A New Reliable Device to Assess Trunk Extensors Strength

Purpose: This study aims to examine the reliability of trunk extensor strength assessment with a functional electromechanical dynamometer (FEMD). Methods: Thirty-one men performed strength assessment at different velocities (V) (V₁=0.15 m·s⁻¹, V₂=0.30 m·s⁻¹, V₃=0.45 m·s⁻¹) and range of movement (R) (R₁=25% cm; R₂=50% cm), and isometric contraction at 90º. Reliability was obtained through the intraclass correlation coefficient (ICC), typical error (TE), and coefficient of variation (CV). Results: The absolute reliability provided stable repeatability of the average eccentric strength in the V1R1 condition (CV=9.52%) and the maximum eccentric strength in V₁R₁ (CV=9.63%) and V₂R₂ (CV=9.66%). The relative reliability of the trunk extensor's average strength was good (ICC=0.77-0.83) for concentric and good (ICC=0.78-0.85) and moderate (ICC=0.67-0.74) for eccentric contraction. Also, good (ICC=0.77-0.81) and moderate (ICC=0.55-0.74) reliability of the maximum strength were obtained for concentric and eccentric contraction. The most reliable manifestation to evaluate the concentric (CV=11.33%) and eccentric (CV=9.52%) strength was the average strength in the V₁R₁ condition and the maximum strength (CV=10.29%) to isometric assessment. The average concentric strength in the V₂R₂ condition (r=0.69) and the maximum eccentric strength in the V₁R₁ condition (r=0.65) were the best related to the maximum isometric strength. Conclusion: FEMD is a highly reliable device to evaluate trunk extensors strength.