Simulation of Stress-Fracture in Human Vertebral Body due to Extreme Weight Lifting

Lumbar vertebrae are a heavily loaded component of human body. They are subjected to repetitive loading in daily activities. However, limited information on failure mechanism of lumbar vertebrae are available to date. Thus, the need to develop an analytical model to predict stress-fracture characteristics of vertebral body. A linear elastic fracture mechanics approach has been considered and a mathematical model has been proposed so that the predictions can be made more easily related to the occurrence of injury. Study reveals that for a person weighing 1334 N and lifting a weight of 345 kg during squat exercise causes a vertebral stress-fracture at 12 repetitive standing lifting. While same load at lowest position yields a stress-fracture at less than 3 lifting. Numerical study shows that for change of position from standing to lowest position resultant compressive force acting on spine increases by two times whereas the possibility of stress-fracture increases by five times. Similarly at dead lift exercise, lifting 325 kg from standing to lowest position increases resultant compressive forces on vertebrae by 2.5 times. However, stress-fracture ratio increases by six times. Study reveals that for a person weighing 800 N (height = 1.8 m) and lifting a weight of 900 N, vertebrae can be subjected to stress-fracture by three cyclic lifting. Rate of injury is dependent on flexion angle i.e. as flexion angle increases, so does rate of injury.Copyright © 2011 by ASME