Power as a predictor of lifting capacity



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Texas Tech University


An experiment was conducted to examine the role that maximal lifting power has in predicting the maximum acceptable weight of lift (MAWL) for a frequency of one lift per 8 hours. The secondary aim of the study was to compare the ability of power to predict MAWL to previously used measures of capacity, including two measures of isometric strength, five measures of isokinetic strength, and isoinertial capacity on an isoinertial incremental lifting test.

Twenty-five male subjects volunteered to participate in the experiment, and were examined by a physician prior to participation to ensure fimess for the experimental tasks. The experimental tasks were comprised of isometric, isokinetic, and isoinertial tests. The isometric tests involved maximum voluntary contractions for composite lifting tests at vertical heights of 15 and 75 cm. Peak isokinetic strength was measured at velocities of 0.1 m. • sec.'l, 0.2 m. • see."^ 0.4 m. • sec^, 0.6 m. • see."^ and 0.8 m. • sec."^ using a modified CYBEX II isokinetic dynamometer. Isoinertial lifting capacity was measured on the incremental lifting machine and peak power was measured on the incremental lifting machine by having subjects lift a 25 kg. load as quickly as possible.

The results indicate that peak isoinertial power is significandy correlated with MAWL, and this correlation was higher than any of the correlations between the other predictor variables and MAWL. The relationships between the isokinetic strength measures and MAWL were stronger than the relationships between the isometric measures and MAWL.

The magnitudes of the strength measures compared favorably with the values from previous studies. The mean MAWL value was shghtly lower than comparable values from databases in the hterature that are based on indusuial subject pools. The results provide indirect support for the hypothesis that lifting capacity and dynamic strength tests may be affected by the distribution of slow- and fast-twitch muscle fibers. Overall, the results suggest that tests used to predict MAWL should be dynamic rather than static. Suggestions for future research are presented which include repHcating the study with female subjects and an industrial subject pool.



Muscle strength, Lifting and carrying