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Adults (N = 54, 80.78 ± 6.08 years) who reported falling during the previous 12 months participated in a 12-week wobble board training program with internal focus or external focus (EF) instructions. Verbal manipulation checks were performed after training sessions as a self-report of the attentional foci used. The percentage of sessions in which participants reported using an EF (EF[subscript SR]) was subsequently calculated. Mean velocity and mean power frequency in the anterior-posterior (MVELO[subscript AP] and MPF[subscript AP]) and medial-lateral (MVELO[subscript ML] and MPF[subscript ML]) direction were assessed during a 35-s wobble board task at Weeks 0, 6, 12, 13, 16, and 20, with the latter three as retention tests. Piecewise linear growth models estimated treatment effects on individual growth trajectories of MVELO[subscript AP] and [subscript ML] and MPF[subscript AP] and [subscript ML] during intervention and retention periods. Regardless of condition, MVELOML significantly decreased ([pi] = -0.0019, p = 0.005) and MPF[subscript ML] increased ([pi] = 0.025, p < 0.02) during the intervention period. In analyses including interaction terms, participants in the EF group who reported greater EF[subscript SR] had superior progression of MPF[subscript AP] during the intervention ([pi] = 0.0013, p = 0.025). Verbal manipulation checks suggest a preference for and advantage of EF for facilitating postural control performance and automaticity.

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]

Gait asymmetries are a common problem in clinical populations, such as those with a history of stroke or Parkinson's disease. The use of a split-belt treadmill is one way to enhance gait symmetry but relies on specialty (and typically expensive) equipment. Alternatively, visual cues have been shown as a method to alter gait mechanics, but their utility in altering gait symmetry has been relatively understudied. Before deploying this method to clinical populations, a proof-of-concept study is needed to explore using visual cues to alter gait symmetry in healthy adults. Therefore, the purpose of this study was to examine the extent to which healthy adults could synchronize to an asymmetric visual cue with a small or large gait asymmetry using wearable sensors to measure gait asymmetries. Seventy-two healthy adults (ages: 23.89 ± 6.08 years) walked on the treadmill for two conditions: with and without the visual cue. Each walking condition lasted 10 min at the participant's preferred walking speed. Inertial sensors were used to measure gait asymmetries. Some participants did not respond to the visual cue, and groups were separated into responders and non-responders. Participants in the small and large asymmetry-responder groups exhibited statistically significant increased asymmetries in single limb support % (p < 0.01) and step duration (s) (p < 0.05, p < 0.01, respectively). Only the large asymmetry-responder group showed statistically significant (p < 0.01) increased asymmetries in stride length. Overall, asymmetrical walking visual cues can alter gait asymmetries, and inertial sensors were sensitive enough to detect small changes in gait asymmetries. [ABSTRACT FROM AUTHOR]

There has been a substantial increase in the number of health-related smartphone applications (apps) available to consumers in recent years. How does one decide which apps have scientific evidence backing their claims and which are "fake news"? In this Commentary, we explore the hierarchy of scientific claims and review recent literature to identify areas of Health Education and health promotion in which evidence-based smartphone apps are available. Further, we present a theory-based framework to help app developers optimize their potential to enhance human health.

Context: Previous work suggests that balance behavior is a sex-dependent, complex process that can be characterized by linear and nonlinear metrics. Although a certain degree of center of pressure variability may be expected based on sexual dimorphism, there is evidence to suggest that these effects are obscured by potential interactions between sex and anthropometric factors. To date, no study has accounted for such interactive effects using both linear and nonlinear measures. Objective: This investigation sought to analyze interactive models featuring sex, height, and weight as predictors of linear and nonlinear aspects of postural control. Design: Cross-sectional study. Setting: Controlled laboratory. Participants: A total of 26 males (23.80 [3.44] y, 177.87 [6.44] cm, 81.70 [10.80] kg) and 28 females (21.14 [2.03] y, 169.57 [8.80] cm, 64.48 [8.86] kg) were sampled from a healthy university population. MainOutcomeMeasures: Linear (range [RNG], velocity [VEL], and SD) and nonlinear (detrended fluctuation analysis scaling exponent, multivariate multiscale sample entropy [MMSECI]) summary metrics of center of pressure time series. Procedure: Participants stood on a force plate for 20 seconds in 3 conditions: double (D), single (S), and tandem (T) stance. Data for each stance condition were analyzed using regression models with interaction terms for sex × height and sex × weight. In D, weight had a positive, significant main effect on VELy, MMSECId, and MMSECIv. In men, height was observed to have a positive effect on SDy (S), RNGy (S), and RNGx (T) and a negative effect on MMSECIv (T). In women, weight was observed to have a positive effect on SDy and VELx (both T). Conclusions: Our findings suggest that men and women differ with respect to certain linear and nonlinear aspects of balance behavior, and that these differences may reflect sex-specific behavioral patterns in addition to effects related to sexual dimorphism. [ABSTRACT FROM AUTHOR]

Falls in older adults are a public health challenge due to their influence on well-being and health-care costs. One way to address this challenge is to discover new methods to enhance postural control in older adults so they are better prepared to maintain an upright stance. Older and younger adults (N = 32) performed a static balance task on a force plate with no instructions, internal focus instructions, or external focus instructions. Center of pressure displacement time series were analyzed using sample entropy and standard deviation. Only the external focus condition significantly increased postural control entropy, which was observed across both age groups. This study showed that an external focus of attention can be used to increase postural control entropy within a single session of testing. [ABSTRACT FROM AUTHOR]

Transitioning between different sensory environments is known to affect sensorimotor function and postural control. Water immersion presents a novel environmental stimulus common to many professional and recreational pursuits, but is not well-studied with regard to its sensorimotor effects upon transitioning back to land. The authors investigated the effects of long-duration water immersion on terrestrial postural control outcomes in veteran divers. Eleven healthy men completed a 6-hour thermoneutral pool dive (4.57 m) breathing diver air. Center of pressure was observed before and 15 minutes after the dive under 4 conditions: (1) eyes open/stable surface (Open-Stable); (2) eyes open/foam surface (Open-Foam); (3) eyes closed/stable surface (Closed-Stable); and (4) eyes closed/foam surface (Closed-Foam). Postdive decreases in postural sway were observed in all testing conditions except for Open-Stable. The specific pattern of center of pressure changes in the postdive window is consistent with (1) a stiffening/overregulation of the ankle strategy during Open-Foam, Closed-Stable, and Closed-Foam or (2) acute upweighting of vestibular input along with downweighting of somatosensory, proprioceptive, and visual inputs. Thus, our findings suggest that postimmersion decreases in postural sway may have been driven by changes in weighting of sensory inputs and associated changes in balance strategy following adaptation to the aquatic environment. [ABSTRACT FROM AUTHOR]

Military service members are frequently subjected to subconcussive blast events during training and deployment. Emerging evidence suggests blast exposures of these magnitudes may have long-term consequences for dimensions of cognitive function. Less is known about cognitive sequelae acutely following deployment-related subconcussive blast events. The current study addressed this knowledge gap by assessing the extent to which subconcussive blast exposure affected performance on the Automated Neuropsychological Assessment Metrics 4 TBI-MIL (ANAM). Baseline-referenced and normative comparisons of archival ANAM data were analyzed for a cohort of personnel who were exposed to blast (blast group; n = 27) and personnel who were not exposed to blast (no-blast group; n = 36) that were otherwise asymptomatic for a concussion. The blast group exhibited statistically significant lower scores compared to the no-blast group (between-subjects), baseline assessments (within-subjects), and an age-matched normative population. Normative comparisons revealed that the scores for the reaction time subtests (i.e., procedural and both simple reaction time tasks) were outside the range of normal functioning (1 SD) and reliable change indices revealed clinically meaningful change only for simple reaction time. The results highlight covert effects of subconcussive blast exposure that may warrant further monitoring in the immediate aftermath of a blast event. [ABSTRACT FROM AUTHOR]

Much has been learned about the characteristics of gait in overground and treadmill walking. However, there are many contexts in which overground or treadmill walking might not be possible, such as in home-based physical therapy. In those cases, a surrogate task to index gait behavior would be a valuable tool. Thus, the purpose of this study was to evaluate the stride behavior characteristics of stationary stepping compared with treadmill walking. Healthy young adults (N = 10) preformed two 15-minute tasks: (1) treadmill walking and (2) stationary stepping. Several stride behavior characteristics were recorded, including the number of strides taken, minimum and maximum knee angle, stride interval mean, stride interval standard deviation, and detrended fluctuation analysis (DFA) alpha of the stride interval time series. The results showed that stride behavior was similar between tasks when examined at the group level. However, when individual level analyses were used to examine the reliability of each metric between tasks, poor reliability was observed in most metrics, indicating that stationary stepping may not be an appropriate surrogate task for overground or treadmill walking. These results are discussed in the context of a gait dynamics framework, with attention to task constraints that may have influenced the findings. [ABSTRACT FROM AUTHOR]

Heart rate variability (HRV) is a noninvasive marker of cardiac autonomic function that has been extensively studied in a variety of populations. However, HRV analyses require stationarity--thus, limiting the conditions in which these data can be analyzed in physiologic and health research (e.g. postexercise). To provide evidence and clarity on how non-stationarity affects popular indices of variability and complexity. Simulations within physiologic (restricted to values similar to exercise and recovery RR-intervals) and non-physiologic parameters, with homoscedastic and heteroscedastic variances, across four sample lengths (200, 400, 800, and 2000), and four trends (stationary, positivelinear, quadratic, and cubic) were detrended using 1-3 order polynomials and sequential differencing. Measures of variability [standard deviation of normal intervals (SDNN) and root mean square of successive differences (rMSSD)] as well as complexity [sample entropy (SampEn)] were calculated on each of the raw and detrended time-series. Differential effects of trend, length, and fit were observed between physiologic and non-physiologic parameters. rMSSD was robust against trends within physiologic parameters while both SDNN and SampEn were positively and negatively biased by trend, respectively. Within nonphysiologic parameters, the SDNN, rMSSD, and SampEn of the raw time-series were all biased, highlighting the effect of the scale between these two sets of parameters. However, indices of variability and complexity on the original (trended) times-series were furthest from those of the stationary time-series, with indices coming closer to the known values as fit become more optimal. Detrending with polynomial functions provide reliable and accurate methods of assessing the variability and complexity of non-stationary time-series--such as those immediately following exercise. [ABSTRACT FROM AUTHOR]