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Abstract: Miralles-Iborra, A, Del Coso, J, De Los Ríos-Calonge, J, Elvira, JLL, Barbado, D, Urban, T, and Moreno-Pérez, V. Deceleration capacity during directional change as a time-efficient (ecological) prescreening of hip adductor force status in amateur soccer players. J Strength Cond Res XX(X): 000-000, 2024-Reduced isometric adductor muscle strength has been identified as a modifiable risk factor contributing to injury in soccer players. However, the measurement of hip adductor muscle strength is habitually laboratory-based, with isolated hip movements that do not reflect soccer-specific movements that induce groin injury during match play. This study aimed to determine the usefulness of deceleration capacity during a change of direction (COD) as a time-efficient (ecological) prescreening of hip adductor force status in soccer players. Nineteen amateur soccer players completed unilateral isometric hip adductor strength assessments and a 180° COD test. Isometric hip strength assessment included the maximum peak torque (PT) and maximum rate of torque development (RTDmax) relative to players' body mass. Players' deceleration capacity during the COD test was determined for each leg through maximum deceleration normalized to the linear momentum. A linear regression analysis was performed to associate isometric hip strength variables with the deceleration capacity during the COD test at each leg. There was not a statistically significant association between deceleration capacity and hip isometric maximum PT of the dominant and nondominant legs (r ≤ 0.14, p > 0.05). Nevertheless, a moderate association was found between deceleration capacity and RTDmax for both legs (r ≥ 0.58, p < 0.05). The optimal linear regression model suggests that measuring deceleration capacity during a directional change test could explain RTDmax by 33 and 43% for the dominant and nondominant legs, respectively. During a 180° COD test, the deceleration capacity captured through GPS-accelerometer device was limited as a prescreening tool to evaluate hip adductor force status in soccer players., (Copyright © 2024 National Strength and Conditioning Association.)

Background: Variable practice is a broadly used tool to improve motor learning processes. However, controversial results can be found in literature about the success of this type of practice compared to constant practice. This study explored one potential reason for this controversy: the manipulation of variable practice load applied during practice and its effects according to the initial performance level and the initial intrinsic variability of the learner., Method: Sixty-five participants were grouped into four practice schedules to learn a serial throwing task, in which the training load of variable practice was manipulated: one constant practice group and three groups with different variable practice loads applied. After a pre-test, participants trained for 2 weeks. A post-test and three retests (96 h, 2 weeks and 1 month) were carried out after training. The participants' throwing accuracy was assessed through error parameters and their initial intrinsic motor variability was assessed by the autocorrelation coefficient of the error., Results: The four groups improved their throwing performance. Pairwise comparisons and effect sizes showed larger error reduction in the low variability group. Different loads of variable practice seem to induce different performance improvements in a throwing task. The modulation of the variable practice load seems to be a step forward to clarify the controversy about its benefits, but it has to be guided by the individuals' features, mainly by the initial intrinsic variability of the learner., Competing Interests: The authors declare that they have no competing interests., (© 2024 Caballero et al.)

Movement control can be an indicator of how challenging a task is for the athlete, and can provide useful information to improve training efficiency and prevent injuries. This study was carried out to determine whether inertial measurement units (IMU) can provide reliable information on motion variability during strength exercises, focusing on the squat. Sixty-six healthy, strength-trained young adults completed a two-day protocol, where the variability in the squat movement was analyzed at two different loads (30% and 70% of one repetition maximum) using inertial measurement units and a force platform. The time series from IMUs and force platforms were analyzed using linear (standard deviation) and non-linear (detrended fluctuation analysis, sample entropy and fuzzy entropy) measures. Reliability was analyzed for both IMU and force platform using the intraclass correlation coefficient and the standard error of measurement. Standard deviation, detrended fluctuation analysis, sample entropy, and fuzzy entropy from the IMUs time series showed moderate to good reliability values (ICC: 0.50-0.85) and an acceptable error. The study concludes that IMUs are reliable tools for analyzing movement variability in strength exercises, providing accessible options for performance monitoring and training optimization. These findings have implications for the design of more effective strength training programs, emphasizing the importance of movement control in enhancing athletic performance and reducing injury risks.

Abstract: Heredia-Elvar, JR, Juan-Recio, C, Prat-Luri, A, Barbado, D, Ríos-Calonge, Jdl, and Vera-Garcia, FJ. Exercise intensity progressions and criteria to prescribe core stability exercises in young physically active men: a smartphone accelerometer-based study. J Strength Cond Res 38(2): 266-273, 2024-The establishment of core stability (CS) exercise intensity progressions in sport and clinical settings is normally based on subjective criteria. Therefore, this study aimed to develop exercise intensity progressions for some of the most common CS exercises through smartphone accelerometry and to analyze the effect of the subjects' lumbopelvic postural control on these progressions. Fifty-seven healthy young physically active male students performed 7 isometric variations of front bridge, back bridge, side bridge, and bird-dog exercises with a smartphone accelerometer placed on the pelvis. Mean pelvic accelerations were calculated during each variation to evaluate the lumbopelvic postural control challenge imposed on the subjects as an index of exercise intensity of difficulty. For the bridge exercises, long bridging produced higher pelvic accelerations than short bridging, bridging with single-leg support was more intense than bridging with double-leg support (even with both legs on a hemisphere ball for the back and front bridge), and the most difficult variations were those performed on a Swiss ball, mainly the variations with single-leg support. For the bird-dog exercise, the 2-point positions were more intense than the 3-point positions, the variations performed with a knee on the hemisphere ball produced higher pelvic accelerations than similar variations performed with the forearm on the hemisphere ball, and the variations with limb motions generated higher pelvic accelerations than similar variations performed without limb motions. Although the CS exercise progressions were very similar across subjects, our results showed the need to individualize the prescription of the CS exercise progressions based on the subjects' lumbopelvic postural control level., (Copyright © 2023 National Strength and Conditioning Association.)

Introduction: Sitting on an unstable surface is a common paradigm to investigate trunk postural control among individuals with low back pain (LBP), by minimizing the influence lower extremities on balance control. Outcomes of many small studies are inconsistent (e.g., some find differences between groups while others do not), potentially due to confounding factors such as age, sex, body mass index [BMI], or clinical presentations. We conducted a systematic review with an individual participant data (IPD) meta-analysis to investigate whether trunk postural control differs between those with and without LBP, and whether the difference between groups is impacted by vision and potential confounding factors., Methods: We completed this review according to PRISMA-IPD guidelines. The literature was screened (up to 7th September 2023) from five electronic databases: MEDLINE, CINAHL, Embase, Scopus, and Web of Science Core Collection. Outcome measures were extracted that describe unstable seat movements, specifically centre of pressure or seat angle. Our main analyses included: 1) a two-stage IPD meta-analysis to assess the difference between groups and their interaction with age, sex, BMI, and vision on trunk postural control; 2) and a two-stage IPD meta-regression to determine the effects of LBP clinical features (pain intensity, disability, pain catastrophizing, and fear-avoidance beliefs) on trunk postural control., Results: Forty studies (1,821 participants) were included for the descriptive analysis and 24 studies (1,050 participants) were included for the IPD analysis. IPD meta-analyses revealed three main findings: (a) trunk postural control was worse (higher root mean square displacement [RMSdispl], range, and long-term diffusion; lower mean power frequency) among individuals with than without LBP; (b) trunk postural control deteriorated more (higher RMSdispl, short- and long-term diffusion) among individuals with than without LBP when vision was removed; and (c) older age and higher BMI had greater adverse impacts on trunk postural control (higher short-term diffusion; longer time and distance coordinates of the critical point) among individuals with than without LBP. IPD meta-regressions indicated no associations between the limited LBP clinical features that could be considered and trunk postural control., Conclusion: Trunk postural control appears to be inferior among individuals with LBP, which was indicated by increased seat movements and some evidence of trunk stiffening. These findings are likely explained by delayed or less accurate corrective responses., Systematic Review Registration: This review has been registered in PROSPERO (registration number: CRD42021124658)., Competing Interests: The authors have declared that no competing interests exist., (Copyright: This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.)

Smartphone accelerometry has potential to provide clinicians with specialized gait analysis not available in most clinical settings. The Gait&Balance Application (G&B App) uses smartphone accelerometry to assess spatiotemporal gait parameters under two conditions: walking looking straight ahead and walking with horizontal head turns. This study investigated the validity of G&B App gait parameters compared with the GAITRite® pressure-sensitive walkway. Healthy young and older adults (age range 21-85 years) attended a single session where a smartphone was secured over the lumbosacral junction. Data were collected concurrently with the app and GAITRite® systems as participants completed the two walking conditions. Spatiotemporal gait parameters for 54 participants were determined from both systems and agreement evaluated with partial Pearson's correlation coefficients and limits of agreement. The results demonstrated moderate to excellent validity for G&B App measures of step time (r p 0.97, 95 % CI [0.96, 0.98]), walking speed (r p 0.83 [0.78, 0.87]), and step length (r p 0.74, [0.66, 0.80]) when walking looking straight ahead, and results were comparable with head turns. The validity of walking speed and step length measures was influenced by sex and height. G&B App measures of step length variability, step time variability, step length asymmetry, and step time asymmetry had poor validity. The G&B App has potential to provide valid measures of unilateral and bilateral step time, unilateral and bilateral step length, and walking speed, under two walking conditions in healthy young and older adults. Further research should validate this tool in clinical conditions and optimise the algorithm for demographic characteristics., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Background: Body tilt changes could affect the intensity/difficulty of core stability exercises, but there is still a lack of knowledge about its impact., Objective: To analyse the trunk muscles activation during prone plank exercises at different body tilts., Methods: Twenty-four young adults who performed recreational gymnastic activities participated in this study. Electromyography activity of the rectus abdominis (RA), external oblique (EO), internal oblique (IO) and erector spinae (ES) was recorded during the performance of six variations of the prone plank exercise (planking with feet supported on the ground [conventional horizontal position] and planking with feet supported on wall bars at five different heights increasing the angle tilt) and an inverted position exercise., Results: The RA, EO and IO activation in all prone plank variations were higher than those observed in the conventional prone plank. In addition, the coefficient of variation of the muscle activation increased with the declination angle, reaching the highest values in the inverted position for the RA and ES muscles., Conclusion: The results seem to indicate that the body tilt variation could be used as an easy and inexpensive strategy for modulating the neuromuscular demands and the motor control challenge during planking exercises.

An accurate trunk muscle strength assessment seems very important to design and individualize training and rehabilitation programs in clinical and sport settings. Hand-held dynamometers (HHDs) are interesting alternatives to isokinetic dynamometers for assessing trunk isometric muscle strength because they are inexpensive instruments and easy to use. This cross-sectional observational study aimed to examine the reliability of two novel sitting tests for assessing trunk flexion and extension isometric strength using an HHD and their relationship with two other novel isometric tests that use an isokinetic dynamometer. Twenty-four female amateur athletes (age: 24.5 ± 2.64 years; body height: 164.45 ± 6.33 cm; body mass: 63.17 ± 10.35 kg) participated in this study. A test-retest design was carried out one-week apart to examine the reliability. The relationship and the degree of agreement between the HHD and the isokinetic dynamometer measurements were analysed using Pearson correlation and Bland-Altman analysis, respectively. In general, the reliability of all isometric strength tests was good, with ICCs ranging from 0.65 to 0.87 and typical error < 15%. Pearson correlations were moderate, with values of r = 0.47 (R 2 = 0.22) and r = 0.42 (R 2 = 0.18) for flexion and extension strength, respectively. Bland-Altman plots showed no agreement between HHDs and isokinetic measurements. All trunk isometric tests using both, an isokinetic dynamometer and HHDs, provide reliable measurements for assessing trunk flexion and extension strength. According to the comparative analysis, both measurement types are different and cannot be used interchangeably. Health and sport professionals should choose the test that best suits the biomechanical characteristics required for functional goals or success in a given sport., Competing Interests: The authors declare no conflict of interest., (Copyright: © Academy of Physical Education in Katowice.)

Background and Purpose: Optimal reporting is a critical element of scholarly communications. Several initiatives, such as the EQUATOR checklists, have raised authors' awareness about the importance of adequate research reports. On these premises, we aimed at appraising the reporting quality of published randomized controlled trials (RCTs) dealing with rehabilitation interventions. Given the breadth of such literature, we focused on rehabilitation for multiple sclerosis (MS), which was taken as a model of a challenging condition for all the rehabilitation professionals.A thematic methodological survey was performed to critically examine rehabilitative RCTs published in the last 2 decades in MS populations according to 3 main reporting themes: (1) basic methodological and statistical aspects; (2) reproducibility and responsiveness of measurements; and (3) clinical meaningfulness of the change., Summary of Key Points: Of the initial 526 RCTs retrieved, 370 satisfied the inclusion criteria and were included in the analysis. The survey revealed several sources of weakness affecting all the predefined themes: among these, 25.7% of the studies complemented the P values with the confidence interval of the change; 46.8% reported the effect size of the observed differences; 40.0% conducted power analyses to establish the sample size; 4.3% performed retest procedures to determine the outcomes' reproducibility and responsiveness; and 5.9% appraised the observed differences against thresholds for clinically meaningful change, for example, the minimal important change., Recommendations for Clinical Practice: The RCTs dealing with MS rehabilitation still suffer from incomplete reporting. Adherence to evidence-based checklists and attention to measurement issues and their impact on data interpretation can improve study design and reporting in order to truly advance the field of rehabilitation in people with MS.Video Abstract available for more insights from the authors (see the Video, Supplemental Digital Content 1 available at: http://links.lww.com/JNPT/A424 )., Competing Interests: The authors declare no conflict of interest., (Copyright © 2023 The Authors. Published by Wolters Kluwer Health, Inc. on behalf of Academy of Neurologic Physical Therapy, APTA.)

Objectives: The purpose of this study was 1) to determine and compare kinetic parameters during the realization of a countermovement jump (CMJ) between footballers with cerebral palsy (CP) and non-impaired footballers, and 2) to analyze the differences in this action between different players' impairment profiles and a group of non-impaired footballers. Methods: This study involved 154 participants comprising 121 male footballers with CP from 11 national teams and 33 male non-impaired football players recruited as the control group (CG). The footballers with CP were described according to the different impairment profiles (bilateral spasticity = 10; athetosis or ataxia = 16; unilateral spasticity = 77; minimum impairment = 18). All participants performed three CMJs on a force platform to record kinetic parameters during the test. Results: The group of para-footballers presented significantly lower values than the CG in the jump height ( p < 0.01, d = -1.28), peak power ( p < 0.01, d = -0.84), and the net concentric impulse ( p < 0.01, d = -0.86). Concerning the pairwise comparisons between CP profiles and the CG, significant differences were found for the bilateral spasticity, athetosis or ataxia, and unilateral spasticity subgroups compared to the non-impaired players for jump height ( p < 0.01; d = -1.31 to -2.61), power output ( p < 0.05; d = -0.77 to -1.66), and concentric impulse of the CMJ ( p < 0.01; d = -0.86 to -1.97). When comparing the minimum impairment subgroup with the CG, only significant differences were found for jump height ( p = 0.036; d = -0.82). Footballers with minimum impairment presented higher jumping height ( p = 0.002; d = -1.32) and concentric impulse ( p = 0.029; d = -1.08) compared to those with bilateral spasticity. Also, the unilateral spasticity subgroup reports a higher jump height performance than the bilateral group ( p = 0.012; d = -1.12). Conclusion: These results suggest that the variables related to power production during the concentric phase of the jump are crucial for the performance differences between groups with and without impairment. This study provides a more comprehensive understanding of kinetic variables that would differentiate CP and non-impaired footballers. However, more studies are necessary to clarify which parameters better differentiate among different profiles of CP. The findings could help to prescribe effective physical training programs and support the classifier's decision-making for class allocation in this para-sport., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Henríquez, Sabido, Barbado, Roldan, Elvira, Yanci and Reina.)

Background: Core stability exercise programs have become popular in recent years for preserving balance and functional independence in people with multiple sclerosis (PwMS); however, their real impact is not well-known as the main intervention target (i.e., core stability) theoretically responsible for balance or functional improvements is not measured. The objective of this study was to test the reliability of accelerometers integrated into smartphones for quantifying core stability and developing exercise progressions in PwMS., Methods: Twenty participants with MS [age: 47.5±8.0 years; height: 1.62±0.07 m; mass: 63.4±10.9 kg; EDSS: 3.0 (1.5-6)] participated voluntarily in this study. CS was assessed in different variations of the front, side, and back bridges and bird-dog exercises by measuring the mean lumbopelvic acceleration in two testing sessions, separated by one week. Relative and absolute reliability of lumbopelvic acceleration of those exercise variations performed by more than 60% of the participants was analyzed by the intraclass correlation coefficient (ICC 3,1 ), and the standard error of measurement (SEM) and the minimal detectable change (MDC), respectively. Repeated measures ANOVAs were performed to detect a potential learning effect between test-retest assessments. Statistical significance was set at p < 0.05., Results: Reliability analyses revealed that good to excellent relative and absolute scores (0.850.05)., Conclusion: Smartphone accelerometry seems a low cost, portable and easy-to-use tool to objectively and reliably track core stability changes in PwMS through. However, in spite of the popularity of bridging and bird-dog exercises, only the short and long bridges and the three-point bird-dog positions proved feasible for most participants. Overall, this study provides useful information to evaluate and guide the prescription of core stability exercise programs in PwMS with mild-to-moderate impairment., Competing Interests: Conflict of Interest The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 The Author(s). Published by Elsevier B.V. All rights reserved.)

Background: Tennis is one of the most popular sports among youths. At elite levels, a notable increase in injury incidence and a temporary decline in performance may occur when children progress through puberty. However, limited research has explored maturity-associated variations in clinical measurements suggested as predictors of injury and tennis performance in elite youth players. Therefore, the main purpose of this study was to analyze the association between chronological age and maturity status on several measures of neuromuscular capability and physical performance as well as bilateral (interlimb) asymmetries in elite youth tennis players., Hypothesis: Youth tennis players around peak height velocity (PHV) will show higher growth-related impairments or deficits in measures of neuromuscular capability and physical performance than their less (pre-PHV) and more (post-PHV) mature counterparts irrespective of sex., Level of Evidence: Level 4., Methods: A total of 68 male (age, 13.7 ± 1.1 years; height, 162.4 ± 9.4 cm; body mass, 51.4 ± 10.3 kg [Mean values ± SD]) and 60 female (age, 13.6 ± 1.1 years; height, 162.8 ± 7.2 cm; body mass, 52.7 ± 7.5 kg [Mean values ± SD]) elite youth tennis players from 2 different age groups (under 13 [U13] and under 15 [U15]) and maturity status (pre-PHV, around PHV, and post-PHV), were tested during national training camps. Tests included the Y Balance Test, isometric hip abduction and adduction strength, hip ranges of motion (ROMs), and countermovement jump (CMJ) height. Bayesian analysis was used to establish any significant between-group differences., Results: Only dynamic balance (in boys; Bayesian factor [BF 10 ] = 88.2) and jump height (in both boys and girls; BF 10 >100) were significatively associated with chronological age, whereby the U15 group showed lower Y Balance Test reach distances (-6%; standardized effect size δ = 0.62) but higher CMJ height scores (+18%; δ = 0.73) than the U13 group. Although boys jump higher (+11%; δ = 0.62) and were stronger in isometric hip adduction strength (+14%; δ = 0.92) than girls, the latter had greater hip internal ROM values (+15%; δ = 0.75). Furthermore, relevant maturity-associated effects (BF 10 = 34.6) were solely observed for the CMJ test in boys, with the most mature players demonstrating higher jump height scores (+12%; δ = 0.93). Finally, a significant percentage (>25%) of tennis players, independent of sex, demonstrated bilateral asymmetries in hip ROM, hip strength, and jump height values., Conclusion: The findings of this study show that in U13 and U15 male and female tennis players, there were neither positive nor negative maturity-associated variations in the clinical measurements analyzed (with the exception of jump height in male players). The high proportion of tennis players showing bilateral asymmetries in dynamic balance, hip ROM, and strength and jump performance highlight the need of future studies to analyze these factors in relation to unilateral tennis-specific adaptations in the musculoskeletal and sensorimotor systems., Clinical Relevance: These results may help to better understand how different clinical measurements are associated with the process of growth and maturation in elite youth tennis players and may aid in the design of specific training interventions during these stages of development.

Motor variability is a prominent feature of the human movement that, nowadays, can be easily measured through different sensors and analyzed using different types of variables, and it seems to be related to functional and adaptative motor behavior. It has been stated that motor variability is related to the system's flexibility needed to choose the right degrees of freedom (DoFs) to adapt to constant environmental changes. However, the potential relationship between motor variability and DoFs is unknown. The aim of this study was to analyze how motor variability, both the amount and structure, changes depending on the mechanical DoFs involved in the movement control. For this purpose, movement variability was assessed by a tracking sensor in five tasks with different DoFs, and the amount, using standard deviation, and the structure of variability, through fuzzy entropy and detrended fluctuation analysis, were also assessed. The results showed a higher amount of variability and a less predictable and more auto-correlated variability structure in the long-term when more mechanical DoFs are implied. The studies that analyze motor variability should consider the type of movement and the DoFs involved in the analyzed task since, as the findings have shown, both factors have a noticeable influence on the amount and the structure of motor variability.

OBJECTIVE: To analyze the effect of trunkfocused exercise programs (TEPs) and moderator factors on chronic nonspecific low back pain (LBP). DESIGN: Systematic review with meta-analyses. LITERATURE SEARCH: We searched the PubMed, Scopus, Embase, SPORTDiscus, and CENTRAL databases from their inception to June 2022. STUDY SELECTION CRITERIA: We included randomized controlled trials comparing TEPs to control or general exercises. DATA SYNTHESIS: We used random-effects models to calculate the standardized mean difference (SMD) plus confidence interval (CI) and heterogeneity ( I 2 ) for pain, disability, quality of life, and trunk performance. The impact of moderator factors was analyzed through meta-regression. RESULTS: Forty randomized controlled trials (n = 2391) were included. TEPs showed positive effects for all outcomes versus control (SMD 0.90-2.46; 95% CI, -0.04 to 4.96; I 2 61%-98%). There were small effects in favor of TEPs versus general exercises for pain (SMD = 0.20; 95% CI, 0.03-0.37; I 2 = 13.4%) and disability (SMD = 0.20; 95% CI, 0.02-0.38; I 2 = 0%). Trunk and/or hip range-of-motion improvements were associated with greater reductions in pain ( P <.01; β = 0.56; 95% CI, 0.25-0.87) and disability ( P <.01; β = 0.66; 95% CI, 0.27-1.05). Low body mass was associated with higher pain reduction ( P = .03; β = -0.17; 95% CI, -0.32 to -0.02). CONCLUSIONS: Trunk-focused exercise programs had positive effects on pain, disability, quality of life, and trunk performance compared to control groups, and on pain and disability compared to general exercises. Increasing trunk and/or hip range of motion was associated with greater pain and disability reduction, and lower body mass with higher pain reduction. J Orthop Sports Phys Ther 2023;53(2):64-93. Epub: 16 January 2023. doi:10.2519/jospt.2023.11091 .

Background: The Gait&Balance (G&B) App has produced valid and reliable measures of gait and balance in young healthy adults but has not been tested in older adults., Research Question: In healthy middle-to-older aged adults, are G&B App measurements sensitive to age, valid against clinical and kinematic measures, and reliable?, Method: Healthy participants (n = 34, 14 male, 42-94 years) completed the G&B App protocol three times within a single session. 3D kinematics were collected concurrently. Clinical balance measures were collected (Modified Clinical Test of Sensory Interaction in Balance (mCTSIB), Mini Balance Evaluation Systems Test (MBT), and Functional Gait Assessment (FGA)). Sensitivity to age was assessed with Pearson's correlations. Validity tests included Pearson's correlations and Bland-Altman limits of agreement. Reliability tests included intra-class correlation coefficients and standard error of the measure., Results: During quiet stance on a compliant surface, the G&B App was sensitive to age-related differences not detectable with the mCTSIB. During walking tasks, there was adequate convergent validity between the MBT and G&B App measures of step length, and between the FGA and G&B App measures of walking speed, step length, and periodicity. The G&B App had moderate-to-excellent validity against 3D kinematics for postural stability during quiet stance (r 0.98 [0.98, 0.99]), step time (r 0.97 [0.96, 0.98]), walking speed (r 0.79 [0.7, 0.86]), and step length (r 0.73 [0.61, 0.81]). Test-retest reliability was moderate-to-excellent for G&B App measures of postural stability, walking speed, periodicity, step length, and step time. G&B App measures of step length asymmetry, step length variability, step time asymmetry, and step time variability had poor validity and reliability., Significance: The G&B App was sensitive to age-related differences in balance not detectable with clinical measurement. It provides valid and reliable measures of postural stability, step length, step time, and periodicity, which are not currently available in standard practice., Competing Interests: Conflict of Interest The authors declare no conflict of interest., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Induced variability by the use of unstable surfaces has been proposed to enhance proprioceptive control to deal with perturbations in the support base better. However, there is a lack of evidence about its benefits facilitating motor adaptions in upper body skills. In this experiment, practice on an unstable surface was applied to analyze the adaptations in an upper limb precision throwing skill. After a pretest, twenty-one participants were randomly allocated into two groups: one group practiced the throwing task on a stable surface and the other group practiced the same task on an unstable support base. Differences in throwing performance between pre- and post-practice were analyzed in accuracy, hand movement kinematics and variability of the throw in both surface conditions. Fuzzy entropy of the horizontal force was calculated to assess the complexity dynamics of postural sway. Participants improved their performance on the stable and the unstable surface. Induced variability using an unstable surface reduced participants' variability and the complexity of postural sway, but it did not facilitate a superior adaptation of the throwing task. The results suggest that the variations induced by unstable surfaces would fall far from the family of specific motor solutions and would not facilitate additional motor performance of the throwing task., Competing Interests: The authors declare there are no competing interests., (©2023 Moreno et al.)

The side bridge test (SBT) is one of the most popular tests to assess isometric trunk lateral flexor endurance. The aim of this study was to assess the validity and reliability of the SBT in healthy females. Twenty-four (24.58 ± 3.92 years) physically active (1-2 h of moderate physical activity, 2-3 times a week) females voluntarily participated in this study. The surface electromyography (EMG) of eight abdominal, back, shoulder and hip muscles was measured during the SBT. Normalized median frequency slopes (NMF slope ) were calculated to analyze the muscle fatigue. The EMG amplitudes were normalized to maximum EMG values to assess muscle activity intensity. A one-week test-retest design was performed to evaluate the SBT reliability through the ICC 3,1 and typical error. Higher NMF slopes and normalized EMG amplitudes were found in deltoids, abdominal obliques, rectus abdominis, and erector spinae in comparison to latissimus dorsi, gluteus medius, and rectus femoris. However, no significant differences were found between the trunk lateral flexors and the deltoids. Linear regression analysis showed that SBT performance could be significantly predicted by external oblique and deltoid NMF slope (adjusted R 2 = 0.673) and by body mass and trunk height (adjusted R 2 = 0.223). Consistency analysis showed a high intraclass correlation coefficient (0.81) and a relatively high typical error (10.95 s). Despite the good relative reliability of the SBT, its absolute reliability was low and its validity questionable, as the shoulder muscle activation and fatigue and the individuals' anthropometric characteristics played an important role in SBT performance.

Background: The aim of this study was to analyze the shoulder functional profile (rotation range of motion [ROM] and strength), upper and lower body performance, and throwing speed of U13 versus U15 male handball players, and to establish the relationship between these measures of physical fitness and throwing speed., Methods: One-hundred and nineteen young male handball players (under (U)-13 (U13) [n = 85]) and U15 [n = 34]) volunteered to participate in this study. The participating athletes had a mean background of sytematic handball training of 5.5 ± 2.8 years and they exercised on average 540 ± 10.1 min per week including sport-specific team handball training and strength and conditioning programs. Players were tested for passive shoulder range-of-motion (ROM) for both internal (IR) and external rotation (ER) and isometric strength (i.e., IR and ER) of the dominant/non-dominant shoulders, overhead medicine ball throw (OMB), hip isometric abductor (ABD) and adductor (ADD) strength, hip ROM, jumps (countermovement jump [CMJ] and triple leg-hop [3H] for distance), linear sprint test, modified 505 change-of-direction (COD) test and handball throwing speed (7 m [HT7] and 9 m [HT9])., Results: U15 players outperformed U13 in upper (i.e., HT7 and HT9 speed, OMB, absolute IR and ER strength of the dominant and non-dominant sides; Cohen's d: 0.76-2.13) and lower body (i.e., CMJ, 3H, 20-m sprint and COD, hip ABD and ADD; d: 0.70-2.33) performance measures. Regarding shoulder ROM outcomes, a lower IR ROM was found of the dominant side in the U15 group compared to the U13 and a higher ER ROM on both sides in U15 (d: 0.76-1.04). It seems that primarily anthropometric characteristics (i.e., body height, body mass) and upper body strength/power (OMB distance) are the most important factors that explain the throw speed variance in male handball players, particularly in U13., Conclusions: Findings from this study imply that regular performance monitoring is important for performance development and for minimizing injury risk of the shoulder in both age categories of young male handball players. Besides measures of physical fitness, anthropometric data should be recorded because handball throwing performance is related to these measures., (© 2022. The Author(s).)

Background: Ankle fractures are among the most common traumatic fractures and have a great socio-economic impact. Consequences of an ankle fracture requiring surgical treatment (e.g. pain, reduced ankle range of motion (ROM), muscle weakness, etc.) lead to balance deterioration, which has a profound impact on activities of daily living. However, to the best of the authors' knowledge, no reliable clinical tests are available to monitor balance in patients after ankle surgery., Objectives: To quantify single-leg dynamic balance in patients with bimalleolar ankle fracture through the Y-Balance test (YBT). The second objective was to analyze the impact of ankle dorsiflexion ROM and hip strength on balance to optimize balance rehabilitation programs., Design: Cross-sectional study., Methods: 22 participants, who had undergone surgery after bimalleolar ankle fractures, were assessed for ankle ROM, hip strength, and dynamic balance six-months after the surgical intervention. The within-session reliability of YBT was calculated through the intraclass correlation coefficient (ICC) and the standard error of measurement (SEM). Student's t-tests were used to assess leg differences. A multiple regression analysis was performed to evaluate the role of ankle dorsiflexion ROM and hip abductor and adductor strength in predicting balance performance., Results: YBT showed high-to-excellent within-session relative reliability (Healthy leg: 0.85 ≤ ICC≤0.96; Operated leg: 0.84 ≤ ICC≤0.96). SEM values were below 3.3 %. The operated leg showed significant lower YBT scores for anterior reach direction (-9.0 %; g=-0.70) and composite score (-4.5 %; g=-0.34). Multiple regression analysis showed that both, ankle dorsiflexion and hip abductor and adductor strength explained 66 % of the variance in the YBT anterior direction of the operated leg., Conclusions: The YBT is a reliable tool that allows the quantification of single-leg dynamic balance impairments from 6-months after surgery in patients with bimalleolar ankle fracture. Between-leg YBT differences in the anterior direction can be used as reference scores (3.3 %) for balance restoration. Balance rehabilitation programs should focus on improving ankle functionality and reducing hip muscle weakness with specific hip strength exercises and balance exercises with similar demands to the reaching tasks of the YBT to promote a faster recovery., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Background: Visually induced dizziness can develop as a sequala of a vestibular disorder and is characterized by symptoms of nausea, dizziness, and imbalance in rich visual environments such as supermarkets and shopping malls. To date the mechanisms underlying visually induced dizziness are poorly understood., Research Question: What are the characteristics of visual fixations and postural sway in adults with visually induced dizziness compared to healthy adults when exposed to increasingly complex visual environments?, Methods: We recruited 20 adults with visually induced dizziness and 20 healthy adults to this cross-sectional exploratory study. Participants were instructed to maintain gaze on letters projected on a large screen with backgrounds of differing visual complexity. The number of visual refixations, movement of the centre of pressure, and movement of the head and body centres of mass were recorded., Results: Adults with visually induced dizziness showed a significantly higher number of visual refixations (F= 10.592, p < 0.01), and increased mean velocity of head and body centres of mass movement (F= 14.034, p < 0.01 and F= 6.553, p < 0.05 respectively) compared to healthy adults., Significance: Adults with visually induced dizziness exhibited visual fixational instability and increased postural and head sway compared to healthy adults. This was mainly observed in conditions with complex and moving backgrounds. This may account for reports from adults with visually induced dizziness of worsening symptoms in busy environments. The results from the study may assist in guiding intervention development to reduce symptoms of visually induced dizziness., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: Balance impairment is a common feature in people with cerebral palsy (CP), affecting the performance of daily-life and physical activities., Objectives: To (1) explore the absolute and relative intrasession reliability of two balance tests to assess dynamic and static balance in ambulant para-athletes with CP; (2) explore the relationships between the two balance tests to determine potential application in sport classification; (3) assess the differences between CP profiles (ie, spastic diplegia, athetosis/ataxia, and spastic hemiplegia) in comparison to those with a minimum impairment; and (4) compare the outcomes of the static and dynamic balance of ambulant para-athletes with CP regarding controls., Methods: A group of 129 male well-trained para-footballers with CP, classified as Level I according to the Gross Motor Function Classification System, participated in the present study. Static balance was assessed using the One-Leg Stance test, performed bilaterally on a force platform, and the dynamic balance was assessed in two conditions of the Tandem Walk test (TW): walking heel-toe contact over a 5 -m straight line and performing 10 steps., Results: Moderate-to-excellent intrasession reliability (intraclass correlation coefficient = 0.60-0.98) was obtained for all the measurements and groups. However, only small to moderate correlations were found between the dynamic and the static measurements of balance for the CP group when performing the One-Leg Stance test with the unimpaired or dominant leg (0.23 < r < 0.30; P < .01). The TW performed over 10 steps revealed more sensitivity to discriminate between CP profiles. Those para-athletes with ataxia/athetosis performed worse in all the tests whereas all CP profiles performed worse than the control group (P < .01)., Conclusions: Balance performance and postural control are constrained to a higher extent in those with impaired voluntary control due to ataxia or with involuntary contractions of the muscles due to athetosis., (© 2021 The Authors. PM&R published by Wiley Periodicals LLC on behalf of American Academy of Physical Medicine and Rehabilitation.)

Advances in technology provide an opportunity to enhance the accuracy of gait and balance assessment, improving the diagnosis and rehabilitation processes for people with acute or chronic health conditions. This study investigated the validity and reliability of a smartphone-based application to measure postural stability and spatiotemporal aspects of gait during four static balance and two gait tasks. Thirty healthy participants (aged 20-69 years) performed the following tasks: (1) standing on a firm surface with eyes opened, (2) standing on a firm surface with eyes closed, (3) standing on a compliant surface with eyes open, (4) standing on a compliant surface with eyes closed, (5) walking in a straight line, and (6) walking in a straight line while turning their head from side to side. During these tasks, the app quantified the participants' postural stability and spatiotemporal gait parameters. The concurrent validity of the smartphone app with respect to a 3D motion capture system was evaluated using partial Pearson's correlations (r p ) and limits of the agreement (LoA%). The within-session test-retest reliability over three repeated measures was assessed with the intraclass correlation coefficient (ICC) and the standard error of measurement (SEM). One-way repeated measures analyses of variance (ANOVAs) were used to evaluate responsiveness to differences across tasks and repetitions. Periodicity index, step length, step time, and walking speed during the gait tasks and postural stability outcomes during the static tasks showed moderate-to-excellent validity (0.55 ≤ r p ≤ 0.98; 3% ≤ LoA% ≤ 12%) and reliability scores (0.52 ≤ ICC ≤ 0.92; 1% ≤ SEM% ≤ 6%) when the repetition effect was removed. Conversely, step variability and asymmetry parameters during both gait tasks generally showed poor validity and reliability except step length asymmetry, which showed moderate reliability (0.53 ≤ ICC ≤ 0.62) in both tasks when the repetition effect was removed. Postural stability and spatiotemporal gait parameters were found responsive ( p < 0.05) to differences across tasks and test repetitions. Along with sound clinical judgement, the app can potentially be used in clinical practice to detect gait and balance impairments and track the effectiveness of rehabilitation programs. Further evaluation and refinement of the app in people with significant gait and balance deficits is needed.

The lack of training load control, mainly exercise intensity, is one of the main limitations of core stability (CS) programs, which makes the training individualization and the analysis of the dose-response relationship difficult. The objectives of this study were to assess the inter-and intra-rater agreement when using new observational screening guidelines to decide if a core stability exercise represents an adequate training intensity level for a given participant. Besides, the relationship between experts' ratings based on these criteria and pelvic accelerations recorded with a smartphone accelerometer was also analyzed. Ten healthy physically active participants with a smartphone accelerometer placed on their pelvis were video-taped while performing a progression of seven variations of the front bridge, back bridge, side bridge and bird-dog exercises. Two expert and four non-expert raters watched the videos and used the observational screening guidelines to decide for each exercise variation if it represented an adequate training intensity level or not. In order to analyze the inter-and intra-rater agreement, several Kappa (κ) statistics were used. Receiver operating characteristic (ROC) curves to explore if the accelerometry allowed to establish pelvic acceleration thresholds representing the minimum level of exercise intensity for CS training. Cut-off acceleration values were calculated balancing sensitivity (Se) and 1-specifity (1-Sp) indexes (i.e., Youden index) or minimizing 1-Sp. The intra-and inter-rater analysis showed a substantial-high level of agreement with a prevalence-adjusted bias-adjusted Kappa > 0.69. The ROC curves showed that the acceleration thresholds for the bridging exercises were very similar, with global cut-off values of 0.35 m/s 2 (Se = 82%; 1-Sp = 15%) when using the Youden Index and of 0.50 m/s 2 when minimizing 1-Sp (Se = 31%), whilst the bird-dog exercise showed lower cut-off values (Youden Index: 0.21 m/s 2 , Se = 90%, 1-Sp = 16%; minimizing 1-Sp: 0.32 m/s 2 , Se = 40%). Overall, this study provides observational screening guidelines and smartphone accelerometer thresholds to facilitate the decision-making process when setting the intensity of some of the most popular core stability exercises in young physically active individuals., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Heredia-Elvar, Juan-Recio, Prat-Luri, Barbado and Vera-Garcia.)

Core stability (CS) deficits can have a significant impact on lower limb function. The aim of this study was to investigate the relationship between two dynamic core exercise assessments and dynamic knee valgus during single-leg squats. In total, 20 physically active female students participated in this study. The OCTOcore smartphone application assesses CS during two dynamic exercise tests, the partial range single-leg deadlift (SLD) test and the bird-dog (BD) test. A two-dimensional assessment of a single-leg squat test was used to quantify participants' hip frontal angle (HFA SLS ) and knee frontal plane projection angle (FPPA SLS ). Ankle dorsiflexion was evaluated through the weight-bearing dorsiflexion test. The correlational analyses indicated that the HFA SLS was significantly related to the partial range single-leg deadlift test ( r = 0.314, p < 0.05) and ankle dorsiflexion ( r = 0.322, p < 0.05). The results showed a significant difference ( p < 0.05) in the CS test between cases categorised as dynamic knee valgus (>10°) and normal (≤10°). The CS deficit may influence the neuromuscular control of the lumbopelvic-hip complex during single-leg movements. The link between CS and kinematic factors related to knee injuries was only observed when CS was measured in the SLD test but not in the BD test.