The role of the dominant leg while assessing balance performance. A systematic review and meta-analysis

Assessment of Balance During a Single-Limb Stance Task in Healthy Adults: A Cross-Sectional Study

Single-limb stance (SLS) is a demanding postural task, widely used for balance assessment in both research and clinical practice. Despite extensive data on elderly and clinical populations, less is known about younger and healthier adults. Our aim in this study was to assess balance during a SLS task among a cohort of healthy adults to determine whether there are age or sex group or testing condition differences in performances. In this cross-sectional study, we involved 120 participants aged 30-65 years and divided them into four age sub-groups with equal numbers of males and females in each. We assessed balance during a 45-s SLS task on a] the Delos Postural Proprioceptive System for both lower limbs in two conditions - open eyes (OE) and closed eyes (CE). We calculated stability (SI) and autonomy (AU) indices and used analysis of variance to determine that there was no significant effect of limb dominance or sex on balance parameters. However, there was a significant interaction effect between age group and testing condition for both SI and AU (p < .001 for both), with balance worsening as age increased only in the CE condition. These results highlight a pattern of balance decline with age when vision is eliminated from balance performance, underscoring the critical relationship between sensory input and postural control as people age.

Effects of High-Intensity Interval Walking on Cognitive and Physical Functions in Older Adults: A Randomized Pilot Study

BACKGROUND

Walking is widely recognized as a prevalent form of daily exercise worldwide. However, fewer studies have explored the health outcomes of different intensities of walking exercise for older adults. Thus, the study aimed to investigate the effects of walking at different exercise intensities on body composition, emotions, cognition, and physical function among older adults.

PURPOSE

This study aimed to investigate the effects of walking at different exercise intensities on body composition, emotions, cognition, and physical function after eight weeks of group walking. Specifically, the study focused on the potential benefits of high-intensity interval walking (HIIW), exploring whether HIIW could have a more positive impact on the physical function and overall health of older adults compared to moderate-intensity continuous walking (MICW).

METHODS

Participants aged 65 years or older were randomly assigned to either HIIW (n=13, 85% HRmax and 55% HRmax, alternating every three minutes) or MICW (n=13, 70% HRmax), engaging in group walking exercises for 30 minutes three times a week. The pre-test and post-test evaluations included body composition, cognition, emotions, and physical function.

RESULTS

The two-minute step test showed significant improvements over time (p<0.0001) and time-group interaction (p=0.004), and sit and reach showed significant changes over time (p<0.0001). The independent T-test showed significant differences between the HIIW and MICW groups (two-minute step test: t (24)=1.80, p=0.04; sit and reach test: t (19)=3.65, p<0.001) at post-measurement. Additionally, no significant differences were found in body composition (weight, p=0.74; body mass index (BMI), p=0.35; body fat mass, p=0.45; skeletal muscle mass (SMM), p=0.77), emotions (geriatric depression scale (GDS), p=0.79; quality of life (QOL), p=0.54; Pittsburgh Sleep Quality Index, p=0.24), and cognitive function (CoSAS total score, p=0.25) between the HIIW and MICW groups after exercise. Grip strength, balance, 30-second chair stand, back scratch, and eight-foot up and go tests showed no significant effects in the time-group interaction.

CONCLUSION

Regular HIIW exercise has positive effects on physical functions such as cardiorespiratory endurance and flexibility in older adults, indicating the potential for establishing a foundation for developing customized exercise programs in the future.

A Pilot Study to Evaluate the Relationships between Supine Proprioception Assessments and Upright Functional Mobility

Long-duration bedrest impairs upright postural and locomotor control, prompting the need for assessment tools to predict the effects of deconditioning on post-bedrest outcome measures. We developed a tilt board mounted vertically with a horizontal air-bearing sled as a potential supine assessment tool for a future bedrest study. The purpose of this pilot study was to examine the association between supine proprioceptive assessments on the tilt board and upright functional mobility. Seventeen healthy participants completed variations of a supine tilt board task and an upright functional mobility task (FMT), which is an established obstacle avoidance course. During the supine tasks, participants lay on the air-bearing sled with axial loading toward the tilt board. Participants tilted the board to capture virtual targets on an overhead monitor during 30 s trials. The tasks included two dynamic tasks (i.e., double-leg stance matching mediolateral tilt targets over ±3° or ±9° ranges) and two static tasks (i.e., single-leg stance maintaining a central target position). The performances during the dynamic tasks were significantly correlated with the FMT time to completion. The dominant-leg static task performance showed a moderate trend with the FMT time to completion. The results indicate that supine proprioceptive assessments may be associated with upright ambulation performance, and thus, support the proposed application in bedrest studies.

Differential Back Muscle Flexion-Relaxation Phenomenon in Constrained versus Unconstrained Leg Postures

Previous studies examining the flexion-relaxation phenomenon (FRP) in back muscles through trunk forward flexion tests have yielded inconsistent findings, primarily due to variations in leg posture control. This study aimed to explore the influence of leg posture control and individual flexibility on FRP in back and low limb muscles. Thirty-two male participants, evenly distributed into high- and low-flexibility groups, were recruited. Activities of the erector spinae, biceps femoris, and gastrocnemius muscles, alongside the lumbosacral angle (LSA), were recorded as participants executed trunk flexion from 0° to 90° in 15° increments, enabling an analysis of FRP and its correlation with the investigated variables. The findings highlighted significant effects of all examined factors on the measured responses. At a trunk flexion angle of 60°, the influence of leg posture and flexibility on erector spinae activities was particularly pronounced. Participants with limited flexibility exhibited the most prominent FRP under constrained leg posture, while those with greater flexibility and unconstrained leg posture displayed the least FRP, indicated by their relatively larger LSAs. Under constrained leg posture conditions, participants experienced an approximate 1/3 to 1/2 increase in gastrocnemius activity throughout trunk flexion from 30° to 90°, while biceps femoris activity remained relatively constant. Using an inappropriate leg posture during back muscle FRP assessments can overestimate FRP. These findings offer guidance for designing future FRP research protocols.

Unveiling the influence of hip isokinetic strength on lower extremity running kinematics in male national middle-distance runners: a correlational analysis

BACKGROUND

The relationship between hip strength deficiency in various planes and musculoskeletal injuries within the movement system has been well-established in numerous studies. The present study sought to explore the relationships between hip strength and specific aspects of lower extremity running kinematics.

METHODOLOGY

To achieve this objective, the three-dimensional running kinematics of 21 male elite middle-distance runners (mean age: 19.7 ± 1.2 years; mean experience 6.5 ± 1.0 years) were assessed using nine high-speed cameras on a treadmill at a speed of 16 km·h⁻¹. Concurrently, isokinetic hip strength was measured at a speed of 60 deg·s⁻¹ in both the dominant and non-dominant legs. The Pearson correlation coefficient and Paired Samples t-test were utilized.

RESULTS

While no significant differences were found in several isokinetic strength measurements, notable differences in running kinematics were observed. Specifically, pelvic drop at midstance (MS) was significantly lower in the DL (5.79 ± 3.00°) compared to the NDL (8.71 ± 1.39°) with a large effect size (t=-4.04, p < 0.001, Cohen's d = 1.25). Additionally, knee adduction at maximum showed a moderate effect size difference, with the DL at 2.99 ± 1.13° and the NDL at 3.81 ± 1.76° (t=-2.74, p = 0.03, Cohen's d = 0.55). Results indicated a moderate to highly positive association between running knee adduction in the dominant leg and hip external rotation (r = 0.67, p < 0.05), concentric extension (r = 0.77, p < 0.05), and concentric abduction (r = 0.78, p < 0.05). Additionally, the running tibial external rotation angle in the dominant leg exhibited an inverse relationship with all strength measurements, with statistical significance observed only for concentric extension force (r=-0.68, p < 0.05). Furthermore, hip internal rotation force demonstrated a highly inverse correlation with foot pronation in the dominant leg (r=-0.70, p < 0.05) and anterior pelvic tilt in the non-dominant leg (r=-0.76, p < 0.05).

CONCLUSIONS

These findings underscore the interrelation between hip strength and running kinematics, particularly on the dominant side. In light of these observations, it is imperative to consider hip strength exercises as integral components for correcting running kinematics. Coaches should also be mindful that kinematic deviations contributing to running injuries may manifest unilaterally or specifically in the dominant leg.

Differences in left and right lower limb control strategies in coping with visual tracking tasks during bipedal standing

Introduction

Differences in motor control between the lower limbs may influence the risk of sports injury and recovery from rehabilitation. In this study, differences in the visual feedback ability of the left and right lower limbs were assessed using visual target tracking tasks.

Methods

Thirty-four healthy young subjects (aged 20.4 ± 1.2 years) were asked to move their bodies back and forth while tracking a visual target displayed on a monitor in front of them for 30 s. The two target motions were sinusoidal (i.e., predictable patterns) and more complex (random) patterns. To assess the ability of the lower limbs to follow visual target tracking, antero-posterior CoP (right limb, CoPap-r; left limb, CoPap-l) and medio-lateral CoP (right limb, CoPml-r; left limb, CoPml-l) data were measured using a stabilometer. Tracking ability by visual feedback ability was calculated as the difference in displacement between the target signal and the trajectories of the right and left pressure centers as trapezoidal areas, and a smaller sum of area (SoA) over the entire measurement time was defined as a greater tracking ability.

Results

Regarding the SoA in the anterior-posterior CoP, the mean SoA in the sinusoidal and random tasks was significantly lower in the CoP-r data than in the CoP-l data, indicating that the right lower limb had a more remarkable ability to follow visual target tracking. Regarding the SoA in the medial-lateral direction (CoP), the mean SoA in the sinusoidal and random tasks did not significantly differ between the two legs.

Discussion

The right lower limb may have a tracking function activated by the target signal when responding to visual stimuli. Identifying the motor strategies of each lower limb in response to visual stimuli will not only help identify potential differences between each lower limb but also suggest the possibility of enhancing the role of each lower limb in balance control.

Validation of the Equidyn protocol for evaluation of dynamic balance in older adults through a smartphone application

BACKGROUND

Different tasks and proxy measurements have been employed to evaluate dynamic balance in older individuals. However, due to inherent limitations, results from most evaluations could hardly be taken as valid measurements of dynamic balance.

RESEARCH QUESTION

Is the Equidyn smartphone application-based protocol valid and sensitive for assessment of dynamic balance in older adults?

METHODS

Dynamic balance was evaluated in 52 physically active individuals, age range 60-80 years (M = 69.36). The dynamic tasks were one-leg sway either in the mediolateral (ML) or anteroposterior (AP) direction while supported on the contralateral leg, and cyclic sit-to-stand with a narrow support base. These tasks were performed under standardized movement amplitude and rhythm. Outcomes were correlated with unipedal quiet standing. A smartphone was attached to the trunk backside, and a custom-made application (Equidyn) was employed to provide guidance throughout evaluation, timed beeps to pace the movements, and three-dimensional trunk acceleration measurement for balance evaluation.

RESULTS

Our data showed (a) that both ML and AP leg sway tasks were sensitive to aging and to direction of leg sway movements; (b) referenced to quiet unipedal stance, moderate/strong correlations for the ML/AP leg sway tasks and moderate correlations for the sit-to-stand task; and (c) moderate/strong correlations between the ML and AP leg sway tasks, and moderate correlations between the sit-to-stand and the two unipedal dynamic tasks in the ML acceleration direction.

SIGNIFICANCE

The current results support the conclusion that the Equidyn protocol is a sensitive and valid tool to evaluate dynamic balance in healthy older individuals. The protocol tasks standardized in amplitude and rhythm favor their reproducibility and trunk acceleration data interpretation. As the whole assessment is made through a smartphone application, this dynamic balance evaluation could be made in a low-cost simple way both in the laboratory and clinical settings.

Symmetric unipedal balance in quiet stance and dynamic tasks in older individuals

Previous evidence of increased difference of muscular strength between the dominant and non-dominant legs in older adults suggests the possibility of dissimilar balance control between the legs (between-leg asymmetry) associated with aging. In the current investigation, we evaluated between-leg asymmetries in older adults when performing quiet and dynamic balance tasks. Fifty-two physically active and healthy older adults within the age range of 60 to 80 years were recruited. Participants performed balance tasks in unipedal stance, including quiet standing and cyclic sway (rhythmic oscillation) of the non-supporting leg in the anteroposterior or mediolateral directions, producing foot displacements with amplitudes of 20 cm paced in 1 Hz through a metronome. Body balance was evaluated through trunk accelerometry, by using the sensors embedded into a smartphone fixed at the height of the 10th-12th thoracic spines. Analysis revealed lack of significant differences in balance control between the legs either when comparing the right versus left or the preferred versus non-preferred legs, regardless of whether they were performing quiet stance or dynamic tasks. Further examination of the data showed high between-leg correlation coefficients (rs range: 0.71-0.84) across all tasks. Then, our results indicated symmetric and associated between-leg balance control in the examined older adults.

Deficits in neurocognitive performance in patients with chronic ankle instability during a neurocognitive balance task - A retrospective case-control study

OBJECTIVES

To assess the neurocognitive performance while maintaining balance of patients experiencing CAI compared to healthy controls. In patients with CAI, the affected limb was also compared to the contralateral limb.

DESIGN

A retrospective case-control study.

SETTING

Laboratory study.

PARTICIPANTS

We included 27 patients with CAI and 21 healthy controls.

METHODS

The study consisted of two sessions, namely familiarisation and experimentation, which were scheduled with a gap of at least one week between them. During the experimental trial, both groups performed the Y-Balance Test and Reactive Balance Test once on each limb.

MAIN OUTCOME MEASURES

The main outcome measures are accuracy and visuomotor response time (VMRT) calculated via video-analysis and with the Fitlight™-hardware and software respectively during the Reactive Balance Test (RBT).

RESULTS

No data was excluded from the final analysis. Patients with CAI exhibited significantly lower accuracy than healthy controls, with a mean difference of 8.7% (±3.0)%. There were no differences for VMRT between groups. Additionally, no significant differences were observed between the affected and contralateral limb of the patient group for both accuracy and VMRT.

CONCLUSIONS

Patients with CAI showed lower accuracy, but similar VMRT compared to healthy controls during a neurocognitive balance task, indicating impaired neurocognitive function. Patients exhibit comparable speed to healthy individuals when completing neurocognitive balance tasks, yet they display a higher frequency of accuracy errors in accurately perceiving their environment and making decisions under time constraints. Future research should gain more insights in which other cognitive domains are affected in patients with CAI for a better grasp of this condition's underlying mechanism.

Characteristics of static balance performance in 4-Stage Balance test in the Healthy Older Adults

Background: The 4-Stage Balance test is one of the most commonly used tests to assess balance for older adults. Although it is generally accepted that the four positions (including side-by-side (SBSS), semi-tandem (STS), tandem (TS), and single-leg stance (SLS)) in this test are progressively more difficult, there are no studies comparing the balance parameters of the four positions in older adults to prove this result. The purpose of this study is to determine the difficulty of 4 positions in the 4-Stage Balance test and the effect of the dominant and non-dominant lower extremities on static balance among healthy older adults; Methods: A total of 115 community-dwelling healthy older adults were included. The postural parameters (including sway range standard deviation (SR), velocity of body sway (V), total sway area (TSA) and sway perimeter (TSP) of the center of pressure) were measured during 8 static postures (including SBSS, left STS, right STS, left TS, right TS, left SLS, right SLS and comfortable stance (CS)). Repeated measures ANOVA was used to analyze the postural parameters in 8 static postures; Results: The static balance stability of the five stances in older adults can be ranked in the following sequence: CS > SBSS/STS > TS > SLS. Moreover, changing foot placement in STS, TS and SLS tasks has no influence on stability. This study has been registered in China Clinical Trial Registry (ChiCTR2200065803). Conclusions: Our findings suggest that it is feasible to simplify the 4-Stage Balance test to a 3-Stage Balance test in the older adults.

Correlations between plantar pressure and postural balance in healthy subjects and their comparison according to gender and limb dominance: A cross-sectional descriptive study

BACKGROUND

Lower extremity injuries rank among the most common injuries affecting young population, and numerous factors affect the outcomes of plantar pressure and balance assessment.

RESEARCH QUESTION

Does a correlation exist between plantar pressure and postural balance in healthy subjects and are there any difference in the results based on gender and limb dominance?

METHODS

This study involved thirty healthy recreationally active young adults (15 females, 15 males). Plantar pressures were analyzed using the MatScan Pressure Mat System, and postural balance was evaluated using Biodex Balance System. All assessments conducted under both static and dynamic conditions. Correlations were tested by Spearman Correlation Coefficient, and comparative tests were performed for gender and limb dominance.

RESULTS

Correlations were observed between plantar pressure parameters and balance scores, particularly in the dynamic conditions (p < 0.05). Gender-based differences were noted in plantar pressure parameters (p < 0.05), with females demonstrating improved balance stability scores. No significant differences were found based on limb dominance in plantar pressure and postural balance data (p > 0.05).

SIGNIFICANCE

This study provides valuable detailed insights into the existing literature concerning plantar pressure and postural balance assessments within the healthy population. A strong correlation was observed between plantar pressure and postural balance, and the comparisons of these assessments were affected by gender but not by limb dominance. These results could lead the way for better rehabilitation approaches by considering the correlations and differences across diverse populations.

Normalized stability time analysis within the boundaries between adults with and without fear of falling

BACKGROUND

The unilateral stance test, measured by the center of pressure (COP), has been widely used to identify balance deficits. However, there is a critical gap in understanding the specific COP thresholds on postural stability in adults with a fear of falling (FOF).

AIMS

To investigate the normalized stability time, which was defined as the ratio of time spent within stability boundaries to the total test duration, under different visual conditions and specific thresholds between adults with and without FOF.

METHODS

Twenty-one older adults with FOF and 22 control subjects completed the unilateral limb standing test in eyes-open and eyes-closed conditions. Normalized stability times were computed based on five pre-determined COP sway range thresholds: 10 mm, 15 mm, 20 mm, 25 mm, and 30 mm.

RESULTS

Receiver operating characteristic analysis determined the diagnostic accuracy of FOF. There were significant differences in the effects of both visual conditions (F = 46.88, p = 0.001) and threshold settings (F = 119.38, p = 0.001) on stability time between groups. The FOF group significantly reduced normalized stability time at the 10 mm COP threshold under eyes-closed conditions (t = - 1.95, p = 0.03).

DISCUSSION

The findings highlight the heightened sensitivity of the 10 mm COP threshold in identifying group variances in postural stability when eyes are closed. Moreover, the FOF group displayed a marked reduction in stability duration based on visual scenarios and normalized thresholds.

CONCLUSION

The study highlights the need to account for both COP boundaries and visual conditions in adults with FOF. When assessing postural control during unilateral stances, clinicians must also give attention to non-visual cues.

Effects of dominance and vision on unipedal balance tests in futsal players using a triaxial accelerometer

Optimal postural control improves performance and reduces the risk of injury in futsal. In this context, wearable accelerometers may detect velocity changes of the centre of mass during a task, enabling the analysis of postural control in different environments. This work aimed to determine the influence of vision and dominance on unipodal static postural balance in non-professional athletes. Twenty-four university male futsal players performed a unipodal balance test to assess their body sway using a triaxial accelerometer. To assess dominance, the preferred limb for kicking the ball was considered, while vision was manipulated by asking participants to close their eyes during the test. Root mean square (RMS) and sample entropy (SaEn) of centre of mass variables were analysed. For statistical analysis, a multivariate analysis of variance model was used. Our results suggest an effect of vision, but not of dominance nor the interaction between vision and limb dominance. Specifically, a higher-acceleration RMS in the mediolateral axis was observed, as well as an increased SaEn in the three axes. To conclude, unipodal postural demand in futsal players under visual input suppression was not influenced by their limb dominancy.

Reference value of knee position sense in weight-bearing and non-weight-bearing conditions

BACKGROUND

Our study aimed to identify age-related changes in knee proprioception to provide reference values for weight-bearing (WB) and non-weight-bearing (NWB) conditions and to identify factors (age, WB condition, dominance, and sex) that can affect knee proprioception.

METHODS

A total of 84 healthy adult men and women were recruited. Active knee joint position sense (JPS) was measured using a digital inclinometer for knee proprioception. The participants performed the required movements actively, with verbal feedback from the examiner, slowly moving to the target angles (30° and 50°) and maintaining them for 5 s before returning to the starting position. Afterward, without assistance from the examiner, the participants actively moved back to the same angle, and the examiner confirmed the angles. This procedure was repeated twice for each target angle, and the average values were used as the data. The participants were barefoot, wearing shorts, and closed their eyes while the measurements were obtained. The measurements were first obtained on the dominant side under the NWB conditions. When a change in posture was needed during the measurement, the participants sat in a resting position for 2 min.

RESULTS

Except for age, all other factors (WB condition, dominance, sex) were not statistically significant. Age showed a significant difference in knee JPS, except for the non-dominant side at 30° and the dominant side at 50° in the NWB condition.

CONCLUSION

This study indicates that the WB condition, dominant side, and sex need not be considered when measuring and assessing knee JPS. Age shows a negative correlation with knee joint position sense, and the reference values presented in this study can be used as objective target values during the rehabilitation process.

Posture of Healthy Subjects Modulated by Transcutaneous Spinal Cord Stimulation

Transcutaneous electrical stimulation of the spinal cord is used to restore locomotion and body weight support in patients with severe motor disorders. We studied the effects of this non-invasive stimulation on postural control in healthy subjects. Stimulation at the L1-L2 vertebrae was performed to activate the extensor muscles of the lower limbs. Because postural regulation depends on the cognitive style, the effects of the stimulation were analyzed separately in field-dependent (FD) and field-independent (FI) participants. During the study, FD and FI participants (N = 16, 25 ± 5 years, all right dominant leg) stood on a force platform in a soundproof chamber with their eyes closed. Stimulation was applied in the midline between the L1 and L2 vertebrae or over the left or right dorsal roots of the spinal cord; under the control condition, there was no stimulation. Stimulation destabilized posture in healthy subjects, whereas patients with movement disorders usually showed an improvement in postural control. In the FD participants, left dorsal root and midline stimulation increased several postural parameters by up to 30%. Dorsal root stimulation on the side of the supporting leg reduced postural control, while stimulation on the side of the dominant leg did not. No significant changes were observed in the FI participants.

Facilitating or disturbing? An investigation about the effects of auditory frequencies on prefrontal cortex activation and postural sway

Auditory stimulation activates brain areas associated with higher cognitive processes, like the prefrontal cortex (PFC), and plays a role in postural control regulation. However, the effects of specific frequency stimuli on upright posture maintenance and PFC activation patterns remain unknown. Therefore, the study aims at filling this gap. Twenty healthy adults performed static double- and single-leg stance tasks of 60s each under four auditory conditions: 500, 1000, 1500, and 2000 Hz, binaurally delivered through headphones, and in quiet condition. Functional near-infrared spectroscopy was used to measure PFC activation through changes in oxygenated hemoglobin concentration, while an inertial sensor (sealed at the L5 vertebra level) quantified postural sway parameters. Perceived discomfort and pleasantness were rated through a 0-100 visual analogue scale (VAS). Results showed that in both motor tasks, different PFC activation patterns were displayed at the different auditory frequencies and the postural performance worsened with auditory stimuli, compared to quiet conditions. VAS results showed that higher frequencies were considered more discomfortable than lower ones. Present data prove that specific sound frequencies play a significant role in cognitive resources recruitment and in the regulation of postural control. Furthermore, it supports the importance of exploring the relationship among tones, cortical activity, and posture, also considering possible applications with neurological populations and people with hearing dysfunctions.

Healthy aging reduces dynamic balance control as measured by the simplified Star Excursion Balance Test

BACKGROUND

Detecting and classifying factors that contribute to age-related balance decline are essential for targeted interventions. Dynamic postural tests that challenge neuromuscular balance control are important to detect subtle deficits that affect functional balance in healthy aging.

RESEARCH QUESTION

How does healthy aging affect specific components of dynamic postural control as measured by the simplified Star Excursion Balance Test (SEBT)?

METHODS

Twenty healthy younger (18-39 years) and twenty healthy older (58-74 years) adults performed the standardized simplified SEBT, which involved standing on one leg and reaching the contralateral leg as far as possible in the anterior, posteromedial, and posterolateral directions. Optical motion capture was used to quantify the maximum reach distance normalized by body height (%H) for three repeated trials in each direction per leg. Linear mixed effects models and pairwise comparisons of estimated marginal means were used to assess differences (p < 0.05) in normalized maximum reach distance by age group, reach direction, and leg dominance. Intersubject and intrasubject variability were also assessed by age group using coefficients of variation (CV).

RESULTS

Healthy older adults had less dynamic postural control compared to younger adults, with shorter reach distances in the anterior (7.9 %), posteromedial (15.8 %), and posterolateral (30.0 %) directions (p < 0.05). Leg dominance and sex did not significantly affect SEBT score for either age group (p > 0.05). Low intrasubject variability (CV<0.25 %) was found for repeated trials in both the older and younger participants. Therefore, the comparatively higher intersubject variability (Range CV=8-25 %) was mostly attributed to differences in SEBT performance across participants.

SIGNIFICANCE

Quantifying dynamic postural control in healthy older adults in a clinical setting is important for early detection of balance decline and guiding targeted and effective treatment. These results support that the simplified SEBT is more challenging for healthy older adults, who may benefit from dynamic postural training to mitigate age-related decline.

Leg Dominance—Surface Stability Interaction: Effects on Postural Control Assessed by Smartphone-Based Accelerometry

The preferential use of one leg over another in performing lower-limb motor tasks (i.e., leg dominance) is considered to be one of the internal risk factors for sports-related lower-limb injuries. The current study aimed to investigate the effects of leg dominance on postural control during unipedal balancing on three different support surfaces with increasing levels of instability: a firm surface, a foam pad, and a multiaxial balance board. In addition, the interaction effect between leg dominance and surface stability was also tested. To this end, a tri-axial accelerometer-based smartphone sensor was placed over the lumbar spine (L5) of 22 young adults (21.5 ± 0.6 years) to record postural accelerations. Sample entropy (SampEn) was applied to acceleration data as a measure of postural sway regularity (i.e., postural control complexity). The results show that leg dominance (p < 0.001) and interaction (p < 0.001) effects emerge in all acceleration directions. Specifically, balancing on the dominant (kicking) leg shows more irregular postural acceleration fluctuations (high SampEn), reflecting a higher postural control efficiency or automaticity than balancing on the non-dominant leg. However, the interaction effects suggest that unipedal balancing training on unstable surfaces is recommended to reduce interlimb differences in neuromuscular control for injury prevention and rehabilitation.

Advanced cueing of auditory stimulus to the head induces body sway in the direction opposite to the stimulus site during quiet stance in male participants

Under certain conditions, a tactile stimulus to the head induces the movement of the head away from the stimulus, and this is thought to be caused by a defense mechanism. In this study, we tested our hypothesis that predicting the stimulus site of the head in a quiet stance activates the defense mechanism, causing a body to sway to keep the head away from the stimulus. Fourteen healthy male participants aged 31.2 ± 6.8 years participated in this study. A visual cue predicting the forthcoming stimulus site (forehead, left side of the head, right side of the head, or back of the head) was given. Four seconds after this cue, an auditory or electrical tactile stimulus was given at the site predicted by the cue. The cue predicting the tactile stimulus site of the head did not induce a body sway. The cue predicting the auditory stimulus to the back of the head induced a forward body sway, and the cue predicting the stimulus to the forehead induced a backward body sway. The cue predicting the auditory stimulus to the left side of the head induced a rightward body sway, and the cue predicting the stimulus to the right side of the head induced a leftward body sway. These findings support our hypothesis that predicting the auditory stimulus site of the head induces a body sway in a quiet stance to keep the head away from the stimulus. The right gastrocnemius muscle contributes to the control of the body sway in the anterior-posterior axis related to this defense mechanism.

Differences in the manifestation of balance according to BMI levels for women students of the Faculty of Physical Education and Sports

Abstract Background: Static and dynamic balance are factors of major importance in the manifestation of human motor skills at a higher level. Purpose: The determination of vari-ations in the performance of balance tests for young women students at the Faculty of Physical Education and Sports (48 cases in the 1st year of bachelor's degree), divided and analyzed 3 BMI levels (underweight / 7 cases, normal weight / 34 cases and overweight / 7 cases) and comparing these results with other similar research. Material and method: The testing of the group was scheduled at the Research Center for Human Performance, be-longing to the Faculty of Physical Education and Sports in Galați, in the month of April of the 2018-2019 academic year. For the assessment of balance, 7 tests were used, of which 4 associated with dynamic postural stability (Walk and turn field sobriety test/errors, Func-tional reach test/cm, Fukuda test/degrees of rotation, Bass test/ points) and 3 measuring static stability (Flamingo test/falls, One leg standing with eyes closed/sec, Stork test/sec). Nonparametric tests (Mann-Whitney U) were applied to compare differences between batches. Results: The average values of underweight and normal-weight women are better than those of overweight women for the entire set of assessment tests. The underweight group has the best results for the Standing balance test, Functional reach test, Flamingo test, Walk and turn field sobriety test, Fukuda test, and the normal weight women for Stork test, respectively Bass test. We found a lack of significant thresholds when comparing the results between the 3 groups (P> 0.05) for Stork test, Standing balance test and Functional reach test, so the working hypothesis formulated is only partially confirmed. The only significant difference between underweight and normal weight (P <0.05) is found in the Flamingo test, with better values for underweight. Significant difference thresholds for Flamingo test and Fukuda test are recorded between the underweight and overweight groups (Z values have associated thresholds P<0.05). The most significant differences are found between the normal weight and overweight groups (P <0.05), respectively for the Bass test, Fukuda test and Walk and turn field sobriety test. Conclusion: Constant physical activity (as a feature of the analyzed group) reduces the chances of significant differences in all balance tests between BMI levels. Keywords: female students; university specialization; static and dynamic postural control; physical activity

Successful 10-second one-legged stance performance predicts survival in middle-aged and older individuals

OBJECTIVES

Balance quickly diminishes after the mid-50s increasing the risk for falls and other adverse health outcomes. Our aim was to assess whether the ability to complete a 10- s one-legged stance (10-second OLS) is associated with all-cause mortality and whether it adds relevant prognostic information beyond ordinary demographic, anthropometric and clinical data.

METHODS

Anthropometric, clinical and vital status and 10-s OLS data were assessed in 1702 individuals (68% men) aged 51-75 years between 2008 and 2020. Log-rank and Cox modelling were used to compare survival curves and risk of death according to ability (YES) or inability (NO) to complete the 10-s OLS test.

RESULTS

Overall, 20.4% of the individuals were classified as NO. During a median follow-up of 7 years, 7.2% died, with 4.6% (YES) and 17.5% (NO) on the 10-s OLS. Survival curves were worse for NO 10-s OLS (log-rank test=85.6; p<0.001). In an adjusted model incorporating age, sex, body mass index and comorbidities, the HR of all-cause mortality was higher (1.84 (95% CI: 1.23 to 2.78) (p<0.001)) for NO individuals. Adding 10-s OLS to a model containing established risk factors was associated with significantly improved mortality risk prediction as measured by differences in -2 log likelihood and integrated discrimination improvement.

CONCLUSIONS

Within the limitations of uncontrolled variables such as recent history of falls and physical activity, the ability to successfully complete the 10-s OLS is independently associated with all-cause mortality and adds relevant prognostic information beyond age, sex and several other anthropometric and clinical variables. There is potential benefit to including the 10-s OLS as part of routine physical examination in middle-aged and older adults.

Acute effects of ankle plantar flexor force-matching exercises on postural strategy during single leg standing in healthy adults

BACKGROUND

Ankle plantar flexor force steadiness, assessed by measuring the fluctuation of the force around the submaximal target torque, has been associated with postural stability.

RESEARCH QUESTION

To investigate whether a force-matching exercise, where submaximal steady torque is maintained at the target torque, can modulate postural strategy immediately.

METHODS

Twenty-eight healthy young adults performed ankle plantar flexor force-matching exercises at target torques of 5%, 20%, and 50% of maximum voluntary contraction (MVC), in a randomized crossover trial. Participants with their ankle in a neutral position were instructed to maintain isometric contraction at each target torque, as measured by a dynamometer, for 20 s with 3 sets of 5 contractions. Before and after the force-matching exercises, the anterior-posterior velocities and standard deviation of the center of pressure (COP) on the stable platform and the tilt angle of the unstable platform during 20-seconds single-leg standing were measured. The velocities and standard deviations of the COP and tilt angle before and after the exercises were compared using paired t-tests.

RESULTS

The tilt angle velocity of an unstable platform significantly decreased after the force-matching exercise at a target torque of 5% MVC (p = 0.029), whereas it was unchanged after the exercises at target torques of 20% and 50% MVC. The standard deviations of the tilt angle of unstable platform test did not change significantly after any exercise. Furthermore, no significant differences were observed in the COP velocities or standard deviations on the stable platform test after any exercise.

SIGNIFICANCE

Our findings suggest that repeated exertion training at low-intensity contractions can affect postural stability in an unstable condition. Particularly, force-matching exercise at very low-intensity torque, such as 5% of MVC, may be an effective method to improve postural control in the unstable condition, but not in a stable condition.

The relationships between knee extensors/ flexors strength and balance control in elite male soccer players

Background

Strength and balance are important factors for soccer players to be successful. This study’s aim was to determine the relationship between lower-limb muscle strength and balance control in elite male soccer players (n = 77).

Methods

Concentric isokinetic strength (peak torque of quadriceps (PT-Q) and hamstrings (PT-H), hamstrings/quadriceps (H/Q) ratio) was measured for the dominant and non-dominant leg at angular velocities of 60°s⁻¹and 240°s⁻¹, as well as the total work for extensors (TW-Q) and flexors (TW-H) for both legs (at an angular velocity of 240°s⁻¹only). Balance score (BAL score) was used for unilateral assessment of balance control using a Delos Postural System Test measurement tool. Hierarchical multiple regression analyses were performed to predict balance control using isokinetic knee strength performance for dominant and non-dominant legs.

Results

Final modelling included peak torque of hamstrings at 240°s⁻¹ and peak torque of the quadriceps at 240°s⁻¹ for the non-dominant leg (R² = 19.6%; p ≤ 0.001) and only peak hamstring torque at 240°s⁻¹ for the dominant leg (R² = 11.3%; p = 0.003) as significant predictors of balance score.

Conclusion

Findings indicate that balance control is widely influenced by peak hamstring torque and peak quadriceps torque at high angular velocity particularly in the non-dominant leg i.e., the supporting leg in soccer players.

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).