Measurement Agreement Between Samozino's Method and Force Plate Force-Velocity Profiles During Barbell and Hexbar Countermovement Jumps

Measurement agreement between Samozino's method and force plate force-velocity profiles during barbell and hexbar countermovement jumps. J Strength Cond Res 36(12): 3290-3300, 2022 - This study aimed to measure agreement between using Samozino's method and force plates to determine mean force, velocity, and power during unloaded and loaded barbell and hexbar countermovement jumps. Twenty-one subjects performed countermovement jumps against incremental loads using both loading conditions. Ground reaction force was recorded using a dual-force plate system (1,000 Hz) and used as the criterion method to compare with Samozino's method. Reliability and validity was determined by intraclass correlation coefficients (ICCs), coefficient of variation (CV), limits of agreement plots, and least products regression analysis. Samozino's method provided acceptable levels of reliability for mean force, velocity, and power (ICC > 0.90, CV% < 5.5) across both loading conditions. Limits of agreement analysis showed the mean bias was 2.7, 15.4, and 7.2% during barbell countermovement jumps and 1.8, 12.4, and 5.0% during hexbar countermovement jumps for mean force, velocity, and power, respectively. Based on these findings, Samozino's method not only is reliable when measuring mean force, velocity, and power during loaded and unloaded barbell and hexbar countermovement jumps but also identifies limitations regarding concurrent validity compared with the gold standard. Across loading conditions, Samozino's method overestimated mean force (0.5-4.5%) and underestimated mean velocity (11.81-16.78%) and mean power (2.26-7.85%) compared with the force plates. Because of fixed and proportional bias between criterion and predictor, the results do not support the use of Samozino's method to measure mean force, velocity, and power. Therefore, it is not recommended for practitioners to use Samozino's method to estimate mechanical variables during loaded and unloaded countermovement jump actions using a barbell and hexbar.