Examination of a lumbar spine biomechanical model for assessing axial compression, shear, and bending moment using selected Olympic lifts

Abstract

Background/aims: Loading during concurrent bending and compression associated with deadlift, hang clean and hang snatch lifts carries the potential for injury to the intervertebral discs, muscles and ligaments. This study examined the capacity of a newly developed spinal model to compute shear and compressive forces, and bending moments in lumbar spine for each lift.

Methods: Five male subjects participated in the study. The spine was modeled as a chain of rigid bodies (vertebrae) connected via the intervertebral discs. Each vertebral reference frame was centered in the center of mass of the vertebral body, and its principal directions were axial, anterior-posterior, and medial-lateral.

Results: The results demonstrated the capacity of this spinal model to assess forces and bending moments at and about the lumbar vertebrae by showing the variations among these variables with different lifting techniques.

Conclusion: These results show the model's potential as a diagnostic tool.

Keywords: Deadlift; Lumbar spine biomechanics; Motion capturing; Power clean; Snatch.

Fig. 1

The static trial and the definition of the lumbar spine.

Fig. 2

The coordinate system for relative motion at L₃/L_4.

Fig. 3

Schematic of two rigid bodies: L3, fixed, and L2, moving relative to L3.

Fig. 4

Coordinate frames of the spine biomechanical model. (a) The pelvic segment is defined by the left anterior superior iliac spine (LASI), the right anterior superior iliac spine (RASI), the left posterior superior iliac spine (LPSI), and the right posterior superior iliac spine (RPSI). The principal directions are axial (red arrow), medial-lateral (green arrow), and anterior-posterior (blue arrow). The position and scale of the pelvis is determined by RASI and LASI markers, since they determine the origin of the coronal orientation of the pelvis. The LPSI and RPSI markers determine the anterior tilt of the pelvis. (b) The thoracic segment is defined by C7, CLAV, STRN, and T10 markers. Its origin is in CLAV, and its principal directions are axial (red arrow), anterior-posterior (blue arrow), and medial-lateral (green arrow). (c) The spine model includes thoracic vertebrae (from T10 to T12), all the lumbar vertebrae, and the sacrum. Each vertebral reference frame is centered in the center of mass of the vertebral body, and its principal directions are axial (red arrow), anterior-posterior (blue arrow), and medial-lateral (green arrow).

Fig. 5

Weightlifting exercise performed in the study. Deadlift: (a) starting position; (b) hang position; (c) recovery. Hang power clean: (d) hang position; (e) second pull; (f) starting catch; (g) end of catch (recovery). Hang power snatch: (h) hang position; (i) second pull; (j) catch; (k) recovery.

Fig. 6

Lumbar spine intersegmental rotation in the sagittal plane following unconstrained flexion-extension motion. Model estimates (black) are compared to experimental measurements previously reported by Wong et al (white) and Li et al (gray).

Fig. 7

Loads on lumbar vertebrae during deadlift cycle. (a) Shear force on L1; (b) Axial compression on L1; (c) Bending moment in sagittal plane on L1; (d) Shear force on L5; (e) Axial compression on L5; (f) Bending moment in sagittal plane on L5. For all the data reported, vertical dotted lines indicate reach of the hang position.

Fig. 8

Loads on lumbar vertebrae during hang power clean cycle. (a) Shear force on L1; (b) Axial compression on L1; (c) Bending moment in sagittal plane on L1; (d) Shear force on L5; (e) Axial compression on L5; (f) Bending moment in sagittal plane on L5. For all the data reported, vertical dotted lines indicate completion of the second pull.

Fig. 9

Loads on lumbar vertebrae during hang snatch cycle. (a) Shear force on L1; (b) Axial compression on L1; (c) Bending moment in sagittal plane on L1; (d) Shear force on L5; (e) Axial compression on L5; (f) Bending moment in sagittal plane on L5. For each diagram reported, the first vertical dotted line form left to right indicates completion of the second pull, the second at the completion of the catch.