Influence of Isometric and Dynamic Fatiguing Protocols on Dynamic Strength Index Smajla, Darjan Šarabon, Nejc García Ramos, Amador Janicijevic, Danica Kozinc, Žiga Dynamic strength Vertical jump Mid-thigh pull Background: Strength and conditioning experts widely recognize the dynamic strength index (DSI) as a tool for assessing an athlete’s ability to utilize strength in dynamic actions. The DSI is calculated as the ratio of peak force in dynamic actions versus isometric ones. To date, the influence of fatigue on the DSI is still not fully understood. This study aimed to explore the effects of both dynamic and isometric fatigue tasks on the DSI.Methods: A total of 24 physically active participants underwent fatigue tests involving repeated countermovement jumps (dynamic) and repeated isometric mid-thigh pulls (isometric) in separate visits. Results: The results revealed a marked drop in performance, with dynamic force showing amore significant reduction (p < 0.001; d = 1.57) than isometric force (p = 0.015; d = 0.30). After the isometric fatigue task, the DSI increased, indicating a more substantial decline in isometric force (p < 0.001; d = 1.75) compared to dynamic force (p = 0.313; d = 0.08). Following this trend, the DSI decreased post-dynamic fatigue (p < 0.001; d = 0.99) and increased post-isometric fatigue (p < 0.001; d = 3.11). Conclusion: This research underscores the need to consider fatigue’s task-specific effects on the DSI, enabling more tailored training methodologies for athletes. 2024-06-04T08:03:13Z 2024-06-04T08:03:13Z 2024-03-24 journal article Smajla, D.; Šarabon, N.; García Ramos, A.; Janicijevic, D.; Kozinc, Ž. Influence of Isometric and Dynamic Fatiguing Protocols on Dynamic Strength Index. Appl. Sci. 2024, 14, 2722. https://doi.org/10.3390/app14072722 https://hdl.handle.net/10481/92291 10.3390/app14072722 eng http://creativecommons.org/licenses/by/4.0/ open access Atribución 4.0 Internacional MDPI