Validation evidence of the Actigraph® GT3X inertial sensor for assessing vertical jump height

Abstract

Objective: To evaluate the validity of the Actigraph® GT3X inertial sensor for measuring vertical jump height compared with a force plate considered the gold standard. Methods: This cross-sectional validation study included 42 athletes from track and field (n=16), basketball (n=12), and football (n=14), with a mean age of 22.40 ± 5.8 years. Participants performed Squat Jump (SJ) and Countermovement Jump (CMJ) tests according to the Bosco protocol on an AMTI force plate while simultaneously wearing an Actigraph® GT3X accelerometer positioned at the waist. Jump height was calculated from flight time derived from both systems. Pearson correlation coefficients, Intraclass Correlation Coefficients (ICC), and Bland-Altman agreement analyses were performed to compare measurements between devices. Results: High correlations were observed between the force plate and the inertial sensor across all sport modalities and jump conditions. Correlation ranged from 0.836 to 0.997. ICC (A,1) values ranged from 0.842 to 0.996, indicating excellent agreement for most comparisons. Bland-Altman analysis revealed a mean bias of 0.0076 m (95% limits of agreement: −0.0287 to 0.0438 m) for SJ and 0.0012 m (95% limits of agreement: −0.0254 to 0.0277 m) for CMJ in the combined sample. A one-sample t-test of the mean difference against zero indicated a statistically significant systematic bias for the SJ total (p = 0.011); no significant bias was detected for CMJ or any modality-specific comparison (all p > 0.05). Conclusion: The Actigraph® GT3X demonstrated strong validity for assessing vertical jump height in athletes, showing high correlation, excellent ICC values, and clinically acceptable agreement with the gold-standard force plate.