2015 ISAKOS Biennial Congress ePoster #1101
Comparison of Clinical Quadriceps Strength Tests to Isometric Dynamometry to Identify Clinically Meaningful Deficits in Quadriceps Strength
Andrew David Lynch, PT, PhD, Blackwood, NJ UNITED STATES
John Anthony Sinacore, SPT, ATC, Pittsburgh, PA UNITED STATES
Andrew M. Evans, SPT, Pittsburgh, PA UNITED STATES
Brittany Patterson, PT, DPT, SCS, Pittsburgh, PA UNITED STATES
Richard Joreitz, PT, ATC, SCS, Pittsburgh, PA UNITED STATES
James J. Irrgang, PT, PhD, FAPTA, Pittsburgh, Pennsylvania UNITED STATES
University of Pittsburgh & UPMC Center for Sports Medicine, Pittsburgh, PA, USA
FDA Status Not Applicable
Summary: Clinical tests for measuring strength are poor substitutes for measuring quadriceps strength asymmetries in comparison to isometric dynamometry.
To assess hand-held dynamometry and one-repetition maximum testing on clinical equipment to identify quadriceps strength asymmetry.
Subjects: 57 subjects (25 females) between 17 and 59 years old (mean 29.9 years ± 10.5) participated.
Subjects performed three maximal isometric quadriceps contractions for 5 seconds on a Biodex Dynamometer. Subjects performed three maximal isometric quadriceps contractions seated on a standard treatment table with an inelastic strap resisting knee extension and force was measured with a hand-held dynamometer. One-repetition maximum (1-RM) testing was completed on a standard leg press machine (LP) and knee extension machine from 90° knee flexion through a 90-degree arc (KX90) and a 45-degree arc from 90° to 45° of flexion (KX45). Subjects participating after surgery were cleared by their physician for testing, however, no subject was tested through the full arc within 6 months after ACL reconstruction (n = 6). Subjects extended their knee against the resistance and held the end position for 2 seconds before returning the weight stack to the resting position. Testing alternated between limbs and progressed to failure, defined as three consecutive unsuccessful attempts to lift a weight.
Peak Biodex torque, peak HHD force and 1-RM weight lifted were recorded and used to calculate quadriceps indices (QI = involved/uninvolved limb *100%). Agreement for clinical decisions based on QI for return to running (80%) and practice (90%) was compared with percent agreement and Kappa coefficients.
Biodex QIs ranged from 39.0% to 128.0% (mean 87.4% ± 14.6%) compared to HHD QI of 23.0% to 128.0% (mean 89.8% ±19.0%, p = 0.299); LP-QI of 67.0% to 114.0% (mean 94.9% ± 10.0%; p < 0.001); KX90 QI of 50% to 135.0% (mean 88.4% ± 14.9%; p =0.656), and KX45 QI of 44% to 139.0% (mean 84.6% ± 19.1%; p =0.165).
LP and Biodex demonstrated 78.9% agreement for return to running (kappa = 0.201) and 61.4% agreement for return to practice (kappa = 0.197), although the LP consistently over-estimated quadriceps strength symmetry. HHD and Biodex demonstrated 78.9% agreement for return to running (kappa = 0.432) and 64.9% agreement for return to practice (kappa = 0.293). KX90 and KX45 demonstrated better agreement with Biodex for return to running (78.0%, kappa = 0.382; and 78.9%, kappa = 0.504 respectively). The percent agreement and Kappa coefficients between Biodex testing for KX90 and KX45 for return to practice decisions were 66.0% and kappa=.316 and 66.7% and kappa=.334, respectively.
Leg press tests are not a substitute for measuring strength asymmetry compared to dynamometry due to overestimation of symmetry leading to inconsistent classification as ready to begin running or practice after injury or surgery. Leg extension and HHD tests approach moderate agreement with the Biodex for returning to running, but not for practice.
Leg press tests should not be used to assess quadriceps symmetry. Without access to isometric dynamometry, a leg extension 1-RM or HHD can be used to estimate quadriceps strength asymmetry for clinical decision making, but further research is necessary to identify more accurate thresholds for estimating symmetry.