Abdominal bracing during lifting alters trunk muscle activity and body kinematics

Abstract

We assessed whether participants are able to perform abdominal bracing during lifting, and described its effects on trunk muscle activity and body kinematics. Fourteen participants performed 10 lifts (symmetrical lifting of a 15 kg load from floor level), 5 with abdominal bracing and 5 without. Activity of the lumbar multifidus (LM) and internal oblique (IO) muscles, and trunk and lower body kinematics were obtained. During non-bracing lifting, IO activity did not increase beyond rested standing levels (with average muscle activity ranging between 8.2 and 9.1% maximum voluntary contraction; %MVC), while LM activity did (range: 8.5–21.0 %MVC). During bracing lifting, muscle activity was higher compared to non-bracing in IO and LM at the start of the lift (with average between condition differences up to 10.9 %MVC). Upper leg, pelvis and lumbar spine angles were smaller, but thorax flexion angles were larger while lifting with bracing compared to without (with average between condition differences ranging from 0.7° to 4.3°). Although participants do not typically brace their abdominal muscles while lifting, they can be trained to do so. There appears to be no clear advantage of abdominal bracing during lifting, leaving its value for low-back pain prevention unclear.