Effects of a Pneumatic External Abdominal Pressure Assist Belt on Trunk and Lower Limb Muscle Activity and Joint Kinematics During Lifting Tasks

Abstract

Manual lifting is a major risk factor for low back pain, with intra-abdominal pressure playing a key role in spinal stability. This study investigated the effects of a pneumatic external abdominal pressure assist belt on trunk and lower limb muscle activity and joint kinematics during lifting. Twenty-four healthy adults performed lifting tasks under four external abdominal pressure assist conditions. Trunk and lower limb muscle activities were measured using surface electromyography. Sagittal limb angles were assessed using 3D motion analysis. Peak and mean muscle activities (%MVIC) and joint angles were analyzed with repeated-measures ANOVA or Friedman tests. Peak muscle activity significantly decreased in the internal oblique, erector spinae, and biceps femoris (all p < 0.05), while increases were observed in the multifidus, rectus femoris, and vastus lateralis (all p < 0.05). Mean amplitude analysis showed reduced internal oblique activity (p < 0.001) and significant increases in rectus femoris and multifidus (p < 0.05). Hip and knee flexion angles were significantly greater under assisted conditions (p = 0.002), indicating a shift toward squat-type lifting. The pneumatic external belt redistributed peak loads from the back to the knee extensors, reduced internal oblique activity, and modestly increased multifidus activation. It also induced greater hip and knee flexion, suggesting a shift toward squat-type lifting. These effects were statistically significant but small, indicating limited practical relevance.