Abstract
AimTo determine the absolute and relative reliability of functional trunk tests, using a functional electromechanical dynamometer to evaluate the isokinetic strength of trunk flexors and to determine the most reliable assessment condition, in order to compare the absolute and relative reliability of mean force and peak force of trunk flexors and to determine which isokinetic condition of evaluation is best related to the maximum isometric.MethodsTest-retest of thirty-seven physically active male student volunteers who performed the different protocols, isometric contraction and the combination of three velocities (V1 = 015 m s−1 , V2 = 0.30 m s−1, V3 = 0.45 m s−1) and two range of movement (R1 = 25% cm ; R2 = 50% cm) protocols.ResultsAll protocols to evaluate trunk flexors showed an absolute reliability provided a stable repeatability for isometric and dynamic protocols with a coefficient of variation (CV) being below 10% and a high or very high relative reliability (0.69 < intraclass correlation coefficient [ICC] > 0.86). The more reliable strength manifestation (CV = 6.82%) to evaluate the concentric contraction of trunk flexors was mean force, with 0.15 m s−1 and short range of movement (V1R1) condition. The most reliable strength manifestation to evaluate the eccentric contraction of trunk flexors was peak force, with 0.15 m s−1 and a large range of movement (V1R2; CV = 5.07%), and the most reliable way to evaluate isometric trunk flexors was by peak force (CV = 7.72%). The mean force of eccentric trunk flexor strength with 0.45 m s−1 and short range of movement (V3R1) condition (r = 0.73) was best related to the maximum isometric contraction.ConclusionFunctional electromechanical dynamometry is a reliable evaluation system for assessment of trunk flexor strength.
Highlights
Trunk flexion is present in daily activities, such as walking or sit-to-stand (RoldánJiménez, Bennett & Cuesta-Vargas, 2015; Silva et al, 2015; Moon & Kim, 2017), and in different sports performance actions, such as overhead throwing (Van den Tillaar & Ettema, 2009; Liu, Leigh & Yu, 2010; Wagner et al, 2012; Wagner et al, 2014; Palmer et al, 2015) or hitting a ball (Lindsay, Horton & Paley, 2002; Chang et al, 2016)
The evaluation of the mean force of the eccentric contraction of trunk flexor strength was sensitive to the test and retest (p < 0.05, effect size (ES) 0.13–0.32)
The absolute reliability provided a stable repeatability for the isometric and dynamic protocols, with coefficient of variation (CV) being below 10% in most instances
Summary
Trunk flexion is present in daily activities, such as walking or sit-to-stand (RoldánJiménez, Bennett & Cuesta-Vargas, 2015; Silva et al, 2015; Moon & Kim, 2017) , and in different sports performance actions, such as overhead throwing (Van den Tillaar & Ettema, 2009; Liu, Leigh & Yu, 2010; Wagner et al, 2012; Wagner et al, 2014; Palmer et al, 2015) or hitting a ball (Lindsay, Horton & Paley, 2002; Chang et al, 2016). Due to the importance of trunk strength, clinicians and coaches must know whether changes in strength over time reflect a real gain or loss, or are the result of the measurement error (Atkinson & Nevill, 1998). The validity and reliability of data are important when assessing strength. The validity of data concern to which an individual’s test performance reflects true performance and the reliability measures in tests and retests concern the repeatability of the data observed in a sample (Hopkins, 2000; Hopkins, Schabort & Hawley, 2001). It is a requirement to have relative (intraclass correlation coefficient (ICC)) and absolute reliability (standard error of measurement (SEM) or coefficient of variation (CV)) of data. Absolute reliability is related to the consistency of individual scores (Hopkins, 2000; Hopkins et al, 2009)
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