Potential mediators of load-related decreases in movement quality in young, healthy adults

Abstract

Context: Predicting and promoting physical performance are important goals within the tactical professional community. Movement screens are frequently used in this capacity but are poor predictors of performance outcomes. It has recently been shown that prediction improved when movement quality was evaluated under load, but the mechanisms underlying this improvement remain unclear. Because balance, range of motion, and strength are mutually relevant to physical performance and movement quality, these attributes may mediate load-related decreases in movement quality and account for the resulting increase in performance prediction. Objective: To quantify the roles of balance, range of motion, and strength in mediating load-related decreases in clinical movement-screen scores. Design: Crossover study. Setting: Research laboratory. Patients or Other Participants: Twenty-five male (age ¼ 23.96 6 3.74 years, height ¼ 178.82 6 7.51 cm, mass ¼ 79.66 6 12.66 kg) and 25 female (age ¼ 22.00 6 2.02 years, height ¼ 165.40 6 10.24 cm, mass ¼ 63.98 6 11.07 kg) recreationally active adults. Intervention(s): Participants completed a clinical movement screen under a control condition and while wearing an 18.10-kg weighted vest as well as tests of balance, range of motion, and strength. Main Outcome Measure(s): Item score differences were assessed using Wilcoxon signed rank tests for matched pairs. Interactions between (1) balance, range of motion, and strength and (2) load condition were modeled using penalized varying-coefficients regression with item scores as the dependent measure. Results: Except for the hurdle step, item scores were lower in the weighted-vest than in the control condition for all tests (P, .05). Except for rotary stability, F statistics were significant for all models (P values, .05, R 2 values ¼ 0.22-0.77). Main effects of balance, range of motion, and strength on Functional Movement Screen scores were observed (P, .05); however, little evidence was found to suggest that these attributes mediated load-related decreases in Functional Movement Screen item scores. Conclusions: Balance, range of motion, and strength affected movement quality but did not mediate the effect of the load treatment.