A new method of quantitative measurement of abdominal and back muscle strength.

A new method of quantitative measurement with a cybex machine is applied to the trunk muscles. The curves of muscle torque and muscle fatigue are easily obtained in clinical medicine. In normal controls, maximal muscle torque is greater in back muscles than in abdominal muscles, and the definite influence of aging is found in both muscles. Furthermore, the trunk muscles are more easily fatigued by a sustained contraction than by repeated contractions, and abdominal muscles are more easily fatigued than back muscles. The role of the trunk muscles in the mechanism of pain production and prevention is still to be determined.