An Attempt to Assess the Indications for Reverse Total Shoulder Arthroplasty Based on Biomechanical Analysis.

BACKGROUND: Starting from the 1950s, shoulder arthroplasty has been developing, one consequence of which has been the concept of reverse shoulder arthroplasty (RSA). Initially, it was supposed to be used only in patients with irreversible rotator cuff damage, but it quickly gained more and more indications for use. The aim of the present study was to assess biomechanical, objective indications for RSA in patients with shoulder osteoarthritis (OA) based on an inertial measurement system with electromyography. MATERIAL AND METHODS: 20 patients were qualified to this prospective study, 10 each in a control and experimental group. The study was conducted between August 2020 and October 2021. The experimental group consisted of 9 women and 1 man aged 55 to 85 years old, with osteoarthritis of the shoulder associated with rotator cuff damage. The study utilised the myoMotion inertial sensor system (Noraxon, USA) synchronized with the surface electromyography system Myotrace 400 (Noraxon, USA). RESULTS: Movement phase diagrams were used to assess the movement patterns. To examine the movement pattern in the shoulder, three motor tests can be proposed: flexion-extension, flexion in the scapular plane and abduction-adduction. The observation of trends for the operated limb showed the highest absolute improvement in the group with the greatest impairment of the movement pattern in the initial test. However, on final evaluation, these results were still twice as low as those obtained in the group with the least impairment. CONCLUSIONS: 1. Early qualification of patients with shoulder OA for RSA could mean a greater likelihood of functional and quality-of-life improvement. 2. Movement patterns after RSA may improve, but will probably not return to physiological values.

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 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).

Presence of an Overhead Goal Does Not Improve the Effectiveness of Jump Training.

ABSTRACT: Akbas, A, Marszalek, W, and Król, H. Presence of an overhead goal does not improve the effectiveness of jump training. J Strength Cond Res 37(4): e280-e288, 2023-This study investigated the effectiveness of jump training with and without an overhead goal (OG) on a modified countermovement jump (CMJ) tested in a similar manner, with and without OG. Fifty-two men divided into 3 groups-trained with OG, trained without OG, and untrained-were examined: before the commencement of training; after 2, 4, and 6 weeks of training; and 2 weeks after the discontinuation of training. Each session consisted of 50 modified CMJ and was performed 3 times per week. Countermovement jump height, mean power, peak power, countermovement depth, and take-off phase time were quantified, and the statistical level was set at p < 0.05. Although the results showed the beneficial effect of OG on jump height ( p < 0.01), the training with OG did not bring significantly better results than training without OG. In addition, the group trained without OG improved after 2 weeks in both testing conditions (with and without OG), whereas the group trained with OG improved after 2 weeks when tested with OG and only after 6 weeks when tested without OG. We believe the use of OG in jump training may be detrimental when the OG is withdrawn from the testing procedure because of its strong motivational and feedback features. Consequently, athletes in disciplines which require them to jump toward an object located over their head during a game, e.g., a ball or crossbar, should be tested with the presence of OG. Despite this, OG is still an important factor in maximizing jump performance.

Treatment of Jumper's Knee with Extracorporeal Shockwave Therapy: A Systematic Review and Meta-Analysis.

The aim of this systematic review and meta-analysis was to determine the therapeutic efficacy of extracorporeal shockwave therapy (ESWT) for athletes with patellar tendinopathy. We searched PubMed, EBSCOHost and Ovid for randomized controlled trials (RCTs) which evaluated the therapeutic efficacy of ESWT in athletes with jumper's knee. The methodological quality of RCTs was rated with the Physiotherapy Evidence Database scale. Data in the meta-analysis were expressed as standardized mean difference (SMDs) and 95% confidence intervals (CIs). Heterogeneity was assessed with I2 statistics. Of 192 records identified, a total of seven articles met the inclusion criteria. The ESWT and control groups with any other conservative treatment did not differ significantly with respect to the Visual Analogue Scale (VAS) long-term scores obtained at ≥ 6 months of therapy completion (SMD: -0.33; 95% CI: -4.64 to 3.98; p = 0.87; I2= 98%). Furthermore, no significant differences were found between the ESWT and control groups regarding the pooled Victorian Institute of Sports Assessment for Patella (VISA-P) scores for long-term outcomes (SMD: 8.21; 95% CI: -39.3 to 55.73; p = 0.73; I2= 99%). The ESWT and control groups did not differ significantly on the VAS and VISA-P scores for long-term outcomes. In both cases, heterogeneity was considered to be high. Hence, no clear and generalized conclusions can be drawn regarding ESWT effectiveness in athletes with patellar tendinopathy.

Effectiveness of Warm-Up Exercises with Tissue Flossing in Increasing Muscle Strength.

Tissue flossing is an increasingly popular method in physiotherapy and sports. There is a belief that tissue flossing can improve range of motion and muscle strength, shorten muscle recovery time, and reduce the risk of injury. The aim of this study was to analyse the effectiveness of tissue flossing for immediately improving muscle strength in recreational athletes when it is performed during warm-up. All participants were randomly assigned to either an experimental group (n = 36) or a control group (n = 34) using a random number generator. The experimental group (n = 36) performed an intervention comprising exercises with muscle tissue flossing and exercises without flossing. The control group (n = 30) performed the same protocol without a floss band. Muscle strength was measured for knee flexion end extension at three speeds (60, 120, and 180 °/s) 3 times. Analysed parameters include peak torque, work, and power related to body weight, flexors−extensors ratio, and time to peak torque. There were no significant changes in the muscle strength parameters from before to after the warm-up in either group (p > 0.05). Significantly lower values of peak torque, work, and power were observed in the experimental group during the warm-up with the floss band applied to muscles (p < 0.05). No clinically significant changes in time to peak torque or flexors−extensors ratio were observed. A single application of flossing does not improve muscle strength or power and can even reduce individuals' maximum muscle strength capabilities.

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.

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.

Reverse Shoulder Arthroplasty in Osteoarthritis Evaluation of the Results.

BACKGROUND: The aging structure of society results in a growing need for treatment of shoulder osteoarthritis. Reverse shoulder arthroplasty (RSA) has been developed to improve the motor function and strength of the shoulder joint without increasing the risk of dislocation. The aim of the study was to assess the change in quality of life and functional assessment of the shoulder joint after RSA in patients with osteoarthritis, based on the Oxford Shoulder Score (OSS) and an assessment of joint mobility parameters. MATERIAL AND METHODS: A total of 10 patients were admitted to our centre for shoulder arthroplasty between August 2020 and October 2021. The assessment of the degenerative changes was based on the Walch classification and the Samelson & Prieto classification. The OSS questionnaire was used to assess function of the affected shoulder joint and pain in each patient. The range of motion in the shoulder joint was assessed in the pre- and postoperative period. A follow-up examination was performed approximately 6 months after surgery. RESULTS: Analysis of the OSS scores revealed a mean value of 46 points preoperatively and 25 points postoperatively. The OSS scores six months after the procedure were an average of 20.5 points lower. A statistically significant improvement was noted in shoulder flexion (mean 37), abduction (42), external rotation (34), and internal rotation (5)(p<0.05). CONCLUSION: Each patient reported reduced pain and demonstrated an increased range of motion in the affected shoulder joint and functional improvement.

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.

Biomechanical measures of balance after balance-based exergaming training dedicated for patients with Parkinson's disease.

INTRODUCTION: Although previous studies have contributed to our understanding of the effects of implementing the virtual reality as a rehabilitation tool in patients with Parkinson's disease (PD), additional research is needed to examine the effects of applying balance-based exergaming training on quantitative biomechanical measures of balance. RESEARCH QUESTION: To investigate the effects of balance-based conventional and exergaming training on posture parameters. METHODS: The study involved 24 patients with PD (Hoehn and Yahr stages II-III).Participants underwent twelve training sessions during the 4-week training period. The experimental group (n=12) was trained with a custom-made exergaming balance based training system, the control group (n=12) underwent a conventional balance training. All objective outcomes were measured before intervention and the day after completion of training program. Postural stability was assessed using the quiet standing test, dynamic balance was assessed using limits of stability (LOS) and functional balance (FBT) tests. RESULTS: After training, participants in both groups showed significantly better results in static balance performance. However, only exergaming training significantly improved LOS performance (higher values of Range of forward lean (p = 0.039, dz = 0.67) and leaning rate (p=0.007, dz=0.96). Also FBT test improved significantly only in experimental group (decrease in time to target hit (p=0.02, dz=0.76) and significant increase of average COP velocity (p=0.008, dz=0.93). CONCLUSION: This study found that exergaming training created for patients with PD enhanced static and dynamic balance whereas conventional balance training improved static balance. Posturography is sensitive enough to reveal differential effects of training for both groups. These findings support the inclusion of our exergaming training in the exercise program for participants with PD.

The Effects of Exergaming Training on Balance in Healthy Elderly Women-A Pilot Study.

Our aim was to observe, through objective testing using an assessment module incorporated in a new exergaming system, whether elderly people's static and functional balance is improved by a balance exergaming training program based on movements performed in everyday life. Thirteen healthy elderly women participated in 12 sessions of balance-based exergaming training (three times a week, 30 min per session). All objective outcomes, the quiet standing test, functional balance test (FBT), and limit of stability (LOS) test, were measured on three occasions: before intervention, after six training sessions, and after the completion of the four-week program. The results showed a significant improvement in LOS performance after the intervention. In FBT, participants exhibited a significant decrease (p < 0.01; Kendall's W = 0.5) in the average time to target hit after six trainings. The average center of pressure velocity increased after six and 12 sessions, however did not reach significance (p = 0.053); nevertheless the size of the effect was large (ηp2 = 0.22). The parameters of the quiet standing test were not significantly affected by the training. The results support the need for more definite and objective studies assessing exergaming for balance in elderly.

The Use of Frequency Analysis as a Complementary and Explanatory Element for Time Domain Analysis in Measurements of the Ability to Maintain Balance.

Assessment of human balance is one of the most common diagnostic tests, both in medical applications and during sports training. Many new methods of measuring are introduced in these studies; however, the analysis of results is still carried out mainly based on the values determined in the time domain - the average COP speed or the ellipse field of the prediction. The aim of the current work is to present the possibilities for the practical application of frequency analyses in assessment of the ability to maintain body balance as a method supplementing standard analyses. As part of the study, measurements of the ability to maintain balance in sensory conflict conditions introduced in the form of an oscillating, three-dimensional, virtual scenery were carried out. 27 healthy volunteers (13 women and 14 men) took part in the study. The three-dimensional scenery, presented by means of the Oculus system, oscillated in the sagittal plane with frequencies equal to 0.7 Hz and 1.4 Hz. The frequency value during the measurement was constant or changed in the middle of the test. Measurements were conducted on the FDM Zebris platform. The results were analyzed using developed coefficients determined on the basis of the Short-time Fourier transform (STFT). The use of frequency-domain analyses confirmed that in the COP movement, one can observe a cyclical component corresponding to following the scenery, as well as the appearance of other cyclical components whose observation is important in terms of assessing the ability to maintain balance. It has been shown that the changes in the average COP speed that occur during the measurement can result from changes related to the movement of following the scenery as well as additional body movements indicating a greater or lesser loss of balance. It has been shown that there are differences in the COP movement provoked by the movement of the surrounding scenery, which depend on the parameters of the introduced disturbances - something that can only be observed in results obtained in the frequency domain. The conducted research shows that in measurements involving the ability to maintain one's balance conducted in sensory conflict conditions, standard time-domain analyses should be supplemented with other types of data analysis, e.g. frequency domain analyses.

Number of Trials Necessary to Apply Analysis Within the Framework of the Uncontrolled Manifold Hypothesis at Different Levels of Hierarchical Synergy Control.

The uncontrolled manifold hypothesis is a method used to quantify motor synergies, defined as a specific central nervous system organization that maintains the task-specific stability of motor actions. The UCM allows for inter-trial variance analysis between consecutive trials. However, despite the large body of literature within this framework, there is no report on the number of movement repetitions required for reliable results. Based on the hypothetical hierarchical control of motor synergies, this study aims to determine the minimum number of trials necessary to achieve a good to excellent level of reliability. Thirteen young, healthy participants performed fifteen bilateral isometric contractions of elbow flexion when visual feedback was provided. The force and electromyography data were recorded to investigate synergies at different levels of hierarchical control. The intraclass correlation coefficient was used to determine the reliability of the variance indices. Based on the obtained results, at least twelve trials are required to analyze the inter-trial variance in both force and muscle synergies within the UCM framework.

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.

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.

Movement Variability during the Flight Phase in a Single Back Sideflip (Wildcat) in Snowboarding.

Understanding the structure and variability of motion is essential for sports technique development and an effective training design. Biomechanical analysis is particularly important in new disciplines with spatially complex motions, such as snowboarding. This study aimed to evaluate the level of variability of the kinematic variables in a single backside snowboard flip known as a "wildcat". Forty-six correct flips performed by 7 experienced athletes (age: 24.9 ± 4.34 year; body mass: 71.6 ± 12.87 kg; body height: 177.4 ± 6.99 cm) were recorded using an optoelectronic VICON system in the controlled setting of an indoor freestyle park. Athletes were equipped with special boards with wheels and the geometry of the ramps corresponded to the actual on-snow conditions. The analysis revealed two distinct single flip strategies, which differed in the way the tuck position was sustained. For all the measured variables, the coefficient of variation was computed, which allowed to identify the athlete with the highest (average 45.3%) and lowest (average 20.5%) variability of kinematic variables. Moreover, it was shown that the lowest values of the coefficient of variation occurred at the end of the grouping phase (average 14%) and that among all the different variables, those related to the duration of motion were most unstable (average 63%, SD = 48.5%).