Self-Selected walking speed increases when individuals are aware of being recorded

BackgroundTypical gait data collections consist of discrete walking trials where participants are aware when data are being recorded. Anecdotally, some investigators have reported that participants often walk differently between trials or before or after data collection compared to when they know they are being recorded. In addition, walking speed, which affects a number of gait variables, is known to be different when individuals complete discrete and continuous walking trials.Research questionThe purpose of this study was to determine whether changes in walking speed occurred as a result of participants being aware, versus unaware that data were being recorded, during both discrete and continuous walking trials.MethodsKinematic data were collected for twenty two individuals walking continuous trials or discrete trials, while they were both aware and unaware of being recorded. Comparisons of walking speeds were made between groups (continuous walking; discrete trials) and awareness of being recorded (aware; unaware) using a two way ANOVA.ResultsThe results indicated that participants walked significantly faster during discrete trials when they were aware that data were being recorded compared to when they were unaware. However, when they walked continuously their walking speed was not affected by their awareness.SignificanceThe results suggest that awareness of data collection, and the type of protocol used during data collection, affect an individual’s walking speed during gait analysis. Therefore, care should be taken when determining gait analysis protocols where variables are sensitive to walking speeds.     

Walking speed as a predictor of community mobility and quality of life after stroke

Background: Community mobility (CM) is considered a part of community reintegration that enhances Quality of Life (QoL). Achieving an appropriate gait speed is essential in attaining an independent outdoor ambulation and satisfactory CM.

Objective: The aim of this study was to identify whether gait speed is a predictor of CM and QoL in patients with stroke following a multimodal rehabilitation program (MRP).

Methods: This was a baseline control trial with 6-months follow-up in an outpatient rehabilitation setting at a university hospital. Twenty-six stroke survivors completed the MRP (24 sessions, 2 days/wk, 1 hr/session). The MRP consisted of aerobic exercise, task-oriented exercises, balance exercises and stretching. Participants also performed an ambulation program at home. Outcome variables were: walking speed (10-m walking test) and QoL (physical and psychosocial domains of Euroquol and Sickness Impact Profile).

Results: At the end of the intervention, comfortable and fast walking speed increased by an average of 0.16 (SD 0.21) (*p < .05) and 0.40 (SD 0.51) (**p < .001) m/s, respectively. After the intervention, all participants achieved independent outdoor ambulation with an increase of 34.14 of walking minutes/day in the community and a decrease of sitting time of 95.45 minutes/day. Regarding QoL there were increased mean scores on the physical and psychosocial dimensions of Euroquol and the Sickness Impact Profile, respectively (**p < .001).

Conclusions: The results suggest that improved walking speed after the MRP is associated with CM and higher scores in QoL. These findings support the need to implement rehabilitation programs to promote increased speed.     

Gait parameters,functional performance and physical activity in active and inactive Juvenile Idiopathic Arthritis

BackgroundChildren with Juvenile Idiopathic Arthritis (JIA) may adopt different movement patterns and participate in physical activity during different states of disease.Research questionWhich specific features of gait and physical function performance differ among children with active or inactive JIA compared to healthy children?MethodsForty-three children participated (14.5 ± 4.2 yrs; 60 % female). 3D-motion analysis methods were coupled with force measures from an instrumented treadmill captured gait mechanical measures. The 30-second Chair Rise Test (repetitions) and stair ascent-descent tests were performed, and the 11-point Wong-Baker face scale assessed pain after each test.ResultsCompared to healthy controls children with active and inactive JIA had worse outcomes (12–21 % slower self-selected and fast walking speeds, 28–34 % slower stair navigation times, 28 % fewer chair rise repetitions in 30 s; all p < .05). Children with active JIA had 8–13 % slower gait speeds, 4 % fewer chair rise repetitions and 14–16 % slower stair navigation times. At faster walking speed, children with active JIA had less hip joint flexion/extension excursion in the sagittal plane during the gait cycle, produced higher leg stiffness, and demonstrated greater interlimb asymmetry in GRF vertical impulse during loading than healthy children (all p < .05). The Pedi-FABS subscore of “Duration: performing athletic activity for as long as you would like without stopping” was rated lower in children with active JIA compared to controls (p < .05).ConclusionGait speed, specific load-bearing functional tasks and leg stiffness features of gait may be informative ‘functional biomarkers’ for assessing JIA burden and tracking treatment efficacy. Additional prospective studies are needed to determine how these features change over time with pain change, and understand impact on quality of life and physical activity participation.     

An uncertainty principle for neural coding: Conjugate representations of position and velocity are mapped onto firing rates and co‐firing rates of neural spike trains

The hippocampal system contains neural populations that encode an animal's position and velocity as it navigates through space. Here, we show that such populations can embed two codes within their spike trains: a firing rate code ( R ) conveyed by within‐cell spike intervals, and a co‐firing rate code () conveyed by between‐cell spike intervals. These two codes behave as conjugates of one another, obeying an analog of the uncertainty principle from physics: information conveyed in R comes at the expense of information in , and vice versa. An exception to this trade‐off occurs when spike trains encode a pair of conjugate variables, such as position and velocity, which do not compete for capacity across R and . To illustrate this, we describe two biologically inspired methods for decoding R and , referred to as sigma and sigma‐chi decoding, respectively. Simulations of head direction and grid cells show that if firing rates are tuned for position (but not velocity), then position is recovered by sigma decoding, whereas velocity is recovered by sigma‐chi decoding. Conversely, simulations of oscillatory interference among theta‐modulated “speed cells” show that if co‐firing rates are tuned for position (but not velocity), then position is recovered by sigma‐chi decoding, whereas velocity is recovered by sigma decoding. Between these two extremes, information about both variables can be distributed across both channels, and partially recovered by both decoders. These results suggest that populations with different spatial and temporal tuning properties—such as speed versus grid cells—might not encode different information, but rather, distribute similar information about position and velocity in different ways across R and . Such conjugate coding of position and velocity may influence how hippocampal populations are interconnected to form functional circuits, and how biological neurons integrate their inputs to decode information from firing rates and spike correlations.     

Influence of the Punch Speed on the Die Wall/Powder Kinematic Friction During Tableting

Influence of the compaction speed on the final tablet properties is an important challenge during the scale-up of a solid dosage form. This strain rate sensitivity is generally attributed to the time dependent deformation behavior of the powder. In this work, we studied the influence of the speed on another important factor during compaction: friction between the tablet/powder and the die. An original experimental methodology was developed to study the evolution of the kinematic friction coefficient between the tablet and the die as a function of the sliding speed of the tablet on the die wall. This methodology made it possible to separate the speed used to make the tablet from the speed used to measure the friction coefficient. Results indicate that the kinematic coefficient of friction increases with the sliding speed following a logarithmic trend. This trend was observed for 4 different pharmaceutical excipients. Moreover, it was proved that the speed dependency is an intrinsic property of the friction between a tablet and a die lubricated using magnesium stearate.     

Motoric cognitive risk syndrome is associated with processing speed and executive function,but not delayed free recall memory: The Korean frailty and aging cohort study (KFACS)

BackgroundThe motoric cognitive risk (MCR) syndrome, characterized by slow gait and cognitive complaints, is a high risk for transitioning to dementia. However, little is known regarding the cognitive profile among individuals with MCR. This study was performed to examine the association of MCR with cognitive functional domains.MethodsWe analyzed 2881 community-dwelling older adults aged 70–84 years (52 % women, mean age: 75.9 years) from the nationwide Korean Frailty and Aging Cohort Study. MCR was defined as the presence of subjective cognitive complaints and slow gait ≥ 1.0 standard deviations below age- and sex-specific means. Cognitive function was assessed using the Korean version of the Consortium to Establish a Registry for Alzheimer’s Disease Assessment Packet and the Frontal Assessment Battery.ResultsA total of 231 participants met MCR criteria (prevalence = 8.02 %; 95 % confidence interval [CI]: 7.07–9.08 %). The prevalence of MCR did not increase with advancing age: 70–74 years, 8.90 %; 75–79 years, 7.06 %; and 80–84 years, 8.04 %; moreover, there were no sex-related differences. After adjusting for various confounders, MCR was associated with decline in global cognitive function, attention, processing speed and executive function (all P < 0.05). In particular, MCR was significantly associated with impairments in processing speed (odds ratio [OR]: 1.89, 95 % CI: 1.16–3.07) and executive function (OR: 1.94, 95 % CI: 1.28–2.93) (P > 0.05).ConclusionsMCR was associated with deficits in global cognition, processing speed, and executive function, but not delayed free recall memory. Individuals with MCR had an increased risk of poor cognitive profile related to brain frontal and prefrontal function.     

The gait profile score characterises walking performance impairments in young stroke survivors

BackgroundThe Gait Profile Score (GPS) provides a composite measure of the quality of joint movement during walking, but the relationship between this measure and metabolic cost, temporal (e.g. walking speed) and spatial (e.g. stride length) parameters in stroke survivors has not been reported.Research Question: The aims of this study were to compare the GPS (paretic, non-paretic, and overall score) of young stroke survivors to the healthy able-bodied control and determine the relationship between the GPS and metabolic cost, temporal (walking speed, stance time asymmetry) and spatial (stride length, stride width, step length asymmetry) parameters in young stroke survivors to understand whether the quality of walking affects walking performance in stroke survivors.MethodsThirty-nine young stroke survivors aged between 18 and 65years and 15 healthy age-matched able-bodied controls were recruited from six hospital sites in Wales, UK. Joint range of motion at the pelvis, hip, knee and ankle, and temporal and spatial parameters were measured during walking on level ground at self-selected speed with calculation of the Gait Variable Score and then the GPS.ResultsGPS for the paretic leg (9.40° (8.60–10.21) p < 0.001), non-paretic leg (11.42° (10.20–12.63) p < 0.001) and overall score (11.18° (10.26–12.09) p < 0.001)) for stroke survivors were significantly higher than the control (4.25° (3.40–5.10), 5.92° (5.11 (6.73)). All parameters with the exception of step length symmetry ratio correlated moderate to highly with the GPS for the paretic, non-paretic, and/or overall score (ρ = <−0.732 (p < 0.001)).SignificanceThe quality of joint movement during walking measured via the GPS is directly related to the speed and efficiency of walking, temporal (stance time symmetry) and spatial (stride length, stride width) parameters in young stroke survivors.