Table 4.
Internal disc loads at disc mid-heights and muscle forces (on each side) at different levels for the optimal posture without T12 (minimum sum of muscle forces, no abdominal co-activity) (IC iliocostalis, LG longissimus, MF multifidus muscles)
| Level | P=0 N | P=200 N | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Held on sides | Held in front | |||||||||||
| *Passive segmental load | Muscle force | *Passive segmental load | Muscle force | *Passive segmental load | Muscle force | |||||||
| - | Comp | Shear | Moment | Comp | Shear | Moment | Comp | Shear | Moment | |||
| - | (N) | (N) | (Nm) | (N) | (N) | (N) | (Nm) | (N) | (N) | (N) | (Nm) | (N) |
| T12 | 413 | −56 | −5.3 | 113 (IC) | 717 | −79 | −5.5 | 217 (IC) | 1,121 | −126 | −12.3 | 437 (IC) 187 (LG) |
| L1 | 431 | −57 | −3.9 | - | 735 | −75 | −3.2 | 0.1 (MF) | 1,136 | −149 | −7.6 | - |
| L2 | 448 | −63 | −2.3 | - | 754 | −72 | −0.9 | 0.5 (LG) | 1,152 | −169 | −2.0 | - |
| L3 | 471 | 4 | −0.6 | - | 780 | 60 | 0.0 | 6.3 (LG) | 1,184 | 34 | 0.8 | 2 (LG) |
| L4 | 502 | 43 | −1.6 | 15 (MF) | 807 | 121 | −2.7 | 18.3 (MF) | 1,195 | 150 | −2.2 | 1 (MF) |
| L5 | 504 | 195 | −3.3 | 18 (MF) | 778 | 346 | −7.9 | 16.6 (MF) | 1,134 | 478 | −10.3 | 6 (MF) |
*Shear force: positive in anterior direction; Moment: positive in extension direction