Dynamic Postural Stability Research Articles

Females have Lower Knee Strength and Vertical Ground Reaction Forces During Landing than Males Following Anterior Cruciate Ligament Reconstruction at the Time of Return to Sport

Purpose There is a high rate of second anterior cruciate ligament (ACL) injury (ipsilateral graft or contralateral ACL) upon return-to-sport (RTS) following ACL reconstruction (ACLR). While a significant amount of epidemiological data exists demonstrating sex differences as risk factors for primary ACL injury, less is known about sex differences as potential risk factors for second ACL injury. The purpose of this study is to determine if there are sex-specific differences in potential risk factors for second ACL injury at the time of clearance for RTS. Methods Ten male and eight female athletes (age: 20.8 years ±6.3, height: 173.2 cm ±10.1, mass: 76.6 kg ±18.3) participated in the study following ACLR at time of RTS (mean 10.2 months). Performance in lower extremity isokinetic and isometric strength testing, static and dynamic postural stability testing, and a single leg stop-jump task was compared between the sexes. Results Normalized for body weight, males had significantly greater isokinetic knee flexion (141±14.1 Nm/kg vs. 78±27.4 Nm/kg, p=0.001) and extension strength (216±45.5 Nm/kg vs. 159±53.9 Nm/kg, p=0.013) as well as isometric flexion (21.1±6.87% body weight vs. 12.5±5.57% body weight, p=0.013) and extension (41.1±7.34% body weight vs. 27.3±11.0% body weight, p=0.016) strength compared to females. In the single-leg stop jump task, males had a greater maximum vertical ground reaction force during landing (332±85.5% vs. 259±27.4% body weight, p=0.027) compared to females. Conclusions Based on these results, there are significant differences between sexes following ACLR at the time of RTS. Lower knee flexion and extension strength may be a potential risk factor for second ACL injury among females. Alternatively, the increased maximum vertical force observed in males may be a potential risk factor of second ACL injury in males. Although these results should be interpreted with some caution, they support that rehabilitation programs in the post-ACLR population should be individualized based on the sex of the individual. Level of Evidence Level 3

The Effect of Different Physiotherapy Programs on Pain, Balance and Trunk Functional Capacity in Adolescents with Low Back Pain

Background. Low back pain is a common problem, adversely affecting balance and strategy for controlling the trunk muscles. There are various methods to treat low back pain, therefore, studies comparing the effectiveness of different programs can help improve the rehabilitation program for patients with low back pain.
 The aim. To evaluate the effect of trunk stabilization and balance exercises performed with different devices on pain, balance and trunk functional capacity in adolescents with low back pain.
 Methods. 12 adolescents with low back pain participated in this study. They were divided into two groups. The first group received 20 minutes of stabilization exercises and 10 minutes of balance training using the Biodex balance system. The second group received 20 minutes of stabilization exercises and 10 minutes of balance training using a vibration platform. All subjects were evaluated before and after 10 physiotherapy procedures. Self-reported pain, balance and static endurance of trunk muscles were assessed before and after the interventions.
 Results. Both programs significantly reduced pain, improved control of the center of gravity within the base of support, reduced the time required to shift weight in different paths, reduced sway index in conditions of eyes open or eyes closed on a firm or foam surface, improved dynamic and static overall postural stability and increased static endurance of trunk muscles. Improvement in control of the center of gravity within the base of support, and reduction in the time required to shift weight in different paths, were more significant in the group that received balance training using the Biodex balance system compared with that in the group that received balance training using a vibration platform.
 Conclusions. Balance training using the Biodex balance system was more effective in improving control of the center of gravity within the base of support and reducing the time required to shift weight in different paths than balance training using a vibration platform.
 Keywords: low back pain, balance, trunk stability, Biodex balance system, vibration platform.
 

Effects of Patellofemoral Pain Syndrome on Changes in Dynamic Postural Stability during Landing in Adult Women.

Background This study investigated the effects of lower limb movements on dynamic postural stability (DPS) during drop landing in adult women with patellofemoral pain syndrome (PFPS). Methods Thirty-eight adult women were recruited and divided into two groups, the PFPS group and the control group. The study participants performed a single-leg drop landing from a 30 cm box, and their lower limb movements and DPS were measured. Differences between groups were examined using independent sample t-tests. In addition, stepwise multiple linear regression was used to examine the kinematic parameters that contribute to the DPS. Results The PFPS group had significantly lower hip flexion, internal rotation, knee flexion, ankle external rotation, pelvic oblique, tilt, rotation, and higher hip abduction, knee valgus, and ankle plantarflexion. In terms of DPS, the PFPS group had a significantly higher anteroposterior and a lower mediolateral than that of the control group. In the control group, regression analysis revealed a controlled anteroposterior using knee flexion, while the PFPS group controlled mediolateral through ankle plantarflexion. Conclusions Patients with PFPS experienced more shock on their knee joint during landing than patients in the control group with greater anteroposterior instability and lower mediolateral instability.

Prospective Study on Dynamic Postural Stability in Youth Competitive Alpine Skiers: Test-Retest Reliability and Reference Values as a Function of Sex, Age and Biological Maturation.

This study aimed 1) to assess the test-retest reliability of dynamic postural stability index (DPSI) assessments using a ski-specific jump protocol that consists of single-leg landings on a three-dimensional force plate after forward-performed double-leg drop jumps from a box over a hurdle (DJSLLs), 2) to provide reference values for female and male youth competitive alpine skiers; 3) to explore their changes in DPSI over 3 years during adolescence; and 4) to investigate potential associations of DPSI with age and biological maturation. Using three-dimensional force plates, 16 healthy subjects were tested on the same day (test-retest reliability experiment; five test-retest assessments of right leg landings), and 76 youth skiers aged 13–15 years were tested 3 times within 2 years (main experiment; average of two trials per leg each time). The test-retest reliability experiment revealed an ICC(3,1) and 95% CI of 0.86 [0.74, 0.94] for absolute DPSI assessment. The within-subject SEM of absolute DPSI was 16.30 N [13.66 N, 20.65 N], and the standardized typical error was moderate (0.39 [0.33, 0.50]). Both absolute and relative DPSI values were comparable between male and female youth competitive alpine skiers. The mean absolute DPSI in year 1 (195.7 ± 40.9 N), year 2 (196.5 ± 38.9 N) and year 3 (211.5 ± 41.3 N) continuously increased (i.e., worsened) (p < 0.001). Mean relative, i.e. body weight force normalized, DPSI values significantly decreased, i.e., improved, from year 1 to 2 (0.42 ± 0.01 vs. 0.36 ± 0.004; p < 0.001) and year 1 to 3 (0.42 ± 0.01 vs. 0.36 ± 0.01; p < 0.001). Absolute DPSI correlated with age and biological maturation, while no such correlations were found for relative DPSI values. Our findings suggest that DPSI is a reliable and sensitive measure of dynamic postural control during DJSLLs and that relative DPSI improves annually in competitive youth skiers when accounting for body weight. Future work should consider biological maturation testing during the growth spurt, and normalizing to body weight force could be a possible solution.

Does insole hardness affect the dynamic postural stability of basketball athletes during jump landing?

This study aimed to examine the effects of shoe insole hardness on the dynamic postural stability of basketball athletes during jump landing manoeuvres. Twenty college basketball athletes were recruited to complete a single-leg jump landing task on a force plate in three insole conditions (soft-, rigid- and no-insole). Kistler force plate and Pedar-X insole system were used to collect the ground reaction force (GRF) and plantar pressure data. Dynamic Postural Stability Index (DPSI), Anterior-Posterior Stability Index (APSI), Medial-Lateral Stability Index (MLSI), and Vertical Stability Index (VSI) were then calculated from GRF data. DPSI, APSI, MLSI, and VSI were statistically conducted among the three insole conditions by a one-way ANOVA with repeated measures. MLSI were decreased when wearing soft- and rigid insoles compared with no-insole condition (p &lt; 0.05). However, there were no significant differences in APSI and VSI among the three insole conditions. In the midfoot region, contact areas were increased in the soft- and rigid insole than the no-insole condition (p &lt; 0.0001). Dynamic balance of basketball athletes in the medial-lateral direction could be enhanced by wearing insoles during jump landings tasks. However, the postural stability of basketball athletes did not increase with insole hardness increasing.

Higher Hamstrings Strength and Stability Are Related to Lower Kinematics Alteration during Running after Central and Peripheral Fatigue.

Fatigue can be classified as peripheral or central depending on the extent of its effects. Muscle strength reduction, associated with the appearance of fatigue during running, produces kinetics and kinematics modifications which could lead to an increased risk of injury. This study aimed to analyze the effect of peripheral and central fatigue protocols in running kinematics and to investigate the relationship between isokinetic strength and dynamic stability in fatigue related changes. Eighteen male recreational runners participated in the study. The dynamic postural stability index (DPSI) and quadriceps and hamstring isokinetic strength were assessed before the fatigue test. Then, angular kinematics during treadmill running were evaluated in pre- and post-fatigue states (central and peripheral). The results showed that runners with higher hamstring isokinetic strength and better DPSI had lower modifications after central fatigue of stance time, knee flexion, vertical and leg stiffness, and ankle dorsiflexion during the absorption and propulsion phases (r > 0.400, p < 0.05). Moreover, small changes in ankle dorsiflexion at initial contact after peripheral fatigue are related to a better DPSI and higher hamstring isokinetic strength (r > 0.400, p < 0.05). In summary, high values of hamstring isokinetic concentric strength and dynamic stability are related to lower increases of range of movements during running after central and peripheral fatigue. So, fatigue may affect to a lesser extent the running technique of those runners with higher hamstring strength and stability values.

Effects of balance training on dynamic postural stability in patients with chronic ankle instability: systematic review and meta-analysis of randomized controlled trials

Chronic ankle instability (CAI), which is characterized by deficient postural control, is associated with functional limitations and diminished self-reported quality of life. Recent studies have suggested that balance training can improve postural control, but high-quality evidence-based research to confirm the effect of balance training on dynamic postural stability in CAI patients is lacking. The purpose of this study was to synthesize current evidence regarding the effect of balance training on dynamic postural stability in CAI patients. PubMed, Embase, Web of Science and Cochrane Library databases were searched for clinical trials that evaluated the effect of balance training on posture and balance in CAI patients from their inception to 15 July 2021. All statistical analyses were performed in RevMan 5.4. The risk of bias was assessed by the Cochrane Collaboration's risk of bias tool, and studies that reported statistically comparable outcomes were analyzed in meta-analyses using random effects models. Heterogeneity was assessed using the I2 statistic index. A total of 12 RCTs included in this meta-analysis and revealed that balance training was effective for improving the dynamic posture stability of CAI patients (SMD=0:90; 95% CI: 0.54 to 1.26; P<0:00001, I2=71%; Star Excursion Balance Test). Subgroup analysis (balance training vs. other training) revealed a small negative effect size, but this was not statistically significant (SMD=-0.12, 95% CI=-0.53 to 0.29, P=0.56, I2=9%). Another subgroup analysis (balance training vs. no training) revealed that balance training was more likely to have greater improvement on the dynamic posture stability of CAI patients (SMD=0.94, 95% CI: 0.71 to 1.17; P<0.00001, I2=0%). Balance training yielded a statistically significant and clinically meaningful improvement in dynamic postural stability in CAI patients. Limited evidence indicates that balance training was more effective than other training methods.

Altered Visual Reliance Induced by Stroboscopic Glasses during Postural Control.

Little is known about how disrupted vision affects visual reliance during postural control. postural control. Twenty-four physically active adults volunteered to participate in the study. Static postural control was quantified with center of pressure measures during a one-legged balance test with four different visual inputs (eyes-open (EO), high frequency of strobe vision (HSV), low frequency of strobe vision (LSV), and eyes-closed (EC)) and on two different surfaces (firm and foam). Dynamic postural control was calculated by the dynamic postural stability index and the Y-Balance test for three different visual inputs (EO, HSV, and LSV) and the two different surfaces. Romberg ratios (HSV/EO, LSV/EO, and EC/EO) were then calculated and used for statistical analysis to assess visual contribution during postural control. In the results, Romberg ratios were higher when people were on the foam surface than the firm surface in center of pressure total path in medial-lateral and anterior-posterior directions (p < 0.05, both directions). Similarly, Romberg ratios were higher on the foam surface than the firm surface in dynamic stability index in medial-lateral and anterior-posterior directions (p < 0.05, both directions). Stroboscopic glasses could alter visual reliance when the somatosensory system is disturbed by a foam pad during both static and dynamic postural control. Clinicians could use the glasses to manipulate visual reliance during dynamic balance training for patients with musculoskeletal injuries.

Assessing changes in static and dynamic postural stability in youth football players following the FIFA 11+ injury prevention program

To examine the effect of FIFA 11+ warm-up program on static and dynamic postural stability in football players. Equipment and methods: Thirty young male football players (mean ± SD; age: 14.96 ± 0.76 years were recruited and divided into two groups (FIFA 11+ exercise group, n = 15 and control group, n = 15). The exercise group performed the FIFA 11+ injury prevention exercises as part of their warm-up and the control group continued their traditional warm up routines. The FIFA 11+ exercises were performed three times a week, for eight weeks. A single leg test with eyes closed, on a force platform, was used to measure static postural stability measurement, and time to stability after single leg drop-landing test was used for dynamic postural stability measurement. The repeated measures (Anova) showed that the experimental group performed significantly better (adjusted mean difference [95% CI] or percentage %) in static postural stability (center of pressure displacement in the anterior-posterior direction [0.03 (95% CI 0.003 to 0.06), 8.56%] and medial-lateral [0.05 (95% CI 0.02 to 0.08), 9.19%]), and in dynamic postural stability (time to stability in the anterior-posterior direction [0.64 (95% CI 0.09 to 1.2), 15.82%] and medial-lateral [0.6 (95% CI 0.01 to 1.2), 18.92%]), compared with the control group. In conclusion, The FIFA 11+ injury prevention program may improve static and dynamic postural stability. Examiner l’effet du programme d’échauffement FIFA 11+ sur la stabilité posturale statique et dynamique des joueurs de football. Trente jeunes footballeurs masculins (moyenne ± ET; âge : 14,96 ± 0,76 ans ont été recrutés et répartis en deux groupes (groupe d’exercice FIFA 11+, n = 15 et groupe témoin, n = 15). Le groupe d’exercice a effectué les exercices de prévention des blessures FIFA 11+ dans le cadre de son échauffement et le groupe témoin a poursuivi ses routines d’échauffement traditionnelles. Les exercices FIFA 11+ ont été effectués trois fois par semaine, pendant huit semaines. Un seul membre se tient avec les yeux fermés de la plaque de force a été utilisée pour la mesure de stabilité posturale statique, et le temps de stabilité après le test d’atterrissage sur une jambe a été utilisé pour la mesure de stabilité posturale dynamique. Les mesures répétées (Anova) ont montré que le groupe expérimental obtenait des résultats significativement meilleurs (différence moyenne ajustée [CI 95 %] ou pourcentage %) en stabilité posturale statique (centre de déplacement de pression dans le sens direction antéro-postérieur [0,03 (CI 95 %) 0,003 à 0,06), 8,56 %] et médio-latérale [0,05 (CI à 95 % 0,02 à 0,08), 9,19 %]), et en stabilité posturale dynamique (temps de stabilisation dans la direction antéro-postérieure [0,64 (CI à 95 %) 0,09 à 1,2), 15,82 %] et médio-latérale [0,6 (CI à 95 % 0,01 à 1,2), 18,92 %]), par rapport au groupe témoin. En conclusion, le programme de prévention des blessures FIFA 11+ peut améliorer la stabilité posturale statique et dynamique.

Abstract TP64: Determining The Role Of Single Support Center Of Pressure Distance For Characterizing Post-stroke Walking Impairment And Response To Rehabilitation Training

Introduction: Stroke is a major cause of balance and walking impairment and is on the rise. The most widely used walking impairment measure is the 10-meter walk test (10-mWT), which provides information about walking speed but does not inform about walking kinematics or neuromuscular control. Objective: Herein, we evaluate single support center of pressure distance (SS CoP Dist), a kinematic measure of dynamic postural control and walking stability, as a complementary measure of walking impairment. We hypothesize that SS CoP Dist will be closely associated with baseline walking speed, and will improve with Backward Locomotor Treadmill Training (BLTT). Methods: Thirty-six chronic stroke survivors with residual walking impairment, based on 10-mWT speed [ mild &gt;0.8 m/s (n =7); moderate 0.4-0.8m/s (n =18); and severe &lt;0.4 m/s (n = 11)] , underwent six 30-minute BLTT sessions over two consecutive weeks. During testing (10-mWT), participants were instructed to walk as fast as possible over the gait analysis mat to capture SS CoP Dist and walking speed. Results: At baseline, there was a weak to moderate positive relationship between walking speed and SS CoP Dist (R 2 paretic = 0.22, p = 0.0036; R 2 Nonparetic = 0.44, p &lt; 0.0001). Following BLTT, SS COP Dist increased (more stable) in the mild and moderate groups [mild paretic ( p = 0.0039)/mild Nonparetic ( p = 0.0034) , moderate paretic ( p = 0.0360)/ moderate Nonparetic ( p = 0.0087)], with improved interlimb symmetry in the mild group. In contrast, no significant improvement in SS CoP Dist was seen in participants with severe walking impairment ( p = 0.3830). Training-related changes in walking speed were strongly correlated with change in SS CoP Dist (R 2 Nonparetic = 0.54, p = 0.0007). Conclusion: Our preliminary findings suggest that SS CoP Dist compliments walking speed for characterizing walking severity and response to training in chronic stroke survivors. In addition, BLTT significantly improved SS CoP Dist in mild-moderately impaired stroke survivors but not in survivors with severe walking impairment. Future well-powered, prospective studies with BLTT and other training paradigms are needed to validate these findings.

The Effect of 6-Week Combined Balance and Plyometric Training on Dynamic Balance and Quickness Performance of Elite Badminton Players.

The study aimed to investigate the effect of combined balance and plyometric training on dynamic balance and quickness performance of elite badminton athletes. Sixteen elite male badminton players volunteered to participate and were randomly assigned to a balance-plyometric group (PB: n = 8) and plyometric group (PT: n = 8). The PB group performed balance combined with plyometric training three times a week over 6 weeks (40 min of plyometrics and 20 min of balance training); while the PT group undertook only plyometric training for the same period (3–4 sets × 8–12 reps for each exercise). Both groups were given the same technical training (badminton techniques for 6 days a week). The dynamic stability and quick movement ability were assessed at baseline and after the intervention by measuring the performance of dynamic posture stability test (DPSI and COP), T-running test and hexagon jump test. The results showed that compared to PT, PB induced significantly greater improvements in F-DPSI, L-DPSI (p = 0.003, 0.025, respectively), F-COPAP, F-COPML, F-COPPL, L-COPPL (p = 0.024, 0.002, 0.029, 0.043, respectively), T-running test and hexagon jump test (p < 0.001). The change in L-DPSI, L-COPAP, L-COPML did not differ between PB and PT (p > 0.907). The findings suggest that combined training holds great promise of improving the dynamic balance and quickness performance in elite badminton athletes.

The effect of leg length asymmetry on leg stiffness and dynamic postural stability in vertical landing

Background: Assessment of asymmetries in dynamic postural stability and lower extremities kinetics during landing technique are considered factors for injury prevention and achieve optimal athletic performance. Nevertheless, the relationship between these factors has not been established. This study aimed to investigate the effects of leg length asymmetry on dynamic stability and leg stiffness upon initial contact with the ground after vertical landing. Methods: Twenty healthy adult men landed on the ground from a height of 30 cm; we measured leg length, leg stiffness, lateral pelvic tilt angle, peak vertical force (PVF), the loading rate, dynamic postural stability index (DPSI), and the correlations among these variables. Results: At initial contact, the right leg was significantly longer and showed greater lateral pelvic tilt than the left leg. These characteristics increased the loading rate at the time of PVF on the right leg, which in turn affected leg stiffness and pelvic tilt. The DPSI was also decreased for the right leg compared with the left leg. In the correlation analysis, we observed strong, positive correlations and high explanatory power for PVF, the loading rate, vertical stability index, and DPSI, with r ≥0.822 and R2 ≥57%. Conclusions: The identified associations support the validity of the result, showing that the right leg failed in its rapid stabilization strategy. The leg length asymmetry is suspected to affect asymmetrical impact patterns, DPSI, and leg stiffness. Given the number of individuals with leg-length inequalities who play sports relying on jumping and landing patterns, reducing the rate of injury possibly incurred.

Age-Related Vestibular Dysfunction; Vestibulo-Ocular Reflex, Dynamic Visual Acuity, Dizziness and Falls: A Review

Background: Vestibular and vision functions are important contributors to posture control and fall avoidance. This review examines how the vestibulo-ocular reflex can be rehabilitated to help restore postural control. Methods: PubMed searches (7th April 2021) using the terms ‘vestibulo-ocular reflex’, ‘imbalance and vestibular dysfunction’, ‘vestibular dysfunction and dizziness’, ‘dynamic visual acuity’, ‘vestibular dysfunction rehabilitation’, and ‘gaze stabilization exercises’ yielded 4986, 495, 3576,1830, 3312, and 137 potentially useful publications respectively. Selections of those which were found to be the most relevant and representative of a balanced and current account of these topics, as well as selections from the most relevant reports referenced in those publications, were included in this review. Results: Just as there are age-related losses of static visual acuity even when there are no specific visual pathologies diagnosed, patients may also present with age-related loss of vestibular functions in the absence of specific vestibular pathologies. For example, cases of dizziness which are diagnosed as idiopathic might be usefully classified as age-related as the basis for the initiation of rehabilitation exercises. Conclusions: Apart from age-related loss of vestibular functions, cases diagnosed as having a particular form of vestibular pathology may have that condition exacerbated by age-related losses of vestibular functions. The effects of vestibular rehabilitation gaze stability exercises in patients with vestibular dysfunction are well established and include both improved dynamic acuity and postural stability. Improvements in posture control following rehabilitation of the vestibulo-ocular reflex are apparently due to improved peripheral and/or central vestibular balance control which has occurred in conjunction with enhanced gaze stability. The complex nature of increased fall risk suggests that an interdisciplinary approach to rehabilitation that includes vestibulo-ocular reflex rehabilitation appears likely to be associated with optimum outcomes for both pathological and age-related cases.

Copers adopt an altered dynamic postural control compared to individuals with chronic ankle instability and controls in unanticipated single-leg landing

BackgroundSeveral prior studies involving “expected” single-leg landings have not succeeded in establishing a difference between copers and a control group. Research questionDoes expected and unanticipated single-leg landing affect dynamic postural stability in lateral ankle sprain individuals with chronic ankle instability (CAI), copers, and controls? MethodsIn this prospective cross-sectional study, physically active adults with CAI (n = 12), copers (n = 12), and controls (n = 12) were included. Participants performed expected single-leg landing by stepping off a 30-cm box. They also performed unanticipated landings including side-step cutting, side-step cutting at 60°, single-leg landing, and forward stepping. The expected and unanticipated conditions of each groups were compared in terms of time to stabilization (TTS) and center of pressure (COP) for the anterior-posterior (AP) and medial-lateral (ML) conditions. To analyze the data, a mixed-model one-way analysis of variance and a Tukey-Kramer post hoc test were performed. ResultsA significant condition × group interaction was observed in only TTS ML, with the CAI group demonstrating a significantly longer TTS ML than the coper (p < 0.001) and control (p < 0.001) groups during unanticipated trials. In addition, group interaction effects were observed for COP AP and TTS AP. The coper group demonstrated significantly longer COP AP and TTS AP than the control group (p < 0.001). SignificanceThe CAI group demonstrated a significantly longer TTS ML than the coper and control groups during the unanticipated condition, and the coper group demonstrated significantly longer TTS AP and COP AP than the control group. Thus, longer COP AP and TTS AP sway time in the coper group may be a protection mechanism, allowing greater freedom in the AP plane while quickly controlling ML sway and preventing lateral ankle sprains. These findings can help in the prevention of lateral ankle sprains and assessment of dynamic postural control.

Evaluation of gait termination strategy in individuals with Essential Tremor and Parkinson's disease

IntroductionGait termination (GT) is a challenging transitory task involving converting from a dynamic state of motion to a static state. These transitional locomotor tasks are particularly troublesome for populations with postural deficits, i.e., Parkinson’s disease (PD) and Essential Tremor (ET). They demand greater postural control and intricate integration of the neuromuscular system. The mechanisms involved in GT in these populations have not been well studied despite the safety concerns and potential risk for falls. The purpose of this investigation was to examine the different control strategies utilized during GT between individuals with ET and PD. MethodsTwenty-four individuals with ET (66 ± 8 yrs), twenty-four individuals with PD (64 ± 8 yrs), and twenty healthy older adults (HOA: 63 ± 9 yrs) participated in this study. Average self-selected gait velocity for each group was collected during the GT trial walking portion. Ground reaction force (GRF) data were used to calculate braking and propulsive forces from the last two steps during GT. GRF data measured the dynamic postural stability index (DPSI), defined as an individual’s ability to maintain balance while transitioning from a dynamic to a stable state. ResultsPersons with ET had a significantly slower approach velocity (0.63 m/s) when compared to HOA (0.92 m/s) and PD (0.77 m/s). Persons with PD had significantly slower approach velocity when compared to HOA. Examination of GRF data found that those with ET generated significantly smaller propulsive and braking forces (p < .05). Forces increased in those with PD and then even more in the HOA group. Postural stability analysis revealed that ET had significantly worse stability scores than PD and HOA (p < .05). ConclusionIndividuals with PD and ET utilize different control strategies for planned GT, which suggests both the cerebellum and the basal ganglia play central yet potentially different roles in anticipatory control during self-directed activities.

Training potential of visual feedback to improve dynamic postural stability

BackgroundDeficits in single-limb dynamic postural stability are predictive for reinjuries of the lower extremities, which are very common in sports. The use of force plates has become increasingly common to measure dynamic postural stability. Visual feedback on force-plate based stability outcomes have been shown to improve performance during static tasks. A similar effect might occur in dynamic tasks. Since dynamic tasks are generally more specific for performance during sport, this could have important training implications. Research questionWhat is the effect of visual feedback on postural stability outcomes during a dynamic stability task? MethodsTwenty-four healthy participants participated in this study. During measurements, subjects were standing on one leg while mediolateral position-controlled platform perturbations were used to evoke and measure balance responses. All participants were tested under three conditions: with visual Time-to-Stability (TTS) feedback, with visual Center of Pressure speed (COPs) feedback and without visual feedback. TTS and COPs outcomes were calculated over a 5-second time window after each perturbation and were compared between conditions. ResultsVisual feedback resulted in significantly better stability outcomes during the dynamic stability task. TTS feedback resulted in a task-specific feedback learning effect, as it resulted in a gradual improvement of TTS scores (from 1.09 s to 0.68 s; −38%) in absence of a significant change in COPs. COPs feedback resulted in a non-specific attention effect, directly improving COPs (without feedback 5.26 cm/s with feedback 4.95 cm/s; −6%) and TTS scores (without feedback 1.47 s with feedback 0.99 s; −39%) in absence of an apparent further improvement over time. SignificanceThe ability to improve performance of dynamic stability tasks when visual feedback is added could have substantial impact for rehabilitation. Possibly, the use of visual feedback during stability training could improve the effectiveness of postural stability training.

Do Athletes With a Reconstructed Anterior Cruciate Ligament Respond Differently Than Controls to Visual Challenges When Dynamic Postural Stability is Assessed?

Individuals returning to sport after anterior cruciate ligament reconstruction (ACLR) are at an increased risk of sustaining a subsequent ACL injury. It is suspected that increased reliance on visual information to maintain stability may factor into this increased risk. The connection between visual reliance and ACLR is not well understood during dynamic tasks. Examination of the proposed visual reliance may help improve returning to sport standards and reduce subsequent ACL injury risk. A total of 12 ACLR individuals and 12 age- and sex-matched controls completed several trials of a normalized dynamic hop task on both limbs under 3 different visual conditions (eyes open, low visual disruption, and high visual disruption). Stroboscopic eyewear were worn by each participant to disrupt vision during testing. Ground reaction force data were collected during landing. Dynamic postural stability was assessed using 2 separate calculations: dynamic postural stability index and time to stability. No significant statistical interactions or group differences were observed. The stroboscopic eyewear did increase the medial-lateral stability index from the eyes open to the low visual disruption condition (P < .05). These findings suggest that ACLR individuals do not rely on visual information more than controls during a dynamic hop task.

The effects of visual cognitive tasks on landing stability and lower extremity injury risk in high-level soccer players

BackgroundVisual cognition plays a pivotal role in sports. It is widely recognized that there is an intriguing coupling that they could affect each other through interaction between visual cognition and motor control, but few studies linked the effects of visual cognitive tasks on landing stability to postural control and injury risk. Research questionWhether visual cognitive tasks affect the landing stability and lower limb injury risk of professional soccer players? MethodsThe current study used a three-dimensional Multiple Object Tracking (MOT) task to simulate visual cognitive difficulties experienced in soccer matches. Fifteen male high-level soccer athletes (height: 181.43 ± 7.36 cm, weight: 75.37 ± 10.67 kg, training years: 10.07 ± 2.98 yr) from our school team were recruited and completed a landing action from a high platform with and without MOT tasks. Vicon infrared high-speed motion capture system and three-dimensional force measuring platform were used to collect various outcomes simultaneously. ResultsThe Time to Stabilization (TTS) during landing was significantly prolonged, while the Medial-Lateral Stability Index (MLSI), Anterior-Posterior Stability (APSI), Dynamic Postural Index Stability Index (DPSI), the trajectory lengths, and envelope area of COP during landing were also increased during MOT dual-task. DiscussionThe decline of these indicators reflected the deterioration in postural stability and greater requirements for maintaining balance which could increase the risk of injury in soccer athletes. We advocate that adequate visual attention and visual information processing might play critical roles in maintaining dynamic balance through the supraspinal neural network.

Effects of balance training with stroboscopic glasses on postural control in chronic ankle instability patients.

To compare (1) the effects of balance training with and without stroboscopic glasses on postural control and (2) the effects of the training on visual reliance in patients with CAI. A randomized controlled clinical trial. Twenty-eight CAI patients were equally assigned to one of 2groups: strobe or control group. The strobe group wore stroboscopic glasses during a 4-week balance training. Static postural control, a single-leg hop balance test calculated by Dynamic Postural Stability Index (DPSI), and the Y-Balance test (YBT) were measured. During the tests, there were different visual conditions: eyes-open (EO), eyes-closed (EC), and strobe vision (SV). Romberg ratios were then calculated as SV/EO, and EC/EO and used for statistical analysis. The strobe group showed a higher pretest-posttest difference in velocity in the medial-lateral direction and vertical stability index under SV compared with the control group (p<.05). The strobe group showed higher differences in EC/EO for velocity in the medial-lateral and anterior-posterior directions, and 95% confidence ellipse area (p<.05), and in SV/EO for velocity in the medial-lateral, 95% confidence ellipse area, and YBT-anterior direction (p<.05). The 4-week balance training with stroboscopic glasses appeared to be effective in improving postural control and altering visual reliance in patients with CAI.

The effects of leg preference and leg dominance on static and dynamic balance performance in highly-trained tennis players.

In this study, 90 (51 males, 39 females) tennis players performed single-leg quiet stance and single-leg landing tasks. For the static standing task, center-of pressure (CoP) velocities, amplitudes, frequency and area were calculated. For the landing tasks, time to stabilization as well as dynamic postural stability index were considered. The analysis of differences between the legs was done based on two methods for a priori determination of leg preference, one based on the preference of kicking a ball and one based on the preference for single-leg jumping. An additional analysis was done based on the leg dominance (determined post hoc), based on the observed performance of the tasks. In case of the classification based on kicking a ball, there was a statistically significantly lower CoP anterior-posterior velocity and anterior-posterior amplitude in static balance task (p ≤ 0.017; 0.17 ≤ d ≤ 0.28) for the preferred leg. The CoP frequency was higher in the preferred leg for both directions (p ≤ 0.002; 0.10 ≤ d ≤ 0.22). For the landing task, CoP medial-lateral time to stabilization was statistically significantly shorter for the preferred leg (0.28 ± 0.38 s) compared to the non-preferred leg (0.47 ± 0.60 s) (p = 0.012; d = 0.38). There were no differences between the legs for the landing task. Moreover, there were no differences between the legs when we used the preference based on jumping for either of the tasks (d ≤ 0.14). The differences between legs in terms of observed dominance were larger than the differences based on the preference, which stresses the need for clear distinction of limb preference and limb dominance in research and practice. Regarding the effect of leg preference, small differences in static balance may exist between the legs (when the preference is based on kicking a ball).