Fast gait spatiotemporal parameters in adults and association with muscle strength – The Yishun study

BackgroundThere is limited data on fast gait speed and spatial-temporal parameters across age groups among Asian adults, and the associations between upper and lower extremity muscle strength with gait.Research questionWhat values characterise fast gait spatiotemporal parameters across the age groups of an Asian population? Are hand grip strength (HGS) and knee extension strength (KES) associated with fast gait speed and spatiotemporal parameters?MethodsHealthy community-living adults between 21–90 years (n = 487) were recruited. Fast gait was assessed using a 6 m instrumented walkway, and spatiotemporal parameters including variability for fast gait speed, stride length, stride width, stride time, stance time, swing time, single support time and double support time were analysed. Maximum HGS and KES were also assessed. Linear regression modelling was used to explore the association of HGS and KES with fast gait speed, spatiotemporal parameters and their variability.ResultsAge reduced fast gait speed and stride length, but increased stride width, stance time, stride time and double support time. Age increased all investigated gait variabilities except stride width variability. Gender differences were observed for all gait features except for fast gait speed and double support time. Both HGS and KES were positively associated with fast gait speed in both young and old adults. KES was positively associated with spatiotemporal variations in stride length, stride time, stance time and double support time. HGS was also significantly associated with two additional temporal parameters – positively with swing time and negatively with double support time variability.SignificanceThe data from this study contributes to reference values database for the use of fast gait assessments in adults.     

Normative database of spatiotemporal gait parameters using inertial sensors in typically developing children and young adults

BackgroundInertial sensors are increasingly useful to clinicians and researchers to detect gait deficits. Reference values are necessary for comparison to children with gait abnormalities.ObjectiveTo present a normative database of spatiotemporal gait and turning parameters in 164 typically developing children and young adults ages 5−30 utilizing the APDM Mobility Lab® system.MethodsParticipants completed the i-WALK test at both self-selected (SS) and fast as possible (FAP) walking speeds. Spatiotemporal gait and turning parameters included stride length, stride length variability, gait speed, cadence, stance, swing, and double support times, and foot strike, toe-off, and toe-out angles, turn duration, peak turn velocity and number of steps to turn.ResultsAbsolute stride length and gait speed increased with age. Normalized gait speed, absolute and normalized cadence, and stride length variability decreased with age. Normalized stride length and all parameters of gait cycle phase and foot position remained unaffected by age except for greater FSA in children 7−8. Foot position parameters in children 5−6 were excluded due to aberrant values and high standard deviations. Turns were faster in children ages 5–13 and 7–13 in the SS and FAP conditions, respectively. There were no differences in number of steps to turn. Similar trends were observed in the FAP condition except: normalized gait speed did not demonstrate a relationship with age and children ages 5–8 demonstrated increased stance and double support times and decreased swing time compared to children 11−13 and young adults (ages 5−6 only). Females ages 5−6 demonstrated increased stride length variability in the SS condition; males ages 7−8 and 14–30 ha d increased absolute stride length in the FAP condition. Similarities and differences were found between our values and previous literature.SignificanceThis normative database can be used by clinicians and researchers to compare abnormal gait patterns and responses to interventions.     

Characteristics of functional gait among people with and without peripheral neuropathy

It is advantageous from a rehabilitation standpoint to determine physiological factors associated with functional gait. These factors may be fundamentally different in those with peripheral neuropathy (PN) compared to age-matched healthy individuals. The purpose of this investigation was to examine associations between functional gait and measures of leg strength, standing balance, and locomotor kinematics in people with and without PN.MethodsIndividuals with PN and age-matched controls were assessed for functional gait by the 6-min walk and timed up-and-go tests. Leg strength was measured as isokinetic peak torque of the knee extensors. Standing balance was assessed by center-of-pressure sway velocity and area during quiet stance. Locomotor kinematics from treadmill walking were used to compute stride duration variability and local instability (i.e., finite-time Lyapunov exponents), which estimate kinematic divergence caused by small-scale perturbations.ResultsLeg strength and locomotor kinematics – in particular local instability – correlated with functional gait performance in controls. Conversely, reduced functional gait performance in the PN group was primarily mediated by impaired standing balance control.DiscussionLocomotor kinematics predicts functional gait, and the magnitude of variability and local instability should be calculated to fully evaluate locomotor system health. The observation that different factors associated with functional gait between groups speaks to the uniqueness of the PN-related movement disorder. Functional gait-related rehabilitation programs for PN patients should be tailored toward this uniqueness.     

Balance is impaired in symptomatic ankle osteoarthritis: A cross-sectional study

BackgroundAnkle osteoarthritis (OA) is associated with several physical impairments but investigations into balance impairments in this population are limited. Understanding balance impairments in ankle OA may help inform the management of this condition.Research questionDoes balance overall performance differ between individuals with symptomatic radiographic ankle OA, asymptomatic radiographic ankle OA and healthy controls? Are there any differences in mediolateral or anteroposterior balance, or confidence to perform balance tasks between these groups?MethodsNinety-six volunteers (31 symptomatic radiographic ankle OA, 41 asymptomatic radiographic ankle OA and 24 healthy controls) completed six static balance tasks: bilateral stance on a firm surface, bilateral stance on foam, and tandem stance, all performed with eyes open and closed. Centre of pressure (COP) data were collected using force plates. Confidence to perform each balance task was collected using an 11-point numerical rating scale.ResultsCompared to controls, participants with symptomatic radiographic ankle OA had greater COP area when standing on a firm surface, foam and in tandem with eyes closed (all p < 0.05) and greater total COP sway in both firm surface and tandem stance conditions (p < 0.04). Participants with symptomatic ankle OA had greater COP area (p < 0.04) and total COP sway (p = 0.01) than those with asymptomatic ankle OA during tandem stance. Total COP sway and area were similar between asymptomatic ankle OA and control participants. Some differences in mediolateral and anteroposterior balance were identified between groups. Individuals with symptomatic ankle OA had lower confidence to perform the tandem stance eyes closed task compared to controls.SignificanceBalance impairments and decreased balance confidence were identified in those with symptomatic radiographic ankle OA compared to asymptomatic individuals with and without radiographic ankle OA. This suggests that balance deficits in ankle OA may be related to symptoms, rather than radiographic evidence of disease.     

Postural sway in children: A literature review

Background and aimStatic posturography can serve as an easy and fast way to determine whether a child possesses sufficient balance control in different sensory conditions. Therefore, the aim of this review is to map age-related differences in postural sway during childhood in typically developing children, using static posturography and to provide an overview of the available (age-specific) reference values in scientific literature.MethodsThe search strategy was performed in five databases (Pubmed, Web of Science, ScienceDirect, Cochrane Clinical Trials, Medline (Ovid)) November 2nd 2014 and updated twice: March 16th 2015 and July 20th 2015. The following keywords were used: (children OR child) AND (“postural control” OR “postural stability” OR equilibrium OR posture OR “postural balance”[mesh]) AND (“quiet stance” OR standing OR stance OR “quiet stance” OR static) AND (“postural sway” OR posturography OR “body sway” OR stabilography OR “trunk sway” OR “medio-lateral sway” OR “antero-posterior sway”). Relevant studies were identified using predefined selection criteria, applied on title and abstract (phase 1) and on full text (phase 2), supplemented with reference screening after the second phase.ResultsA total of 14 studies met the criteria. This review showed three main findings: 1) during natural bipedal stance with the eyes open, all studies reported a decrease in postural sway with increasing age, with conflicting results on the (non-)linearity of its development, 2) with eyes closed, all children show more sway than with eyes open and 3) only four studies reported numeric sway values that could serve as reference values, mainly focusing on children aged five and older.ConclusionConsiderable disagreement exists on the (non-)linearity of the development of postural sway in children. By choosing arbitrary age categories, it remains unclear between which age groups differences are situated. Future research is necessary to determine for which age groups age-specific reference values are relevant.     

Stance time and step width variability have unique contributing impairments in older persons

Gait variability may have multiple causes. We hypothesized that central nervous system (CNS) impairments would affect motor control and be manifested as increased stance time and step length variability, while sensory impairments would affect balance and be manifested as increased step width variability. Older adults (mean+/-standard deviation (S.D.) age=79.4+/-4.1, n=558) from the Pittsburgh site of the Cardiovascular Health Study participated. The S.D. across steps was the indicator of gait variability, determined for three gait measures, step length, stance time and step width, using a computerized walkway. Impairment measures included CNS function (modified mini-mental state examination, Trails A and B, Digit Symbol Substitution, finger tapping), sensory function (lower extremity (LE) vibration, vision), strength (grip strength, repeated chair stands), mood, and LE pain. Linear regression models were fit for the three gait variability characteristics using impairment measures as independent variables, adjusted for age, race, gender, and height. Analyses were repeated stratified by gait speed. All measures of CNS impairment were directly related to stance time variability (p<0.01), with increased CNS impairment associated with increased stance time variability. CNS impairments were not related to step length or width variability. Both sensory impairments were inversely related to step width (p<0.01) but not step length or stance time variability. CNS impairments affected stance time variability especially in slow walkers while sensory impairments affected step width variability in fast walkers. Specific patterns of gait variability may imply different underlying causes. Types of gait variability should be specified. Interventions may be targeted at specific types of gait variability.     

The cross-sectional relationships between age,standing static balance,and standing dynamic balance reactions in typically developing children

BackgroundStatic balance performance is a common metric for evaluating the development of postural control in children. Less is known about the potentially independent development of dynamic balance performance.Research questionHow does age relate to static (i.e. postural sway) and dynamic (i.e. stepping thresholds) standing balance performance, and what is the relationship between postural sway and stepping thresholds?MethodsTwenty-six typically developing children (12 males, 14 females; 5–12 years of age) were recruited for this cross-sectional study. Static balance performance was quantified as the total path length during a postural sway assessment using a force platform with conditions of eyes open and eyes closed. Dynamic balance performance was quantified using a single-stepping threshold assessment, whereby participants attempted to prevent a step in response to treadmill-induced perturbations in the anterior and posterior directions. Relationships between age and body-size scaled measures of static and dynamic balance performance were assessed using Spearman rank correlations.ResultsThere was a weak correlation between age and postural sway (|r_s| < 0.10, p > 0.68), but a moderate-to-strong correlation between age and single-stepping thresholds (r_s > 0.68, p < 0.001). A weak correlation was found between postural sway and single-stepping thresholds (|r_s| < 0.20, p > 0.39).SignificanceDynamic, but not static standing balance performance, may improve with typical development between the ages of 5 and 12 years. Static and dynamic balance should be considered as unique constructs when assessed in children.     

Reliability and concurrent validity of spatiotemporal stride characteristics measured with an ankle-worn sensor among older individuals

BackgroundWearable inertial sensors have been shown to provide valid mean gait characteristics assessments, however, assessment of variability is less convincingly established.Research questionWhat level of concurrent validity, and session-to-session reliability does an ankle-worn inertial measurement unit (IMU)-based gait assessment with a novel angular velocity-based gait event detection algorithm have among older adults?MethodsTwenty seven (women N = 17) participants volunteered (age 74.4 (SD 4.3) years, body mass 74.5 (12.0) kg, height 165.9 (9.9) cm). Right leg stance, swing, and stride duration and stride length, and stride velocity were concurrently assessed with motion capture and with an IMU from a 3 min self-paced walk up and back a 14 m track repeated twice a week apart. Gait variability was assessed as the SD of all of the registered strides.ResultsSignificant difference was observed between methods for many of the mean stride characteristics and stride variability (all p < 0.05), fair to excellent agreement was observed for mean values of all of the five stride characteristics evaluated (intra-class correlation coefficient [ICC] from 0.43 to 1.00). However, poor agreement was observed for the SD of all of the evaluated stride characteristics (ICC from -0.25 to 0.00). Both methods indicated excellent session to session reliability for all of the five stride characteristics evaluated (ICC from 0.84 to 0.98, CV%_RMS from 1.6% to 3.6%), whereas the variability characteristics exhibited poor to good reliability (ICC from 0.0 to 0.69, CV%_RMS from 18.0% to 34.4%).SignificanceExcellent concurrent validity and reliability was observed for mean spatiotemporal stride characteristics, however, gait variability exhibited poor concurrent validity and reliability. Although IMUs and the presented algorithm could be used to assess mean spatiotemporal stride characteristics among older individuals, either a more reliable gait event detection algorithm or alternative analytical approaches should be used for gait variability.     

Visual deprivation leads to gait adaptations that are age- and context-specific: I. Step-time parameters

In children, visual information is crucial for static postural control, although age-related differences exist in the impact of visual perturbation on postural sway. Since static postural control and locomotion are closely related, we expect age-related differences in the impact of visual deprivation on dynamic stability and gait. It is hypothesised that this is related to the important role of vision in postural control. Postural stability and gait was tested in 20 adults and 40 children (3–11 years old) under two different visual conditions: eyes open (EO) and eyes closed (EC).Significant differences were found between EO and EC for postural sway, dimensionless walking speed, dimensionless stride length and duration of double support. Thus, we can state that visual deprivation affects locomotion both in adults and children. Concerning walking speed a significant interaction effect was observed with age. The difference in walking speed between EO and EC is larger in children than in adults.Furthermore, we found significant correlations between postural sway and walking speed, step frequency and stride length. These observations support the hypothesis that gait adaptations in situations of visual deprivation are related to balance problems.     

Comparison of standing balance between female collegiate dancers and soccer players

STUDY DESIGN: This study was designed as a comparison study of two cohorts. OBJECTIVES: The hypothesis of this study was that soccer players and dancers have different balance abilities and that these differences could be objectively measured using center of pressure measurements. BACKGROUND: Center of pressure (COP) measurements are reproducible and have been validated in the literature for assessing standing balance. The literature does not provide sensitive enough techniques for discriminating between two groups of athletes with excellent standing balance. METHODS AND MEASURES: A Matscan pressure mat (Tekscan, Boston, MA) was used to compare COP change variability between 32 female collegiate soccer players and 32 dancers. COP was used to calculate sway index, center acquisition time, sway path length and sway velocity as measures of standing balance. RESULTS: The dancers had significantly better balance scores (p<0.05) in 5 of 20 balance tests. Results for the remaining 15 balance tests were not significantly different. CONCLUSION: These data show that standing balance characteristics of dancers and soccer players can be objectively measured using COP data. Dancers have certain standing balance abilities that are better than those of soccer players. The COP measurements in this study can be used as a tool in future studies investigating standing balance in different groups of athletes.     

Gait characteristics under single-/dual-task walking conditions in elderly patients with cerebral small vessel disease: Analysis of gait variability,gait asymmetry and bilateral coordination of gait

BackgroundDual-task walking (DTW) is common in daily life and represents an ideal paradigm for elucidating gait irregularity. Under single-task walking (STW) and DTW conditions, the symmetric and bilaterally coordinated human gait pattern found in healthy individuals is absent in individuals with neurological ailments such as Parkinson’s disease, Alzheimer’s disease and post-stroke issues. Cerebral small vessel disease (CSVD) is a neuropathological and radiological issue that has been reported to be associated with cognitive and motor disorders. However, few gait analyses have focused on elderly individuals with CSVD under DTW conditions.Research questionAre parameters of gait analysis helpful in elucidating gait abnormalities in elderly patients with CSVD under DTW conditions?MethodsA total of 46 elderly patients with CSVD (CSVD group) and 22 healthy, age-matched individuals (HE group) were recruited. Gait data were collected from both groups under STW and DTW conditions. Direct parameters and metrics reflecting gait variability, gait asymmetry, and bilateral coordination of gait in the two groups were compared.ResultsUnder STW conditions, elderly individuals with CSVD showed markedly shorter stride length, were slower, and had higher gait asymmetry (GA) and phase coordination index (PCI) than healthy controls after adjusting for age, sex and level of education. Under DTW conditions, there were statistically significant differences between the two groups in stride time, stride length, cadence, stride time variability, GA and PCI after adjusting for age, sex, and level of education.SignificanceReanalysis-generated parameters, such as gait variability, GA, and PCI, are biomarkers for gait dysfunction in elderly patients with CSVD. In this study, elderly individuals with CVSD showed abnormal gait features under both STW and DTW conditions.     

Effect of sensorimotor training on balance measures and proprioception among middle and older age adults with diabetic peripheral neuropathy

PurposeThe aim of the study was to evaluate the effect of sensorimotor training on balance measures, and proprioception, among middle-aged and older adults with diabetic peripheral neuropathy (DPN).MethodsA randomized controlled study with four parallel arms (two intervention groups and two control groups) was conducted at CPRS, Jamia Millia Islamia. Thirty-seven individuals were selected on the basis of inclusion and exclusion criteria. Of these, 16 middle-aged and 21 older adults were randomly allocated to intervention and control groups, respectively. Subjects in the intervention group were administered eight weeks (3days/week) of sensorimotor training, involving 10 different types of exercises, progressed from easy to hard every two weeks, along with diabetes and foot care education; subjects in control group received diabetes and foot care education only. Outcomes measures involved static and dynamic balance measures, centre of pressure (COP) range, COP sway, and proprioception, measured before and after eight weeks.ResultsBaseline measures showed significant age effect for timed up and go test (TUG) (p = 0.002), one leg stance (OLS) in eyes open (EO) and eyes closed (EC) (p ≤ 0.041), COP range in front (p = 0.007), back (p = 0.009) and right direction (p = 0.013), COP sway with visual feedback in front-back direction (p = 0.027), COP sway without visual feedback in left-right direction (p = 0.028), and proprioception in right direction (p = 0.026). After intervention, OLS EO and EC on both legs showed significant time effect (p ≤ 0.003), group effect as well as time×group interaction (p < 0.05), and age effect and time×age interaction (p ≤ 0.04). Functional reach test, TUG, COP range, COP sway, and proprioception were found with significant time effect (p < 0.03), group effect, and time×group interaction (p ≤ 0.035). Age effect and time×age interaction were found to be non-significant for all COP ranges and COP sway.ConclusionSensorimotor training improved static and dynamic balance as well as proprioception measures after eight weeks of exercise intervention. Static balance showed greater improvement in the middle-aged than older aged adults, while dynamic balance and proprioception showed similar results for both.     

Outcome-dependent effects of walking speed and age on quantitative and qualitative gait measures

BackgroundWalking speed predicts many clinical outcomes in old age. However, a comprehensive assessment of how walking speed affects accelerometer based quantitative and qualitative gait measures in younger and older adults is lacking.Research questionWhat is the relationship between walking speed and quantitative and qualitative gait outcomes in younger and older adults?MethodsYounger (n = 27, age: 21.6) and older participants (n = 27, age: 69.5) completed 340 steps on a treadmill at speeds of 0.70 to a maximum of 1.75 m·s^-1. We used generalized additive mixed models to determine the relationship between walking speed and quantitative (stride length, stride time, stride frequency and their variability) and qualitative (stride regularity, stability, smoothness, symmetry, synchronization, predictability) gait measures extracted from trunk accelerations.ResultsThe type of relationship between walking speed and the majority of gait measures (quantitative and qualitative) was characterized as logarithmic, with more prominent speed-effects at speeds below 1.20 m·s⁻¹. Changes in quantitative measures included shorter strides, longer stride times, and a lower stride frequency, with more variability at lower speeds independent of age. For qualitative measures, we found a decrease in gait symmetry, stability and regularity in all directions with decreasing speeds, a decrease in gait predictability (Vertical, V, anterior-posterior, AP) and stronger gait synchronization (AP-mediolateral, ML, AP-V), and direction dependent effects of gait smoothness, which decreased in V direction, but increased in AP and ML directions with decreasing speeds. We found outcome-dependent effects of age on the quantitative and qualitative gait measures, with either no differences between age-groups, age-related differences that existed regardless of speed, and age-related differences in the type of relationship with walking speed.SignificanceThe relationship between walking speed and quantitative and qualitative gait measures, and the effects of age on this relationship, depends on the type of gait measure studied.     

Postural control development from late childhood through young adulthood

BackgroundThe development of stable postural control is characterized by changes in sway variability and periods of rapid reorganization of motor system components.Research questionThe current study examined whether changing biomechanical and perceptual demands influences the postural control behavior during development.MethodThe 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.ResultsThe 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).SignificanceThe 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.     

Hearing loss and increased gait variability among older adults

BackgroundThe influence of age-related hearing loss on slow gait has been suggested; however, whether it is associated with increased gait variability, an important predictor of fall risk, remains unclear.Research questionIs poor auditory acuity associated with increased gait variability, and does this gait change relate to accidental falls among older adults with hearing loss?MethodsWe studied 107 older adults (mean age, 76.5 years; 80.5 % women). Auditory acuity was measured using a pure tone average (PTA) of hearing thresholds for 0.5–4 kHz tones in the better-hearing ear. Hearing loss was defined as a PTA of >25 dB. Gait speed and spatiotemporal variability (i.e., stride length and time variabilities) were assessed using a 5-m electronic walkway. We also assessed the occurrence of multiple falls within the previous year.ResultsFifty-two participants (48.6 %) experienced hearing loss. Multiple regression analysis adjusted for potential covariates showed that poor PTA was associated with slower gait speed and stride length variability, but not stride time variability. Among older adults with hearing loss, fall occurrence was associated with an increased stride length variability and not a slow gait or increased stride time variability.SignificanceThe association between hearing loss and increased gait variability observed in the present study suggests that age-related hearing loss can jeopardize gait control during daily activities. This leads to increased gait variability and increased risk of accidental falls. Our results provide additional information on how age-related hearing loss increases the risk of falls.     

Familiarity with music influences stride amplitude and variability during rhythmically-cued walking in individuals with Parkinson’s disease

BackgroundEntrainment of walking with rhythmic auditory cues (e.g., metronome or music) induces gait improvements in people with Parkinson’s disease (PD). However, evidence regarding acute impacts of music cues on parkinsonian gait is lacking. Findings in healthy adults imply that familiarity with music cues modulates stride amplitude and stride-to-stride variability; yet the role of familiarity with music on parkinsonian gait remains unknown.Research questionTo investigate 1) whether familiar and unfamiliar music cueing differentially influences stride and arm swing amplitude and stride-to-stride variability, 2) how stride and arm swing amplitude and stride-to-stride variability are altered by enhanced familiarity with music by repeated listening and walking during rhythmically-cued walking in persons with PD.MethodsTwenty individuals with idiopathic PD (mean age = 68.9 years, 7 females, H&Y stage 1–3) walked in time with familiar and unfamiliar music cues (Session 1). Participants then repeatedly listened and walked to the same familiar and unfamiliar music cues (Session 2). Spatiotemporal gait parameters in each 2-min trial were recorded with motion capture wearable sensors.ResultsIn Session 1, gait velocity, stride length, arm swing peak velocity and range of motion, and stride-to-stride variability increased with both music cues compared with baseline; stride length, enjoyment and beat salience were greater in familiar than unfamiliar music cues. In Session 2, repeatedly listening and walking to unfamiliar music, but not familiar music, increased gait velocity, stride length, familiarity, enjoyment, and beat salience, and reduced stride-to-stride time variability.SignificanceMusic cues in general induced acute improvements of stride and arm swing amplitude but not stride-to-stride variability, and enhanced familiarity with music improved stride amplitude and variability along with increased enjoyment and reduced cognitive demand in people with PD. Our findings aid in understanding the role of familiarity with music in alleviating gait disturbance and optimizing music-based interventions for PD.     

Dynamic balance is impaired after a match in young elite soccer players

PurposeThe aim of this study is to assess the effect of actual match effort on dynamic balance abilities in young elite soccer players.MethodsSeventeen Under 15 male players who compete at national level participated in the study. Their dynamic balance was assessed by having them jump starting with both feet on the ground in a standing position and land on one foot only. Their vertical time to stabilization (vTTS) and postural sway were calculated before and after 35 min of an unofficial match. Postural sway was assessed on the basis of center-of-pressure (COP) trajectories. Parameters considered were sway area, COP displacements in the antero-posterior (AP) and medio-lateral (ML) directions and COP path length.ResultsAfter the match, a significant increase in vTTS (p = 0.007) COP path length (p = 0.001) and COP displacements in ML (p < 0.001) was observed. Such effects involve both non-dominant (vTTS, path length) and dominant limb (COP displacements).ConclusionsThe physical effort associated with the match induces significant impairments of players' dynamic balance abilities. On the basis of such findings, coaches might consider integrating training sessions with specific balance exercises as well as performing injury-prevention routines even when players are fatigued, to better adapt them to match conditions.     

Spatiotemporal gait deviations in a virtual reality environment

Previous research suggests that postural sway in standing increases in virtual reality (VR) environments. This study was conducted to examine whether gait instability is prevalent when people walk in a VR environment. Ten healthy adults participated in the study. Subjects walked on a treadmill in a VR environment and a non-VR environment at each of three walking speeds: 0.9, 1.1, and 1.3 m/s. In the VR environment, an endless corridor with colored vertical stripes comprising the walls was projected onto a hemispherical screen placed in front of the treadmill. The speed of the moving corridor image was matched to the speed of the treadmill to create the illusion that subjects were walking through the endless corridor. Spatiotemporal data during gait were collected with an instrumented treadmill housing two piezoelectric force platforms. Gait parameters reflective of gait instability (stride length, step width, variability in stride velocity, and variability in step width) were compared between the VR and non-VR environments. Subjects walked in the VR environment with reduced stride lengths (p = 0.001), increased step widths (p = 0.001), and with increased variability in stride velocity (p < 0.001) and step width (p = 0.002). The gait deviations suggest that walking in a VR environment may induce gait instability in healthy subjects.     

Effects of light finger touch on the regularity of center-of-pressure fluctuations during quiet bipedal and single-leg postural tasks

BackgroundThe use of extra sources of sensory information associated with light fingertip touch to enhance postural steadiness has been associated with increased attentional demands, whereas the regularity of center of pressure (COP) fluctuations has been interpreted as a marker of the amount of attention invested in posture control.Research questionThis study addressed whether increased attentional demands associated with postural tasks involving light finger touch might be reflected by measures of COP regularity.MethodsThe experiments involved quiet bipedal stance (n = 8 participants) and single-legged stance (n = 14 participants). Each participant was instructed to stand as quietly as possible on a force plate, either touching an external rigid surface (applied force < 1 N, light touch condition), or not (no touch condition). Postural steadiness was assessed by traditional COP measurements (COP Area, RMS, and velocity), whereas the regularity of postural sway was based on estimates of the sample entropy (SaEn) of the COP time series.ResultsTraditional parameters of postural sway and COP regularity (inversely related to SaEn COP measurements) were reduced during the touch conditions as compared to the no-touch conditions, for both bipedal quiet stance and single-legged stance. Decreased COP regularity with light touch was mainly reflected in the direction of the largest postural sway (i.e. in the sagittal plane for bipedal stance and in the frontal plane for single-legged stance).SignificanceThe present results suggest that actively touching an external surface with the fingertip, besides increasing postural steadiness, generated an externally oriented (presumably cognitive-dependent) focus of attention, so that participants invested less attention on the postural task per se (as suggested by increased SaEn), which might be associated with a more “automatic” control of posture.