Summary Aim: This pilot study successfully established a framework for IMU-based technique diagnostics in hammer throwing, demonstrating that a single wrist-worn sensor provides high-fidelity data for both performance analysis and injury prevention. By deriving 19 specific parameters based on a biomechanical rationale of progressive acceleration, the research bridge the gap between raw inertial data and elite coaching requirements. Key Findings and Statistical Insights: The application of repeated measures correlation revealed that performance determinants are highly individualized. Advanced athletes (Athletes 1 and 2) exhibited a significantly higher number of parameters that correlated strongly with throwing distance, particularly regarding acceleration magnitudes in the final turns. Furthermore, technical proficiency was objectively quantified through the Coefficient of Variation (CV). Technical Progression and Rhythmic Structure: The analysis of acceleration time courses confirmed that optimal technical execution is marked by a steep increase in acceleration during the power position of the final turn. The derived acceleration ratios (Qa) provided an objective measure of the rhythmic buildup, identifying whether an athlete maintained sufficient "acceleration reserve" for the final phase of the throw. Clinical and Practical Implications: From a sports medicine perspective, this study highlights the potential of wearable technology for proactive injury prevention. By monitoring intra-individual variability in real-time, the sensor can detect early signs of neuromuscular fatigue. A sudden rise in the CV serves as a proxy for technical instability, which increases the risk of suboptimal joint loading and acute musculoskeletal strain under high centrifugal forces. Thus, IMU-based monitoring facilitates a biofeedback-driven approach to training load management. Future Perspectives: In conclusion, the wrist-worn sensor appears to be a valid and practical tool for analyzing movement execution in elite junior athletes. Future research should expand this scope to a longitudinal outlook, investigating how alternating implement weights (overweight/underweight) impacts the rhythmic structure and long-term technical stability. Such data will be crucial for refining individualized training protocols and ensuring the long-term orthopedic health of developing elite throwers.
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