Dynamic strength index in athletic performance

Background and purposeThe development of athletic performance requires a detailed assessment of the relationship between maximal strength and the ability to express it explosively. Traditional tests one-repetition maximum do not differentiate the rate of force development, which led to the introduction of the Dynamic Strength Index, defined as the ratio between force in the countermovement jump and the isometric mid-thigh pull . The aim of this paper was to present the theoretical background, methodological approaches, and practical applications of Dynamic Strength Index in order to optimize training and prevent injuries.Materials and methodsDynamic Strength Index is calculated by measuring peak force in countermovement jump and isometric mid-thigh pull tests using a force plate. Standardization of protocols (body position, contraction duration, software processing) is essential for validity. Test–retest reliability is high (Intraclass Correlation Coefficient >0.90). Normative values vary by sport and playing position: for example, sprinters and jumpers often record Dynamic Strength Index values >0.80, while weightlifters usually show lower values (<0.60).ResultsFindings indicate that DSI is an effective tool for training individualization. Values below 0.60 suggest the need for plyometric and ballistic training, while values above 0.80 point to a focus on maximal strength development. The optimal range (0.60–0.80) reflects a balanced profile. DSI is also useful for longitudinal monitoring of adaptations, adjusting training loads, and identifying injury risks. However, variability in testing protocols, anthropometric differences, and software processing may limit its applicability and comparability across studies.ConclusionDynamic Strength Index is a valuable biomechanical indicator linking maximal and explosive strength, allowing precise programming of training and performance monitoring. Its use has already been established in elite sports, but full validation requires measurement standardization and the development of sport-specific normative databases. Future directions include phase-specific force analysis within contraction cycles, expanding testing protocols, and integrating digital platforms for automated analysis.