European Journal of Applied Physiology
Publisher: Springer Berlin / Heidelberg
ISSN: 1439-6319 (Paper) 1439-6327 (Online)
Issue: Volume 57, Number 2
Date: March 1988
Pages: 146 - 153
Comparison of isokinetic and isoinertial lifting tests as predictors of maximal lifting capacity
Ira Jacobs1 , Douglas G. Bell1 and Jan Pope1
(1) Defence and Civil Institute of Environmental Medicine, P.O. Box 2000, Downsview, Ontario, Canada
Summary This study compared the relationship between isokinetic lifting test (ILT) performance and a maximal operational lifting test (OLT) with that between an isoinertial progressive lifting test (PLT) and OLT. Fifty subjects performed the ILT, PLT and OLT after familiarization trials. OLT was defined as the weight of the heaviest crate that could be lifted to 1.34 m with a progressive, incremental test. ILT performance was the force generated during a single maximal simulated lift on an isokinetic dynamometer. PLT performance was the maximal weight lifted to 1.52 m with a progressive, incremental protocol on a weight stack. OLT was highly correlated with ILT (r=0.96) and PLT (r=0.97); the standard error was similar for both linear regression equations. The results demonstrate that a single maximal voluntary lift on an isokinetic dynamometer is as good a predictor of OLT as in the PLT presently used in military recruit centers.
Key words Muscle strength - Ergometry - Occupational - Military - Lifting
Isoinertial dynamometry involves natural activities. Previously this was called isotonic (constant tension) work, but the nature of dynamic work is hardly that and so the "new" label is more appropriate. Isoinertial means constantly resistant to motion, and in most activities resistances such as gravity, water, air, and equipment are always impeding progress and performance. Maximum successful exertion for one repetition of a task (1RM) is the usual measure of maximum isoinertial strength and is used commonly in sport profiling.
However, isoinertial movements also bear little resemblance to sporting activities. They are usually performed relatively slowly and are trained by a low number of repetitions. This nonspecific measure and training mode is questionable for its relevance and transfer value to actual sporting movements. Some argue that the dynamic accelerative motion associated with these tests more closely approximates movements in many sports. Those who argue against this form of assessment emphasize the potential for athlete injury and poor reliability and objectivity due to intertrial, interathlete, and interlaboratory variations. Much of the gains in these forms of tests results from learning to do the movements of the tests rather than reflecting training effects from sporting participation.
There may be a load threshold beyond which reductions in reliability of this form of movement seriously compromise its validity. For example, several acute variables, including preloading and recovery between 1RM efforts, may affect 1RM strength. The number of trials to achieve maximum and the type of movement will also affect reliability. Further, it is also very possible that maximum values of exertion may not be the best measure of a strength and power capacity in a number of sports. (http://www-rohan.sdsu.edu/dept/coachsci/csa/vol21/aberneth.htm)