Test-Retest Reliability of Isokinetic Strength Measurement in Standardized and Lengthened Hamstring Positions Among Healthy Adults

Introduction: Strength is a key modifiable risk factor for hamstring strains with significant differences between injured and non-injured sides in the lengthened position. Ensuring the test-retest reliability of measurement protocols ensures consistent injury prevention, rehabilitation and return-to-sport planning. Objective: To evaluate the test-retest reliability of hamstring strength protocols in both standardized and lengthened positions among healthy adults. Study Design: Test-retest reliability study Setting: Human Performance Laboratory, Fr. Roque Ruano building, University of Santo Tomas, Espana Manila Participants: Ten healthy adults (six males and four females; mean age: 26.5 ± 4.03 years) Main Outcome Measures: Absolute and relative peak torque for concentric and eccentric hamstring and quadriceps were measured at 60°/sec, 180°/sec and 240°/sec in the standardized position (hip and knee flexed at 90°). In the lengthened position (hip flexed at 85° and knee at 30°), isometric knee flexion and peak torque for concentric and eccentric hamstring and quadriceps were assessed at 60°/sec and 180°/sec. Strength ratios were calculated for both positions. Results: Intraclass Correlation Coefficient (ICC) values demonstrated good to excellent reliability for peak torque measurements, with higher reliability in the standardized position (ICC 0.83-0.94) than in the lengthened position (ICC 0.79-0.96). Conventional and functional ratios varied, with lower ICCs for the right leg in the standardized position (ICC 0.32-0.92) and moderate to good reliability in the lengthened position (ICC 0.63-0.87). Conclusion: Standardized and lengthened positions provide reliable assessments of absolute and relative peak torque for hamstring and quadriceps muscles during concentric and eccentric contractions across all speeds, including conventional and functional strength ratios.