Reliability of Isokinetic Muscle Endurance Tests

The reliabilities of two methods of measuring quadriceps endurance were tested at two speeds using the Cybex II.® These were the work ratio of the work done during the last 5 of 25 maximum contractions to the work done during the first five, and the number of contractions until peak torque fell below 50% of initial peak torque. The reliability of work ratio in measuring hamstring endurance was also tested. Thirty-six healthy young adults were tested twice at 180°/sec and twice at 240°/sec using both methods, with only one test per day and at least 2 days rest between tests. Test-retest correlation coefficients indicated that peak torque, absolute work, and average power were more reliable measurements than either endurance measurement, and that the number of contractions was more reliable in measuring muscle endurance than was the work ratio. These results suggest that the work ratio may not be a reliable method of measuring muscle endurance during rehabilitation.