Isoinertial tests to predict lifting performance

Previous research has found isoinertial strength testing to be superior to isometric and isokinetic strength testing for prediction of task performance. The purpose of this study was to investigate tests on an isoinertial lifting machine (ILM) and their ability to predict performance on actual lifting tasks. Sixteen male subjects performed two lifting tasks: maximum box lift to truck-bed height of 1.35 m; and 'speed lifts' of 60 concrete blocks (each 22.7 kg) to the same height. These performance tests were compared to three ILM tests: a maximal lift to 1.83 m, a second maximal lift to 1.52 m, and an endurance test that entailed 60 timed ILM lifts of 22.7 kg to 1.83 m. Pearson product-moment correlations between ILM tests and performance tasks varied from r = 0.55 to 0.71. Therefore, the isoinertial test protocols employed in this study were able to account for only 30% to 50% of the variance in the performance of maximal lifting and endurance tasks. In was concluded that prediction of maximal lifting ability or endurance ability using an ILM might be enhanced by closer approximation of specific task variables, or by inclusion of dynamic parameters to measure technique.