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The Reliability and Validity of a Novel Isometric Trunk Rotation Strength Test
Kari Arnason1, Hildur H Sigmarsdottir1, Rosey Bjorgvinsdottir1
1Department of Physical Therapy University of Iceland.
Background:
Trunk rotation (TR) strength and power play an important role in overhead sports for both sport-specific performance and injury risk-reduction. However, clinically applicable, reliable and valid methods to measure isometric TR strength have not been previously described.
Purpose:
To assess a) the test-retest reliability of a novel isometric TR strength test, performed in a half-kneeling position, and b) the convergent validity of the isometric TR strength test by assessing its correlation with a seated dynamic TR power test.
Study Design:
Cross-sectional cohort study.
Methods:
Eighteen participants, recruited from the general public, took part in this study. Isometric TR strength was measured over two consecutive days in a half-kneeling position using a digital dynamometer. Dynamic TR power was measured once in a seated position, using a pulley system and inertial sensors. The test-retest reliability of the isometric TR strength test was assessed with Intraclass Correlation Coefficient (ICC) 3.3, and standard error of measurement (SEM) and minimal detectable change (MDC90) were calculated. The convergent validity was interpreted based on the correlation between peak values of the isometric TR strength test and the dynamic TR power test.
Results:
The results showed excellent test-retest reliability for the isometric TR strength test (ICC 3.3 = 0.95, 95% CI 0.91-0.98), with a SEM of 6.7 N, and a MDC90 value of 15.6 N. A strong correlation was found between the peak values for the isometric TR strength test and the dynamic TR power test (rs = 0.73, p < 0.001, 95% bootstrap confidence interval 0.40- 0.89).
Conclusions:
This study addresses a gap in the literature regarding reliable and valid methods to measure isometric TR strength, thus contributing to our understanding of injuries and performance in overhead sports. The results provide professionals working with overhead athletes with a convenient and practical test to measure isometric TR strength.
Level Of Evidence:
3.
