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Magnetic Resonance Imaging Assessment of Trunk Muscles During Prolonged Bed Rest

Hides, Julie A. PhD*†; Belavý, Daniel L. PhD*‡§; Stanton, Warren PhD*†; Wilson, Stephen J. PhD‡; Rittweger, Jörn PhD∥; Felsenberg, Dieter PhD§; Richardson, Carolyn A. PhD*

doi: 10.1097/BRS.0b013e318074c386
Diagnostics

Study Design. Prospective longitudinal study.

Objective. To investigate, using magnetic resonance imaging (MRI), the influence of bed rest on the lumbopelvic musculature.

Summary of Background Data. Reduced gravitational loading and inactivity (bed rest) are known to result in significant change in musculoskeletal function, although little is known about its effects on specific muscles of the lumbopelvic region.

Methods. Ten healthy male subjects underwent 8 weeks of bed rest with 6 months of follow-up. MRI of the lumbopelvic region was conducted at regular time-points during and after bed rest. Using uniplanar images at L4, cross-sectional areas (CSAs) of the multifidus, lumbar erector spinae, quadratus lumborum, psoas, anterolateral abdominal, and rectus abdominis muscles were measured.

Results. Multifidus CSA decreased by day 14 of bed rest (F = 7.4, P = 0.04). The lumbar erector spinae and quadratus lumborum CSA showed no statistically significant difference to baseline across the time of bed rest (P > 0.05). The anterolateral abdominal, rectus abdominis, and psoas CSA all increased over this time. Psoas CSA increased by day 14 (F = 6.9, P = 0.047) and remained so until day 56, whereas the anterolateral abdominal CSA (F = 29.4, P = 0.003) and rectus abdominis CSA (F = 8.9, P = 0.03) were not statistically larger than baseline until day 56. On reambulation after completion of the bed rest phase, multifidus, anterolateral abdominal, and rectus abdominis CSA returned to baseline levels (P > 0.05) by day 4 of follow-up, whereas psoas CSA returned to baseline level after day 28 of the follow-up period.

Conclusions. Bed rest resulted in selective atrophy of the multifidus muscle. An increased CSA of the trunk flexor musculature (increases in psoas, anterolateral abdominal, and rectus abdominis muscles) may reflect muscle shortening or possible overactivity during bed rest. Some of the changes resemble those seen in low back pain and may in part explain the negative effects of bed rest seen in low back pain sufferers.

Ten male subjects underwent 8 weeks of bed rest with 6 months of follow-up. MRI of the lumbopelvic region was conducted at regular intervals during and after bed rest. Results showed preferential atrophy of the multifidus muscle and increased cross-sectional area of the abdominal flexor muscles.

From the *Division of Physiotherapy, School of Health and Rehabilitation Sciences, University of Queensland, Brisbane, Queensland, Australia; †Mater Misericordiae Health Services Brisbane Limited, South Brisbane, Queensland, Australia; ‡School of Information Technology and Electrical Engineering, University of Queensland, Brisbane, Queensland, Australia; §Zentrum für Muskel- und Knochenforschung, CHARITÉ Campus Benjamin Franklin, Berlin, Germany; and ∥Institute for Biophysical and Clinical Research into Human Movement, Manchester Metropolitan University, Cheshire, England.

Acknowledgment date: October 20, 2006. First revision date: December 20, 2006. Acceptance date: December 20, 2006.

Supported by Grant No. 14431/02/NL/SH2 from the European Space Agency.

The manuscript submitted does not contain information about medical device(s)/drug(s).

Institutional funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript.

Address correspondence and reprint requests to Julie A. Hides, PhD, Division of Physiotherapy, School of Health and Rehabilitation Sciences, University of Queensland, Brisbane Qld 4072, Australia; E-mail: j.hides@shrs.uq.edu.au

© 2007 Lippincott Williams & Wilkins, Inc.