A Novel Way of Testing Hip Extension and Flexion Strength, and Strength Ratio in the Clinical Setting: Is it Reliable?
Anders Pålsson, August Estberger, Kristian ThorborgBackground
Hip muscle strength is considered an important parameter to assess in patients with hip and groin pain. However, hip extension and flexion strength measures are often performed in hip angles suboptimal for force production and do not allow for calculating meaningful strength ratios.
Purpose
The objective was to evaluate the test-retest reliability of testing maximal isometric strength in extension and flexion in a semi-standing position with 60° hip flexion.
Study Design
Observational reliability study
Methods
Thirty healthy subjects (mean age 27 (SD 7), 43% women) were recruited. An anchored dynamometer was used to measure maximal isometric force production in hip extension and flexion in a semi-standing position with the hip at 60° flexion. One tester performed the tests on two separate occasions. For relative reliability, intraclass correlation (ICC2,1, (Two-way mixed effects, single measurement, absolute agreement) was used. For absolute reliability, standard error of measurement (SEM%), and minimal detectable change at both group (MDC%group), and individual level (MDC%ind) was used.
Results
No statistically significant differences between test sessions were observed (p≥0.193). The results showed good to excellent relative reliability for extension (ICC 0.933) and flexion (ICC 0.884) and moderate relative reliability for strength ratio (ICC 0.694). For absolute reliability SEM% for extension was 8.2%, flexion 9.1%, and strength ratio 10.6%, MDC%group ranged from 4.2% to 5.6%, and MDC%ind ranged from 22.6% to 29.5%.
Conclusion
Assessing isometric hip extension and flexion strength with the hip at 60° flexion in a semi-standing position demonstrated good intra-tester reliability in healthy young adults. The method appears suitable for detecting changes at the group level, while the relatively large individual-level variability should be considered when interpreting changes over time in individual subjects.
Level of Evidence
3