Validity and inter-day reliability of a free-oscillation test to measure knee extensor and knee flexor musculo-articular stiffness

Publication Type:
Journal Article
Citation:
Journal of Electromyography and Kinesiology, 2011, 21 (3), pp. 492 - 498
Issue Date:
2011-06-01
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The purpose of this study was to assess the validity and inter-day reliability of musculo-articular stiffness (MAS) in the knee-extensor (KE) and knee-flexor (KF) muscle groups, measured with a free-oscillation technique. Fourteen participants were measured, on two occasions, for KE and KF maximal isometric voluntary contraction, rate of torque development (RTD) and electromechanical delay (EMD), along with MAS using multiple sub-maximal loads relative to the individual's maximal voluntary contraction (MAS%MVC). Furthermore, 18 participants were tested for MAS using one fixed assessment load for each muscle group (MASFL) during a separate series of tests on three occasions. MAS%MVCwas significantly increased as load increased both in KE and in KF (p<0.01) fitting a curvilinear relationship as depicted in similar studies. Validity was demonstrated relating MAS%MVCto RTD (r=0.51-0.71, p<0.05) and to EMD (r=-0.56 to -0.67, p<0.05). While MAS%MVCreliability (ICC=0.62-0.89; CV=8.1-13.1%) was questionable to acceptable, MASFLexhibited good to excellent reliability (ICC=0.81-0.94; CV=3.7-6.5%). No significant systematic bias was detected for any of the variables considered. The assessment of KE and KF MAS using the free-oscillation technique appears to be valid and reliable, with the use of MASFLyielding higher reliability than the use of MAS%MVC. © 2010 Elsevier Ltd.
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