Postural control before and after transitional locomotor tasks in children on the autism spectrum: A case-control study

BACKGROUND

Instrumented measurements of postural control provide a more accurate insight into the motor development of children with autism. This study aimed to identify postural control deficits in autistic children during quiet standing before and after transient locomotor task. It was hypothesized that the parameters that characterize the trajectory of center of foot pressure (COP) displacement would be higher in autistic children compared to typically developing children.

METHODS

Sixteen autistic children aged 6-10 but without a comorbidity diagnosis, were enrolled in the study group. The control group comprised 16 typically developing peers. The assessment of the transitional task comprised four different conditions: unperturbed and perturbed transition, stepping up, and stepping down tasks. Analysis of the COP signal was carried out for three distinct phases, i.e., phase 1 - quiet standing before step initiation, phase 2 - transit, and phase 3 - quiet standing until measurement completion.

FINDINGS

The two-way ANOVA with a 2 × 4 factorial design (group × testing condition) revealed a group effect on all posturographic variables in the antero-posterior and medio-lateral directions of phase 1 and in the antero-posterior direction of phase 3. The Bonferroni post-hoc test showed the means of all those variables were significantly higher for the autistic than for typically developing children. Group allocation also had an effect on the time of transit and step length, which turned out to be significantly longer in autistic children compared to healthy peers.

INTERPRETATION

Autistic children show increased postural sway before and after transitional locomotor tasks compared to typically developing children. The trial was prospectively registered in the Australian and New Zealand Clinical Trials Registry (no. ACTRN12621001113842; date registered: 23.08.2021).

Balance assessment in selected stages of Parkinson's disease using trend change analysis

BACKGROUND

Balance disorders in patients diagnosed with Parkinson's disease (PD) are associated with a change in balance-keeping strategy and reflex disorders which regulate the maintenance of vertical body posture. Center of foot pressure (COP) displacement signals were analyzed during quiet standing experiments to define such changes. The research aimed to apply stock exchange indices based on the trend change analyses to the assessment of a level of the Parkinson disease progression on the grounds of the analysis of the COP signals.

METHODS

30 patients in two stages of PD, 40 elderly participants, and 20 individuals at a young age were studied. Each person was subjected to 3 measurements with open and closed eyes. A technical analysis of the COP displacement signal was performed, and the following quantities were determined: indices related to the number of trend changes (TCI), indices defining a mean time (TCI_dT), and mean displacement (TCI_dS) and mean velocity (TCI_dV) between such changes.

RESULTS

The results indicate a higher TCI value for PD than for aged-matched control group (p < 0.05). In the case of PD patients, there was also an increase in the TCI_dS value by 2-5 mm, which mainly contributed to the increase in TCI_dV. Statistically significant differences for the TCI_dT values occurred between all groups in which differences in the average COP velocity were noted.

CONCLUSIONS

The TCI and TCI_dV results obtained for the healthy participants enabled the development of indices supporting PD diagnostics. The causes of the TCI_dV changes in patients were determined, i.e., whether they resulted from an increase in the TCI_dT or TCI_dS between the moments of trend changes indicated by the developed algorithm. The developed methodology provides new information on the impact of PD on the strategy of maintaining balance, which was impossible to obtain using currently used analyses. Trial registration The conducted research is an observational study and does not include a health care intervention. Participants gave their consent to participate in the research and the procedure was approved by the Institutional Bioethics Committee.

A preliminary investigation into the impact of shock wave therapy and sonotherapy on postural control of stepping tasks in patients with Achilles tendinopathy

Objective

The outcomes of physical therapy are commonly assessed with subjective scales and questionnaires. Hence, a continuous search to identify diagnostic tests that would facilitate objective assessment of symptom reduction in those patients with Achilles tendinopathy who undergo mechanotherapy. The main aim of this study was to evaluate and compare the effectiveness of shock wave and ultrasound treatments, using objective posturographic assessment during step-up and step-down initiation.

Materials and methods

The patients with non-insertional Achilles tendinopathy and pain lasting for more than 3 months were randomly assigned to one of the experimental groups, i.e., radial shock wave therapy (RSWT), ultrasound therapy, or placebo ultrasound. All groups also received deep friction massage as the primary therapy. The transitional locomotor task was performed with the affected and unaffected limb in random order, on two force platforms under two conditions (step-up and step-down). The recording of center of foot pressure displacements was divided into three phases: quiet standing before step-up/step-down, transit, and quiet standing until measurement completion. Pre-intervention measurements were performed and then short-term follow-ups at weeks 1 and 6 post-therapy.

Results

The three-way repeated measures ANOVA showed few statistically significant two-factor interactions between therapy type, time point of measurement and the type of the locomotor task. Significant increases in postural sway were observed in the entire study population throughout the follow-up period. Three-way ANOVAs revealed a group effect (shock wave vs. ultrasound) on almost all variables of the quiet standing phase prior to step-up/step-down initiation. Overall, postural stability before the step-up and step-down tasks appeared to be more efficient in patients who had undergone RSWT compared to the ultrasound group.

Conclusion

Objective posturographic assessment during step-up and step-down initiation did not demonstrate therapeutic superiority of any of the three therapeutic interventions used in patients with non-insertional Achilles tendinopathy.Clinical Trial Registration: The trial was prospectively registered in the Australian and New Zealand Clinical Trials Registry (no. ACTRN12617000860369; registration date: 9.06.2017).

How partnering changes the process of postural control?

The aim of the study was to identify changes in the mechanism of postural control among ballroom dancers between standing solo and standing with a partner during specific standard dance positions. Specifically, the study attempted to determine whether the male partner plays a stabilising role in the dance couple. A total of seven competitive dance couples participated in the study. The experimental procedure comprised four dance positions characteristic of international standard dances: standard, starting, chasse and contra check. The dance positions were staged twice - while standing solo and while standing with a partner. The assumption of the assessed position was preceded by a dance phase after which the participants were instructed to freeze on a force plate and hold the position for 30 s. To examine whether subjects standing solo or with partners had greater rambling (RM) or trembling (TR) components in their dance postural profile, the ratios of RM to the center of foot pressure (COP) and TR to COP were computed for velocity. No significant differences were observed in the velocity of COP between standing solo and standing with a partner (p > 0.05). However, during the standard and starting positions, female and male dancers standing solo were characterised by higher values of the velocity of RM/COP ratio and lower values of the velocity of TR/COP ratio than those standing with a partner (p < 0.05). According to the theory behind the RM and TR decomposition, an increase in TR components could indicate a higher reliance on spinal reflexes, which would suggest greater automaticity.

Modulation of center-of-pressure signal in children on the autism spectrum: A case-control study

BACKGROUND

Proper postural and motor control plays a fundamental role in the child's ontogenetic development. So far, the postural control in children on the autism spectrum has mainly been assessed with standard posturographic measurements of center of pressure (COP) displacements.

RESEARCH QUESTION

What are the differences in postural control between autistic and typically developing children?

METHODS

The study group comprised 16 autistic children aged 6-10 years, identified by a psychiatrist. The control group consisted of 16 typically developing children aged 6-10 years with no posture deformities, no pervasive developmental disorder and no history of postural control or movement deficits. The data were collected during quiet standing with eyes open using a force plate. To gain a better insight into the postural control processes, the rambling-trembling and sample entropy analyses were used in COP data processing.

RESULTS

Compared to typically developing children, those with autism spectrum had significantly higher values of COP and rambling trajectory parameters in the antero-posterior direction during quiet standing. The variables of the trembling trajectory did not differ significantly between the groups. The autistic children had significantly lower values of sample entropy in the antero-posterior direction compared to typically developing children.

SIGNIFICANCE

More advanced measures of COP displacements including the rambling-trembling method and sample entropy revealed differences in postural control between autistic and typically developing children. These methods may therefore contribute to functional assessment of postural control deficits in children on the autism spectrum.

Influence of Target Width and Distance on Postural Adjustments in a Fencing Lunge

The aim of this study was to examine whether target width and target distance influence the planning phase of a fencing lunge (early and anticipatory postural adjustments) as well as the execution phase of a fencing lunge. Eight elite female fencers participated in the study. The displacement of the center of foot pressure, muscle activity of the tibialis anterior, and kinematics of center of mass were recorded using force plates. The results show that target width and distance have no effect on early and anticipatory postural adjustments as well as the acceleration and velocity of the center of mass at the moment of foot-off. However, a greater target distance was associated with a greater max center of mass acceleration and velocity, and larger target width resulted in a greater max center of mass acceleration during lunging (p < 0.05). We suppose that the effect of task parameters on preparing a fencing lunge may be mitigated due to the specific technique adopted by expert fencers and the ballistic nature of a fencing lunge.

Analysis of pain intensity and postural control for assessing the efficacy of shock wave therapy and sonotherapy in Achilles tendinopathy - A randomized controlled trial

BACKGROUND

The troublesome symptoms of Achilles tendinopathy prompt patients to seek effective forms of conservative treatment. The main aim of the study was to determine the therapeutic efficacy of shock wave and ultrasound therapies for Achilles tendinopathy in reducing pain intensity. Treatment efficacy was also assessed using objective posturographic measurements.

METHODS

Thirty-nine patients patients were randomly allocated to one of three experimental groups that received shock wave therapy (group A), ultrasound therapy (group B) and placebo ultrasound (group C). Posturographic measurements and subjective assessment of pain intensity were taken prior to therapy and at weeks 1 and 6 of therapy completion.

FINDINGS

A comparison of percentage change in activity-related pain from baseline to 6 weeks post-therapy revealed a significantly greater pain reduction in group A compared to group B. The three-way ANOVA demonstated an effect of treatment type on all posturographic variables. The Bonferroni post-hoc test showed the means of all variables were significantly smaller for group A than group B. Limb condition also had an effect on the center-of-pressure trajectories in anteroposterior plane; the post-hoc test showed the mean values of the variables were significantly greater for the non-affected compared to affected limb.

INTERPRETATION

Shock wave therapy was significantly more effective than sonotherapy for alleviation of activity-related pain of Achilles tendinopathy. An association was also shown between shock wave therapy and more efficient postural control in patients with Achilles tendinopathy. The parameters of center-of-pressure trajectories in the sagittal plane were significantly greater for the non-affected compared to affected limb. The trial was prospectively registered in the Australian and New Zealand Clinical Trials Registry (no. ACTRN12617000860369; registration date: 9.06.2017).

Influence of base of support on early postural adjustments and fencing lunge performance

The aim of the study was to examine whether the width of the base of support (BOS) has an influence on early postural adjustments (EPA) and armed upper limb and COM kinematics during lunging. Eight elite female fencers participated in the study. The displacement of the centre of foot pressure (COP) and kinematics of centre of mass (COM) were recorded using force platforms. The kinematics of the wrist of the armed upper limb were obtained using a 3D accelerometer. The results show that EPA were characterised by a very small COP displacement (about 0.6 to 1.2 cm). The COP amplitude showed a tendency to decrease with an increase in BOS width under reaction time conditions. In contrast, a greater BOS width was associated with a significant increase in COM acceleration at foot-off and peak COM acceleration during lunging also under reaction time instructions. The kinematics of the wrist were not influenced by BOS. The results show that in elite fencers, the upper limb movement is dissociated from the whole body movement. We suppose that a small COP amplitude is a postural skill which is integrated into the lunging skill and might influence the acceleration of COM.

Two Aspects of Feedforward Control During a Fencing Lunge: Early and Anticipatory Postural Adjustments

The present study investigated whether expertise in fencing influences the onset of postural preparation during the fencing lunge and how it changes under different performance conditions. We also questioned if the onset of feedforward control can be categorized into one of the postural phases: anticipatory or early postural adjustment. Eight elite fencers and nine physical education students performed an attack with a lunge in self-paced and reaction time conditions from three different initial stance widths. The onset of the center of pressure (COP) displacement and EMG activities for the tibialis anterior (TA) of both limbs were recorded. The results show that expertise in fencing delays the onset of the activity of TA of the front leg and the onset of COP displacement during fencing lunge performance in comparison to controls. Additionally, in contrast to the control group, fencers produce typical APA patterns in the activation of TA under different performance conditions, delayed reaction time in comparison to self-initiated lunging, and constant time of APA onset under different widths of stance. According to different times and functions of TA activity and COP displacement in lunging, we propose to address them as anticipatory postural adjustment and early postural adjustment, respectively.

Postural sway in young female artistic and acrobatic gymnasts according to training experience and anthropometric characteristics

BACKGROUND

Gymnastics training enhances the development of postural control in children and adolescents. In competitive gymnastics, the training regimen is specific to the given gymnastic discipline and is usually followed from the early years of practicing. This study aimed to determine whether postural steadiness differed between young gymnasts practicing two distinct disciplines, and whether it was related to the duration of their training experience, age, and their anthropometric characteristics.

METHODS

Thirty 10-13-year-old females ̶ ten artistic gymnasts, ten acrobatic gymnasts (training as "tops"), and ten non-athletes ̶ were examined during 60-s quiet standing trials on a force platform with the eyes open and closed. Their postural sway was represented by directional components of centre of foot pressure mean velocity. Mann-Whitney U, Wilcoxon and Spearman's ρ tests were used for analyses.

RESULTS

Anterior-posterior and medial-lateral centre of foot pressure mean velocities were not different between the artistic and acrobatic gymnasts (p > 0.05). In the artistic gymnasts, the duration of training experience, age, body height, body mass, and maturity offset were negatively correlated with the anterior-posterior centre of foot pressure mean velocity under eyes-open conditions. The acrobatic gymnasts' body mass and BMI percentiles were negatively correlated with their anterior-posterior and medial-lateral centre of foot pressure mean velocities under both visual conditions (r ranged from - 0.64 to - 0.93; p < 0.05). The non-athletes' centre of foot pressure mean velocities were non-significantly correlated with their age and anthropometric measures under both visual conditions (p > 0.05).

CONCLUSIONS

The artistic gymnasts' longer training experience, greater age, body height, body mass, and biological maturity were associated with better anterior-posterior postural steadiness when vision was available; the acrobatic gymnasts' greater body mass and BMI percentiles were associated with better overall postural steadiness regardless of visual conditions. Relationships were observed between postural steadiness and discipline-specific training experience and anthropometric characteristics; however, causes and effects were not proven.

Detection of postural control in early Parkinson's disease: Clinical testing vs. modulation of center of pressure

INTRODUCTION

Little is known about the early stage balance changes in PD. Many clinicians assume that there are no postural issues in early PD because of failure to identify them on bedside and clinical testing. Here, we quantify balance changes in early and moderate stage PD and compared these values to healthy controls (HC) using clinical assessments of balance and posturography.

METHODS

We compared 15 HC with 15 early PD (PD-II; Hoehn and Yahr stage II) and 15 moderate PD (PD-III; H&Y stage III). Participants performed various clinical tests of balance and a standing postural task on a force platform. We quantified the spatiotemporal parameters of the center of pressure (COP), the sample entropy and power spectral density (PSD) of the COP.

RESULTS

The PSD of the COP differentiated PD-II from HC from 0-0.5 Hz and PD-II from PD-III from 0.5-1 Hz. Specifically, PD-II and PD-III manifested greater power than HC from 0-0.5 Hz, whereas PD-III exhibited greater power than PD-II and HC from 0.5-1.0 Hz (p<0.05). However, there were no significant differences between PD-II and HC in all clinical tests and in spatiotemporal parameters of the COP (p>0.05). Although the sample entropy was significantly lower in the PD groups (p<0.05), entropy failed to differentiate PD-II from PD-III.

CONCLUSION

The low-frequency modulation of the COP in this small cohort differentiated early PD from HC and from moderate PD. Clinicians should be aware that there are early balance deficits in PD. A larger sample size is needed to confirm these findings.

Age-related changes in postural control in older women: transitional tasks in step initiation

Background

Aging, being a natural process, involves many functional and structural changes within the body. Identifying the age-related postural changes will provide insight into the role of aging on postural control during locomotion. The aim of this study was to identify age-related postural changes during a transitional task under different conditions.

Methods

Sixty healthy females divided into three age groups: A (50-60 y/o), B (60-70 y/o), and C (70-80 y/o). The transitional task was measured by two force platforms. The procedure consisted of three phases: quiet standing, transfer onto a second platform, and quiet standing on the second platform. Four different conditions were applied: unperturbed transfer, obstacle crossing, step-up, and step-down. Double-support time, transit time, and stability time before and after the step task were analyzed.

Results

The transit time was longer by 30% for subjects over 70 y/o. The double-support time was longer by 11% among adults 60-70 y/o, while in people over 70 y/o it was longer by almost 50% compared to the 50-60 y/o subjects. The stability time before the transitional task was longer by 17% among adults over 60 y/o compared to middle-age subjects. The stability times before and after the transitional task were longer for adults in the 50-60 y/o category.

Conclusion

The proposed procedure is adequate for assessing age-related changes in postural control while undergoing a transitional task. An analysis of the double-support time and stability time before and after the step task enabled the detection of early signs of balance changes in middle-age adults. Independent of age, the transitional task parameters changed with the increasing difficulty of the tasks.

Rambling-trembling analysis of postural control in children aged 3-6 years diagnosed with developmental delay during infancy

BACKGROUND

Preschool age is fundamental for the development of gross motor skills. Timely detection of postural stability deficits using objective methods would facilitate early implementation of therapeutic strategies.

RESEARCH QUESTION

What are the age- and gender-related differences in postural control between preschool children diagnosed with developmental delay in their first year of life and children with typical development?

METHODS

The study group consisted of 59 children diagnosed with developmental delay during infancy, who had received physiotherapy in the first year of their life for disorders of postural control and prone locomotion as well as abnormal distribution and magnitude of postural tone. The control group comprised 66 nursery school children with typical development and no history of postural control or movement deficits and no physiotherapy interventions in the first year of their life. The study and control groups were subdivided into four subgroups based on age (3-4 years, 5-6 years) and gender (boys, girls). The data were collected during quiet standing using a force plate. Three 30-second trials were recorded. Stabilographic recordings were analysed using the rambling-trembling approach.

RESULTS

Three-way ANOVA revealed a gender effect on all measured variables (p < 0.05). The Tukey HSD (honest significant difference) post-hoc test showed that some of the values of sway range and mean velocity of COP, rambling and trembling in sagittal and frontal plane were significantly greater in control boys aged 3-4 years compared to other subgroups (p < 0.05).

SIGNIFICANCE

Long-term postural control monitoring by a pediatrician and/or physiotherapist seems justified and not only in children with a history of infantile developmental delay but also in their healthy peers, especially boys.

Fall-related measures in elderly individuals and Parkinson's disease subjects

Falls pose a serious problem in elderly and clinical populations. Most often, they lead to a loss of mobility and independence. They might also be an indirect cause of death. The aim of this study was to determine an objective predictor of the fear of falling and falls in elderly subjects (ESs) and Parkinson's disease (PD) subjects. Thirty-two ESs were examined in this study, of whom sixteen were diagnosed with PD. The testing procedures comprised force plate measurements (limit of stability test-LOS test) and clinical tests (Berg Balance Scale, Functional Reach Test, Timed Up and Go test, Tinetti test). The Falls Efficacy Scale International (FES-I) was used to evaluate the fear of falling. The range of the maximum forward lean was normalized to the length from the ankle joint to the head of the first metatarsal bone and was named the functional forward stability indicator (FFSI). The FFSI, derived from the LOS test, allowed us to demonstrate the real deficit in functional stability and individual safety margins. Moreover, the FFSI was highly correlated with the FES-I score and almost all clinical test results in elderly subjects (r>0,6; p<0.05). In PD subjects, the FFSI was poorly correlated with the fear of falling, the BBS score and the FR distance; however, a high correlation with the Tinetii test (r>0,6, p<0.05) was noted. The PD subjects presented a different balance strategy when close to their stability limits, which was also reflected in the lower values of sample entropy (t = (-2.40); p<0.05; d = 0.87). The FFSI might be a good predictor of the fear of falling in the group of elderly people. Additionally, the FFSI allows us to show real balance deficits both in PD subjects and in their healthy peers without the need for a reference group and norms. In conclusion, it is postulated that the popular clinical assessments of postural balance in PD subjects should be accompanied by reliable posturography measurements.

Transitional Locomotor Tasks in People With Mild to Moderate Parkinson's Disease

Background: People with Parkinson's disease (PD) exhibit deficits in maintaining balance both during quiet standing and during walking, turning, standing up from sitting, and step initiation. Objective: The purpose of this study was to examine balance disorders during a transitional task under different conditions in participants with PD. Methods: The research was conducted on 15 PD-II (mild) and 15 PD-III (moderate) individuals (H&Y II-III stage) and 30 healthy elderly. The transitional task was measured on two force platforms (A and B). The procedure consisted of three phases: (1) quiet standing on platform A, (2) crossing to platform B, and (3) quiet standing on platform B, each until measurements were completed. There were four conditions: crossing without an obstacle, crossing with an obstacle, and walking up and down the step. Results: There were no significant differences between mild PD individuals and healthy elderly during quiet standing before the transitional task and after completing the task. The temporal aspects describing the different transitional tasks were comparable between mild PD and healthy subjects. Moderate PD participants presented a significantly higher COP velocity after the transitional task compared to the healthy older adults (p < 0.05). Additionally, the moderate PD group showed significantly higher values for transit time relative to healthy subjects during the transitional task in all conditions (p < 0.05). Conclusions: Disease severity affects the temporal aspects of different transitional tasks in people with PD. The procedure of completing a transitional task under different conditions allowed differences between moderate and mild PD stages and healthy subjects to be observed.

Assessment of dynamic balance during step initiation in Parkinson's disease patients and elderly - a validity study

PURPOSE

The aim of this study was to evaluate the reliability of the novel posturographic procedure and to investigate the relationships between parameters of this procedure and clinical tests. We hypothesised the proposed step initiation procedure to be reliable method of balance and motor disability assessment, especially in patients with neurological deficits. Also, we assumed high significant correlation between parameters of step initiation procedures and clinical tests.

METHODS

The 35 subjects with idiopathic PD and 35 agedmatched healthy controls participated in this study. The gait initiation was measured using two force platforms. The procedure consisted of three phases: (1) quiet standing on a first platform (2) crossing on the second platform, (3) quiet standing on a second platform. Testing was carried out in four conditions: unperturbed trial, obstacle crossing, step-up and step-down.

RESULTS

In the proposed gait initiation procedure, the vCOP, raCOP and rmsCOP showed an excellent reliability (ICC > 0.80). For transit phase, reliability of all variables in all conditions also was excellent (ICC = 0.8-0.9). There were only a few associations between Tinetti scores and posturographic variables in controls, but in PD patients the significant correlations were found between the proposed measures and the UPDRS, Tinetti, FRT, TUG and with the BBS.

CONCLUSIONS

The proposed gait initiation procedure is reliable and very suitable for the assessment of patients with Parkinson's disease. It can be used as an objective assessment of the clinical condition and dynamic balance, and help in the designing and programming of the appropriate rehabilitation and treatment.

Extracorporeal Shock Wave Therapy for Achilles Tendinopathy

Extracorporeal shock wave therapy (ESWT) is among the conservative treatments for Achilles tendinopathy. Unfortunately, no optimal application parameters have been determined that would ensure ESWT effectiveness in this condition. The aim of the paper is to use research reports on ESWT in patients with Achilles tendinopathy to help practising physiotherapists establish the most effective intervention parameters. A search was conducted using the following databases: PubMed, Scopus, EBSCOhost, and Web of Science. The papers were checked for relevant content and were included based on the following criteria: full-text article published in English and including comprehensive description of shock wave application. Twenty-two articles met the inclusion criteria. Most studies on the effectiveness of ESWT for Achilles tendinopathy included in this narrative review were randomized controlled trials. Two case-control studies, a case series study, prospective audit, clinical trial protocol, and a pilot study were also considered. The majority were prospective studies. Only a few authors presented the findings from retrospective observations. The two modalities of shock wave therapy used for Achilles tendinopathy are focused shock waves and radial shock waves. The literature contains reports presenting mainly beneficial effects of ESWT in patients with Achilles tendinopathy.

Forward functional stability indicator (FFSI) as a reliable measure of limits of stability

Functional stability has been studied in diverse populations, yet the possibility to compare the results across them and the knowledge about actual performance referenced to the maximum capacity is limited. Our aim was to improve the functional limits of stability testing and introduced Forward Functional Stability Indicator (FFSI) as a reliable measure of functional stability. The study participants were not able to cross the projected forward anatomical stability limit (FASL). It is located at the level of first metatarsophalangeal joints and should be considered a mechanical limit of the maximal voluntary centre of foot pressure (COP) excursion (MVE). It was only true when the whole feet were in contact with the ground. There were statistically significant differences in limits of stability (LOS) test results in the conditions when the heels were raised and the toes muscles were contracted isometrically. The proposed forward functional stability indicator (FFSI) is a highly reliable measure of functional stability, which provides information about the actual performance with reference to maximum capacity and is easy to compare across normal and clinical populations.

•

The proposed forward functional stability indicator (FFSI) is a highly reliable measure of functional stability.

•

FFSI provides information about the actual performance with reference to maximum capacity and is easy to compare across normal and clinical populations.

•

The forward anatomical stability limit (FASL) is located at the level of first metatarsophalangeal joints and should be considered a mechanical limit of the maximal voluntary centre of pressure (COP) excursion when certain measurement criteria are met.

A posturographic procedure assessing balance disorders in Parkinson's disease: a systematic review

Postural instability is common in Parkinson's disease (PD), often contributing to falls, injuries, and reduced mobility. In the clinical setting, balance disorder is commonly diagnosed using clinical tests and balance scales, but it is suggested that the most sensitive measurement is the force platform. The aim of this systematic review was to summarize the methods and various posturographic procedures used to assess the body balance and gait in PD. A systematic review was conducted of papers published from 2000 to 2017. Databases searched were PubMed and EBSCO. Studies must have involved patients with PD, used force platform or motion analysis system as a measurement tool, and described posturographic procedure. The Physiotherapy Evidence Database (PEDro) scale was used to assess the methodological quality of the included studies. A total of 32 studies met the inclusion criteria. The PEDro scores ranged from 5 to 7 points. The analysis of the objective methods assessing balance disorders revealed a large discrepancy in the duration and procedures of measurements. The number of repetitions of each trial fluctuated between 1 and 8, and the duration of a single trial ranged from 10 to 60 seconds. Overall, there are many scales and tests used to assess the balance disorders and disabilities of people with PD. Although in many included studies the authors have used posturography as a method to evaluate the postural instability of PD patients, the results are contradictory. To solve this issue, it is indicated to establish a "gold standard" of procedures of measures of balance.

Standards of Virtual Reality Application in Balance Training Programs in Clinical Practice: A Systematic Review

OBJECTIVE

To determine the effect of virtual reality (VR) games on improving balance in different groups of neurological patients with a particular focus on the study quality and to determine the gold standard in VR training in these groups.

MATERIALS AND METHODS

A systematic review of controlled trials published between January 2009 and December 2017 was conducted. The PubMed, SCOPUS, SPORTDiscus, and Medline databases were searched. Studies involved patients with stroke or Parkinson's disease or children with cerebral palsy. The Physiotherapy Evidence Database (PEDro) scale was used to assess the methodological quality of the included studies.

RESULTS

A total of 20 studies met the inclusion criteria. The PEDro scores ranged from 4 to 8 points. Analysis of the rehabilitation programs revealed a very large discrepancy in the planned volume of exercises in different subgroups of patients.

CONCLUSIONS

Overall, the comparison of VR interventions between conventional rehabilitation and no intervention exhibited significantly better results. However, these results should be interpreted with great caution due to the large diversity of the systems, games, and training volume used in the VR therapy. In all included studies, only several articles included objective methods to assess the effect of VR. In addition, most of the articles showed a high risk of bias, such as a lack of randomization and blinding or a small sample size. That is why further well-designed randomized control trials are required to evaluate the influence of VR on balance in different groups of neurological patients.

A comparison of a step-initiation task in women with and without urinary incontinence. A case-control study

AIMS

The aim of the study was to objectively determine differences in postural response by women with and without urinary incontinence during a step-initiation task depending on the degree of bladder filling.

METHODS

The study comprised 22 women with stress urinary incontinence and 20 women without urinary incontinence. All women participated in four trials: unperturbed and perturbed (obstacle crossing) transition between platforms, step-up and step-down trials. Velocities of center of pressure displacement, double-support period, time from exit from steady standing until the lead foot resting on the other platform and time from raising the foot from the first platform until gaining quiet standing on the other platform were measured and compared.

RESULTS

No significant differences were noted between the performance of a step-initiation task by incontinent women with full/empty bladder whereas continent women performed differently during unperturbed transition with full/empty bladder. The step-up trial revealed significant intergroup differences. The antero-posterior mean velocity of center of pressure during the empty bladder test was significantly higher in women with stress urinary incontinence (effect size = 1.02). During the same bladder condition the women with stress urinary incontinence performed significantly more slowly in unperturbed (effect size = 1.09) and perturbed (effect size = 0.84) transition compared to control group.

CONCLUSIONS

Our results indicate that women with incontinence performed the step initiation task slowly on the empty bladder tests compare to continent women.

Effect of expertise in ballet dance on static and functional balance

RESEARCH QUESTION

The purpose of this study was to examine the postural sway characteristics of the ballet dance experts in quiet standing and at their limits of stability with an approach not used before in dancers.

METHODS

The study was conducted on thirteen female ballet dancers and thirteen non-training females. The data were collected with a use of a force plate. To gain a better insight into the postural control processes, we used the rambling-trembling and sample entropy analyses in the COP data processing.

RESULTS

The main findings of the study showed professional dancers to have higher values of postural sway characteristics in comparison to the non-trainees while performing simple motor tasks. Also, higher values of the trembling component in the group of dancers during quiet standing and the inclined positions were observed. This might be a sign of higher capacity of the postural system to deal with postural instability in dancers.

IMPORTANCE

Our results confirmed that the visual information is important in the process of postural control of dancers', which is proven by increased dislocations of the COP without visual feedback. The sample entropy results indicated more irregular characteristics of postural sway in ballet dancers representing more automated postural control. The data analysis methods showed high sensitivity to the subtle changes in postural control due to the dance training.

The Effects of Cryotherapy on Knee Joint Position Sense and Force Production Sense in Healthy Individuals

The proprioceptive information received from mechanoreceptors is potentially responsible for controlling the joint position and force differentiation. However, it is unknown whether cryotherapy influences this complex mechanism. Previously reported results are not universally conclusive and sometimes even contradictory. The main objective of this study was to investigate the impact of local cryotherapy on knee joint position sense (JPS) and force production sense (FPS). The study group consisted of 55 healthy participants (age: 21 ± 2 years, body height: 171.2 ± 9 cm, body mass: 63.3 ± 12 kg, BMI: 21.5 ± 2.6). Local cooling was achieved with the use of gel-packs cooled to -2 ± 2.5°C and applied simultaneously over the knee joint and the quadriceps femoris muscle for 20 minutes. JPS and FPS were evaluated using the Biodex System 4 Pro apparatus. Repeated measures analysis of variance (ANOVA) did not show any statistically significant changes of the JPS and FPS under application of cryotherapy for all analyzed variables: the JPS’s absolute error (p = 0.976), its relative error (p = 0.295), and its variable error (p = 0.489); the FPS’s absolute error (p = 0.688), its relative error (p = 0.193), and its variable error (p = 0.123). The results indicate that local cooling does not affect proprioceptive acuity of the healthy knee joint. They also suggest that local limited cooling before physical activity at low velocity did not present health or injury risk in this particular study group.

Quiet standing postural sway of 10- to 13-year-old, national-level, female acrobatic gymnasts

PURPOSE

The aim of the study was to determine whether 10- to 13-year-old, national-level, female acrobatic gymnasts present a different quiet standing postural control (with and without visual cues) than untrained female peers.

METHODS

The mean velocity of the center of pressure (in anterior-posterior and medial-lateral directions) was computed from 60-s long quiet-standing trials on a stationary force plate in fifteen 10- to 13-year-old female acrobatic gymnasts and thirteen sex- and age-matched non-athletes. A two-way repeated measures ANOVA (acrobatic gymnasts vs. non-athletes and eyes open vs. eyes closed) was used for the anterior-posterior and mediallateral COP mean velocity. The relation between subjects' body mass and COP mean velocity was tested with the used Spearman's Rank Correlation Coefficient.

RESULTS

Postural sway (represented by COP mean velocity) was not significantly different between the acrobatic gymnasts and the non-athletes ( p > 0.05), except for the faster medial-lateral sway in eyes-open conditions in the acrobatic gymnasts ( p < 0.05). The gymnasts' body mass negatively correlated with their anterior-posterior sway velocity in both visual conditions (eyes open: r = -0.7; eyes closed: r = -0.6) and with medial-lateral sway velocity during eyes-closed trials (r = -0.5; p < 0.05).

CONCLUSIONS

Results of the study indicate that in quiet standing postural control 10- to 13-year-old acrobatic gymnasts did not make use of their trained abilities. Heavier gymnasts might have been more stable than lighter ones during quiet standing.

The influence of different intensity treadmill efforts on the sense of rhythm of non-professional runners - pilot study

PURPOSE

The purpose of this study was to determine how global effort affects the rhythm of multi-joint coordination in the global task. We wanted to examine how this specific kind of fatigue impacts sense of rhythm.

METHODS

In this study, fourteen non-professsional runners performed two effort trials of different intensity, where speed was set individually according to the speed of running when par- ticipants reached lactate threshold. Before and after each effort trial they had to perform the rhythm test.

RESULTS

Two-way analysis of variance ANOVA did not reveal significant differences among the variables of pre- and post-effort rhythm test. It is suggested that these results are supported by the application of different movement strategies to compensate for fatigue, and possible motor learning effect of simple timing performance.

CONCLUSIONS

In our opinion the training workout routine should include cyclic technical exercises after fatigue. Not only to develop and improve energetics of movement, but also to learn and perfect different movement patterns and develop novel movement strategies.

Balance Training Programs in Athletes - a Systematic Review

It has become almost routine practice to incorporate balance exercises into training programs for athletes from different sports. However, the type of training that is most efficient remains unclear, as well as the frequency, intensity and duration of the exercise that would be most beneficial have not yet been determined. The following review is based on papers that were found through computerized searches of PubMed and SportDiscus from 2000 to 2016. Articles related to balance training, testing, and injury prevention in young healthy athletes were considered. Based on a Boolean search strategy the independent researchers performed a literature review. A total of 2395 articles were evaluated, yet only 50 studies met the inclusion criteria. In most of the reviewed articles, balance training has proven to be an effective tool for the improvement of postural control. It is difficult to establish one model of training that would be appropriate for each sport discipline, including its characteristics and demands. The main aim of this review was to identify a training protocol based on most commonly used interventions that led to improvements in balance. Our choice was specifically established on the assessment of the effects of balance training on postural control and injury prevention as well as balance training methods. The analyses including papers in which training protocols demonstrated positive effects on balance performance suggest that an efficient training protocol should last for 8 weeks, with a frequency of two training sessions per week, and a single training session of 45 min. This standard was established based on 36 reviewed studies.

Manifestations of Proprioception During Vertical Jumps to Specific Heights

Artur, S, Bogdan, P, Kawczyński, A, Winiarski, S, Grzegorz, J, and Andrzej, R. Manifestations of proprioception during vertical jumps to specific heights. J Strength Cond Res 31(6): 1694–1701, 2017—Jumping and proprioception are important abilities in many sports. The efficiency of the proprioceptive system is indirectly related to jumps performed at specified heights. Therefore, this study recorded the ability of young athletes who play team sports to jump to a specific height compared with their maximum ability. A total of 154 male (age: 14.8 ± 0.9 years, body height: 181.8 ± 8.9 cm, body weight: 69.8 ± 11.8 kg, training experience: 3.8 ± 1.7 years) and 151 female (age: 14.1 ± 0.8 years, body height: 170.5 ± 6.5 cm, body weight: 60.3 ± 9.4 kg, training experience: 3.7 ± 1.4 years) team games players were recruited for this study. Each participant performed 2 countermovement jumps with arm swing to 25, 50, 75, and 100% of the maximum height. Measurements were performed using a force plate. Jump height and its accuracy with respect to a specified height were calculated. The results revealed no significant differences in jump height and its accuracy to the specified heights between the groups (stratified by age, sex, and sport). Individuals with a higher jumping accuracy also exhibited greater maximum jump heights. Jumps to 25% of the maximum height were approximately 2 times higher than the target height. The decreased jump accuracy to a specific height when attempting to jump to lower heights should be reduced with training, particularly among athletes who play team sports. These findings provide useful information regarding the proprioceptive system for team sport coaches and may shape guidelines for training routines by working with submaximal loads.

Static postural stability in women with stress urinary incontinence: Effects of vision and bladder filling

AIMS

This case-control study was designed to compare static postural stability between women with stress urinary incontinence and continent women and it was hypothesized that women with incontinence aged around 50 years also have balance disorders.

METHODS

Eighteen women with incontinence and twelve women without incontinence aged 50-55 years participated in two 60-s trials of each of four different testing conditions: eyes open/full bladder, eyes open/empty bladder, eyes closed/full bladder, eyes closed/empty bladder. The center of foot pressure (COP): sway range, root mean square, velocity (in the antero-posterior and medio-lateral directions), and COP area were recorded. The stabilograms were decomposed into rambling and trembling components.

RESULTS

The groups of women with and without incontinence differed during the full bladder condition in antero-posterior COP sway range, COP area, and rambling trajectory (range in the antero-posterior and medio-lateral directions, root mean square in the antero-posterior and medio-lateral directions and velocity in the antero-posterior direction).

CONCLUSION

The women with incontinence had more difficulty controlling their postural balance than continent women while standing with a full bladder. Therefore, developing therapeutic management focused on strengthening the women's core muscles and improving their postural balance seems advisable.

Step-Initiation Deficits in Children with Faulty Posture Diagnosed with Neurodevelopmental Disorders during Infancy

BACKGROUND

Early detection of movement deficits during step initiation will facilitate the selection of the optimal physiotherapy management strategy. The main aim of the study was to assess potential differences in step initiation between 5- and 6-year-old children with faulty posture who had been diagnosed with neurodevelopmental disorders during infancy and healthy children.

METHODS

The experimental group consisted of 19 children aged 5-6 years with faulty posture, who had been diagnosed with neurodevelopmental disorders during infancy and were given physiotherapy in the first year of their lives. The control group comprised 19 nursery school children aged 5-6 years with no postural defects, no history of postural control or movement deficits, and no physiotherapy interventions in the first year of their lives. Step initiation was performed on force platforms under various conditions, i.e., with and without an obstacle, stepping up onto a platform placed at a higher level, stepping down onto a platform placed on a lower level. The recording of center of foot pressure (COP) displacements was divided into three phases: phase 1 (P1)-quiet standing before step initiation, phase 2 (P2)-transit, phase 3 (P3)-quiet standing until measurement completion.

RESULTS

The Tukey post hoc test showed that the means of sway range (raCOP) and mean velocity (vCOP) in sagittal (_AP) plane for phase 1 and vCOP in frontal (_ML) plane for phase 3 registered in the step-up trial were significantly higher (p < 0.05) in children with faulty posture compared to children with typical development. P1vCOP_ML, P3vCOP_AP, P3raCOP_ML, and P3vCOP_MLof the step-down trial were also significantly higher in children with faulty posture (p < 0.05).

CONCLUSION

Inclusion of functional movement exercises (stair-walking tasks) in physiotherapy interventions for children with postural defects seems well justified.The trial was registered in the Australian and New Zealand Clinical Trials Registry (no. ACTRN12617001068358).

Evaluation of reliability and concurrent validity of two optoelectric systems used for recording maximum vertical jumping performance versus the gold standard

PURPOSE

The objective of this study was to evaluate the reliability and validity of two alternative systems used for jumping performance measurement.

METHODS

Two groups of subjects were tested. The first group consisted of 15 male adults (21.3 ± 1.7 years) and the second group consisted of 16 female volleyball players (17.2 ± 0.9 years). We used three different systems of data collection in the study. Two of the used systems are based on optoelectric components. The Optojump Next system is referred to as the optoelectric system, and BTS Smart-E is refered to as the video system. Concurrent validity of these systems was verified with the use of "gold standard" which is force platform. All systems were used to estimate the height of vertical jumps.

RESULTS

Both optoelectric systems turned out to be highly reliable with the ICCs = 0.98 for Optojump and 0.9 for BTS Smart. Their concurrent validity with the force platform data was also very high r = 0.99 and r = 0.97, respectively.

CONCLUSIONS

Comparison of these two systems shows distinct differences between them. Out of the two systems, Optojump system is more suitable for quick and reliable sports testing while when BTS-Smart is better for research and clinical testing.

Effect of drop jump technique on the reactive strength index

The basic drill of plyometric training aimed at improving lower limb power and jump height is a drop jump. This exercise can be performed using different techniques, which substantially affects jump variables. Therefore, the aim of this study was to compare the values of the reactive strength index (RSI) for countermovement drop jumps (CDJs) and bounce drop jumps (BDJs). The study was carried out in a group of 8 male youth basketball players. The tests were conducted using the AMTI BP600900 force plate to measure ground reaction forces and the Noraxon MyoMotion system to record kinematic data. Each player performed two CDJs and two BDJs from the height of 15, 30, 45 and 60 cm. The RSI was calculated as a ratio of jump height and contact time. Moreover, the RSI was determined for the amortization and take-off phases separately. Significant differences (p < 0.05) between RSI values for CDJs and BDJs were recorded for jumps from 30, 45 and 60 cm. Differences in RSI values for jumps from 15 cm were not significant. Furthermore, CDJ height values were significantly higher (p < 0.05) than the values recorded for BDJs. Times of contact, amortization and take-off during BDJs were significantly shorter (p < 0.05) than the respective values obtained for CDJs. Therefore, the use of the RSI to monitor plyometric training should be based on the drop jump technique that is commonly performed by basketball players.

Directional measures of postural sway as predictors of balance instability and accidental falls

Despite the obvious advantages and popularity of static posturography, universal standards for posturographic tests have not been developed thus far. Most of the center-of-foot pressure (COP) indices are strongly dependent on an individual experimental design, and are susceptible to distortions, which makes results of their analysis incomparable. In this research, we present a novel approach to the analysis of the COP trajectory based on the directional features of postural sway. Our novel output measures: the sway directional indices (DI) and sway vector (SV) were applied to assess the postural stability in the group of young able-bodied subjects. Towards this aim, the COP trajectories were recorded in 100 students standing still for 60 s, with eyes open (EO) and then, with eyes closed (EC). Each record was subdivided then into 20, 30 and 60 s samples. Interclass correlation coefficients were calculated from the samples. The controlled variables (visual conditions) uniquely affected the output measures, but only in case of proper signal pretreatment (low-pass filtering). In filtering below 6 Hz, the DI and SV provided a unique set of descriptors for postural control. Both sway measures were highly independent of the trial length and the sampling frequency, and were unaffected by the sampling noise. Directional indices of COP filtered at 6 Hz showed high to very high reliability, with ICC range of 0.7-0.9. Results of a single 60 s trial are sufficient to reach acceptable reliability for both DI and SV. In conclusion, the directional sway measures may be recommended as the primary standard in static posturography.

Intra-Personal and Inter-Personal Kinetic Synergies During Jumping

We explored synergies between two legs and two subjects during preparation for a long jump into a target. Synergies were expected during one-person jumping. No such synergies were expected between two persons jumping in parallel without additional contact, while synergies were expected to emerge with haptic contact and become stronger with strong mechanical contact. Subjects performed jumps either alone (each foot standing on a separate force platform) or in dyads (parallel to each other, each person standing on a separate force platform) without any contact, with haptic contact, and with strong coupling. Strong negative correlations between pairs of force variables (strong synergies) were seen in the vertical force in one-person jumps and weaker synergies in two-person jumps with the strong contact. For other force variables, only weak synergies were present in one-person jumps and no negative correlations between pairs of force variable for two-person jumps. Pairs of moment variables from the two force platforms at steady state showed positive correlations, which were strong in one-person jumps and weaker, but still significant, in two-person jumps with the haptic and strong contact. Anticipatory synergy adjustments prior to action initiation were observed in one-person trials only. We interpret the different results for the force and moment variables at steady state as reflections of postural sway.

The impact of the Swedish massage on the kinesthetic differentiation in healthy individuals

Background:

Swedish massage is one of the common treatments to provide optimal start and readiness of athletes. The ability of kinesthetic differentiation (KD) is crucial in sport performance. This skill allows to adapt demanded muscle forces to optimize the motor tasks, and it is responsible for the precision. In the literature, there is no evidence how Swedish massage influences the kinesthetic differentiation.

Purpose:

The objective of the study was to evaluate the impact of Swedish massage on the kinesthetic differentiation and muscle strength of hand grip.

Methods:

Thirty participants took part in this investigation (17 women and 13 men). The assessment consisted of KD tests conducted on the dominant (DH) and nondominant hand (NDH) after 15 minutes of hand and forearm Swedish massage. The procedure consisted of 13 trials for each extremity. The first three were done for 100% of the participants’ capabilities (F_max), the next five trials were done using 50% of maximum force (50% of F_max), and in the last five trials, the participants tried to use only 50% of their previous force (1/2 of 50%). Finally, the absolute force production error (FPE) was calculated for 50% (FPE_50%) and 25% (FPE_25%).

Results:

The two-way repeated measure analysis of variance ANOVA did not reveal any statistically significant changes in maximal strength grip and KD between pre- and postmassage intervention in both DH and NDH hand. Correlations showed strong relationship between pre- and postmassage for maximum force (r = 0.92, p = .01 for DH, and r = 0.94, p = .01 for NDH), and only for the FPE_50% (r = 0.67, p = .01 for DH, and r = 0.71, p = .01 for NDH).

Conclusions:

The results obtained indicated that the application of the Swedish massage did not affect the kinesthetic differentiation in this particular young adult group.

A prospective, randomized, controlled, clinical study to evaluate the efficacy of high-frequency ultrasound in the treatment of Stage II and Stage III pressure ulcers in geriatric patients

International guidelines recommend high-frequency ultrasound (HFUS; MHz) for treating infected pressure ulcers (PUs). A 2-year, prospective, randomized, controlled study was conducted to evaluate how HFUS affects PU healing among 42 geriatric patients treated in four nursing and care centers in Silesia, Poland. Participants (age range 71-95 years,) all with wounds that did not respond to previous treatment for at least 4 weeks, were randomly assigned to the treatment group (TG) (20 with 21 PUs, mean age 83.60 ± 5.04 years) or control group (CG) (22 with 23 PUs, mean age 82.59 ± 6.65 years). All patients received standard wound care (SWC); the TG additionally was provided HFUS (1 MHz, 0.5 W/ cm2, duty cycle of 20%, 1-3 minutes/cm2; one session per day, 5 days a week). Patients were monitored for 6 weeks or until wounds closed. Percent change in wound surface area (WSA), the Gilman's parameter, the weekly rate of change in WSA, and the percentage of PUs that improved (ie, decreased in size by at least 50% or closed) were used to compare differences. Data were analyzed using Fisher's exact test, the Wilcoxon matched pairs test, and the Mann-Whitney U test (P <0.05). Mean baseline WSA and the pretreatment duration of PUs were 15.38 ± 12.92 cm2 and 1.64 ± 0.73 months and 11.08 ± 7.52 cm2 and 2.26 ± 1.42 months in the TG and CG groups, respectively. After 6 weeks of treatment, the WSA of PUs decreased significantly in both groups (P = 0.000069 in the TG and P = 0.0062 in the CG) with significantly greater improvement in the TG (an average of 68.80% ± 37.23% compared with 37.24% ± 57.84%; P = 0.047). The value of the Gilman's parameter was greater in the TG than in the CG (0.88 ± 0.62 and 0.43 ± 0.50, respectively; P = 0.018). The mean weekly change of WSA was greater in the TG than in the CG but only for Stage II PUs (3.09 ± 2.93 cm2/week and 1.08 ± 1.43 cm2/week; P = 0.045). More Stage II PUs in the TG decreased by at least 50% (11 of 14 = 78.57%) than in the CG (seven of 18 = 38.89%) (P = 0.035). In the TG, seven of 14 (50%) Stage II PUs closed, four of seven (42.86%) Stage III PUs decreased by at least 50%, and one of seven (14.29%) Stage III PUs closed; respective values for the CG are three of 18 (16.67%), three of five (60%,) and zero of five (0%) (P = 0.062, P = 0.999, P = 0.999, respectively). The study showed HFUS therapy can reduce the WSA of PUs regardless of their shape, but further research is necessary, particularly to establish how ultrasound influences the healing of Stage III and Stage IV PUs.

The effect of a short-term and long-term whole-body vibration in healthy men upon the postural stability

The study aimed to establish the short-term and long-term effects of whole-body vibration on postural stability. The sample consisted of 28 male subjects randomly allocated to four comparative groups, three of which exercised on a vibration platform with parameters set individually for the groups. The stabilographic signal was recorded before the test commenced, after a single session of whole-body vibration, immediately after the last set of exercises of the 4-week whole-body vibration training, and one week after the training ended. The subjects were exposed to vibrations 3 times a week for 4 weeks. Long-term vibration training significantly shortened the rambling and trembling paths in the frontal plane. The path lengths were significantly reduced in the frontal plane one week after the training end date. Most changes in the values of the center of pressure (COP) path lengths in the sagittal and frontal plane were statistically insignificant. We concluded that long-term vibration training improves the postural stability of young healthy individuals in the frontal plane.

Sense of Rhythm Does Not Differentiate Professional Hurdlers from Non-Athletes

The importance of rhythm and specific endurance capabilities were examined in the technical skill and performance of hurdle runners. Additionally, interaction effects among rhythm, anaerobic fitness, and body constitution were analyzed. Seven 18-year-old members of the Polish Junior National Team in 110 m hurdles and 8 age-matched controls who were non-athletes participated. Movement coordination tests (rhythm and differentiation tests) and an anaerobic fitness test were performed. There were no statistically significant differences between the athletes and the control group on the coordination or rhythm test variables. No support was found for the hypothesis that a hurdler's timing ability influences performance.

The reliability of a rambling-trembling analysis of center of pressure measures

The center of pressure (COP) measures are most commonly used in postural studies (e.g., COP range, sway path length and mean COP velocity). Relatively new method based on the equilibrium point hypothesis that addresses more explicitly the dynamic nature of COP and represents more subtle aspects of postural control is the rambling (RM) and trembling (TR) decomposition of a stabilogram. With this method, the COP trajectory can be decomposed into deviations resulting from supraspinal (i.e., RM) and spinal processes (i.e., TR). The trajectory generated by shifting COP is referred to as RM and its difference from the original COP signal is referred to as TR. Although there is still scientific discussion as to whether this method gives valuable additional information about postural control processes, it is gaining popularity. Unfortunately, there is lack of standardization in the methodology of data collection for this approach, particularly with respect to the number of trial repetitions and their duration. The objective of this study was to assess the reliability of RM-TR measurements. Fifteen young, healthy male subjects performed ten 120-s trials of quiet standing. Measurements of RM, TR and COP were calculated using the first 30, 60, 90 and 120-s of each trial. An ANOVA-based ICC model was used to estimate the reliability. The results of this study suggest that at least three 60-s trials should be used when using selected measures of RM-TR.

The effect of short- and long-term vibration training on postural stability in men

The study aimed to establish the short- and long-term effects of vibration on postural stability in young men. A single set of exercises and a 4-week vibration training were assessed for their impact on the center of foot pressure (COP) sway. The sample consisted of 49 male subjects randomly allocated to seven comparative groups, six of which exercised on a vibration platform whose parameters were set individually for the groups. Group VII was the control group. The stabilographic signal was recorded before the test commenced, after a single application of vibration, before the last set of exercises of the 4-week vibration training, immediately afterwards, as well as one week and one month after the training ended. The subjects were exposed to vibration 3 times a week for 4 weeks. Both a single application of vibration and the 4-week vibration training had an effect on all parameter values, but most changes were statistically insignificant. Group III was the only one where the COP sway in the anterior-posterior direction significantly increased after a single exposure to vibration and significantly decreased in both anterior-posterior and medio-lateral planes one week after vibration training compared with the pre-test recordings.

Clinical Assessment of Postural Stability

One of the most important applications of postural sway analysis is the detection of such impairments to the motor system that would allow us to predict risk of falling. Force plate posturography is a commonly used clinical method for the evaluation of postural instability. The diagnostic value of postural sway represented here by oscillations of the center-of-foot pressure (COFP) is being questioned very often. These diagnostic problems result from the lack of an adequate and reliable method of sway analysis — a method that would present a clear connection between stability and quality of postural control. To gain better insight into this problem, the following experiments were done and some effective methods of sway analysis typically applied in conventional mechanics and electrical engineering are presented here. Quality of the postural stability was assessed using, in addition to standard parameters, spatial histograms, body transfer function, contour plots as well as the COFP fractal dimension. Such complex analysis allowed us to extract significant sway parameters that are relevant to postural instability. Analysis of the data revealed that spatial histogram has clear peak which maximum was sensitive to sensory conditions. Changes in the postural sway distributions have been confirmed by the increase of the COFP fractal dimension.

The effect of whole-body vibration frequency and amplitude on the myoelectric activity of vastus medialis and vastus lateralis

The aim of this study was to evaluate the efficiency of training protocols for whole body vibration (WBV) training through the modulation of the frequency and amplitude of vibration. Despite the large number of studies regarding effects of such training, there is still lack of knowledge regarding optimum training protocols. The study analyzed the influence of whole-body vibration parameters (i.e., the frequency and amplitude) on the myoelectric activity of vastus lateralis and vastus medialis in 29 females with the use of electromyography (EMG). The first and second of the eight consecutive trials were performed without vibrations; the remaining six trials were performed in a randomized order on a platform vibrating at different amplitude (2mm and 4mm) and frequency (20 Hz, 40 Hz and 60 Hz) combinations. The results revealed significantly higher EMG amplitude of both muscles during the vibration as compared with the non- vibrated trials (trial 1 and 2). Furthermore, the EMG activity significantly increased both with the amplitude and frequency, being the highest when the frequency and amplitude of reached 60 Hz and 4 mm, respectively. The study aims to determine the optimal vibration parameters in the aspect of purposeful stimulation of chosen leg muscles. Based on the results of the presented investigation, sports trainers and physiotherapists may be able to optimize training programs involving vibration platforms. Key pointsThe observed vibration effect significantly increases both with the amplitude and frequency.Certain frequency/amplitude combinations of mechanical vibrations cause the same level of myoelectric muscle activity.

Violations of Fitts' law in a ballistic task

The authors explored changes in the postural preparation and movement times during jumps into targets of different sizes placed at different distances from the participant. Both movement and preparation times scaled with movement distance. Neither movement nor preparation time showed an effect of target size, although preparation time showed a tendency to increase for smaller targets. These observations show that the classical Fitts' law can be violated in tasks that involve a ballistic component. The data corroborate a hypothesis that Fitts' law originates at the level of movement planning.