Table 2
Von-Mises stress results for flexion on the cortical bone, annulus fiber, and nucleus pulposus of lumbar spine.
| Average [MPa] |
Flexion |
Standing | Erect sitting | Slumped sitting | Sitting on floor |
Cortical Bone | L1 | 4.34 | 3.25 | 6.40 | 7.17 |
L2 | 4.40 | 5.02 | 15.90 | 9.89 |
L3 | 2.38 | 2.62 | 11.09 | 4.69 |
L4 | 2.56 | 2.58 | 9.77 | 4.76 |
L5 | 1.82 | 3.71 | 7.11 | 3.82 |
Annulus fiber | L2-L1 | 0.33 | 0.27 | 0.50 | 0.54 |
L3-L2 | 0.22 | 0.29 | 0.42 | 0.56 |
L4-L3 | 0.18 | 0.25 | 0.28 | 0.49 |
L5-L4 | 0.31 | 0.45 | 0.15 | 0.67 |
S-L5 | 0.16 | 0.19 | 0.07 | 0.25 |
Nucleus pulposus | L2-L1 | 0.08 | 0.06 | 0.15 | 0.13 |
L3-L2 | 0.05 | 0.06 | 0.09 | 0.15 |
L4-L3 | 0.05 | 0.06 | 0.07 | 0.10 |
L5-L4 | 0.07 | 0.09 | 0.03 | 0.18 |
S-L5 | 0.03 | 0.03 | 0.01 | 0.05 |
MPa, megapascal | |
Table 3
Von-Mises stress results for lateral bending on the cortical bone, annulus fiber, and nucleus pulposus of lumbar spine
| Average [MPa] |
Lateral bending |
Standing | Erect sitting | Slumped sitting | Sitting on floor |
Cortical Bone | L1 | 4.38 | 3.33 | 6.22 | 7.18 |
L2 | 3.12 | 3.55 | 12.87 | 8.34 |
L3 | 1.71 | 1.89 | 8.58 | 3.88 |
L4 | 1.73 | 1.80 | 7.46 | 3.68 |
L5 | 1.92 | 3.18 | 5.82 | 3.06 |
Annulus fiber | L2-L1 | 0.33 | 0.29 | 0.51 | 0.54 |
L3-L2 | 0.20 | 0.27 | 0.40 | 0.50 |
L4-L3 | 0.20 | 0.22 | 0.29 | 0.42 |
L5-L4 | 0.26 | 0.31 | 0.26 | 0.52 |
S-L5 | 0.12 | 0.13 | 0.06 | 0.20 |
Nucleus pulposus | L2-L1 | 0.08 | 0.06 | 0.15 | 0.13 |
L3-L2 | 0.04 | 0.06 | 0.10 | 0.13 |
L4-L3 | 0.04 | 0.05 | 0.08 | 0.09 |
L5-L4 | 0.06 | 0.07 | 0.05 | 0.14 |
S-L5 | 0.02 | 0.06 | 0.01 | 0.04 |
MPa, megapascal | |
Table 4
Von-Mises stress results for axial rotation on cortical bone, annulus fiber, nucleus pulposus of lumbar spine
| Average [MPa] |
Axial rotation |
Standing | Erect sitting | Slumped sitting | Sitting on floor |
Cortical Bone | L1 | 4.39 | 3.40 | 6.25 | 7.23 |
L2 | 2.99 | 3.15 | 12.76 | 8.31 |
L3 | 1.45 | 1.60 | 8.51 | 3.81 |
L4 | 1.35 | 1.48 | 7.35 | 3.62 |
L5 | 1.48 | 2.83 | 5.71 | 3.03 |
Annulus fiber | L2-L1 | 0.33 | 0.26 | 0.49 | 0.54 |
L3-L2 | 0.19 | 0.20 | 0.38 | 0.49 |
L4-L3 | 0.13 | 0.15 | 0.22 | 0.39 |
L5-L4 | 0.15 | 0.24 | 0.10 | 0.49 |
S-L5 | 0.12 | 0.13 | 0.06 | 0.20 |
Nucleus pulposus | L2-L1 | 0.08 | 0.06 | 0.15 | 0.13 |
L3-L2 | 0.04 | 0.05 | 0.09 | 0.13 |
L4-L3 | 0.03 | 0.04 | 0.06 | 0.08 |
L5-L4 | 0.03 | 0.05 | 0.02 | 0.13 |
S-L5 | 0.02 | 0.02 | 0.01 | 0.04 |
MPa, megapascal | |
Flexion mode
Comparing the L1, L2, L3, L4, and L5 cortical bones during standing and erect sitting on a chair in the flexion mode, the stress in the erect sitting on a chair position increased by -25%, 14%, 10%, 1%, and 104%, respectively. Comparing standing with slumped sitting in a chair, the stress in the slumped sitting in a chair position increased by 48%, 262%, 365%, 282%, and 290%, respectively. Comparing standing with sitting on a floor, the stress while sitting increased by 65%, 125%, 97%, 86%, and 109%, respectively(Table 2)(Fig. 4a).
Comparing the annulus fibers (between L2-L1, L3-L2, L4-L3, L5-L4, and S-L5) in the standing and erect sitting in a chair position, the stress in the erect sitting in a chair position was increased by -17%, 28%, 34%, 44%, and 14%, respectively. Comparing standing and slumped sitting on a chair, the stress in the slumped sitting position increased by 53%, 88%, 50%, -54%, and − 57%, respectively. Comparing standing and sitting on the floor, the stress in the sitting position on the floor increased by 65%, 150%, 164%, 114%, and 52%, respectively(Table 2)(Fig. 4b).
Comparing the L2-L1, L3-L2, L4-L3, L5-L4, and S-L5 nucleus pulposus in the standing and erect sitting on a chair position, the stress in the erect sitting on a chair position increased by -19%, 30%, 25%, 31%, and 3%, respectively. Comparing standing and slumped sitting on a chair, the stress in the slumped sitting position increased by 97%, 94%, 57%, -60%, and − 74%, respectively. Comparing standing and sitting on the floor, the stress in the sitting position on the floor increased by 72%, 206%, 114%, 146%, and 57%, respectively(Table 2)(Fig. 4c).
Lateral bending mode
Comparing the L1, L2, L3, L4, and L5 cortical bones in the standing and erect sitting on a chair position in the lateral bending mode, the stress in the erect sitting on a chair position increased by -24%, 14%, 11%, 4%, and 66%, respectively. Comparing standing with slumped sitting in a chair, the stress in the slumped sitting on a chair position increased by 42%, 313%, 403%, 332%, and 203%, respectively. Comparing the standing position with sitting on the floor, the stress in the latter increased by 116%, 168%, 127%, 113%, and 59%, respectively(Table 3)(Fig. 4d).
Comparing the L2-L1, L3-L2, L4-L3, L5-L4, and S-L5 annulus fibers in the standing and erect sitting in a chair position, the stress in the erect sitting in a chair position was increased by -12%, 36%, 12%, 19%, and 12%, respectively. Comparing standing and slumped sitting on a chair, the stress in the slumped sitting position increased by 53%, 102%, 45%, 0.9%, and 48%, respectively. Comparing standing and sitting on the floor, the stress in the sitting position increased by 62%, 149%, 111%, 103%, and 68%, respectively(Table 3)(Fig. 4e).
Comparing the L2-L1, L3-L2, L4-L3, L5-L4, and S-L5 nucleus pulposus while standing and erect sitting, the stress in the erect sitting on a chair position increased by -15%, 44%, 16%, 17%, and 198%, respectively. Comparing standing and slumped sitting on a chair, the stress in the slumped sitting position increased by 95%, 125%, 72%, -8%, and − 57%, respectively. Comparing standing and sitting on the floor, the stress in the sitting position increased by 69%, 208%, 97%, 146%, and 73%, respectively(Table 3)(Fig. 4f).
Axial rotation mode
Comparing the L1, L2, L3, L4, and L5 cortical bones in the standing and erect sitting on a chair position in the axial rotation mode, the stress in the erect sitting on a chair position increased by -22%, 6%, 10%, 10%, and 92%, respectively. Comparing the standing position with the slumped sitting in a chair, the stress in the slumped sitting in a chair position increased by 43%, 327%, 487%, 446%, and 287%, respectively. Comparing the standing position with sitting on the floor, the stress in the latter position increased by 65%, 178%, 162%, 169%, and 105%, respectively(Table 4)(Fig. 4g).
Comparing the L2-L1, L3-L2, L4-L3, L5-L4, and S-L5 annulus fibers in standing with erect sitting, the stress in the erect sitting in a chair position was increased by -20%, 10%, 17%, 57%, and 11%, respectively. Comparing standing and sitting on the floor, the stress from the sitting on the floor increased by 49%, 107%, 78%, -36%, and − 45%, respectively. Comparing standing and sitting on the floor, the stress in the sitting position on the floor increased by 63%, 161%, 208%, 220%, and 73%, respectively(Table 4)(Fig. 4h).
Comparing the L2-L1, L3-L2, L4-L3, L5-L4, and S-L5 nucleus pulposus in the standing and erect sitting in a chair position, the stress in the erect sitting in a chair position was increased by -22%, 26%, 28%, 50%, and − 0.1%, respectively. Comparing standing and sitting on the floor, the stress in the sitting position on the floor increased by 91%, 132%, 128%, -47%, and − 57%, respectively. Comparing standing and sitting on the floor, the stress in the sitting position on the floor increased by 70%, 226%, 188%, 296%, and 80%, respectively(Table 4)(Fig. 4i).
von Mises stress according to the three load modes
Even in the axial mode, it can be seen that the stress on the annulus fiber and nucleus pulposus appears large in the spine when sitting on a chair and on the floor. Stress increased by an average of 20% in the erect sitting on a chair position, 113% in the slumped sitting on a chair position, and 123% in the sitting position on the floor compared with the standing position. Therefore, it can be seen that sitting on a floor position has a bad effect on the spine.