Force Plate Jump Assessment In The Military: Identifying Lower Body Capabilities During Countermovement Jumps

In tactical settings, tracking neuromuscular function is valuable for assessing physical performance capabilities and wellness. The countermovement jump (CMJ) is a valuable test of lower body neuromuscular function and has become a widely used performance measure and screening tool for capturing changes in neuromuscular function among tactical populations. PURPOSE: To help practitioners identify force plate metrics for informing training and rehabilitation program design in an active-duty military population. METHODS: Subjects (67 men; 44 women) were asked to perform three unweighted, vertical CMJs with an arm swing every Monday and Friday for 12 weeks on a dual force plates platform. A principal component analysis (PCA) was conducted, to determine the key feature groupings that explain the most variance in the data. Preceding the PCA, a measure of sampling adequacy (MSA) was calculated for each measure and the entirety of the data set using the Kaiser-Meyer-Olkin measure. RESULTS: Principal component (PC) 1 explained 38% of overall variance and included metrics relating to Lower-Body Explosiveness (Concentric Mean Power, Modified Reactive Strength Index, Jump Height, Concentric Peak Velocity, and Eccentric Concentric Mean Force Ratio). PC 2 explained 16% of overall variance and included metrics relating to Countermovement Strategy (Eccentric Deceleration Impulse, Eccentric Braking Impulse, Eccentric Peak Velocity, Countermovement Depth, and Weight). PC 3 explained 12% of overall variance and included metrics relating to Phase Asymmetry (Con-centric Peak Force, Eccentric Deceleration Impulse, Eccentric Peak Force, Eccentric Braking Impulse Asymmetries and Eccentric Mean Power). Overall, women exhibited lower jump performance and greater inter-limb asymmetry during CMJs compared to men. CONCLUSIONS: In conclusion, we suggest monitoring jump height as the main CMJ performance outcome and RSIMOD as an additional indicator of lower body explosiveness, while ignoring potentially redundant metrics such as concentric peak velocity and power for detailed analysis. It is additionally useful to monitor metrics related to countermovement strategies, such as eccentric deceleration/braking impulse, eccentric mean power, and/or countermovement depth.