Abdominal muscle recruitment during a range of voluntary exercises

Various exercises are used to retrain the abdominal muscles in the management of low back pain and other musculoskeletal disorders. However. few studies have directly investigated the activity of all the abdominal muscles or the recruitment of regions of the abdominal muscles during these manoeuvres. This study examined the activity of different regions of transversus abdominis (TrA), obliquus internus (OI) and externus abdominis (OE), and rectus abdominis (RA), and movement of lumbar spine, pelvis and abdomen during inward movement of the lower abdominal wall, abdominal bracing, pelvic tilting, and inward movement of the lower and upper abdominal wall. Inward movement of the lower abdominal wall in supine produced greater activity of TrA compared to OI. OE and RA. During posterior pelvic tilting. middle OI was most active and with abdominal bracing. OE was predominately recruited. Regions of TrA were recruited differentially and in inverse relationship between lumbopelvic motion and TrA electromyography (EMG) was found. This study indicates that inward movement of the abdominal wall in supine produces the most independent activity of TrA relative to the other abdominal muscle, recruitment varies between regions of TrA, and observation of abdominal and lumbopelvic motion may assist in evalation of exercise performance. (c) 2004 Elsevier Ltd. All rights reserved.

Widespread brain activity during an abdominal task markedly reduced after pain physiology education: fMRI evaluation of a single patient with chronic low back pain

The way people with chronic low back pain think about pain can affect the way they move. This case report concerns a patient with chronic disabling low back pain who underwent functional magnetic resonance imaging scans during performance of a voluntary trunk muscle task under three conditions: directly after training in the task and, after one week of practice, before and after a 2.5 hour pain physiology education session. Before education there was widespread brain activity during performance of the task, including activity in cortical regions known to be involved in pain, although the task was not painful. After education widespread activity was absent so that there was no brain activation outside of the primary somatosensory cortex. The results suggest that pain physiology education markedly altered brain activity during performance of the task. The data offer a possible mechanism for difficulty in acquisition of trunk muscle training in people with pain and suggest that the change in activity associated with education may reflect reduced threat value of the task.

Postural activity of the abdominal muscles varies between regions of these muscles and between body positions

The abdominal muscles have an important role in control and movement of the lumbar spine and pelvis. Given there is new evidence of morphological and functional differences between distinct anatomical regions of the abdominal muscles, this study investigated whether there are regional differences in postural activity of these muscles and whether recruitment varies between different body positions. Eleven subjects with no history of low back pain that affected function or for which they sought treatment participated in the study. Electromyographic (EMG) activity of the upper, middle and lower regions of transversus abdominis (TrA), the middle and lower regions of obliquus internus abdominis (OI) and the middle region of obliquus externus abdominis (OE) was recorded using intramuscular electrodes. All subjects performed rapid, unilateral shoulder flexion in standing and six subjects also moved their upper limb in sitting. There were regional differences in the postural responses of TrA with limb movement. Notably, the onset of EMG of the upper region was later than that of the lower and middle regions. There were no differences in the EMG onsets of lower and middle TrA or OI. The postural responses of the abdominal muscles were also found to differ between body positions, with recruitment delayed in sitting compared to standing. This study showed that there is regional differentiation in TrA activity with challenges to postural control and that body position influences the postural responses of the abdominal muscles. These results may reflect variation in the contribution of abdominal muscle regions to stability of the trunk. (c) 2004 Elsevier B.V. All rights reserved.

An MRI investigation into the function of the transversus abdominis muscle during "drawing-in" of the abdominal wall

Study Design. An operator blinded dual modality trial of measurement of the abdominal muscles during drawing-in of the abdominal wall. Objectives. 1) To investigate, using magnetic resonance imaging (MRI), the function of the transversus abdominis muscle bilaterally during a drawing-in of the abdominal wall. 2) To validate the use of real-time ultrasound imaging as a measure of the deep abdominal muscle during a drawing-in of the abdominal wall. Summary of Background Data. Previous research has implicated the deep abdominal muscle, transversus abdominis, in the support and protection of the spine and provided evidence that training this muscle is important in the rehabilitation of low back pain. One of the most important actions of the transversus abdominis is to draw-in the abdominal wall, and this action has been shown to stiffen the sacroiliac joints. It is hypothesized that in response to a draw in, the transversus abdominis muscle forms a deep musculofascial corset and that MRI could be used to view this corset and verify its mechanism of action on the lumbopelvic region. Methods. Thirteen healthy asymptomatic male elite cricket players aged 21.3 +/- 2.1 years were imaged using MRI and ultrasound imaging as they drew in their abdominal walls. Measurements of the thickness of the transversus abdominis and internal oblique muscles and the slide of the anterior abdominal fascia were measured using both MRI and ultrasound. Measurement of the whole abdominal cross-sectional area (CSA) was conducted using MRI. Results. Results of the MRI demonstrated that, as a result of draw-in, there was a significant increase in thickness of the transversus abdominis (P < 0.001) and the internal oblique muscles (P < 0.001). There was a significant decrease in the CSA of the trunk (P < 0.001). The mean slide ( +/- SD) of the anterior abdominal fascia was 1.54 +/- 0.38 cm for the left side and 1.48 +/- 0.35 cm for the right side. Ultrasound measurements of muscle thickness of both transversus abdominis and the internal oblique, as well as fascial slide, correlated with measures obtained using MRI (interclass correlations from 0.78 to 0.95). Conclusions. The MRI results demonstrated that during a drawing-in action, the transversus abdominis contracts bilaterally to form a musculofascial band that appears to tighten (like a corset) and most likely improves the stabilization of the lumbopelvic region. Real-time ultrasound imaging can also be used to measure changes in the transversus abdominis during the draw-in maneuver.