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Related Experiment Videos

Errors in the use of isokinetic dynamometers

D A Winter, R P Wells, G W Orr

    European Journal of Applied Physiology and Occupational Physiology
    |January 1, 1981
    PubMed
    Summary

    Constant velocity dynamometers can introduce significant errors in vertical movement testing due to uncompensated gravity. This study highlights the need to account for gravitational forces in functional testing and exercise programs.

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    Area of Science:

    • Biomechanics
    • Exercise Physiology
    • Rehabilitation Science

    Background:

    • Constant velocity dynamometers are increasingly used in functional testing, exercise, and therapy.
    • Vertical movements with these devices are susceptible to gravitational errors.
    • These errors are often overlooked, leading to inaccurate assessments.

    Purpose of the Study:

    • To quantify the error introduced by gravity in vertical movements during dynamometry.
    • To propose a method for compensating gravitational errors.
    • To analyze the impact of these errors on muscle moment calculations.

    Main Methods:

    • A study involving four subjects performing knee extension (against gravity) and flexion (with gravity).
    • Measurement of mechanical work and muscle moments.
    • Development of a compensation method for gravitational forces.

    Main Results:

    • Gravitational errors in mechanical work ranged from 26-43% for extension and 55-510% for flexion.
    • Errors were maximal at low-level contractions and minimal at high-level contractions.
    • Uncorrected errors led to false early peaks in muscle moment curves.

    Conclusions:

    • Gravitational forces introduce substantial errors in vertical dynamometry.
    • Accurate functional testing and exercise prescription require compensation for these errors.
    • Failure to account for gravity can lead to erroneous conclusions about muscle function.

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