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Chronic ankle instability (CAI) is associated with a less flexible and adaptable sensorimotor system. Thus, individuals with CAI may present an inadequate sensory reweighting system, inhibiting their ability to place more emphasis (upweight) on reliable sensory feedback to control posture. However, how individuals with CAI reweight sensory feedback to maintain postural control in bilateral and unilateral stances has not been established. To examine (1) group differences in how the sensory reweighting system changes to control posture in a simple double-limb stance and a more complex single-limb stance (uninjured limb and injured limb) under increased environmental constraints manipulating somatosensory and visual information for individuals with and without CAI and (2) the effect of environmental and task constraints on postural control. Case-control study. Laboratory. A total of 21 individuals with CAI (age = 26.4 ± 5.7 years, height = 171.2 ± 9.8 cm, mass = 76.6 ± 15.17 kg) and 21 individuals without CAI (control group; age = 25.8 ± 5.7 years, height = 169.5 ± 9.5 cm, mass = 72.4 ± 15.0 kg) participated. We examined the equilibrium scores based on the first 10 seconds of trials in which participants completed 6 environmental conditions of the Sensory Organization Test during 3 tasks (double-limb and single-limb [uninjured and injured] stances). Sensory reweighting ratios for sensory systems (somatosensory, vision, and vestibular) were computed from paired equilibrium scores based on the first 10 seconds of the trials. We observed 3-factor interactions between groups, sensory systems, and tasks (F4,160 = 3.754, P =.006) and for group, task, and environment (F10,400 = 2.455, P =.007). The CAI group did not downweight vestibular feedback compared with the control group while maintaining posture on the injured limb (P =.03). The CAI group demonstrated better postural stability than the control group while standing with absent vision (ie, eyes closed), fixed surroundings, and a moving platform on the injured limb (P =.03). The CAI group relied on vestibular feedback while maintaining better postural stability than the control group in injured-limb stance. Group differences in postural control depended on both environmental (absent vision and moving platform) and task (injured limb) constraints. [ABSTRACT FROM AUTHOR]

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]

Context: Greater knee-joint laxity may lead to a higher risk of knee injury, yet it is unknown whether results of self-reported outcome measures are associated with distinct knee-laxity profiles. Objective: To identify the extent to which multiplanar knee laxity is associated with patient-reported outcomes of knee function in healthy individuals during activities of daily living and sport. Design: Descriptive laboratory study. Setting: University research laboratory. Patients or Other Participants: Forty healthy individuals (20 men, 20 women; age = 18-31 years). Main Outcome Measure(s): All participants were given the Knee Outcome Survey Activities of Daily Living Scale (KOSADL) and Sports Activities Scale (KOS-SAS) and subsequently measured for knee laxity in the sagittal, frontal, and transverse planes. Separate backward stepwise regression analyses were performed to determine the extent to which multiplanar kneelaxity values predicted KOS-ADL and KOS-SAS scores within each sex. Results: Women had higher magnitudes of anterior, posterior (POSTLAX), varus (VARLAX), valgus (VALLAX), and internal-rotation laxity than men and trended toward greater external rotation (ERLAX) laxity. Greater POSTLAX, less VALLAX, and greater VARLAX was associated with lower KOS-ADL scores (KOS-ADL = -4.8 [POSTLAX], + 3.3 [VALLAX] - 2.2 [VARLAX] + 100.4, R² = 0.74, P < .001) and greater POSTLAX and less VALLAX was associated with lower KOS-SAS scores (KOS-SAS = -8.2 [POSTLAX],+3.6 [VALLAX]+96.4, R²=0.67, P < .001) in women. In men, greater POSTLAX and less ERLAX was associated with lower KOS-SAS scores (KOS-ADL = -4.7 [POSTLAX], + 0.9 [ERLAX] + 96.4, R² = 0.49, P < .001). Conclusions: The combination of POSTLAX with less relative VALLAX (women) or less relative ERLAX (men) was a strong predictor of KOS scores, suggesting that a self-reported outcome measure may be beneficial as part of a preparticipation screening battery to identify those with perceived functional deficits associated with their knee laxity. [ABSTRACT FROM AUTHOR]