Associations of isometric and isoinertial trunk muscle strength measurements and lumbar paraspinal muscle cross-sectional areas

The relationships of dynamic and static trunk muscle strength measurements and muscle geometry an studied. Physiologically, isometric muscle strength is directly related to muscle cross-sectional area. We measured isometric a nd isoinertial trunk muscle strength of 111 former elite male athletes, age d 45-68, by Isolation B-200. Paraspinal muscle cross-sectional areas were m easured from axial magnetic resonance images at the L3-L4 level. Isometric and isoinertial torques were closely related, but angular velocities were n ot predicted by isometric maximal torque. The area of the psoas muscles cor related with isometric maximal flexion, as well as with isoinertial maximal torque, angular velocity, and power in flexion (r = 0.24-0.27). The area o f the extensor group correlated with isometric maximal extension and with i soinertial maximal torque and power in extension (r = 0.24-0.25). We conclu de that dynamic and static strength measurements are closely related, with angular velocity giving additional information on muscle function. Paraspin al muscle cross-sectional area is one determinant of isometric and isoinert ial trunk muscle strength.