Isokinetic measurement of trunk strength is a reliable and objective method if affecting factors are controlled well. Authors wanted to know the relationship between the constitutional factors of subjects and data from isokinetic trunk strength measurement. Fifty three healthy volunteers were measured for body weight, height, chest circumference and waist circumference as constitutional factors. After warming-up exercise for 5 minutes on bicycle ergometer, trunk strength measurement for flexor and extensor was done using isokinetic instrument with trunk unit. Four repetitions at 4 different angular velocities(30°/sec, 60°/sec, 90°/sec, 120°/sec) with 24 seconds of resting interval between each angular velocity were done. With the resulting isokinetic data, comprehesive parameters such as average performance ratio(APR) and muscle performance index(MPI) were calculated. Normative data of peak torque, peak torque angle, total work, APR and MPI were obtained. MPI was highly correlated with height and body weight(r>0.7, P<0.001), moderately correlated with waist and chest circumference(r>0.4, P<0.01). In multiple regession analysis, APR and MPI could be explained well by constitutional factors(r²>0.6, P<0.05).

Keywords :Isokinetic, Trunk flexion and extension