parnianpour M (2005) Spinal muscle forces, internal loads and stability in standing under various postures and loads–application of kinematics-based algorithm. Eur Spine J 14:381–392PubMedGoogle Scholar
  90. 90.
    Shirazi-Adl A (2006) Analysis of large compression loads on lumbar spine in flexion and in torsion using a novel wrapping element. J Biomech 39:267–275PubMedGoogle Scholar
  91. 91.
    Shirazi-Adl A, Parnianpour M (1999) Effect of changes in lordosis on mechanics of the lumbar spine-lumbar curvature in lifting. J Spinal Disord 12:436–447PubMedCrossRefGoogle Scholar
  92. 92.
    Shirazi-Adl A, Parnianpour M (2000) Load-bearing and stress analysis of the human spine under a novel wrapping compression loading. Clin Biomech 15:718–725Google Scholar
  93. 93.
    Stokes I, Gardner-Morse M (1995) Lumbar spine maximum efforts and muscle recruitment patterns predicted by a model with multijoint muscles and joints with stiffness. J Biomech 28:173–186PubMedGoogle Scholar
  94. 94.
    Stokes IAF, Gardner-Morse M (1999) Quantitative anatomy of the lumbar musculature. J Biomech 32:311–316PubMedGoogle Scholar
  95. 95.
    Tesh KM, Dunn JS, Evans JH (1987) The abdominal muscles and vertebral stability. Spine 12:501–508PubMedGoogle Scholar
  96. 96.
    Toussaint HM, de Winter AF, de Haas Y, de Looze MP, Van Dieen JH, Kingma I (1995) Flexion relaxation during lifting: implications for torque production by muscle activity and tissue strain at the lumbo-sacral joint. J Biomech 28:199–210PubMedGoogle Scholar
  97. 97.
    Toussaint HM, Commissaris DA, Beek PJ (1997) Anticipatory postural adjustments in the back and leg lift. Med Sci Sports Exerc 29:1216–1224PubMedGoogle Scholar
  98. 98.
    Troup JD, Leskinen TP, Stalhammar HR, Kuorinka IA (1983) A comparison of intraabdominal pressure increases, hip torque, and lumbar vertebral compression in different lifting techniques. Hum Factors 25:517–525PubMedGoogle Scholar
  99. 99.
    Tveit P, Daggfeldt K, Hetland S, Thorstensson A (1994) Erector spinae lever arm length variations with changes in spinal curvature. Spine 19:199–204PubMedGoogle Scholar
  100. 100.
    Vakos JP, Nitz AJ, Threlkeld AJ, Shapiro R, Horn T (1994) Electromyographic activity of selected trunk and hip muscles during a squat lift. Effect of varying the lumbar posture. Spine 19:687–695PubMedGoogle Scholar
  101. 101.
    Wang JL, Parnianpour M, Shirazi-Adl A, Engin AE (1998) The dynamic response of L(2)/L(3) motion segment in cyclic axial compressive loading. Clin Biomech 13:S16–S25Google Scholar
  102. 102.
    Wang JL, Parnianpour M, Shirazi-Adl A, Engin AE (2000) Viscoelastic finite-element analysis of a lumbar motion segment in combined compression and sagittal flexion. Effect of loading rate. Spine 25:310–318PubMedGoogle Scholar
  103. 103.
    Winter DA (2005) Biomechanics and motor control of human movement, 3rd edn. John Wiley, HobokenGoogle Scholar
  104. 104.
    Yamamoto I, Panjabi MM, Crisco T, Oxland T (1989) Three-dimensional movements of the whole lumbar spine and lumbosacral joint. Spine 14:1256–1260PubMedGoogle Scholar
  105. 105.
    Zatsiorsky VM, Seluyanov VN (1983) The mass and inertia characteristics of the main segments of the human body. In: Matsui H, Kobayashi K (eds) Biomechanics. Human Kinetics Publishers, Champaign, pp 1152–1159Google Scholar
  106. 106.
    Zhang X, Xiong J (2003) Model-guided derivation of lumbar vertebral kinematics in vivo reveals the difference between external marker-defined and internal segmental rotations. J Biomech 36:9–17PubMedGoogle Scholar

Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  • Babak Bazrgari
    • 1
  • Aboulfazl Shirazi-Adl
    • 1
    Email author
  • Navid Arjmand
    • 1
  1. 1.Department of Mechanical EngineeringEcole PolytechniqueMontrealCanada

Personalised recommendations