Stability In Healthy Young Adults Research Articles

Joint behaviour during arm swing changes with gait speed and predicts spatiotemporal variability and dynamic stability in healthy young adults

BackgroundArm swing is linked to gait stability. How this is accomplished is unclear as most investigations artificially manipulate arm swing amplitude and examine average patterns. Biomechanical evaluation of stride-to-stride upper limb behaviour across a range of gait speeds, where the arm swings as preferred, could clarify this link. Research questionHow do stride-to-stride arm swing behaviours change with gait speed and relate to stride-to-stride gait fluctuations? MethodsYoung adults (n = 45, 25 females) completed treadmill gait at preferred, slow (70% of preferred), and fast speed (130% of preferred) while full-body kinematics were acquired with optoelectronic motion capture. Arm swing behaviour was quantified by shoulder, elbow, and wrist joint angle amplitude (range of motion [ROM]) and motor variability (e.g. mean standard deviation [meanSD], local divergence exponent [λmax]). Stride-to-stride gait fluctuation was quantified by spatiotemporal variability (e.g. stride time CV) and dynamic stability (i.e. trunk local dynamic stability [trunk λmax], centre-of-mass smoothness [COM HR]). Repeated measures ANOVAs tested for speed effects and step-wise linear regressions identified arm swing-based predictors of stride-to-stride gait fluctuation. ResultsSpeed decreased spatiotemporal variability and increased trunk λmax and COM HR in the anteroposterior and vertical axes. Adjustments in gait fluctuations occurred with increased upper limb ROM, particularly for elbow flexion, and increased meanSD and λmax of shoulder, elbow, and wrist angles. Models of upper limb measures predicted 49.9–55.5% of spatiotemporal variability and 17.7–46.4% of dynamic stability. For dynamic stability, wrist angle features were the best and most common independent predictors. SignificanceFindings highlight that all upper limb joints, and not solely the shoulder, underlie changes in arm swing amplitude, and that arm swing strategies pair with the trunk and contrast with centre-of-mass and stride strategies. Findings suggest that young adults search for flexible arm swing motor strategies to help optimize stride consistency and gait smoothness.

Effect of sleep deprivation on postural control and dynamic stability in healthy young adults

BackgroundPostural control results from non-linear interactions of multiple neuromusculoskeletal elements and contextual factors. The use of non-linear analyses that consider the temporal evolution of postural adjustments, such as sample entropy, could inform about the changes in postural control due to contextual disturbances such as sleep deprivation. Research questionWhat are the effects of sleep deprivation on static postural control and dynamic stability in healthy young adults? MethodsA quasi-experimental study was performed with 17 healthy young males submitted to 24 h of monitored sleep deprivation. The postural control was measured using sample entropy, area, and total average velocity of the center of pressure on a force platform. The dynamic stability was measured using the Modified Star Excursion Balance Test (SEBTm) composite score for each lower limb. Repeated-measures analysis of variance (baseline × 12 h × 15 h × 18 h × 21 h × 24 h of sleep deprivation) verified the effect of sleep deprivation in the postural control variables. Paired t-test compared the composite score of the SEBTm between baseline and 24 h sleep deprivation. ResultsSample entropy decreased after 18 h of sleep deprivation (p = 0.032) and 24 h of sleep deprivation (p = 0.001). Despite the significant main effect for the area (p = 0.012) and speed (p = 0.007) of the center of pressure, no pairwise differences were identified in the post hoc analysis. The non-dominant lower limb SEBTm composite score was reduced after 24 h of sleep deprivation (p = 0.033), and no difference was observed in the dominant limb. SignificanceSleep deprivation reduced the adaptability in static postural control and dynamic stability of the non-dominant lower limb of healthy young male adults. Sample entropy seemed more sensitive to capture the effects of sleep deprivation than the classical postural control variables.

Effects of Transcranial Direct Current Stimulation over the Primary Motor Cortex in Improving Postural Stability in Healthy Young Adults.

Simple SummaryTranscranial direct current stimulation (tDCS) is used as an adjuvant rehabilitation treatment to improve postural control and lower limb function. This study explored the effects of sham and anodal tDCS over the leg region of M1 on static and dynamic postural stability in healthy young adults. Jump-landing tasks were used to examine dynamic postural stability. Static postural stability was assessed by a single-leg stand on force plates with open eyes. Anodal tDCS had an immediate improving effect on static and dynamic postural stability, and might evolve as an adjuvant rehabilitation treatment to enhance postural deficits in the future.Transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) is of increasing interest to improve motor performance in healthy adults and patients with respective deficits. This study aimed to examine whether tDCS over M1 can improve static and dynamic postural stability in young healthy adults. Seventeen healthy participants (mean age = 25.14 ± 2.50 (standard deviation, SD) years) received sham and anodal tDCS (2 mA) over the vertex at the Cz electrode position for 15 min. Static and dynamic postural stability were evaluated before and immediately after tDCS. The center of pressure (COP) sway area (COPSA) and COP maximum displacements to medio-lateral (COPML) and antero-posterior directions (COPAP) were used to evaluate static postural stability. The anterior–posterior stability index (APSI), medial–lateral stability index (MLSI), vertical stability index (VSI), dynamic postural stability index (DPSI), and time to stabilization (TTS) in forward (FL), 45° anterior lateral (LL), and 45° anterior medial (ML) direction landing, as well as the Y-balance composite score (YBTCS) were used to assess dynamic postural stability. The results showed that the LL-TTS (p = 0.044), non-dominant leg COPSA (p = 0.015), and YBTCS (p < 0.0001) were significantly improved in the real stimulation as compared with the sham stimulation session, and anodal tDCS significantly changed dominant leg COPAP (p = 0.021), FL-APSI (p < 0.0001), FL-TTS (p = 0.008), ML-TTS (p = 0.002), non-dominant leg YBTCS (p < 0.0001), and dominant leg YBTCS (p = 0.014). There were no significant differences in all obtained balance values in the sham stimulation session, except for non-dominant leg YBTCS (p = 0.049). We conclude that anodal tDCS over M1 has an immediate improving effect on static postural stability and dynamic performance in young healthy adults. This makes tDCS a promising adjuvant rehabilitation treatment to enhance postural stability deficits in the future.

Biosignal processing methods to explore the effects of side-dominance on patterns of bi- and unilateral standing stability in healthy young adults.

We examined the effects of side-dominance on the laterality of standing stability using ground reaction force, motion capture (MoCap), and EMG data in healthy young adults. We recruited participants with strong right (n = 15) and left (n = 9) hand and leg dominance (side-dominance). They stood on one or two legs on a pair of synchronized force platforms for 50 s with 60 s rest between three randomized stance trials. In addition to 23 CoP-related variables, we also computed six MoCap variables representing each lower-limb joint motion time series. Moreover, 39 time- and frequency-domain features of EMG data from five muscles in three muscle groups were analyzed. Data from the multitude of biosignals converged and revealed concordant patterns: no differences occurred between left- and right-side dominant participants in kinetic, kinematic, or EMG outcomes during bipedal stance. Regarding single leg stance, larger knee but lower ankle joint kinematic values appeared in left vs right-sided participants during non-dominant stance. Left-vs right-sided participants also had lower medial gastrocnemius EMG activation during non-dominant stance. While right-side dominant participants always produced larger values for kinematic data of ankle joint and medial gastrocnemius EMG activation during non-dominant vs dominant unilateral stance, this pattern was the opposite for left-sided participants, showing larger values when standing on their dominant vs non-dominant leg, i.e., participants had a more stable balance when standing on their right leg. Our results suggest that side-dominance affects biomechanical and neuromuscular control strategies during unilateral standing.

Bruce Protocol Test affects Postural Stability in Healthy Young Adults

Maintaining balance is key in avoiding falls and injury. However, little is known on how increased cardiac activity may affect postural stability. This study investigated if increase in cardiac activity to 85% maximal heart rate (HR) when exercising with standard Bruce Protocol Test (BPT) influence postural sway. Ten young adults were tested for three postural stances, quiet bilateral standing with i) eyes open, ii) eyes closed, and iii) tandem stance, before and after performing the BPT. Resting Heart Rate (HR) and HR variability along with standard postural sway parameters like sway velocity, sway area, turn index, and power frequency in the anterior-posterior (AP) and medial-lateral (ML) directions were evaluated. We found significant increases in postural sway values for turn index values due to HR changes. Thus, balance demanding tasks may be avoided immediately after performing submaximal cardiac activities in order to avoid fall risk and injury.

Physical activity does not impact mediolateral margin of stability across a range of postural-perturbing conditions in young adults

BackgroundThe maintenance of stability during walking is critical for successful locomotion. While targeted balance training can improve stability, it is unclear how simply meeting recommended physical activity guidelines may impact dynamic stability in healthy young adults. Research questionExamining the differences in the mediolateral margin of stability (ML-MOS) and the variability of the ML-MOS in physically active and inactive young adults across a range of stability-challenging walking tasks MethodTwenty-one physically active and twenty inactive young adults completed four experimental walking conditions: (1) Overground Walking, (2) Tandem Walking, (3) Beam Walking, and (4) Stepping-Stones. The ML-MOS and coefficient of variation of the ML-MOS were calculated at each heel strike while participants walked at their preferred walking speed. A two-way mixed-effects ANOVA was conducted to examine the effects of group and condition and their interaction on ML-MOS and ML-MOS variability ResultsNeither the ML-MOS nor the variability of the ML-MOS was significantly different between physically active and physically inactive young adults during any experimental walking conditions. A significant main effect of the experimental walking condition was observed, with the ML-MOS decreasing from overground walking to the tandem and beam walking conditions. The ML-MOS also became more variable in the tandem, beam, and stepping-stones conditions than in overground gait. SignificancePhysical activity status did not influence frontal plane dynamic balance in healthy young adults, even in stability-challenging environments. Conditions that constrain step width, such as tandem and beam walking, are adequate for challenging frontal plane dynamic balance and indicate that trunk kinematics may be adjusted when step width is constrained.

Neuroticism and Extraversion Are Related to Changes in Postural Stability During Anatomically-Related Cognitive Tasks

The relationship between personality and postural stability has received little attention. This study addressed whether neuroticism and extraversion correlate with changes in postural stability while performing cognitive tasks related to brain regions selectively associated with neuroticism and extraversion. Thirty-two adults stood on a foam mat in tandem stance and completed a 2-back task and a weather prediction task (WPT). As predicted, higher neuroticism was related to increased dual task sway during the 2-back task, r = 0.40, p = 0.023, and lower extraversion was related to increased dual task sway during the WPT, r = –0.43, p = 0.013, suggesting that personality is related to postural stability in healthy young adults and that personality could be considered in the prediction and treatment of individuals with balance difficulties.

Effect of Vibration to Fatigued Plantar Flexor Muscles on Postural Stability in Healthy Young Adults

Objective: The effects of muscle fatigue appear to elicit a transient means of postural instability; however the recovery of postural stability after fatiguing exercise has not been extensively studied. This study aimed to determine the immediate effect of local vibration applied to fatigued plantar flexor muscles on postural stability in healthy young adults. Design: True Experimental (pre test - post test design with a control group) Setting: A tertiary care center Participations: 42 healthy young adults Intervention: Fatigue of plantar flexors muscles was induced by repeated dynamic contractions performed to maximum exhaustion. Experimental group (n= 21) received local vibration to fatigued muscles with a hand held vibrator whereas the control group (n = 21) received no intervention (rest). Postural stability was assessed using one leg stance test (OLST) under three different conditions viz. pre-fatigue, post-fatigue and post rest/vibration. Results: Comparative analysis of postural stability within the group was done pre-fatigue, post-fatigue and post rest/vibration condition using Kruskal-Wallis test. A significant decrease from pre-fatigue to post-fatigue condition (p-value < 0.001); and a significant increase from post-fatigue to post rest/vibration condition (p-value < 0.001) was observed in OLST in both - control group and experimental group. However, further comparison of OLST between the groups (using unpaired t test) showed a significant difference in post-fatigue condition versus post rest/vibration condition in favour of the experimental group. Conclusion: Plantar flexors fatigue significantly affects one leg stance time in healthy young adults. Results of this study show that there is an immediate effect of vibration to fatigued muscles on recovery of postural stability in healthy young adults. Recovery of postural stability achieved quickly with such a simple tool may help increase the degree of participation in sports and other similar activities which can cause muscles to fatigue. However, more studies are required to determine this effect using other clinical measures.

The Impact of a High/Low Fulcrum Rotating Balance Platform on Standing Postural Stability in Healthy Young Adults

Back or lower limb pathology may interfere with standing balance. Knowing the impact of high and low fulcrum balance platforms on tracking rotational activities could tailor stability training interventions. Purpose: To determine the influence of a low and high fulcrum balance platform combined with tracking tasks on postural sway while standing. Method: Twenty-five participants performed seven activities at two difficulty levels. The total sway area and medial-lateral (ML) and anterior-posterior (AP) sway direction, velocity, and distance were measured during balance activities with various tracking platforms with a fixed middle fulcrum. Results: MANOVA revealed that postural sway area (m^2/s^4) with a high fulcrum decreased in front to back, rear twist, and front twist (p = 0.05) balance activities. The Mean velocity (m/s) analysis showed that tasks with a high fulcrum elicited slower velocities in the ML direction than those with low fulcrum activity (p

Smartphone Use and Postural Balance in Healthy Young Adults.

Maintaining an upright posture while talking or texting on the phone is a frequent dual-task demand. Using a within-subjects design, the aim of the present study was to assess the impact of a smartphone conversation or message texting on standing plantar pressure and postural balance performance in healthy young adults. Thirty-five subjects (mean age 21.37 ± 1.11 years) were included in this study. Simultaneous foot plantar pressure and stabilometric analysis were performed using the PoData system, under three conditions: no phone (control), talking on a smartphone (talk) and texting and sending a text message via a smartphone (text). Stabilometric parameters (center of pressure (CoP) path length, 90% confidence area and maximum CoP speed) were significantly affected by the use of different smartphone functions (p < 0.0001). The CoP path length and maximum CoP speed were significantly higher under the talk and text conditions when compared to the control. CoP path length, 90% confidence area and maximum CoP speed were significantly increased in talk compared to text and control. Talking on the phone also influenced the weight distribution on the left foot first metatarsal head and heel as compared with message texting. Postural stability in healthy young adults was significantly affected by talking and texting on a smartphone. Talking on the phone proved to be more challenging.

Effects of head motion on postural stability in healthy young adults with chronic motion sensitivity

BackgroundMotion sensitivity, or motion sickness, is common in modern vehicular and visually stimulating environments. Several studies have shown a relationship between motion sensitivity and decreased postural stability. We aimed to evaluate the effects of head motion (horizontal and vertical) on postural stability in healthy adults with and without chronic motion sensitivity (CMS).MethodsSixty healthy adult men and women (age, 20–40 years) with CMS (CMS group, n = 30) and without CMS (non-CMS group, n = 30) participated in the study. Postural stability was assessed during three conditions (static, horizontal head motion, and vertical head motion) using computerized dynamic posturography. Group and condition-related differences in equilibrium scores were evaluated.ResultsThere was no significant group x condition interaction (F2,114 = 0.9, partial ƞ2 = 0.04, p = 0.35). However, significant condition-related differences in equilibrium scores were observed (F2,114 = 26.4, partial ƞ2 = 0.31, p < 0.001). Equilibrium scores were significantly worse in the horizontal and vertical head motion conditions compared to those in the static condition (p < 0.001), but were comparable in vertical and horizontal head motion conditions (p = 0.27).ConclusionsPostural stability was lower in the horizontal and vertical conditions compared to the static condition. However, horizontal and vertical head motions had comparable effects on postural stability in both CMS and non-CMS groups, contrary to our expectations.

SHORT-TERM EFFECTS OF TRUNK KINESIO TAPING ON TRUNK MUSCLE ENDURANCE AND POSTURAL STABILITY IN HEALTHY YOUNG ADULTS: A RANDOMIZED CONTROLLED TRIAL

Purpose: To investigate short-term effects of trunk kinesio tape (KT) application on trunk muscle endurance and postural stability in healthy young adults. Methods: Fifty-eight healthy subjects were randomly assigned into two groups: KT group and placebo KT group. According to the group assignment, KT was applied on both sides of the abdominal and sacrospinal muscles. The trunk muscle endurance with McGill’s trunk muscle endurance tests and postural stability with a force platform (ProKin, Tecnobody, Bergamo, Italy) in static, eyes-open and closed conditions were assesse d. Chi-Square test, Paired Samples t-test, Wilcoxon test, Independent samples t-test, and Mann Whitney U test were used for analysis. Results: D emographic characteristics of the KT and placebo KT groups were similar (p>0.05). After KT application, the trunk muscle endurance scores improved (p<0.05); however, no differences were found in postural stability scores (p>0.05) in the KT group. In the placebo KT group, there was no difference between trunk muscle endurance and postural stability scores (p>0.05) . It was shown that only trunk flexor and trunk left lateral muscle endurance scores increased in the KT group compared to the placebo KT group (p<0.05). Conclusion: In this study, the trunk KT increased trunk muscle endurance; however, it did not improve postural stability in short term. Thus, the trunk KT might be important for improving or supporting trunk control in different populations.

A-12 Neuroticism and Extraversion are Related to Dual Task Postural Stability in Healthy Young Adults

Abstract Objective The relation between personality and postural stability has received little attention. This study addressed whether neuroticism and extraversion are related to changes in postural stability and cognitive functioning during a standing balance task. Method Thirty-two healthy young adults completed a personality measure and two cognitive tasks, a 2-back task and a weather prediction task (WPT), both while seated and in tandem stance on a foam mat. Sway was quantified via normalized path lengths, and correlation coefficients were calculated between neuroticism, extraversion and dual task changes in postural stability and cognitive functioning. Results Consistent with predictions, higher neuroticism was related to increased dual task sway during the 2-back task, r = 0.40, p = 0.023, and lower extraversion was related to increased dual task sway during the WPT, r = -0.43, p = 0.013. Conclusions The results suggest that personality is related to postural stability in healthy young adults and that personality should be considered in the prediction of individuals at risk for falling or in the treatment of individuals with balance difficulties. The task-specific nature of the relation is discussed and may be due to differences in anxiety or underlying brain mechanisms between high neuroticism and low extraversion.

Effect of Trunk Extensor Muscle Fatigue on Postural Stability in Healthy Young Adults

Effect of Trunk Extensor Muscle Fatigue on Postural Stability in Healthy Young Adults

Effect of Trunk Extensor Muscle Fatigue on Postural Stability in Healthy Young Adults

Objective: To determine the effect of trunk extensor muscle fatigue on postural stability in healthy young adults using clinical measures Design: Prospective, experimental, within subject, repeated measures design Setting: Tertiary care hospital and research centre Participants: 70 healthy adults in the age group of 20 to 25 years, volunteer sample Intervention: Fatigue of trunk extensor muscles was induced by repeated dynamic contractions performed to maximum exhaustion. Postural stability was assessed under three different conditions viz. No fatigue, Fatigue and Recovery. Main Outcome Measures: One-leg standing balance test and Functional reach test were used to assess static and dynamic postural stability respectively. Results: Wilcoxon matched-paired signed ranked test was used for comparison of postural stability in No fatigue and Fatigue condition with p-value<0.001. One-leg standing balance test showed a significant decrease from No fatigue (15.16+8.47 seconds) to Fatigue (5.89+5.7 seconds) condition. Functional reach test values showed a significant decrease from No fatigue condition (12.34+2.61 inches) to fatigue condition (12.27+2.6 inches). Mean recovery time was 12.5+3.27 minutes for One-leg standing balance test and 11.93+3.22 minutes for the Functional reach test. Further analysis using Mann Whitney test showed no significant difference (P=0.288) between the recovery time of one-leg standing balance test and functional reach test. Conclusions: Trunk extensor fatigue significantly affects static and dynamic postural stability in healthy young adults. Complete recovery takes 12.5+3.27 minutes for static and 11.93+3.22 minutes for dynamic postural stability. Results of this study stress the importance of intact trunk extensor muscle function on the regulation of static and dynamic postural stability in healthy young adults. However, more studies are required to determine the effect of trunk extensor muscle fatigue using other clinical measures and in individuals with neuromuscular disorders.

Continuous Cognitive Task Promotes Greater Postural Stability thanan Internal or External Focus of Attention in Older Adults

Background/Study Context: Recent evidence suggests that removing attention from postural control using either an external focus or a cognitive task will improve stability in healthy young adults. Due to increases in attentional requirements of upright stance in older adults, it is unclear if similar benefits would be observed in this population. The aim of the present study was to examine the effect of attentional focus and of a continuous cognitive task on postural control in older adults.Methods: Sixteen healthy older adults (71.9 ± 4.32 years) were asked to stand quietly on a force platform with feet together in three different conditions: internal focus (minimizing movement of the hips), external focus (minimizing movement of markers placed on the hips), and cognitive task (silently counting the occurrence of a single digit in a 3-digit number sequence). A one-way analysis of variance with repeated measures on condition was performed for each postural control measure.Results: Hypotheses were partially supported because the cognitive task led to greater stability than both focus conditions, as evidenced by a smaller sway area (p < .01, ηp2 = .41), reduced sway variability (anterior-posterior: p = .001, ηp2 = .37; medial-lateral: p < .0001, ηp2 = .49), and higher mean power frequency in the anterior-posterior direction (p = .01, ηp2 = .78). However, no difference was observed between internal and external focus conditions.Conclusions: A continuous, attention-demanding cognitive task significantly improved stability in older adults compared with an internal or external focus of attention. This suggests that older adults were able to effectively allocate their attention away from postural control, allowing a more automatic type of control to operate. Future studies should investigate a variety of cognitive tasks to determine the degree of postural improvement that can be observed in older adults.

Quantification of the Balance Error Scoring System with Mobile Technology.

The aim of this project was to develop a biomechanically based quantification of the Balance Error Scoring System (BESS) using data derived from the accelerometer and gyroscope of a mobile tablet device. Thirty-two healthy young adults completed the BESS while an iPad was positioned at the sacrum. Data from the iPad were compared to position data gathered from a three-dimensional motion capture system. Peak-to-peak (P2P), normalized path length (NPL), and root mean squared (RMS) were calculated for each system and compared. Additionally, a 95% ellipsoid volume, iBESS volume, was calculated using center of mass (CoM) movements in the anteroposterior (AP), mediolateral (ML), and trunk rotation planes of movement to provide a comprehensive, 3D metric of postural stability. Across all kinematic outcomes, data from the iPad were significantly correlated with the same outcomes derived from the motion capture system (rho range, 0.37-0.94; P < 0.05). The iBESS volume metric was able to detect a difference in postural stability across stance and surface, showing a significant increase in volume in increasingly difficult conditions, whereas traditional error scoring was not as sensitive to these factors. The kinematic data provided by the iPad are of sufficient quality relative to motion capture data to accurately quantify postural stability in healthy young adults. The iBESS volume provides a more sensitive measure of postural stability than error scoring alone, particularly in conditions 1 and 4, which often suffer from floor effects, and condition 5, which can experience ceiling effects. The iBESS metric is ideally suited for clinical and in the field applications in which characterizing postural stability is of interest.

Postural threat during walking: effects on energy cost and accompanying gait changes.

BackgroundBalance control during walking has been shown to involve a metabolic cost in healthy subjects, but it is unclear how this cost changes as a function of postural threat. The aim of the present study was to determine the influence of postural threat on the energy cost of walking, as well as on concomitant changes in spatiotemporal gait parameters, muscle activity and perturbation responses. In addition, we examined if and how these effects are dependent on walking speed.MethodsHealthy subjects walked on a treadmill under four conditions of varying postural threat. Each condition was performed at 7 walking speeds ranging from 60-140% of preferred speed. Postural threat was induced by applying unexpected sideward pulls to the pelvis and varied experimentally by manipulating the width of the path subjects had to walk on.ResultsResults showed that the energy cost of walking increased by 6-13% in the two conditions with the largest postural threat. This increase in metabolic demand was accompanied by adaptations in spatiotemporal gait parameters and increases in muscle activity, which likely served to arm the participants against a potential loss of balance in the face of the postural threat. Perturbation responses exhibited a slower rate of recovery in high threat conditions, probably reflecting a change in strategy to cope with the imposed constraints. The observed changes occurred independent of changes in walking speed, suggesting that walking speed is not a major determinant influencing gait stability in healthy young adults.ConclusionsThe current study shows that in healthy adults, increasing postural threat leads to a decrease in gait economy, independent of walking speed. This could be an important factor in the elevated energy costs of pathological gait.

Symmetry and reproducibility of the components of dynamic stability in young adults at different walking velocities on the treadmill

In the literature, analysis of dynamic gait stability using the extrapolated center of mass concept is often an objective that assumes reproducible and symmetrical data. Here, we examined the validity of this assumption by analyzing subjects walking at different velocities. Eleven healthy young subjects walked on a treadmill at six different velocities (1.0–2.0m·s−1). Dynamic stability at touchdown of the left and right foot (10 gait trials for each body side) was investigated by using the margin of stability, determined as the difference between base of support and extrapolated center of mass. Dynamic stability parameters showed no significant differences (P>0.05) between gait trials, with a root mean square difference in margin of stability of less than 1.62cm. Correlation coefficients between trials were above 0.70 for all parameters, demonstrating that two gait trials are sufficient to obtain reproducible data. In more than 90% of the cases, the absolute symmetry index was below 8% with no relevant functional differences between body sides. We concluded that analyzing two gait trials for one body side is sufficient to determine representative characteristics of the components of dynamic stability in healthy young adults while walking on the treadmill at a wide range of velocities.

Manipulating balance perceptions in healthy young adults

This study was designed to manipulate balance efficacy using verbal persuasion to investigate its influence on perceived and actual balance in healthy young adults ( n = 46). Participants completed two balance tasks and were then randomized to either a high (performance within the top 10% for age and gender) or low (performance within the bottom 10% for age and gender) balance efficacy group, regardless of actual balance. Following the performance feedback, participants completed the same two balance tasks. Participants rated their balance efficacy prior to all tasks, and their perceived stability following all tasks. Trunk movement was recorded during each task to provide an estimate of actual balance. Results showed that the manipulation failed to alter balance efficacy in either group. However, participants in the good balance information group reported greater stability than those in the poor balance information group following the performance feedback, despite no changes in actual balance. These results suggest that verbal persuasion, independent of changes in balance efficacy or actual balance, can modify perceptions of stability in healthy young adults.