A crossover design was used to evaluate kinematic measurements collected with an infrared-based motion measurement system.
To evaluate belt effects on spine kinematics during asymmetric lifting
of large and small boxes and to test for carryover effects between trials from belts.
Summary of Background Data.
Conflicting evidence in the literature exists regarding whether belts are beneficial or detrimental to manual material handlers. Studies have not examined belt effects when lifting
different sized boxes, nor carryover effects from belts.
Twenty-eight subjects with manual-handling experience (17 male and 11 female) were randomly assigned to lift either a large or small box (weighing 9.4 kg), from a sagittally symmetric origin at pallet height to a 79 cm height, 60° to the right. Spine flexion, lateral bending and twisting, hip and knee flexion, and angular velocity measurements of the torso
with respect to the pelvis were collected for each of three lifting
periods, 50 lifts each at 3 lifts per minute, with 18-minute breaks between periods.
Belts significantly reduced maximum spine flexion, spine flexion and extension angular velocities, and torso
left lateral bending angular velocity, and increased hip and knee flexion, regardless of box size. When lifting
large boxes, belts significantly reduced torso
right lateral bending and torso
left twisting. No significant differential carryover effects were detected from belts.
Subjects with belts lifted more slowly and used more of a squat-lift technique, regardless of box size. Belts reduced more torso
motions while lifting