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Context: Movement screening has become increasingly popular among tactical professionals. This popularity has motivated the design of interventions that cater to improving outcomes on the screens themselves, which are often scored in reference to an objective norm. In contrast to the assumptions underlying this approach, dynamical systems theory suggests that movements arise as a function of continuously evolving constraints and that optimal movement strategies may not exist. To date, few data address behavioral complexity in the fundamental movement tasks commonly used in clinical screenings. Objective: To provide evidence of complex variability during movement screens and test the role of modifiable--that is, trainable--constraints in mediating loss of complexity during experimental-task manipulations. Design: Crossover study. Setting: Research laboratory. Patients or Other Participants: Twenty-five male (age = 23.96 ± 3.74 years, height = 178.82 ± 7.51 cm, mass = 79.66 ± 12.66 kg) and 25 female (age = 22.00 ± 2.02 years, height = 165.40 ± 10.24 cm, mass = 63.98 ± 11.07 kg) recreationally active adults. Intervention(s): Participants performed tests of balance, range of motion, and strength. Additionally, they performed cyclical movement tasks under a control (C) condition and while wearing an 18.10-kg weight vest (W). Main Outcome Measure(s): Ground reaction forces were sampled at 1000 Hz and used to calculate center of pressure during cyclical movement tests. Multivariate multiscale entropy (MMSE) for the center-of-pressure signal was then calculated. Condition effects (C versus W) were analyzed using paired t tests, and penalized varying-coefficients regression was used to identify models predicting entropy outcomes from balance, range of motion, and strength. Results: The MMSE decreased during the W condition (MMSEC > MMSEW; t49 range = 3.17-5.21; all Pvalues < .01). Conclusions: Moderate evidence supported an association between modifiable constraints and behavioral complexity, but a role in mediating load-related loss of complexity was not demonstrated. [ABSTRACT FROM AUTHOR]

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 = 23.96 ± 3.74 years, height = 178.82 ± 7.51 cm, mass = 79.66 ± 12.66 kg) and 25 female (age = 22.00 ± 2.02 years, height = 165.40 ± 10.24 cm, mass = 63.98 ± 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 varyingcoefficients 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, R² values = 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. [ABSTRACT FROM AUTHOR]

Background: Military organizations use movement quality screening for prediction of injury risk and performance potential. Currently, evidence of an association between movement quality and performance is limited. Recent work has demonstrated that external loading strengthens the relationship between movement screens and performance outcomes. Such loading may therefore steer us toward robust implementations of movement quality screens while maintaining their appeal as cost effective, field-expedient tools. Purpose: The purpose of the current study was to quantify the effect of external load-bearing on the relationship between clinically rated movement quality and tactical performance outcomes while addressing the noted limitations. Study Design: Crossover Trial. Methods: Fifty young adults (25 male, 25 female, 22.98±3.09 years, 171.95±11.46 cm, 71.77±14.03 kg) completed the Functional Movement Screen™ with (FMS™W) and without (FMS™C) a weight vest in randomized order. Following FMS™ testing, criterion measures of tactical performance were administered, including agility T-Tests, sprints, a 400- meter run, the Mobility for Battle (MOB) course, and a simulated casualty rescue. For each performance outcome, regression models were selected via group lasso with smoothed FMS™ item scores as candidate predictor variables. Results: For all outcomes, proportion of variance accounted for was greater in FMS™W (R² = 0.22 [T-Test], 0.29 [Sprint], 0.17 [400 meter], 0.29 [MOB], and 0.11 [casualty rescue]) than in FMS™C (R² = 0.00 [T-Tsst], 0.11 [Sprint], 0.00 [400 meter], 0.19 [MOB], and 0.00 [casualty rescue]). From the FMS™W condition, beneficial performance effects (p<0.05) were observed for Deep Squat (sprint, casualty rescue), Hurdle Step (T-Agility, 400 meter run), Inline Lunge (sprint, MOB), and Trunk Stability Push Up (all models). Similar effects for FMS™C item scores were limited to Trunk Stability Push Up (p<0.05, all models). Conclusions: The present study extends evidence supporting the validity of load-enhanced movement quality screening as a predictor of tactical performance ability. Future designs should seek to identify mechanisms explaining this effect. Level of Evidence: 3 [ABSTRACT FROM AUTHOR]

Fractal patterns characterize healthy biological systems and are considered to reflect the ability of the system to adapt to varying environmental conditions. Previous research has shown that fractal patterns in gait are altered following natural aging or disease, and this has potential negative consequences for gait adaptability that can lead to increased risk of injury. However, the flexibility of a healthy neurological system to exhibit different fractal patterns in gait has yet to be explored, and this is a necessary step toward understanding human locomotor control. Fifteen participants walked for 15 min on a treadmill, either in the absence of a visual stimulus or while they attempted to couple the timing of their gait with a visual metronome that exhibited a persistent fractal pattern (contained long-range correlations) or a random pattern (contained no long-range correlations). The stride-to-stride intervals of the participants were recorded via analog foot pressure switches and submitted to detrended fluctuation analysis (DFA) to determine if the fractal patterns during the visual metronome conditions differed from the baseline (no metronome) condition. DFA α in the baseline condition was 0.77 ± 0.09. The fractal patterns in the stride-to-stride intervals were significantly altered when walking to the fractal metronome (DFA α = 0.87 ± 0.06) and to the random metronome (DFA α = 0.61 ± 0.10) (both p < .05 when compared to the baseline condition), indicating that a global change in gait dynamics was observed. A variety of strategies were identified at the local level with a cross-correlation analysis, indicating that local behavior did not account for the consistent global changes. Collectively, the results show that a gait dynamics can be shifted in a prescribed manner using a visual stimulus and the shift appears to be a global phenomenon. [ABSTRACT FROM AUTHOR]

Focus of attention during dual-tasks and practice schedules are important components of motor skill performance and learning; often studied in isolation. The current study required participants to complete a simple key-pressing task under a blocked or random practice schedule. To manipulate attention, participants reported their finger position (i.e., skill-focused attention) or the pitch of an auditory tone (i.e., extraneous attention) while performing two variations of a dual-task key-pressing task. Analyses were conducted at baseline, 10 min and 24h after acquisition. The results revealed that participants in a blocked schedule, extraneous focus condition had significantly faster movement times during retention compared to a blocked schedule, skill focus condition. Furthermore, greatest improvements from baseline to immediate and delayed retention were evident for an extraneous attention compared to the skill-focused attention, regardless of practice schedule. A discussion of the unique benefits an extraneous focus of attention may have on the learning process during dual-task conditions is presented. [ABSTRACT FROM AUTHOR]