Miqueleiz Erburu, UnaiAguado Jiménez, RobertoLecumberri Villamediana, PabloGorostiaga Ayestarán, Esteban2025-07-282025-07-282025-05-21Miqueleiz, U., Aguado-Jimenez, R., Lecumberri, P., Gorostiaga, E. M. (2025) Agreement between an inertial measurement unit (IMU) algorithm and a photoelectric system for analysing spatiotemporal variables during overground and treadmill running. Sports Biomechanics, 1-19. https://doi.org/10.1080/14763141.2025.2502750.1476-314110.1080/14763141.2025.2502750https://academica-e.unavarra.es/handle/2454/54483The aim of this study was to assess the agreement between running stride variables measured simultaneously with an inertial sensor (MTw IMU) using a specific algorithm, and a floor-based photoelectric (Optojump; OJ) system among well-trained endurance runners, during overground and treadmill runs at speeds ranging from 9 to 21 km∙h-1. Five different filter settings (from 0_0 to 4_4) were used with the OJ to detect the contact event, based on the number of LEDs (from 1 to 5). No significant differences (p > 0.05) were found between the two devices in any of the stride variables when the 4_4 filter was implemented using the OJ. The agreement was good for contact time (CT) and flight time (FT) [r = 0.81–0.93; Typical error of the estimate (TEE%) = 3.2–7.5%], whereas for stride frequency (SF), stride length (SL) and stride time (ST) the agreement was almost perfect (r = 0.91–0.99; TEE% = 0.2–1.7%). The agreement worsened as the number of activated LEDs used to detect the contact event decreased. This suggests that the tested inertial sensor using a specific algorithm can achieve highly precise measurement of spatiotemporal parameters during both overground and treadmill running, compared to the OJ (4_4) system.application/pdfeng© 2025 The Author(s). This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License.Running biomechanicsRunning surfaceTriaxial accelerometerReference systemFilter settinginfo:eu-repo/semantics/article2025-07-28info:eu-repo/semantics/openAccess