What happens before the first step? A New Approach to Quantifying Gait Initiation Using a Wearable Sensor

BackgroundWalking is a volitional behavior that requires planning and initiation before a step is observed. Following a signal to begin walking, studies of gait initiation in specialized labs have identified three phases that occur during the transition from a standing position via anticipatory postural adjustment (APA) to the first step. Routine instrumented gait testing outside of the laboratory setting focuses on gait execution and does not include gait initiation measures.Research questionCan a single IMU sensor be used for performing gait initiation evaluations outside the lab?MethodsWe recorded walking in young (N = 41) and older (N = 26) adults using an instrumented gait mat while they were wearing a 3D accelerometer on their lower back. Subjects were instructed to begin walking following an auditory signal. An algorithm was developed to extract the following measures from the acceleration signal: gait initiation time, measured from the start of the auditory cue to begin walking and ends at the heel-strike of the swing leg, time-to-APA (reaction time), APA duration and swing time (execution of the first step).ResultsIntraclass correlation coefficient analysis showed good to excellent agreement between gait initiation metrics obtained with the gait mat and the wearable sensor (mean 0.88, range [0.75-0.96]). Except for swing time, all measures were longer in the older subjects, compared to the young adults (p < 0.01).SignificanceExtracting gait initiation measures from routine instrumented gait testing may facilitate studies that can better determine the extent to which impaired gait planning and execution contribute to mobility impairments.     

Lower Quarter Y Balance Test performance: Reference values for healthy youth aged 10 to 17 years

BackgroundThe Lower Quarter Y Balance Test (YBT-LQ) has been widely used to register dynamic balance performance in children and adolescents. However, studies evaluating age- and sex-specific normative data to assess and classify YBT-LQ performance for these age-cohorts are missing.ObjectiveThus, we investigated YBT-LQ performance in healthy youth to provide age- and sex-specific reference values.MethodsSix-hundred and sixty-nine individuals (286 female, 383 male) aged 10–17 years performed the YBT-LQ with their left and right leg. Normalized maximal reach distances (% leg length) for all three directions (i.e., anterior, posterolateral, posteromedial) and the composite score were calculated. Further, age- and sex-specific percentile values (i.e., 10th to 90th percentile) were computed and plotted.ResultsIn boys, the oldest age group (16−17 years) performed better than the younger ones (14−15, 12−13, and 10−11 years). In girls, the youngest age group (10−11 years) often achieved better values compared to the 12−13-year olds. Further, 16−17-year old boys compared to the same aged girls showed better YBT-LQ performance in all but one measure (except left leg reach in posterolateral direction). For both sexes, curvilinear shaped curves were detected for percentile values across the reach directions.ConclusionsThe generated age- and sex-specific reference values for the YBT-LQ can be used by practitioners to evaluate dynamic balance performance in healthy youth aged 10–17 years.     

1 year test–retest reliability of ImPACT in professional ice hockey players

The Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) battery is widely used to assess neurocognitive outcomes following sports-related concussion. The purpose of this study was to examine the 1 year test–retest reliability of ImPACT in a multilingual sample of professional hockey players. A total of 305 professional hockey players were tested 1 year apart using ImPACT. Reliable change confidence intervals were calculated and test–retest reliability was measured using Pearson and Intraclass correlation coefficients. Results indicated that the 1-year test–retest reliabilities for the Visual Motor and Reaction Time Composites ranged from low to high (.52 to .81). In contrast, 1-year test–retest reliabilities for the Verbal and Visual Memory Composites were low (.22 to .58). The 1-year test–retest results provided mixed support for the use of Visual Motor and Reaction Time Composites in select samples; in contrast, the Verbal and Visual Memory Composites may not be sensitive to clinical change.     

Development of a symmetry index using discrete variables

The objective of this study was to introduce and evaluate a new methodology to quantify lower extremity movement symmetry using data from the stance phase in over-ground running. Seventeen subjects completed five heel–toe over-ground running trials per leg over a force platform at 3.33 ± 0.5 m s^?1 with retro-reflective markers on both legs and the pelvis. Thirty kinetic and kinematic variables were collected and 12 were chosen as important variables for calculating symmetry based on low variance of the data and their functional relevance with respect to symmetry. The developed formula uses the integral of the absolute value of the difference between the left and right leg during the stance phase. The results were divided into a sagittal, transverse, and frontal index, as well as a global index for all three planes of motion. This enabled analyses from both general and categorical perspectives, whereby individuals could be identified as symmetrical in one plane and asymmetrical in the other. The new methodology allows for the evaluation of symmetry over the entire stance phase and accounts for time lags between left and right legs. To learn more about symmetry during particular movements, future research should include larger cohorts, use consecutive force platforms, examine the flight phase of running and include subjects that are known to have asymmetrical gait.