Reliability and Validity of Stryd for Measuring Running Kinematics During an Incremental Treadmill Test.

Abstract

Abstract: Pinedo-Jauregi, A and Ozaeta-Beaskoetxea, E. Reliability and validity of Stryd for measuring running kinematics during an incremental treadmill test. J Strength Cond Res XX(X): 000-000, 2025-Inertial Measurement Unit devices have become indispensable tools for coaches and researchers. In particular, the Stryd device has been used by coaches to improve athletes' running performance. However, its reliability and validity have not been universally accepted by the scientific community. The aim of this study was to assess the reliability and validity of the Stryd device during an incremental running test. For this purpose, subjects performed an incremental test at speeds ranging from 8 to 17 km·h-1. Reliability was tested using 2 Stryd devices placed on the same foot, while validity was assessed against the Optojump Next. The results showed that the Stryd device is reliable for measuring power, cadence, ground contact time (GCT), and leg stiffness (coefficients of variation < 3.34%; intraclass correlation coefficients >0.81; SEM <0.51; r > 0.88), but not for vertical oscillation. In terms of validity, the device was found to be valid for measuring cadence (Lin's Concordance Coefficient > 0.78; Mean Absolute Percent Error <2.18%), but not for GCT. In conclusion, the Stryd device seems reliable and valid for some variables, but not for others. The authors advise trainers and scientists using the Stryd device to be cautious, because its measurements are not fully supported by the scientific community.