Key result
New applied torque instructions substantially improve 90:20 IPCT validity and reliability versus original methods.
Why the study?
The 90:20 Isometric Posterior Chain Test for hamstring strength had not been validated, and its original instruction allowed high variability in execution.
Cross-Sectional (n=23)
Adding instructions to exert both vertical and horizontal force improves the validity and reliability of the 90:20 Isometric Posterior Chain Test for assessing hamstring strength.
Supports refined 90:20 test instructions in research; leaves open clinical adoption for hamstring assessment.
Hamstring injuries are associated with decreased hamstring strength. Matinlauri et al.'s 90:20 Isometric Posterior Chain Test (90:20 IPCT) efficiently assesses hamstring strength, but has not been validated so far. Furthermore, their rather unprecise original instruction allows high variability in test execution. We added a new instruction and variables and examined, whether this measure leads to increased reliability and validity. We assessed hamstring strength of 23 sport students via the 90:20 IPCT under the original instruction, to exert vertical force, and our new instruction, to exert vertical and horizontal force. Instead of only using bare vertical force as variable under the original (Fz_V) and our new instruction (Fz_VH), we also calculated the resultant force (Fres_VH) and the applied torque onto the force place (M_F_ortho_VH). To test for validity, we correlated the outcome variables with peak torque of gold standard dynamometry. Furthermore, we measured muscle activities of the mm. rectus femoris, biceps femoris, semitendinosus, and gluteus maximus under our new instruction and compared them to those under the original variable (Fz_V) via one sample t-tests. To evaluate reliability, tests were repeated on two separate days, for which we calculated intra class correlation coefficients (ICCs) and coefficients of variation (CVs). Our new instruction and variables (Fz_VH, Fres_VH, M_F_ortho_VH) showed better validity (mean r = 0.77, r = 0.81, and r = 0.85) and equally good or better reliability (ICCs: 0.87, 0.89, and 0.94; CVs: 4.7%, 4.1%, and 4.7%) than the original instruction and variable (Fz_V) (mean r = 0.70; ICC: 0.91; CV: 5.6%). There were no differences in muscle activities between the variables and instructions of the 90:20 IPCT. We recommend our new instruction and the applied torque onto the force plate as it makes the 90:20 IPCT a more reliable and valid tool to assess hamstring strength.
No takes yet. Share an insight, caveat, or question.
Rasp et al. (2024) conducted a cross-sectional in Hamstring strength assessment (n=23). New instruction (vertical and horizontal force) for 90:20 IPCT vs. Original instruction (vertical force only) was evaluated on Validity (correlation with gold standard dynamometry) and reliability (ICC and CV). A new instruction for the 90:20 Isometric Posterior Chain Test using applied torque improved validity (mean r=0.85 vs 0.70) and reliability (ICC 0.94 vs 0.91) compared to the original instruction.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: