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.