Biomechanical assessment of lifting dynamics, muscle activity and spinal loads while using three different styles of...

OBJECTIVE: To demonstrate the influence of different types of lifting belts on trunk motion, muscle activity and spine loading during symmetric and asymmetric lifting exertions. DESIGN. IN VIVO: measurements were achieved representing lifting dynamics, applied trunk moments and myoelectric activity. Dynamic spinal loads were determined from a validated biomechanical model of lifting. BACKGROUND: There is a great deal of controversy as to whether lifting belts are a benefit or a liability to manual materials-handling activities. A review of the literature demonstrates that there is a large amount of conflicting evidence and few definitive, well-executed studies upon which to base an opinion regarding these devices. METHODS: Fifteen subjects lifted boxes of 14 kg and 23 kg from sagitally symmetric and asymmetric origins to an upright posture. Dynamic trunk motions, lifting moments, myoelectric activity and modelled spinal loads were examined as a function of three belt styles (elastic, leather, and orthotic) and compared with results from a no-belt condition. RESULTS: Lifting belts reduced peak trunk angles, velocities and accelerations in the sagittal, lateral and transverse planes. However, only the elastic belt successfully reduced trunk motions in all three dimensions. The orthotic belt significantly increased the lifting moment associated with a given weight. A minor redistribution in muscle activity was observed when wearing an elastic belt. A statistically significant reduction in spinal load was associated with the elastic belt. However, a great deal of variability between subjects was noted. Some subjects experienced increased spinal load while wearing the elastic lifting belt. CONCLUSIONS: These results demonstrate that the biomechanical operation of lifting can be influenced by the type of lifting belts used.