TORQUE, TOTAL WORK, POWER, TORQUE ACCELERATION ENERGY AND ACCELERATION TIME ASSESSED ON A DYNAMOMETER - RELIABILITY OF KNEE AND ELBOW EXTENSOR AND FLEXOR STRENGTH MEASUREMENTS

Isometric torque and isokinetic peak torque, total work, power, torque acceleration energy and acceleration time at 30, 120 and 240 degrees . s(-1) of the knee and elbow extensors and flexors were measured usin g an isokinetic dynamometer in 24 healthy women. Intrasession variatio n of the measurements was evaluated and the short-term and long-term r eliability was assessed by repeating all procedures after averages of 2 and 30 days, respectively. The effect of learning on peak torque dur ing a session was also evaluated. Moreover, the effect of general warm ing-up on knee extensor and flexor strength was examined on a separate day. Using correlations, numerous studies have indicated that muscle strength measurements are reliable. Correlations, however, are inappro priate and misleading in studies on reliability. In the present study reliability of each strength variable was expressed as the coefficient of variation (CV). With the protocol used, neither learning nor warmi ng-up had any significant effect on strength. As expected, intra-sessi on variation tended to be less than short-term and longterm inter-sess ion variation. The CVs for strength variables measured 30 days apart e xceeded 5% for all variables and rose to 107% for acceleration time. S ubstantial between-subject variation of individual CVs were found. The study demonstrated that muscle strength measurements may be highly un reliable in the individual subject.