Agreement of Clinical Grade and Laboratory Grade Force Plates for Countermovement Jump Metrics in Youth Athletes.

Background: Recent technological advances have led to the development of user-friendly force plate systems that provide clinicians with the ability to analyze movement with precision that was previously only available within a biomechanics laboratory. While this development is promising, there is limited evidence supporting the concurrent validity of the range of variables provided by these devices, making it difficult for clinicians to interpret how values obtained within a clinical environment compare to published research. Purpose: To compare the concurrent validity of specific performance metrics obtained during a countermovement (CMJ) jump between a clinical grade force plate system and a laboratory grade system. Study Design: Laboratory Based Cohort Study. Methods: Sixty youth basketball athletes performed a CMJ jump on a clinical grade and a laboratory grade force plate system. Raw data from each device was utilized to calculate the following measures: jump height, peak ground reaction force (GRF), eccentric rate of force development (RFD), and concentric and eccentric impulse. Wilcoxon signed-rank tests evaluated differences between measures. Spearman correlations and Bland-Altman plots analyzed the relationship and accuracy between devices across all measures. Results: There were no statistically significant differences and good agreement between devices for jump height, peak GRF, and eccentric RFD (p>0.05, percent difference range -3.35% to 6.14%). Other measures of jump performance, including concentric RFD measures, eccentric impulse, and concentric impulse, were moderately to poorly correlated (R-value range 0.296-0.447) and significantly different (p<0.05) between devices. Conclusion: Measurements between the clinical grade and laboratory grade force plates for jump height, peak ground reaction force, and eccentric RFD were comparable and showed good agreement. Clinicians should exercise caution when comparing data related to impulse measures between these systems. Level of Evidence: 3.