Effects of abdominal belts on the cross-sectional shape of the trunk during intense contraction of the trunk muscles observed by computer tomography

Background Several mechanisms of how abdominal belts affect the trunk have been postulated, but very little is known about how the belts affect the cross-sectional shape of the trunk during trunk muscle exertions. Methods To evaluate the effects of abdominal belts on the cross-sectional shape of the trunk during contraction of the trunk muscles, CT images at the third lumbar vertebra level of 20 healthy males (age: 23–45 years) under 8 different conditions (combinations of performing or not performing the Valsalva maneuver after full inhalation or at neutral respiratory state, while wearing or not wearing a 100-mm-wide abdominal belt) were evaluated. The cross-sectional shapes of the trunk seen on CT images taken at the level of the 3rd lumbar vertebra were compared using three-way ANOVA. Findings Wearing the belt decreased the cross-sectional area of the trunk, and wearing it while performing the Valsalva maneuver and during inhalation compressed the postero-lateral part of the trunk and made the trunk nearly round by increasing the ratio of the anterior–posterior width to the right–left width. Interpretation A wide belt cinched around the abdomen exerts external hoop tension on the trunk and stiffens the trunk. When the belt is worn during the Valsalva maneuver after deep inhalation, the posterolateral portion of the trunk is compressed and the trunk becomes circular.