Reliability and Validity of Digital Inclinometer in Assessing Ankle Dorsiflexion: A Focus on First Detectable Resistance Position in Individuals With and Without Achilles Tendinopathy

Introduction. The dorsiflexion range of motion in the ankle joint within an open kinet­ic chain can be measured by the First Detectable Resistance Position. Understanding such biomechanical alterations is crucial for intervening in the prevention and expe­diting the rehabilitation time of these injuries. Objective. To determine the reliability and concurrent validity of the digital inclinom­eter as a tool for assessing the First Detectable Resistance Position and the maximum dorsiflexion range of motion in the ankle joint complex. Methods. The sample comprised 50 healthy and symptomatic participants with Achil­les tendinopathy of both genders. All participants had their ankle joint’s First Detect­able Resistance Position measured using both a manual goniometer and a digital incli­nometer. Data analysis involved descriptive analysis, independent t-test, Intraclass Correlation Coefficient, and Pearson’s Correlation. Results. The majority of the sample was female (58%), with a mean age of 26.70 ± 10.26 years and BMI (kg/m2) of 25.72 ± 4.52. Intraexaminer and interexaminer reli­ability Intraclass Correlation Coefficients (ICC) for the digital inclinometer were 0.96 (95%CI 0.94-0.98) and 0.94 (95%CI 0.87-0.97), respectively. The Standard Error of Measurement for digital inclinometer measurements in our study was 0.48° and 0.75° for intraexaminer and interexaminer, respectively. Pearson’s Correlation Coefficient showed a strong direct correlation for Examiner A (r = 0.95; p = 0.001) and Examiner B (r = 0.93; p = 0.001) between the digital inclinometer and the manual goniometer. The Bland–Altman plot showed greater agreement in the digital goniometer when comparing measurements with the manual goniometer for evaluating the First Detect­able Resistance Position of the ankle joint complex. Conclusions. The study achieved excellent reliability and validity with a strong correla­tion between the manual goniometer and the digital inclinometer for evaluating the First Detectable Resistance Position of the ankle joint complex.