Ground reaction forces better than center of pressure differentiate postural control between young female volleyball players and untrained peers.

A comprehensive explanation of the relationship between postural control and athletic performance requires compare body balance in athletes with their never training counterparts. To fill this gap in relation to volleyball, the aim of this study was to compare the balance of intermediate adolescent female players (VOL, n = 61) with inactive peers (CON, n = 57). The participants were investigated in normal quiet stance during 20 s trials on a Kistler force plate. The traditional spatial (amplitude and mean speed) and temporal (frequency and entropy) indices were computed for ground reaction forces (GRF) and center-of-pressure (COP) time-series. The spatial parameters of the both time-series did not discriminate the two groups. However, the temporal GRF parameters revealed much lower values in VOL than in CON (p < .0001). This leads to three important conclusions regarding posturography applications. First, GRF and COP provide different information regarding postural control. Second, measures based on GRF are more sensitive to changes in balance related to volleyball training and perhaps to similar training and sports activity regimens. And third, the indicators calculated based on these two time series can complement each other and thus enrich the insight into the relationship between balance and sports performance level.

Postural control through force plate measurements in female AIS patients compared to their able-bodied peers.

The present understanding of the mechanisms responsible for postural deficit in adolescent idiopathic scoliosis (AIS) is still insufficient. This is important because some authors see one of the causes of this disease in the impaired postural control. Moreover, there is a reciprocal link between the level of postural imbalance and the clinical picture of these people. Therefore, we compared the center-of-pressure (COP) indices of 24 patients with AIS to 48 controls (CON) during four 20-s quiet stance trials with eyes open (EO) or closed (EC) and on firm or foam surface. This included sway amplitude, speed, sample entropy and fractal dimension. AIS had poorer postural steadiness only in the most difficult trial. In the remaining trials, AIS did as well as CON, while presenting a greater COP entropy than CON. Thus, the factor that made both groups perform equally could be the increased sway irregularity in AIS, which is often linked to higher automaticity and lower attention involvement in balance control. After changing the surface from hard to foam, puzzling changes in sway fractality were revealed. The patients decreased the fractal dimension in the sagittal plane identically to the CON in the frontal plane. This may suggest some problems with the perception of body axes in patients and reveals a hitherto unknown cause of their balance deficit.

Acute effects of proprioceptive neuromuscular facilitation exercises on the postural strategy in patients with chronic low back pain.

INTRODUCTION: Active treatments focused on improvement in motor function are postulated in chronic low back patients (CLBP). OBJECTIVE: to establish the acute effects of PNF exercise on the postural control strategy. METHODS: The sway of the body was tested before intervention in fifty-three CLBP patients and after that participants were randomly assigned into the intervention PNF group (n = 25). Mean velocity (VEL) and sample entropy (SEn), over the center of pressure in the mediolateral (ML) and anterior-posterior (AP) planes served to estimate the postural strategy and automaticity levels in the neuromuscular controller. Tandem and one-leg standing tests (OLST) with eyes open and eyes closed were used. RESULTS: Pain intensity decreased after the intervention. The VEL was no longer vision-dependent in both planes. The SEn decreased immediately after the exercise and either returned to or even exceeded the baseline values in the OLST ML plane. CONCLUSION: A single session of PNF exercise may have a beneficial effect on pain and postural control in CLBP patients. The statistically significant pain relief combined with newly acquired better control of posture may have encouraged the PNF group participants to a subconscious exploration of the stability area. Postural movements were more automatized in OLST in the delayed test.

Differences in static postural control between top level male volleyball players and non-athletes.

It is argued that elite athletes often demonstrate superior body balance. Despite the apparent significance of perfect balance ability in volleyball, little is known about the specific nature of postural control adjustments among first-rate volleyball competitors. This study compared postural performance and strategies in quiet stance between world vice-champions and young, healthy, physically active male subjects. The center-of-pressure (COP) signals recorded on a force plate were used to compute several measures of sway. In both axes of movement, athletes had lower COP range, but not its standard deviation and higher COP speed and frequency than controls. These findings indicate that postural regulation in athletes was more precise and less vulnerable to external disturbances which support optimal timing and precision of actions. Postural strategies in athletes standing quietly were similar to those exhibited by non-athletes performing dual tasks. It demonstrates a significant effect of sport practice on changes in postural control. In anterior-posterior axis, athletes displayed a much higher COP fractal dimension and surprisingly lower COP-COG frequency than controls. This accounts for their high capacity to use diversified postural strategies to maintain postural stability and significantly reduced the contribution of proprioception to save this function for carrying out more challenging posture-motor tasks.

Postural control in top-level female volleyball players.

BACKGROUND: The aim of this study was to compare the postural control of the Poland national women's volleyball team players with a control group of non-training young women. It was hypothesized that volleyball players use a specific balance control strategy due to the high motor requirements of their team sport. METHODS: Static postural sway variables were measured in 31 athletes and 31 non-training women. Participants were standing on a force plate with eyes open, and their center of pressure signals were recorded for the 20s with the sampling rate of 20 Hz in the medial-lateral (ML) and anterior-posterior (AP) planes. RESULTS: In both AP and ML planes, athletes had lower range and higher fractal dimension of the COP. They had also higher peak frequency than control group in the ML plane only. The remaining COP indices including variability, mean velocity and mean frequency did not display any intergroup differences. CONCLUSION: It can be assumed that due to the high motor requirements of their sport discipline Polish female volleyball players have developed a unique posture control. On the court they have to distribute their sensory resources optimally between balance control and actions resulting from the specifics of the volleyball game. There are no clearly defined criteria for optimal postural strategies for elite athletes, but they rather vary depending on a given sport. The results of our research confirm this claim. TRIAL REGISTRATION: The tests were previously approved by the Bioethical Commission of the Chamber of Physicians in Opole. (Resolution No. 151/13.12.2007). This study adheres to the CONSORT guidelines.

The Effects of Active Self-correction on Postural Control in Girls with Adolescent Idiopathic Scoliosis: The Role of an Additional Mental Task.

Due to balance deficits that accompany adolescent idiopathic scoliosis (AIS), the potential interaction between activities of daily living and active self-correction movements (ASC) on postural control deserves particular attention. Our purpose was to assess the effects of ASC movements with or without a secondary mental task on postural control in twenty-five girls with AIS. It is a quasi-experimental within-subject design with repeated measures ANOVA. They were measured in four 20-s quiet standing trials on a force plate: no task, ASC, Stroop test, and both. Based on the center-of-pressure (COP) recordings, the COP parameters were computed. The ASC alone had no effect on any of the postural sway measures. Stroop test alone decreased COP speed and increased COP entropy. Performing the ASC movements and Stroop test together increased the COP speed and decreased COP entropy as compared to the baseline data. In conclusion, our results indicate that AIS did not interfere with postural control. The effects of the Stroop test accounted for good capacity of subjects with AIS to take advantage of distracting attentional resources from the posture. However, performing both tasks together exhibited some deficits in postural control, which may suggest the need for therapeutic consultation while engaging in more demanding activities.

Postural control in girls with adolescent idiopathic scoliosis while wearing a Chêneau brace or performing active self-correction: a pilot study.

BACKGROUND: It is known that adolescent idiopathic scoliosis (AIS) is often accompanied by balance deficits. This reciprocal relationship must be taken into account when prescribing new therapeutic modalities because these may differently affect postural control, interacting with therapy and influencing its results. OBJECTIVE: The purpose was to compare postural control in girls with AIS while wearing the Chêneau brace (BRA) or performing active self-correction (ASC) with their postural control in a quiet comfortable stance. METHODS: Nine subjects were evaluated on a force plate in three series of two 20-s quiet standing trials with eyes open or closed; three blocks were randomly arranged: normal quiet stance (QST), quiet stance with BRA, and quiet stance with ASC. On the basis of centre-of-pressure (COP) recordings, the spatial and temporal COP parameters were computed. RESULTS AND DISCUSSION: Performing ASC was associated with a significant backward excursion of the COP mean position with eyes open and closed (ES = 0.56 and 0.65, respectively; p < 0.05). This excursion was accompanied by an increase in the COP fractal dimension (ES = 1.05 and 0.98; p < 0.05) and frequency (ES = 0.78; p = 0.10 and ES = 1.14; p < 0.05) in the mediolateral (ML) plane. Finally, both therapeutic modalities decreased COP sample entropy with eyes closed in the anteroposterior (AP) plane. Wearing BRA resulted in ES = 1.45 (p < 0.05) while performing ASC in ES = 0.76 (p = 0.13). CONCLUSION: The observed changes in the fractal dimension (complexity) and frequency caused by ASC account for better adaptability of patients to environmental demands and for their adequate resources of available postural strategies in the ML plane. These changes in sway structure were accompanied by a significant (around 25 mm) backward excursion of the mean COP position. However, this improvement was achieved at the cost of lower automaticity, i.e. higher attentional involvement in postural control in the AP plane. Wearing BRA may have an undesirable effect on some aspects of body balance.

Acute effects of core stability exercises on balance control.

PURPOSE: The aim of this study was to investigate whether a single bout of core stability exercises improves body balance immediately after the bout of exercise and during a retention test. METHODS: The study involved 16 women (age 22-25 years, body weight 60.5 ± 5.2 kg, height 166 ± 5.4 cm). Postural stability was assessed in the mediolateral (ML) and anteroposterior (AP) planes separately on a force plate (Kistler 9286 AA) during quiet standing on a soft support surface with the eyes closed. Subjects were measured 4 times: just before (T0), 1 minutes after (T1 m), 30 minutes after (T30 m), and 24 hours after the workout (T24 h). Postural balance was evaluated by five parameters based on the center of pressure (COP) signal: variability (VAR), mean velocity (VEL), sample entropy (ENT), frequency (FRE), and fractal dimension (FRA). RESULTS: We observed a decrease in VAR and VEL in the ML plane at T30 m and T24 h, compared to T0. The COP entropy significantly increased in the ML plane at T24 h, compared to T0. CONCLUSIONS: A single bout of core stability exercises improved the control of the mediolateral body balance. This effect was evident within 30 minutes after exercise, and remained for at least 24 hours. In addition, 24 hours after exercise we observed an increased automaticity in the strategy to maintain a stable upright stance.

Attentional demands associated with augmented visual feedback during quiet standing.

To investigate how additional visual feedback (VFB) affects postural stability we compared 20-sec center-of-pressure (COP) recordings in two conditions: without and with the VFB. Seven healthy adult subjects performed 10 trials lasting 20 seconds in each condition. Simultaneously, during all trials the simple auditory reaction time (RT) was measured. Based on the COP data, the following sway parameters were computed: standard deviation (SD), mean speed (MV), sample entropy (SE), and mean power frequency (MPF). The RT was higher in the VFB condition (p < 0.001) indicating that this condition was attention demanding. The VFB resulted in decreased SD and increased SE in both the medial-lateral (ML) and anterior-posterior (AP) planes (p < .001). These results account for the efficacy of the VFB in stabilizing posture and in producing more irregular COP signals which may be interpreted as higher automaticity and/or larger level of noise in postural control. The MPF was higher during VFB in both planes as was the MV in the AP plane only (p < 0.001). The latter data demonstrate higher activity of postural control system that was caused by the availability of the set-point on the screen and the resulting control error which facilitated and sped up postural control.

The effect of a single massage based on the tensegrity principle on postural stability in young women.

OBJECTIVE: The aim of this study was to investigate the effects of normalized muscle tension via tensegrity-based massage on postural stability in a sample of female young adults. METHODS: Nineteen females aged 21.8 ± 1.9 years were recruited presenting abnormal tension at muscles adhering to any of the following structural sites: superior iliac spine, lateral sacropelvic surface, linea aspera at 1/2 of femur length, and superior nuchal line of the occiput. Balance and postural control were assessed during bipedal stance using a force platform in multiple conditions: hard surface or soft foam surface with the head in either a neutral posture or tilted backward. Baseline and 3-min and 15-min post-treatment measures were collected while barefoot and eyes closed. Main outcomes measures included center of pressure variability, range, radius, and velocity in the anteroposterior (AP) mediolateral (ML) dimensions. RESULTS: In the solid surface with neutral head posture condition only AP COP measures decreased significantly (p< 0.05). In the soft surface condition, significant differences were observed in the AP and ML dimensions among most measures (p< 0.05). CONCLUSIONS: A single application of tensegrity-based massage positively influenced postural control in young adult females, particularly in the AP direction.

Repeated cryostimulation improves position sense and simple reaction time.

[Purpose] Whole body cryotherapy has been shown to have many benefits, yet nothing is known if and how this modality can improve neuromuscular performance and retain those improvements. [Subjects and Methods] Joint position sense based on the bilateral knee joint matching test and simple reaction time was investigated in 25 young healthy adults who underwent an extended period of whole body cryostimulation. The measurements were taken at baseline and after 10, 20, and 30 whole body cryotherapy sessions, with three days elapsing after the last treatment, and comparing the results with 24 control subjects. [Results] Only when 20 sessions were completed did joint position sense and simple reaction time improve in the intervention group. After 30 sessions, the outcome was similar. Equal results were found at baseline and after 10 sessions in both groups, but the intervention group outstripped controls after 20 and 30 sessions in both joint position sense and simple reaction time. [Conclusion] These results indicate that the common standard of 10 sessions is insufficient, while approximately 20 sessions of whole body cryotherapy may efficiently enhance neuromuscular performance with an ability to sustain the effects for at least three days.

The Effect of Chronic Pain Intensity on Sit-to-Stand Strategy in Patients With Herniated Lumbar Disks.

OBJECTIVE: Recurrent symptoms of low back pain and its transition to a chronic state are associated with specific motor strategies used by people to avoid pain. The aim of the study was to determine the impact of chronic pain intensity on sit-to-stand (STS) strategy in chronic low back pain (CLBP) patients with herniated disks. METHOD: Vertical ground reaction forces (counter, peak, and postpeak rebound) and their respective times of occurrence were measured on 2 Kistler force plates. Thirty-two healthy persons served as a control group. People with CLBP (n = 40) were divided into 2 subgroups according to the reported pain intensity at rest as measured by the numeric pain rating scale (NRS): low pain (NRS ≤ 3) and high pain (HP; NRS > 3). RESULTS: Both CLBP subgroups achieved shorter time to counter force but longer time to postpeak rebound force (P < .01). The time to peak force was extended in HP on the right side (P < .01). HP presented lower peak force on the right and lower postpeak rebound force on the left side (P < .001) compared with controls. CONCLUSION: Patients with CLBP were characterized by an individual, compensatory STS movement strategy with shorter preparation and longer stabilization times. Avoidance behavior in STS execution was presented in HP individuals only, indicating that intensity of chronic pain was a significant factor in decreasing ground reaction peak force and increasing time to peak force.

Postural Stability of Elderly People With Cognitive Impairments.

INTRODUCTION: Falls are one of the major problems among the elderly population. It has been established that people with dementia fall down more often. It is believed that this is a consequence of risky decision making by people with dementia resulting from cognitive deterioration. The aim of the present study was to evaluate the relationship between cognitive status and postural stability while standing. METHODS: A total of 47 people, aged 71.6 years on average (±7.2), were divided based on results of the Mini Mental State Examination (MMSE) into a dementia group (MMSE ≤ 23) and a control group (MMSE > 23). Postural stability was tested using a force plate (with eyes open, with eyes closed, and with visual biofeedback). The parameters of movement of the center of pressure were analyzed. RESULTS: Both in test with eyes open and eyes closed, significant difference was shown between the dementia group and the control groups. In visual feedback test, the dementia group showed 32% poorer performance than the controls. CONCLUSION: The falls experienced in dementia group may be caused by a disturbed balance control process of the central nervous system.

The Relationship Between Postural Control and Self-Reported Engagement in Physical Activity in Young and Older Age.

Physical activity is known to have beneficial effects on a host of factors related to physical and mental health, and positively affects postural control. However, there is no agreement on which measures of postural control and to what extent they are dependent on the past and present physical activity in older adults. To answer this question we compared the postural performance in a 20-s quiet stance with eyes open on a Kistler force plate in 38 subjects, aged 60-92, who were formerly and are currently physically active (AA) with those who were always inactive (II) and those who were either formerly (AI) or are currently (IA) active. Results indicated that only current activity promoted better postural control while former activity was ineffective. Postural control in AA and IA was very similar and much better than in II and AI who, in contrast, displayed similarly deteriorated postural control.

Changes in postural control between 13- and 19-year-old soccer players: is there a need for a specific therapy?

[Purpose] To investigate how increased training participation time and intensity affect postural control in young soccer players. [Subjects and Methods] Variability and mean velocity of sway were compared in U14 and U20 players during two-legged and one-legged quiet stances on a force plate with the player's eyes open or closed. [Results] U20 players performed much better with vision, and eyes closure considerably deteriorated their performance. The increased reliance on vision in the older group most likely resulted from the longer exposure of the U20 players to strenuous exercise, overload, and cumulative residual effects of earlier contusions. [Conclusion] These specific postural deficits in apparently healthy soccer players were found only because of objective and sensitive posturographic tests. The results of this study suggest that such tests should be regularly performed to increase the efficiency and precision of motor control evaluation in athletes. The corresponding results may help therapists mitigate the indiscernible yet detrimental changes in postural control that predispose soccer players to injury and negatively affect their performance.

Postural stability in young adults with Down syndrome in challenging conditions.

To evaluate postural control and performance in subjects with Down syndrome (SwDS), we measured postural sway (COP) in quiet stance in four 20-second tests: with eyes open or closed and on hard or foam surface. Ten SwDS and eleven healthy subjects participated, aged 29.8 (4.8) and 28.4 (3.9), respectively. The time-series recorded with the sampling rate of 100 Hz were used to evaluate postural performance (COP amplitude and mean velocity) and strategies (COP frequency, fractal dimension and entropy). There were no intergroup differences in the amplitude except the stance on foam pad with eyes open when SwDS had larger sway. The COP velocity and frequency were larger in SwDS than controls in all trials on foam pad. During stances on the foam pad SwDS increased fractal dimension showing higher complexity of their equilibrium system, while controls decreased sample entropy exhibiting more conscious control of posture in comparison to the stances on hard support surface. This indicated that each group used entirely different adjustments of postural strategies to the somatosensory challenge. It is proposed that the inferior postural control of SwDS results mainly from insufficient experience in dealing with unpredictable postural stimuli and deficit in motor learning.

The effect of chronic pain intensity on the stability limits in patients with low back pain.

OBJECTIVE: The purpose of this study was to evaluate if the intensity of recurrent chronic pain would modify postural performance in reaching the functional limits of stability (LOS) in chronic low back pain (CLBP) patients. METHODS: Three groups of subjects were investigated. Healthy persons comprised the asymptomatic group (n = 32) while CLBP patients (n = 36) were divided into 2 subgroups, according to the reported intensity of resting pain on a numerical rating scale: patients with low (LP) and high pain (HP) levels. The maximal displacement of the center of pressure (COP) indexing the LOS magnitude and the COP mean velocity indexing the performance in reaching LOS were calculated on a Kistler force plate during forward and backward voluntary body lean with eyes open (EO) or closed (EC). RESULTS: The forward LOS was lower in both the LP (P < .01) and HP (P < .01) subgroups than in the asymptomatic under EO and EC conditions, while no differences between the LP and HP groups were found. The backward LOS was lower in the HP group than in asymptomatic but only with EC (P = .01). Eye closure caused an increase in forward (P = .02) and backward (P = .001) COP velocity in the LP group and forward COP velocity in the asymptomatic (P = .04) only. With EC, the only intergroup difference was lower forward COP velocity in the HP than LP group (P = .04). CONCLUSION: Subjects with CLBP had reduced forward LOS regardless the pain level. However, the higher level of pain was associated with slower execution of voluntary leaning tasks, with EC only.

Acute effects of cryotherapy on postural control.

To investigate the acute effects of whole-body cryotherapy (WBC) on postural control, we measured postural sway (COP) in a quiet stance with eyes open in four consecutive 20-second tests: before and 1, 6 and 11min after the WBC. Twenty-four healthy young subjects aged 19.3±0.9 were exposed to WBC (-110°C) for 2min. The time series recorded with a sampling rate of 100Hz was used to evaluate postural performance (COP variability) and strategies (COP frequency and entropy). There were no differences between the pre- and post-WBC values of these measurements in the frontal plane; however, in the sagittal plane postural sway increased immediately after WBC (p<0.05) and remained elevated throughout the experiment. Deteriorated performance brought about lagged changes in postural strategies, including a decrease in frequency and entropy. These changes remained sustained until the end of the experiment. In conclusion, the WBC caused a drop in complexity, adaptability, and automaticity in postural control, which accounted for specific constraints imposed on the postural system due to cooling.

Altered postural control in persons with cognitive impairment during visual feedback tasks.

We compared postural stability with eyes open (EO) and with visual feedback (VFB) in 15 elderly subjects with cognitive impairment (SwCI) and 17 controls. Postural stability was evaluated using the center-of-pressure (COP) mean radius and velocity, while postural strategies by the frequency and damping of the difference between the COP and the center-of-mass (COM) signals. Performance in the VFB trials was measured by the ratio of time spent by the COP inside the target on the screen to the total trial duration. With EO, both groups demonstrated similar postural stability and strategies. The time spent inside the target during VFB was significantly higher in controls than in SwCI. The VFB did not affect the mean radius in either group, nor velocity and frequency in SwCI, however it increased the mean velocity and frequency in controls. Besides, the VFB increased damping significantly more in the SwCI than in controls. These findings indicate that controls adequately responded to the demands of VFB and used efficient strategy of postural control. In contrast, the SwCI seemed to have lost the natural capability to use augmented feedback demonstrating impaired sway control and deficit of sensory integration. All these symptoms of posture control disorders could be objectively identified by the COP mean velocity and the COP-COM frequency and damping. Increased damping in controls during VFB task may account for early signs of cognitive impairment that cannot be captured by standard tests.

Attention demand and postural control in children with hearing deficit.

To elucidate the mechanisms responsible for deteriorated postural control in children with hearing deficit (CwHD), we measured center-of-pressure (COP) variability, mean velocity and entropy in bipedal quiet stance (feet together) with or without the concurrent cognitive task (reaction to visual stimulus) on hard or foam surface in 29 CwHD and a control group of 29 typically developing children (CON). The CwHD displayed an overall decreased postural performance as compared to the CON in the medial-lateral plane (p<0.05). Standing on foam pad revealed slower simple reaction time in the CwHD (p<0.05) while the results on hard surface were not different. The CwHD decreased (p<0.05) the amount of attention invested in posture during dual task which accounted for the need of more cognitive resources to handle two tasks simultaneously than controls. It was unmistakable that the intergroup differences emerged when the tasks performed were relatively novel and untrained: feet together, foam pad, and reaction time. All these tasks, while being very easy for the CON, made the CwHD deteriorate postural or cognitive performance. These results unravel the difficulty in reaching the consecutive developmental stages in the CwHD and call for specific therapeutic modalities that might facilitate this development.