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We examined sagittal-plane thigh angular kinematics in individuals with and without recurrent ankle sprains using a clinical smartphone app called AccWalker. Sagittal-plane ankle kinematics were also compared to ascertain that altered ankle dorsiflexion, which is typically displayed with chronic ankle instability, is also present in individuals with recurrent ankle sprains. Participants with (n = 22) and without (n = 22) recurrent ankle sprains were evaluated on average sagittal-plane ankle kinematics during walking and average sagittal-plane thigh angular kinematics during stepping-in-place with AccWalker. Significant group-by-limb interactions were found for sagittal-plane ankle kinematics (F (1,42) = 63.786, P <.010) during walking and sagittal-plane average thigh angular range-of-motion (F (1,42) = 6.166, P =.017) with AccWalker. Individuals with recurrent ankle sprains displayed more ankle dorsiflexion in affected (P <.001) and unaffected (P =.001) limbs during walking than healthy controls and exhibited more ankle dorsiflexion in their affected-limb compared to their unaffected-limb (P <.001). The average sagittal-plane thigh angular range-of-motion was lower in the unaffected-limb for recurrent ankle sprains compared to their affected-limb (P =.038) and the assigned unaffected-limb of healthy controls (P =.035). Increased dorsiflexion was present in both limbs of the recurrent ankle sprain group with walking. AccWalker does not assess ankle movement, but uniquely identified thigh motion impairments associated with recurrent ankle sprains in their unaffected-limb, potentially identifying central deficits associated with recurrent ankle sprains. This app has clinical implications for assessing potential pathological movement that can be corrected through rehabilitation. • The Recurrent Ankle Sprains group walked with more dorsiflexion in the affected-limb. • Lower sagittal thigh motion in the limb with ankle sprains was found with stepping-in-place. • The current study has set the groundwork for AcWalker's potential clinical application. [ABSTRACT FROM AUTHOR]

Postural control is commonly assessed by quantifying center of pressure (CoP) variability during quiet stance. CoP data is traditionally filtered prior to analysis. However, some researchers suggest filtering may lead to undesirable consequences. Further, sampling frequency may also affect CoP analysis, as filtering CoP signals of different sampling frequencies may influence variability metrics. This study examined the influence of sampling frequency and filtering on metrics that index the magnitude and structure of variability in CoP displacement and velocity. Healthy adults ( N = 8, 27.4 ± 2.6 years) balanced on their right foot for 60 s on a force plate. CoP data recorded at 100 Hz was then downsampled and/or filtered (2nd order dual-pass 10 Hz low-pass Butterworth) to create six different CoP time series for each participant: (1) original, (2) filtered, (3) downsampled to 50 Hz, (4) downsampled to 25 Hz, (5) downsampled to 50 Hz and filtered, and (6) down-sampled to 25 Hz and filtered. Data were then analyzed using four common variability metrics (standard deviation [SD], root mean square [RMS], detrended fluctuation analysis α [DFA α ], and sample entropy [SampEn]). Data processing techniques did not influence the magnitude of variability (SD and RMS), but did influence the structure of variability (DFA α and SampEn) in CoP displacement. All metrics were influenced by data processing techniques in CoP velocity. Thus, when interpreting changes in CoP variability, one must be careful to identify how much change is driven by the neuromotor system and how much is a function of data processing technique. [ABSTRACT FROM AUTHOR]

The maintenance of upright stance requires the simultaneous control of posture in both the anterior–posterior (AP) and medial–lateral (ML) dimensions. Postural sway is typically measured by quantifying the movement of the center of pressure (CoP) in the AP and ML dimensions independently. Metrics such as path length and 95% ellipse area have been developed to take into account movement in both the AP and ML directions, but these metrics only quantify the magnitude of the CoP movement. The movement of the CoP is technically a vector quantity with both magnitude and direction characteristics. The direction of displacement, or heading, of the CoP may provide further insight into the control of posture. Accordingly, we present a novel variable that describes the rate of change in direction of CoP displacement in two dimensions, the heading change (Δ ϕ ), which is derived from the CoP heading ( ϕ ). We then compared the standard deviation (SD) and the dynamic structure characterized by sample entropy (SampEn) of the heading change time series to previously examined metrics presented in the literature (SD and SampEn of the AP and ML time series, path length, SD and SampEn of the CoP resultant magnitude time series) during a 60 s single-leg stance performed by healthy participants and patients with a ruptured anterior cruciate ligament (ACL) prior to surgical intervention. Patients with an ACL rupture exhibited a different dynamic structure in Δ ϕ compared to healthy controls, t (14) = 2.44, p = 0.029, whereas none of the other metrics differed between groups (all p > 0.05). The novelty and utility of Δ ϕ is that it characterizes directional changes of the CoP, whereas previously documented postural control analyses describe only changes in magnitude. [ABSTRACT FROM AUTHOR]

Background: The development of stable postural control is characterized by changes in sway variability and periods of rapid reorganization of motor system components.Research Question: The current study examined whether changing biomechanical and perceptual demands influences the postural control behavior during development.Method: The center of pressure (COP) was assessed via a cross-sectional design. Data were collected from 48 females in three age groups (late childhood, mid-adolescence, and young adulthood) during four quiet stance conditions: (1) eyes open with feet apart, (2) eyes open with feet together, (3) eyes closed with feet apart, and (4) eyes closed with feet together. Linear measures included total path length of the COP and the mean/standard deviation of the overall COP position and speed. To characterize the sway patterns via nonlinear analyses, the speed and two-dimensional positional time series were submitted to sample entropy and Renyi entropy, respectively.Results: The linear results indicated that the late childhood group displayed longer COP trajectories (p < .001) and faster and more variable COP speed (p's < .001). These results held for both the feet apart and feet together conditions, independent of vision. The nonlinear results indicated that the late childhood group exhibited less regularity, overall, in their COP sway position (i.e., Renyi entropy) compared to the two older groups in the feet apart condition (p's ≤ .041), and to the young adults in the feet together condition, independent of vision (p <  .001). However, the mid-adolescent group demonstrated greater regularity in their COP speed (i.e., sample entropy) when their eyes were closed compared to the other two groups, independent of stance (p's < .05).Significance: The linear results support previous findings, while the nonlinear measures indicate sway characteristics that may provide a window into the development of underlying control processes that regulate quiet standing. [ABSTRACT FROM AUTHOR]

Objective: Examine the acceptability of an evidence-based, contextually tailored, virtual avatar coaching approach for nutrition education among adult-child dyads with low income. Design: Structured observations and semistructured interviews. Setting: Low-income communities in 2 midsized urban areas. Participants: Fifteen African American adult and child (aged 5−10 years old) dyads recruited from community agencies. Phenomenon of Interest: Structured observation during the use of the virtual avatar coaching program and qualitative feedback on program experience after using the program. Analysis: Transcripts were independently coded by 2 trained coders. Content analysis was conducted to determine trends and patterns in responses, and salient quotes were extracted from the manuscripts. Results: The program generated dialogue between the children and adults around preferences and dietary habits. Adults and children described the program as being helpful, informative, motivational, and fun. Adults and children liked that the avatar acknowledged them at a personal level, provided accountability, and was tailored to them and their environment. Children wanted the ability to customize the avatar, more gamification, and avatar demonstration of healthy behaviors. Children felt the program would improve their health behaviors and were interested in using it again. Conclusions and Implications: This study highlights information that can be used to improve avatarbased programs for nutrition education with children and their adult caregivers who have low income. Future work should assess the impact of user customization experience, program impact on dietary behaviors, and resources required to scale and maintain the program with community agencies. [ABSTRACT FROM AUTHOR]

Nonlinear dynamics quantifies gait variability patterns, which can be useful in evaluating functional ability. A commonly used nonlinear technique is detrended fluctuation analysis (DFA). Safety support structures have previously been shown to alter DFA during gait. However, the effect of a nonweight-supporting treadmill harness on DFA during gait has yet to be determined. The purpose of this study was to determine whether a nonweight-supporting harness influenced the DFA alpha metric (DFA α) of variables typically used to examine gait function. Twenty participants (10 young adults and 10 older adults) were recruited for this study. Each participant completed one testing session on a treadmill consisting of three conditions: (1) no harness, (2) harnessed, but not attached to the support frame, and (3) harnessed and attached to the support frame. Participants walked for 15 min at the same self-selected speed for each condition. The gait variables of stride time, stride length, and step width for each condition were analyzed using DFA α to examine gait function. There were no significant interactions between age group and condition for DFA α of each variable. Additionally, there were no main effects for DFA α for age group or condition. These data indicate that a nonweight-supporting harness can be used for safety without impeding the emergence of natural gait dynamics when stride time, stride length, and step width are the primary variables of interest. [ABSTRACT FROM AUTHOR]