Lumbar compressive and shear forces during various trunk curl-up exercises

The lumbar compressive and shear forces were determined using a computer model, BIOMECH6, during the performance of the longlaying, hooklaying and bench curl-ups. The lumbar spine curvature and iliopsoas tension were determined for each position and supplied to BIOMECH6 to determine these forces. The lumbar forces were maximized during the initial position of the longlaying curl-up. During the initial position of the hooklaying curl-up, the compressive forces were only reduced by 5% (male) and 4% (female) while the shear forces were reduced by 46% (male) and 39% (female) The bench curl-up minimized these forces; the compressive forces were reduced by 17% (male) and 18% (female) while the shear forces were reduced by 87% (male) and 97% (female). The lumbar forces were reduced for the 45° curl-up position in all three variations when compared to the initial position, except for the bench curl-up where the shear forces increased slightly. These results indicated that to minimize the lumbar spine forces, the bench curl-up was the most beneficial method.