Abdominal bracing affects kinematics during functional tasks

Rehabilitation specialists around the world advocate activating the abdominal wall muscles in order to enhance spinal stability and prevent injuries to the low back, pelvis and lower limbs. It is proposed that contracting the abdominal wall muscles provides increased stability of the spine, thus reducing excessive spinal movement and reducing the potential for back injuries. Numerous approaches have been used to teach abdominal wall activation but abdominal bracing (AB) has been suggested as the most effective strategy for increasing spinal stability. However, there is little evidence regarding the effect of AB on lower-limb and lumbar spine kinematics and ground reaction forces during functional tasks. Researchers from the Pain-Ed team at Curtin University recently conducted a study investigating the kinematics of the lower limb and lumbar spine during a drop-landing task.

Bracing resulted in reduced peak knee and hip flexion during landing. On average, the peak ground reaction force was significantly greater during the drop-landing trials performed with AB in comparison to the trials performed without AB. There was no difference in ankle dorsiflexion or in lumbar spine kinematics between the brace and no-brace conditions.

Although the study indicated there was no difference in lumbar spine kinematics with or without abdominal bracing, the results of increased ground reaction forces suggest that AB has the potential to lead to increase lower limb and spinal loading. Reduced lower limb flexion during landing and an increased ground reaction force have been associated with an increased risk of lower limb and lumbar spine pain in athletes across different sports. Studies also indicate that runners with a history of low back pain have increased knee stiffness due to reduced knee joint range of motion.

Although this study does not provide a definite link between AB and an increased rate of lower limb and lumbar spine pain, the findings suggest that the therapist should think twice before AB is prescribed during limb loading activities. This is especially the case if the person is sensitised to loading or the aim is to prevent pain – due to its potential negative effects on kinematics and loading.

Amity Campbell is a Senior Research Fellow at the School of Physiotherapy and Exercise Science at Curtin University, Perth. Amity completed her PhD in biomechanics in 2009. Since joining Curtin University she has published over 50 peer review journal articles, half of which have focused on low back pain.

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