An analysis of human postural sway using differential information processing

Time course of stabilometric changes after a strenuous treadmill exercise

Curved walking in hemiparetic patients

Visually-induced illusions of self-motion (vection) can be compelling for some people, but they are subject to large individual variations in strength. Do these variations depend, at least in part, on the extent to which people rely on vision to maintain their postural stability? We investigated by comparing physical posture measures to subjective vection ratings. Using a Bertec balance plate in a brightly-lit room, we measured 13 participants' excursions of the centre of foot pressure (CoP) over a 60-second period with eyes open and with eyes closed during quiet stance. Subsequently, we collected vection strength ratings for large optic flow displays while seated, using both verbal ratings and online throttle measures. We also collected measures of postural sway (changes in anterior-posterior CoP) in response to the same visual motion stimuli while standing on the plate. The magnitude of standing sway in response to expanding optic flow (in comparison to blank fixation periods) was predictive of both verbal and throttle measures for seated vection. In addition, the ratio between eyes-open and eyes-closed CoP excursions during quiet stance (using the area of postural sway) significantly predicted seated vection for both measures. Interestingly, these relationships were weaker for contracting optic flow displays, though these produced both stronger vection and more sway. Next we used a non-linear analysis (recurrence quantification analysis, RQA) of the fluctuations in anterior-posterior position during quiet stance (both with eyes closed and eyes open); this was a much stronger predictor of seated vection for both expanding and contracting stimuli. Given the complex multisensory integration involved in postural control, our study adds to the growing evidence that non-linear measures drawn from complexity theory may provide a more informative measure of postural sway than the conventional linear measures.

Balance can be a main factor contributing to success in many disciplines, and biathlon is a representative example. A more stable posture may be a key factor for shooting scores. The center of foot pressure (COP) is commonly recorded when evaluating postural control. As COP measurements are highly irregular and non-stationary, non-linear deterministic methods, such as entropy, are more appropriate for the analysis of COP displacement. The aim of our study was to investigate whether the longitudinal effects of biathlon training can elicit specific changes in postural control. Eight national-level biathletes, 15 non-athletes who prior to the experiment took part in 3 months of shooting training, and 15 non-athletes with no prior rifle shooting experience took part in our study. The data was collected with the use of a force plate. Participants performed three balance tasks in quiet standing, the shooting position (internal focus-participants concentrated on maintaining the correct body position and rifle), and aiming at the target (external focus-participants concentrated on keeping the laser beam centered on the targets). Biathletes obtained significantly lower values of sample entropy compared to the other groups during the shooting and aiming at the target trials (p<0.05). External and internal focuses influenced the process of postural control among participants who had prior rifle shooting experience and the control group; they obtained significantly higher values of sample entropy while shooting and aiming at the target compared to the quiet standing trial (p<0.05). The biathletes obtained significantly lower values of sample entropy in the aiming at the target position compared to the quiet standing trial. Specific balance training is associated with the ability to deal with a more challenging, non-specific task. The biathletes seemed to employ a different motor control strategy than the beginners and control group, creating repeating patterns (more regular signal for COP) to keep one's balance during the shooting and aiming at the target positions.

The current literature shows no consensus regarding the difference between the dominant leg (D-Leg) and the non-dominant leg (ND-Leg) in terms of postural control. This lack of consensus could stem from motor experience (i.e., symmetric or asymmetric motricity) and/or the physiological state induced by physical exercise. This study aimed to investigate the acute effects of fatiguing exercise on postural control when standing on the D-Leg and the ND-Leg, in athletes practicing symmetric (SYM) and asymmetric (ASYM) sports. Thirty healthy male participants were recruited and divided into two groups, (SYM n = 15) and (ASYM n = 15, on the basis of the motricity induced by the sport they practice. Monopedal postural control was assessed for the D-Leg and the ND-Leg before and after the fatigue period (which consisted of repeating squats until exhaustion). A force platform was used to calculate the spatio-temporal characteristics of the displacements of the center of foot pressure (COP). A significant fatigue effect was observed in both groups on the D-Leg and the ND-Leg for all the COP parameters. There was a tendency (p = 0.06) between the ASYM and SYM groups on the D-Leg, concerning the relative increase in the COP velocity in the frontal plane after the fatigue period. The fatigue condition disturbed postural control in both the SYM and ASYM groups on the D-Leg and ND-Leg. This disturbing effect related to fatigue tends to be more marked in athletes practicing asymmetric sports than in athletes practicing symmetric sports on the D-Leg.

Can osteopathic manipulative treatment modify the posture in elderly people? – A single-case study

This study aimed to determine if pain and balance control are related to meteorological modifications in patients with knee osteoarthritis (OA). One hundred and thirteen patients with knee OA (mean age=65±9years old, 78 women) participated in this study. Static posturography was performed, sway area covered and sway path traveled by the center of foot pressure being recorded under six standing postural conditions that combine three visual situations (eyes open, eyes closed, vision altered) with two platform situations (firm and foam supports). Knee pain score was assessed using a visual analog scale. Balance control and pain measurements recorded in the morning were correlated with the meteorological data. Morning and daily values for temperature, precipitation, sunshine, height of rain in 1h, wind speed, humidity, and atmospheric pressure were obtained from the nearest data collecting weather station. The relationship between postural control, pain, and weather variations were assessed for each patient on a given day with multiple linear regressions. A decrease of postural stability was observed when atmospheric pressure and maximum humidity decreased in the morning (p<0.05) and when atmospheric pressure decreased within a day (p<0.05). Patient's knee pain was more enhanced when it is warmer in the morning (p<0.05) and when it is wetter and warmer within a day (p<0.05). The relationship between weather, pain, and postural control can help patients and health professionals to better manage daily activities.

Noisy galvanic vestibular stimulation (nGVS) can improve postural stability by delivering subthreshold electrical noise to the vestibular system. However, the frequency-specific effects of nGVS on postural control responses-particularly those involving the center of mass (COM) recovery force and movement strategies-remain unclear. We investigated how different nGVS frequencies affect postural control, estimating COM fluctuations using a rigid pendulum model. Thirty-two healthy adults (mean age, 20.3±1.2years; 19 females) underwent three interventions: sham nGVS, low-frequency nGVS (LF-nGVS, 0-100Hz), or high-frequency nGVS (HF-nGVS, 100-640Hz), each with a 200 µA current (0 µA for the sham). During each 40-s trial, participants stood on a platform with eyes closed and the middle 30s were analyzed. Inertial measurement units were affixed to the occipital protuberance to capture head kinematics. Postural control was assessed using conventional metrics (e.g., center of foot pressure [COP], COM sway, and head acceleration) and novel indicators of COM recovery force and head acceleration control based on motor strategies. Both LF-nGVS and HF-nGVS significantly reduced several indices, including COP velocity and head angular velocity, compared with sham stimulation. No significant differences were observed between LF-nGVS and HF-nGVS. Head acceleration was significantly correlated with COM recovery force and joint movement strategies in both stimulation conditions. Although the mechanism of neural network activity at different stimulation frequencies requires careful interpretation, these findings suggest that COM recovery and associated motor strategies contribute to nGVS-induced postural improvements, providing insights into its neuromechanistic effects.

Paillard, T, Kadri, MA, Nouar, MB, and Noé, F. Warm-up optimizes postural control but requires some minutes of recovery. J Strength Cond Res 32(10): 2725-2729, 2018-The aim was to compare monopedal postural control between the dominant leg (D-Leg) and the nondominant leg (ND-Leg) in pre- and post-warm-up conditions. Thirty healthy male sports science students were evaluated before and after a warm-up exercise (12 minutes of pedaling with an incremental effort on a cycle ergometer with a controlled workload). Monopodal postural control was assessed for the D- and ND-Legs before and immediately, 2, 5, 10, and 15 minutes after the warm-up exercise, using a force platform and calculating the displacement velocity of the center of foot pressure on the mediolateral (COPML velocity) and anteroposterior (COPAP velocity) axes. No significant difference was observed between the D-Leg and ND-Leg for both COPML and COPAP velocity in all the periods. In comparison with pre-warm-up, COPML decreased after 15-minute and 10-minute recovery periods for the D-Leg and the ND-Leg, respectively (p < 0.05), whereas COPAP decreased after 10-minute and 15-minute recovery periods (p < 0.001; p < 0.01, respectively) for the D-Leg, and after a 10-minute recovery period for the ND-Leg (p < 0.001). The warm-up optimized monopedal postural control but did not make it possible to distinguish a difference between the D-Leg and the ND-Leg. Some minutes of recovery are required between the end of the whole-body warm-up exercise and the beginning of the postural test to optimize postural control. The optimal duration of recovery turns out to be about 10-15 minutes.

This study examined the acute effect of training on postural balance among young dinghy sailors. By measuring sway path and sway area of the center of pressure (CoP), the objective was to investigate whether training sessions on dinghy sailboat influence sway path and sway area measurements. Twelve competitive sailors (Optimist and Laser Radial class) performed a set of balance tests on both stable and unstable surfaces, with open and closed eyes, measured over three days. The first day served to familiarize the participants with the protocol. On the second and third days, CoP sway path and sway areas were assessed before, during and after the training session using a Wii Balance Board (WBB). A general improvement in balance control was observed in most of the measured parameters. Statistical analysis (RM ANOVA) revealed significant reductions in sway path and sway area with closed eyes on an unstable surface comparing pre-, during- and post- measurement on the second day (p < 0.05), and for sway path with open and closed eyes on an unstable surface on the third day (p < 0.05). Findings of the present study show a short-term effect of sailing sessions on balance, suggesting that a single training session can induce acute improvements in postural control among young athletes. It is possible that the observed acute improvements are associated with immediate neuromuscular adaptation following sailing activity, specifically due to the unpredictable and dynamic environment in which sailing takes place. However, the temporal duration of this effect appears to be limited. As balance is an essential skill in sailing performance, future studies should investigate long-term effects and retention of training-induced improvements in postural control.

The present study examined the differences between male and female gymnasts in bipedal standing position, back standing scale, and stork standing scale testing. 29 young gymnasts (13 boys, 16 girls; ages 12 to 15 years) participated. A portable posturographic digital platform was used to record foot pressure (Foot Checker, Comex SA). Barefoot sole area (cm2), maximal pressure (kPa), center of foot pressure (CoP), sway area (mm2), and CoP linear distance displacement (mm) were analyzed in an integrated software module (Foot Checker, Version 4.0). The intra-class correlation coefficient and the coefficient of variation supported the reliability of the measurements. Results indicated no differences between boys and girls on height, weight, and Body Mass Index. Differences indicated better performance by girls compared to boys in back standing and stork standing.

Maturity offset affects standing postural control in youth male soccer players

ACL Research Retreat V

Postural Effects of the Scaled Display of Visual Foot Center of Pressure Feedback Under Different Somatosensory Conditions at the Foot and the Ankle

The aim of this research was to analyse the development of postural reactions to approaching (AOF) and receding (ROF) ground rectilinear optical flows. Optical flows were shaped by a pattern of circular spots of light projected on the ground surface by a texture flow generator. The geometrical structure of the projected scenes corresponded to the spatial organisation of visual flows encountered in open outdoor settings. Postural readjustments of 56 children, ranging from 7 to 11 years old, and 12 adults were recorded by the changes of the centre of foot pressure (CoP) on a force platform during 44-s exposures to the moving texture. Before and after the optical flows exposure, a 24-s motionless texture served as a reference condition. Effect of ground rectilinear optical flows on postural control development was assessed by analysing sway latencies (SL), stability performances and postural orientation. The main results that emerge from this experiment show that postural responses are directionally specific to optical flow pattern and that they vary as a function of the motion onset and offset. Results showed that greater developmental changes in postural control occurred in an AOF (both at the onset and offset of the optical flow) than in an ROF. Onset of an approaching flow induced postural instability, canonical shifts in postural orientation and long latencies in children which were stronger than in the receding flow. This pattern of responses evolved with age towards an improvement in stability performances and shorter SL. The backward decreasing shift of the CoP in children evolved in adults towards forward postural tilt, i.show $132#e. in the opposite direction of the texture's motion. Offset of an AOF motion induced very short SL in children (which became longer in adult subjects), strong postural instability, but weaker shift of orientation compared to the receding one. Postural stability improved and orientation shift evolved to forward inclinations with age. SL remained almost constant across age at both onset and offset of the receding flow. Critical developmental periods seem to occur by the age of 8 and 10 years, as suggested by the transient 'neglect' of the children to optical flows. Linear vection was felt by 90% of the 7 year olds and decreased with age to reach 55% in adult subjects. The mature sensorimotor coordination subserving the postural organisation shown in adult subjects is an example aiming at reducing the postural effects induced by optical flows. The data are discussed in relation to the perceptual importance of mobile visual references on a ground support.