A comparison of isokinetic and isotonic predictions of a functional task

Controversy still exists regarding the use of isokinetic and isotonic exercise in rehabilitation. Many authors have compared these two types of training methods on various strength measures and functional activity, but have used open kinetic chain training. The purposes of this investigation were to determine: 1) which form of closed kinetic chain training, isokinetic or isotonic, would produce the greatest increase in one-legged jump reaction force, and 2) which training method most accurately predicts peak force produced during a one-legged jump. Forty-two legs from 21 female volunteer subjects were used. Each subject had her dominant and nondominant extremities identified, and then each extremity was randomly assigned to either isokinetic training, isotonic training, or control. Both training groups trained using a leg press exercise 3 days a week for 5 weeks, while the control extremities did not train. The isokinetic extremities were trained using a velocity spectrum (two sets of 10 repetitions at each speed: 60 degrees , 180 degrees and 240 degrees /sec) and the isotonic extremities trained using the DAPRE technique. Data were analyzed with an analysis of variance (ANOVA). There was no difference between the three groups for change in one-legged jump force. Both isokinetic and isotonic groups increased strength after training, but these changes did not correlate with changes in one-legged jump reaction force. These results suggest that changes in neither isokinetic force nor isotonic weight lifted developed in a nonweight-bearing closed kinetic chain, directly translate into increased force production during a functional activity.