Characteristics of transitional locomotor tasks performed by patients with dementia.

Elderly individuals may be at increased risk of falls than their peers. Early identification of balance disorders and their appropriate intervention are crucial for patients with dementia. The aim of this study was to identify postural instability in patients from mild to moderate dementia while performing transitional locomotor tasks under different conditions. Fifty-four patients with dementia and 30 healthy controls voluntarily participated in the study. The transitional locomotor task was performed on two force platforms under four conditions: unimpeded transition, obstacle clearance, step-up and step-down trials. The recording of center of foot pressure displacements was divided into three distinct phases: 1st phase-quiet standing before the transitional locomotor task, 2nd phase-forward stepping, 3rd phase-quiet standing after the transitional locomotor task. Patients with dementia were characterized by a longer transitional locomotor task time than the control group under all conditions (P < 0.03). Significant differences in quiet standing before the transitional locomotor task were observed between patients with dementia and the control group, but only in unimpeded transition and obstacle clearance trials (P < 0.02). No significant differences in quiet standing after step transition were observed between patients with dementia and the control group (P > 0.05). Postural control research in patients with dementia should focus on the functional motor task rather than on a simple motor task (quiet standing). Because even patients with mild dementia have impaired dynamic balance, the assessment of transitional locomotor tasks performed by patients with dementia might provide an indicator of an early diagnosis of dementia and might lead to better individualized physiotherapy.

Age-Related Differences in Intermuscular Coherence EMG-EMG of Ankle Joint Antagonist Muscle Activity during Maximal Leaning.

BACKGROUND: Intermuscular synchronization is one of the fundamental aspects of maintaining a stable posture and is of great importance in the aging process. This study aimed to assess muscle synchronization and postural stabilizer asymmetry during quiet standing and the limits of stability using wavelet analysis. Intermuscular synchrony and antagonistic sEMG-sEMG (surface electromyography) coherence asymmetry were evaluated in the tibialis anterior and soleus muscles. METHODS: The study involved 20 elderly (aged 65 ± 3.6) and 20 young (aged 21 ± 1.3) subjects. The task was to perform a maximum forward bend in a standing position. The prone test was divided into three phases: quiet standing (10 s), dynamic learning, and maintenance of maximum leaning (20 s). Wavelet analysis of coherence was performed in the delta and beta bands. RESULTS: Young subjects modulated interface coherences to a greater extent in the beta band. Analysis of postural stability during standing tasks showed that only the parameter R2b (the distance between the maximal and minimal position central of pressure), as an indicator for assessing the practical limits of stability, was found to be significantly associated with differences in aging. CONCLUSION: The results showed differences in the beta and delta band oscillations between young and older subjects in a postural task involving standing quietly and leaning forward.

COVID-19 and Postural Control-A Stabilographic Study Using Rambling-Trembling Decomposition Method.

Background and Objectives: Some respiratory viruses demonstrate neurotropic capacities. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has recently taken over the globe, causing coronavirus disease 2019 (COVID-19). The aim of the study was to evaluate the impact of COVID-19 on postural control in subjects who have recently recovered from the infection. Materials and Methods: Thirty-three convalescents who underwent COVID-19 within the preceding 2-4 weeks, and 35 healthy controls were enrolled. The ground reaction forces were registered with the use of a force platform during quiet standing. The analysis of the resultant center of foot pressure (COP) decomposed into rambling (RAMB) and trembling (TREMB) and sample entropy was conducted. Results: Range of TREMB was significantly increased in subjects who experienced anosmia/hyposmia during COVID-19 when the measurement was performed with closed eyes (p = 0.03). In addition, subjects who reported dyspnea during COVID-19 demonstrated significant increase of length and velocity of COP (p < 0.001), RAMB (p < 0.001), and TREMB (p < 0.001), indicating substantial changes in postural control. Conclusions: Subjects who had experienced olfactory dysfunction or respiratory distress during COVID-19 demonstrate symptoms of balance deficits after COVID-19 recovery, and the analysis using rambling-trembling decomposition method might point at less efficient peripheral control. Monitoring for neurological sequelae of COVID-19 should be considered.

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.

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.

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.

Relationship between the strength of the ankle and toe muscles and functional stability in young, healthy adults.

This study investigates the relationship between ankle and toe strength and functional stability in young adults, with a sample comprising sixteen females and fourteen males. The research employed force platform data to determine the center of foot pressure (COP) and calculated the forward functional stability index (FFSI) through foot anthropometric measurements. Strength measurements of toe and ankle muscles, during maximal isometric flexion and extension, were conducted using force transducers. Notable positive correlations were found between toe flexor strength and FFSI (left flexor: r = 0.4, right flexor: r = 0.38, p < 0.05), not influenced by foot anthropometry. Contrarily, no significant correlation was observed between ankle muscle strength and FFSI, despite a positive correlation with the COP range. The moderate correlation coefficients suggest that while toe flexor strength is a contributing factor to functional stability, it does not solely determine functional stability. These findings highlight the critical role of muscle strength in maintaining functional stability, particularly during forward movements and emphasize the utility of FFSI alongside traditional COP measures in balance assessment. It is recommended to employ a multifaceted approach is required in balance training programs.

Postural stability at activation and deactivation of the cochlear implant in adolescents with late lateral implantations: a quasi-experiment.

BACKGROUND: Cochlear implantation (CI) surgery has become a prevalent method of hearing rehabilitation, since it has been acknowledged that it impacts effectively on the vestibular system. However, there is still no consensus among clinicians on the most appropriate age and area (lateral/bilateral) of CI surgery in terms of postural control. The present study aimed to assess the postural control in late lateral CI adolescents with different visual (eyes opened(EO)/eyes closed(EC)) and auditory (CI activated/deactivated) conditions and to build a theoretical model of postural control based on sensual compensatory mechanisms that are predominant in late CI individuals. It was hypothesized that kinesthetic sensation and exteroceptors of the superficial sensation are critical for neuromuscular control after late CI. METHODS: A quasi-experimental study protocol was used in this study to assess the postural stability performance in the studied adolescents with different visual and auditory perceptions. 27 adolescent students with hearing loss participated in the study. A force plate (Accu Gait AMTI) with computer software (NetForce) was used in the study to assess the postural stability with four different conditions(EO)/EC), CI activated/deactivated). RESULTS: vCOP was found to have a significant growing tendency within the conditions of CI activated/deactivated.No statistically significant relationships were noted between the range of the displacement of feet pressure (Area) and both the visual and auditory conditions. Hearing loss etiology was statistically significantly related to the values of vCOP, within the conditions of EO, CI activated/deactivated (p < 0.01), what did not occure with the condition of EC (p > 0.05). Neuromuscular control with the condition of EC x CI deactivated was found to be based on the kinesthetic-tactual compensatory model. CONCLUSIONS: Kinesthetic sensation and exteroceptors of the superficial sensation seem to be the predominant source of information to maintain postural control in late CI adolescents, regardless of the visual and auditory conditions. The etiology of hearing loss (congenital/acquired) can be a predictor of the values of the vCOP. In order to improve neuromuscular control in this population, it is recommended that the patients perform physical activity tasks, especially to develop core muscles, based on direct stimulation and rotational stability.

Efficacy of shock wave therapy and ultrasound therapy in non-insertional Achilles tendinopathy: a randomised clinical trial.

Objective: Physiotherapists and physicians continue to seek effective conservative treatments for Achilles tendinopathy. This study aimed to subjectively and objectively determine the therapeutic efficacy of radial shock wave therapy (RSWT) and ultrasound therapy in non-insertional Achilles tendinopathy. Materials and methods: Thirty-nine patients with non-insertional Achilles tendinopathy were randomly assigned to three experimental groups, i.e., RSWT (group A), ultrasound therapy (group B), and placebo ultrasound (group C) groups. Before the intervention and at weeks 1 and 6 after the treatment, the patients were assessed using the Victorian Institute of Sport Assessment-Achilles (VISA-A) questionnaire and posturographic measurements of step initiation performed on the force platforms under two different conditions (non-perturbed transit and perturbed transit). Results: Six weeks after therapy, all groups exhibited significantly increased VISA-A scores against the measurement at week 1 after therapy. The post-therapy percentage changes in VISA-A scores were significantly greater in group A compared to group B. The three-way ANOVA demonstrated that treatment type affected sway range in the frontal plane and mean velocity of the centre of foot pressure displacements in the sagittal and frontal planes during quiet standing before step initiation. The Bonferroni post-hoc test showed that the means of all those variables were significantly smaller for group A than for group B patients. The three-way ANOVA revealed an effect of the platform arrangement on transit time and double-support period. The Bonferroni post-hoc test revealed statistically longer transit time for the perturbed vs. non-perturbed trials; a reverse relationship was observed for the double-support period. Conclusion: The VISA-A showed that RSWT was significantly more effective than sonotherapy for alleviation of pain intensity as well as function and activity improvement in patients with non-insertional Achilles tendinopathy. Therefore, RSWT therapy can be used in clinical practice by physiotherapists to alleviate the symptoms of non-insertional Achilles tendinopathy. Objective data registered by force platforms during quiet standing before and after step initiation did not prove useful for monitoring the progress of treatment applied to patients with non-insertional Achilles tendinopathy between consecutive therapy interventions.Clinical trial registration:https://anzctr.org.au/Trial/Registration/TrialReview.aspx?ACTRN=12617000860369, identifier (ACTRN12617000860369).

Postural Stability of Adolescents with Late Cochlear Implantation and Hearing Aids: A Non-Randomized Trial.

Background: The aim of this study was to assess the neuromuscular control of adolescents with late unilateral cochlear implantation and compare them to adolescents with hearing aids (HAs) while performing a balance task on a platform with the conditions of an activated hearing device (cochlear implant (CI)/HAs) with eyes opened/closed (EO/EC). Methods: Forty-eight adolescents with hearing loss participated in the study and were divided into SG (unilateral CI and HA) and CG (bilateral HA). The evaluation of the postural stability was performed with a force plate during two repeating testing trials with EO/EC. Results: SG was characterized by greater values of vCOP compared to CG (EO), while, in CG, greater values of vCOP were noted in the second trial. The type of hearing device was found to be related to the values of area (EO) (p < 0.001), which were always greater in SG, regardless of the visual perception. Conclusions: Late unilateral CI may impact the activation of different models of the auditory compensatory mechanism than HA, which is related to neuromuscular control. The values of vCOP can be predicted by age in late-CI individuals. Visual perception seems not to be related to the values of the area, which can be impacted both by CI and HA.

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.

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.

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).

Influence of feet's position on maximum forward lean using a new estimate of functional balance.

Functional stability is crucial to the daily activity of an independent person. Functional balance testing is widely used in laboratories and has proven to be a reliable indicator of fall risk. So far, only few studies have paid attention to the impact of foot positioning on the results of functional balance measurements. Thirty healthy adults took part in experiment. LOS test was performed for four stance positions: preferred width, wide stance (feet parallel, 28 cm apart), narrow stance (feet together) and angle stance (heels together, toes pointing outside, 90° angle between them) with eyes opened and closed. The results of the study show significant differences between angle and narrow stance according to wide and preferred width stances - angle and narrow positions didn't allow participants to lean as far as other positions. Vision had stabilizing influence on maximum forward lean in all tested positions.

Performance Level and Strike Type during Ground and Pound Determine Impact Characteristics and Net Force Variability.

The evaluation of strike impact is important for optimal training, conditioning and tactical use. Therefore, the aim of this study was to evaluate ground and pound strikes, in terms of net force variability, across genders and performance levels. Eighty-one participants, professional men (n = 8, 37 ± 6 years, 195 ± 7 cm, 113 ± 27 kg), advanced men (n = 47, 26 ± 8 years, 180 ± 7 cm, 76 ± 11 kg), and advanced women (n = 26, 21 ± 1 years, 167 ± 6 cm, 61 ± 7 kg) performed three strikes from a kneeling position into a force plate on the ground. The elbow strike resulted in the highest impulse and the palm strike in the highest peak force for all three categories. These results support the recommendation that has previously been made to teach the palm strike to beginners and advanced tactical and combat athletes. The direct punch and elbow strike net force were characterized by a double peak curve, where the first peak variability explained 70.2-84% of the net force. The second peak was pronounced in professional men during elbow strikes, which explained 16% of net force variability. The strike type determines the impact net force and its characteristics, where palm strike is typical by highest peak impact tolerance and elbow strike by double force peak with high net force impulse.

The effect of a light finger touch on the signal complexity during quiet standing.

The purpose of the study was to investigate the influence of additional tactile information (light fingertip touch) on the postural sway and regularity of center-of-pressure (COP) fluctuations. Thirty-two young, healthy participants performed a quiet standing task (30 s) on a force platform with and without light fingertip touch. COP time-series were analyzed using standard postural sway measures (range, root mean square error, velocity), COP regularity was measured with Sample entropy. Participants demonstrated significantly smaller postural sway with a light touch, but only in the anteroposterior direction. The amount of sway with additional tactile information in the sagittal plane reached the level of sway in the frontal plane without this information. Similarly, COP fluctuations were more irregular during light touch condition only in the anteroposterior direction, as evidenced by significantly higher Sample entropy. Furthermore, COP regularity decreased in the sagittal plane and reached level in the frontal plane without light touch. These results suggest that postural sway is mostly controlled in the sagittal plane and that in the mediolateral direction the control is mostly automated. In conclusion, our results support the notion that the light touch provides additional information which enhances postural stabilization. Our results expand the relation between COP regularity and the attention invested in posture in the touch domain and prove that light touch, as an attentional demanding task, leads to increased COP irregularity. Nonlinear measures of signal regularity (i.e., SampEn) provide surplus insight into human postural control and can be used as an additional useful tool to traditional balance measures.

Biathletes present repeating patterns of postural control to maintain their balance while shooting.

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

The effect of expertise on postural control in elite sport ju-jitsu athletes.

BACKGROUND: Due to the high postural control demands of sport ju-jitsu, it is likely that long-term sport ju-jitsu training may induce sport-specific adaptations in postural control, especially in positions directly related to combat. The aim of the study was to assess the differences in postural control between elite sport ju-jitsu athletes and untrained controls in non-ecological and ecological conditions and to investigate the relative contribution of spinal and supraspinal mechanisms to postural control in expert athletes. METHODS: The study was conducted on eleven male elite ju-jitsu athletes and ten non-athletes. The data was collected with the use of a force plate under two conditions: quiet standing and ju-jitsu combat stance. Apart from the standard analysis of the spatial-temporal parameters of center of foot pressure, non-linear measures were used, namely rambling-trembling and sample entropy. The non-parametric Mann-Whitney U test was used to compare both groups. RESULTS: The main findings of the study showed that in quiet standing, elite ju-jitsu athletes and non-athletes had comparable postural control in both the anterior-posterior and mediolateral planes. In contrast, in the combat stance, elite athletes had lower values of postural sway and rambling component (range and rms) and higher values of sample entropy in comparison to the non-athletes (p < 0.05). No differences were found in the trembling component of sway between groups in the combat stance (p < 0.05). CONCLUSIONS: Smaller postural sway and its rambling component in sport ju-jitsu athletes may indicate the more precise control of center of foot pressure and improved ability in estimating its position. The sample entropy results confirmed that the displacement of center of foot pressure for sport ju-jitsu athletes was more irregular, which demonstrates greater automatization in postural control. The results also confirm the importance of ecological validity in investigating postural adaptations associated with sports expertise.

The influence of visual control on postural stability in Parkinson disease.

BACKGROUND AND PURPOSE: The aim of the study was to evaluate the influence of visual control on parameters of postural stability among patients with Parkinson disease (PD) in comparison with control subjects. MATERIAL AND METHODS: Fifty patients diagnosed with idiopathic PD and 50 control subjects without features of central nervous system injury were selected for the study. The clinical diagnosis of idiopathic PD was established according to the clinical criteria of the United Kingdom Parkinson's Disease Society Brain Bank. Only patients in stages I-III according to the Hoehn-Yahr scale were included. The range of sway of the centre of foot pressure (COP) in the frontal plane (COPx) and in the sagittal plane (COPy), as well as the total path length in both axes (COPxy), was tested during quiet standing with and without visual control. RESULTS: COPxy with and without visual control was the smallest in the group of patients in stage II in comparison with patients in stage I and III according to Hoehn-Yahr and in comparison with the control group. CONCLUSIONS: Visual control significantly affects the parameters of postural stability in PD patients.

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.