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Background: Balance while seated and the capacity to conduct selective trunk movements are significant predictors of functional outcomes following stroke. Patients with inappropriate muscle activation and inadequate movement control in the trunk muscles cause mobility and daily function difficulties. Stroke patients have weak leg muscles and decreased balance, resulting in compensatory changes. Functional postural strategy training is necessary to restore balance in these patients. Few studies have examined the effect of physical therapy trunk exercises with hip strategy training on improving balance and increasing independence after stroke., Purpose: This study aimed to explore the effect of selective trunk exercises (STE) with hip strategy training in improving balance in patients with stroke as well as independence levels., Method: A multicenter inpatient stroke treatment randomized pre- and post-test control trial. Forty-six stroke survivors were randomly allocated to experimental or control groups (n = 23 each). The experimental group received hip strategy training and trunk exercises. All groups received Neuro-Developmental Treatment (NDT)-based physical therapy four times a week for 6 weeks. Trunk impairment scale, Berg Balance Scale (BBS), and functional independence measure (FIM) measured static and dynamic seated balance, functional balance, and trunk movement coordination pre- and post-therapy., Results: The experimental group's post-therapeutic measures were substantially higher than the control group. The experimental group's TIS score, and subscale improved more than the control group. The experimental group considerably increased the BBS score. The experimental group also showed greater FIM gains., Conclusions: This study demonstrated that adding STE in conjunction with hip strategy training to patients after has a positive impact on trunk control while maintaining static and dynamic sitting balance, functional balance, and independence levels which are effective in stroke rehabilitation., (© 2024 John Wiley & Sons Ltd.)

Purpose: To determine whether the application of continuous lateral trunk support forces during walking would improve trunk postural control and improve gait performance in children with CP., Materials and Methods: Nineteen children with spastic CP participated in this study (8 boys; mean age 10.6 ± 3.4 years old). Fourteen of them were tested in the following sessions: 1) walking on a treadmill without force for 1-min (baseline), 2) with lateral trunk support force for 7-min (adaptation), and 3) without force for 1-min (post-adaptation). Overground walking pre/post treadmill walking. Five of them were tested using a similar protocol but without trunk support force (i.e., control)., Results: Participants from the experimental group showed enhancement in gait phase dependent muscle activation of rectus abdominis in late adaptation period compared to baseline (P = 0.005), which was retained during the post-adaptation period (P = 0.036), reduced variability of the peak trunk oblique angle during the late post-adaptation period (P = 0.023), and increased overground walking speed after treadmill walking (P = 0.032). Participants from the control group showed modest changes in kinematics and EMG during treadmill and overground walking performance. These results suggest that applying continuous lateral trunk support during walking is likely to induce learning of improved trunk postural control in children with CP, which may partially transfer to overground walking, although we do not have a firm conclusion due to the small sample size in the control group., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Maintaining dynamic balance during transitional movements like sit-to-walk (STW) can be challenging for older adults. Age-related neuromuscular decline can alter movement in STW, such as rising with greater trunk flexion, narrowing the feet, or using arms to push off. Initial foot and arm position can affect subsequent movement biomechanics, with different ground reaction forces (GRFs) that stabilize and advance the body center of mass (COM). The purpose of this study was to quantify whole-body biomechanics and trunk control of STW transitions. Fifteen younger adults (18-35 years) and fifteen older adults (50-79 years) performed STW from four initial foot positions and two arm positions. Three-dimensional (3D) GRFs, 3D body COM displacement, and integrated electromyography values from the lumbar paraspinals and gluteus medius were evaluated. Younger adults generated greater mediolateral GRF ranges while rising, whereas older adults generated greater mediolateral GRF ranges when stepping forward suggesting different strategies to laterally control the body COM. Initial foot position affected the STW movement, with narrow foot positions having smaller body COM displacement than wide foot positions, associated with smaller medial GRFs to move the body COM toward the stance limb. Rising with arm support required less lumbar paraspinal excitation, which was further reduced when with a posteriorly offset foot. Gluteus medius activity was greater for older adults compared to younger adults in STW. Completing STW with arm support can reduce the muscle activity required to stabilize the torso when rising, which likely has implications for balance control and low back loading., 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 © 2024 Elsevier Ltd. All rights reserved.)

Visual information affects static postural control, but how it affects dynamic postural control still needs to be fully understood. This study investigated the effect of proprioception weighting, influenced by the presence or absence of visual information, on dynamic posture control during voluntary trunk movements. We recorded trunk movement angle and angular velocity, center of pressure (COP), electromyographic, and electroencephalography signals from 35 healthy young adults performing a standing trunk flexion-extension task under two conditions (Vision and No-Vision). A random forest analysis identified the 10 most important variables for classifying the conditions, followed by a Wilcoxon signed-rank test. The results showed lower maximum forward COP displacement and trunk flexion angle, and faster maximum flexion angular velocity in the No-Vision condition. Additionally, the alpha/beta ratio of the POz during the switch phase was higher in the No-Vision condition. These findings suggest that visual deprivation affects cognitive- and sensory-integration-related brain regions during movement phases, indicating that sensory re-weighting due to visual deprivation impacts motor control. The effects of visual deprivation on motor control may be used for evaluation and therapeutic interventions in the future.

Background: Sitting ability is an important prognostic factor for patients with acute stroke. However, the characteristics of trunk muscle activity and weight-bearing during sitting are unclear., Research Question: Are trunk muscle activity and weight-bearing during static sitting associated with sitting ability in patients with acute stroke?, Methods: Trunk electromyography and sitting posturography were performed during static sitting in 20 patients with acute stroke. The electromyography measured the bilateral external oblique and erector spinae muscles. The symmetry of muscle activity between the paralyzed and non-paralyzed side was calculated using the Symmetry Index (SI) raw value and absolute value. The activity of each muscle during static sitting was calculated as the percent reference voluntary contraction (%RVC) normalized by the maximum contraction in the sitting position. Sitting posturography was used to calculate the weight-bearing pressure (%) on the paralyzed and non-paralyzed side, and the raw and absolute values of weight-bearing SI were calculated as a representative value. The trunk impairment scale (TIS) for sitting ability and the Berg balance scale (BBS) for basic balance ability were used as primary outcomes., Results: None of the SI of electromyography for each trunk muscle correlated significantly with clinical performance tests. The %RVC of paralyzed and non-paralyzed external oblique muscle negatively correlated with TIS. The absolute SI of weight-bearing was negatively correlated with BBS., Significance: This study showed that the amount, but not the symmetry, of external oblique muscle activity during sitting was associated with sitting ability. We also found that the symmetry of the weight-bearing was associated with sitting ability, not the direction, but the absolute amount of deviation. This suggests that it is important to focus on the amount of external oblique muscle activity and weight-bearing deviation during sitting as a measure of sitting ability in patients with acute stroke., Competing Interests: Declaration of Competing Interest We have no conflicts of interest to disclose., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Background: Many children with cerebral palsy (CP) show impairments in trunk posture control, one crucial factor contributing to impairments in gait and arm manipulation., Research Question: The goal of this study was to test the feasibility of the cable-driven hippotherapy system on improving trunk posture control and walking function in children with CP., Method: Ten children were recruited in this study with average age 6.4 ± 3.0 years old, and were randomly assigned to the robotic group and the conventional balance training group. A custom designed cable-driven robotic hippotherapy system was used to deliver controlled pelvis perturbations while children were sitting astride. Participants from both groups underwent intensive robotic hippotherapy training or conventional balance training, depending on their group assignment, for 6 weeks (3 time/week). Outcome measures were assessed pre and post 6 weeks of robotic or conventional balance training, and 8 weeks after the end of training (follow-up test). The primary outcome measure was trunk control, which was measured using the Trunk Control Measurement Scale (TCMS). In addition, the Gross Motor Function Measure (GMFM-66), self-selected overground walking speed, and 6-minute walking distance were also assessed., Results: The change in TCMS score from baseline to the post intervention was significantly greater for the robotic group than that for the conventional group (i.e., 6 ± 3 vs. -1 ± 5, p = 0.048, Mann-Whitney test). GMFM scores, self-selected overground walking speed, and 6-minute walking distance showed no significant improvement after robotic hippotherapy and after conventional balance training (p > 0.05)., Significance: Results from this study indicated that it was feasible to improve trunk posture control in children with CP using a cable-driven robotic hippotherapy system. Knowledge obtained from this study may provide an insight for the development of new perturbation-based intervention approaches for improving trunk posture control in children with CP., Competing Interests: Declaration of Competing Interest No potential conflict of interest was reported by the author(s)., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Background and Objectives: Compared to other subjects, obese people have inferior trunk muscle endurance and balance. A modern method of neuro-muscular training called whole body vibration (WBV) may improve trunk muscle endurance and balance. This study evaluates the impact of a 4-week WBV program on trunk endurance and balance in obese female students. Materials and Methods: Sixty participants from 18 to 25 years of age and with BMI values ≥ 30 were randomly distributed into two equal groups: Group A (WBV group), who received 4 min of WBV, and Group B (sham WBV group), who received WBV with a turn-off device. The training was conducted two days/week for six weeks. Trunk endurance was evaluated using the Sorensen Test (ST) and Trunk Flexor Endurance Test (TFET). The Single-Leg Test (SLT) was used to assess static balance, while the Biodex Stability System measured dynamic balance. Results : The current study demonstrated no significant differences ( p > 0.05) in pre-treatment variables between Groups A and B. Post-treatment, Group A showed a significantly higher duration of the Sorensen test, TFET and SLS than Group B ( p < 0.001). Moreover, Group A showed significantly lower dynamic balance ( p < 0.001) than Group B. Conclusions: WBV has a short-term effect on trunk endurance and balance in obese female students. WBV can be added to the rehabilitation program for obese subjects with deficits in trunk endurance and balance.

Older adults have a decreased trunk movement control which is linked to their higher fall risk. While motor/cognitive dual-tasking deteriorates balance and walking in older adults, there is limited understanding on how trunk kinematics and kinetics are affected by dual-tasking in scenarios where falls can occur. Therefore, the purpose of the study was to determine the impacts of a challenging motor dual-task, specifically obstacle avoidance during walking, on trunk and lower-body kinematics and kinetics of older adults compared to young adults. The study captured three-dimensional kinematic and kinetic data from 12 young adults and 10 older adults as they walked on a treadmill and stepped over an obstacle with both legs. The study analyzed trunk, hip, knee, and ankle angles and torques. Trunk torque was further broken down to trunk muscle torque, gravitational torque, and inertia torque. A linear mixed effects model was used to investigate the difference in each variable between the two groups. Older adults exhibited significantly increased trunk flexion angle and trunk extension muscle torque compared to young adults, with the trunk being the only segment/joint showing differences in both kinematics and kinetics. Trunk torque breakdown analysis revealed that larger trunk flexion led to a larger gravitational torque, which contributed to an increased compensatory trunk muscle torque. Moreover, older adults' less controlled trunk flexion during weight shifting from trail leg to the lead leg, necessitated a compensatory trunk deceleration during trail leg obstacle avoidance which was achieved by generating additional increase in trunk muscle torque. The study demonstrated that motor dual-tasking has the most negative effects on trunk control in older adults compared to young adults. This exposes older adults to a higher fall risk. Therefore, future work should focus on supporting trunk control during daily multi-tasking conditions where falls can occur., Competing Interests: Declaration of competing interest The authors declare that there were no financial or personal relationships that could have affected the quality or integrity the study presented in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Purpose: Many studies have investigated postural reactions (PR) to body-delivered perturbations. However, attention has been focused on the descriptive variables of the PR rather than on the characterization of the perturbation. This study aimed to test the hypothesis that the impulse rather than the force magnitude of the perturbation mostly affects the PR in terms of displacement of the center of foot pressure (ΔCoP)., Methods: Fourteen healthy young adults (7 males and 7 females) received 2 series of 20 perturbations, delivered to the back in the anterior direction, at mid-scapular level, while standing on a force platform. In one series, the perturbations had the same force magnitude (40 N) but different impulse (range: 2-10 Ns). In the other series, the perturbations had the same impulse (5 Ns) but different force magnitude (20-100 N). A simple model of postural control restricted to the sagittal plane was also developed., Results: The results showed that ΔCoP and impulse were highly correlated (on average: r = 0.96), while the correlation ΔCoP-force magnitude was poor (r = 0.48) and not statistically significant in most subjects. The normalized response, ΔCoP n  = ΔCoP/I, was independent of the perturbation magnitude in a wide range of force amplitude and impulse and exhibited good repeatability across different sets of stimuli (on average: ICC = 0.88). These results were confirmed by simulations., Conclusion: The present findings support the concept that the magnitude of the applied force alone is a poor descriptor of trunk-delivered perturbations and suggest that the impulse should be considered instead., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The acquisition of postural control is an elaborate process, which relies on the balanced integration of multisensory inputs. Current models suggest that young children rely on an 'en-block' control of their upper body before sequentially acquiring a segmental control around the age of 7, and that they resort to the former strategy under challenging conditions. While recent works suggest that a virtual sensory environment alters visuomotor integration in healthy adults, little is known about the effects on younger individuals. Here we show that this default coordination pattern is disrupted by an immersive virtual reality framework where a steering role is assigned to the trunk, which causes 6- to 8-year-olds to employ an ill-adapted segmental strategy. These results provide an alternate trajectory of motor development and emphasize the immaturity of postural control at these ages., (© 2021. The Author(s).)

Parkinson's disease (PD) is characterized by motor impairment, affecting quality of life and increasing fall risk, due to ineffective postural control. To this day, the diagnosis remains based on clinical approach. Similarly, motor evaluation is based on heterogeneous, operator-dependent observational criteria. A synthetic, replicable index to quantify motor impairment is still lacking. Hence, we have designed a new measure of postural stability which assesses the trunk displacement in relation to the center of mass, that we named trunk displacement index (TDI). Twenty-three PD patients and twenty-three healthy controls underwent motor examination through a stereophotogrammetric system. A correlation analysis was performed to assess the relationship of TDI with gait parameters and clinical motor scale (UPDRS-III). The TDI sensitivity was estimated, comparing pre- and post- L-DOPA subclinical dose intake. The TDI showed significant correlations with many gait parameters and with the UPDRS-III. Furthermore, the TDI resulted capable in discriminating between off and on state in PD, whereas gait parameters failed two show any difference between those two conditions. Our results suggest that the TDI may be considered a highly sensitive biomechanical index, reflecting the overall motor condition in PD, and provided of clinical relevance due to the correlation with the clinical evaluation.

Postural responses to similar perturbations of standing balance vary widely within and across subjects. Here, we identified two sources of variability and their interactions by combining experimental observations with computational modeling: differences in posture at perturbation onset across trials and differences in task-level goals across subjects. We first collected postural responses to unpredictable backward support-surface translations during standing in 10 young adults. We found that maximal trunk lean in postural responses to backward translations were highly variable both within subjects (mean of ranges = 28.3°) and across subjects (range of means = 39.9°). Initial center of mass (COM) position was correlated with maximal trunk lean during the response, but this relation was subject specific ( R 2 = 0.29-0.82). We then used predictive simulations to assess causal relations and interactions with task-level goal. Our simulations showed that initial posture explains the experimentally observed intrasubject variability with a more anterior initial COM position increasing the use of the hip strategy. Differences in task-level goal explain observed intersubject variability with prioritizing effort minimization leading to ankle strategies and prioritizing stability leading to hip strategies. Interactions between initial posture and task-level goal explain observed differences in intrasubject variability across subjects. Our findings suggest that variability in initial posture due to increased sway as observed in older adults might increase the occurrence of less stable postural responses to perturbations. Insight in factors causing movement variability will advance our ability to study the origin of differences between groups and conditions. NEW & NOTEWORTHY Responses to perturbations of standing balance vary both within and between individuals. By combining experimental observations with computational modeling, we identified causes of observed kinematic variability in healthy young adults. First, we found that trial-by-trial differences in posture at perturbation onset explain most of the kinematic variability observed within subjects. Second, we found that differences in prioritizing effort versus stability explained differences in the postural response as well as differences in trial-by-trial variability across subjects.

The purpose of this study was to determine whether the type and direction of postural perturbation threat differentially affect anticipatory postural control. Healthy young adults stood on a force plate fixed to a translating platform and completed a series of rise-to-toes movements without (No Threat) and with (Threat) the potential of receiving a postural perturbation to either their feet (15 participants) or torso (16 participants). Each type of perturbation threat was presented along the anteroposterior (A-P) or mediolateral (M-L) axis. For each condition, the A-P center of pressure (COP) signal and tibialis anterior (TA) and soleus (SOL) electromyographical (EMG) recordings were used to quantify the anticipatory postural adjustment (APA). Results indicated that across both threat types and directions, postural threat induced a 40.2% greater TA activation (p < 0.001), a 18.5% greater backward COP displacement (p < 0.001) and a 23.9% greater backward COP velocity (p < 0.001), leading to larger and faster APAs than the No Threat condition. Subsequently, a 7.7% larger forward COP displacement (p = 0.001), a 20.4% greater forward COP velocity (p < 0.001) and 43.2% greater SOL activation (p = 0.009) were observed during the execution phase of the rise-to-toes for the Threat compared to the No Threat condition. Despite these threat effects, there were no differences in the magnitude or velocity of APAs between the threat directsion conditions. Since the type and direction of perturbation-induced postural threat had minimal differential effects on anticipatory postural control, these factors are unlikely to explain the discrepancy of previous findings., (Copyright © 2020 Elsevier B.V. All rights reserved.)

We investigated changes in the anticipatory activity of the leg and trunk muscles in preparation for a step during support surface perturbation. Eight healthy subjects performed stepping tasks under three conditions: normal, forward perturbation, and backward perturbation. R and C indices were calculated for the reciprocal and co-activation patterns of muscle pairs within the time intervals typical of anticipatory postural adjustments. When the support surface perturbation occurred, anticipatory muscle activations were predominantly in the C indices in the leg muscles. Significant differences in the maximum displacement of the centre of pressure were seen between conditions (FS vs NS; BS vs FS). The results suggest that activation of the leg muscles rather than the trunk muscles was modified to ensure equilibrium for taking a step in response to support surface perturbation.

Background: For individuals who never achieve independent standing, rehabilitation is focused on trunk posture and balance control. Visual biofeedback has the potential to augment sitting balance training, however previous work in this area has been limited to standing., Research Question: To what extent do different types of visual biofeedback influence trunk sway in sitting?, Methods: Twelve healthy young adults sat on an articulating bench. During 'sway referencing' trials, the bench tilted up and down in proportion to trunk sway in the frontal plane. This paradigm increased difficulty of the balance task and required participants to rely on visual and vestibular cues. Participants were provided different visual biofeedback through a rotating needle-gage display. Trials lasted 165 s, were ordered randomly, and included either direct feedback (needle rotated in proportion to body sway), inverted feedback (needle rotated in the opposite direction of sway), time delayed feedback (0.5 s), random feedback, eyes closed, or control (eyes open with screen off). To explore the impact of inherent stability, trials were repeated with and without external trunk support., Results: Body sway depended on feedback type. Specifically, direct and inverted feedback reduced root-mean-squared (RMS) sway the most, time delayed feedback had a smaller effect, and random visual feedback increased participants' RMS sway compared to control. Frequency domain analyses demonstrated direct and inverted visual feedback reduced sway amplitude at the lower frequencies while having minimal effect on (or increasing) sway amplitude at higher frequencies., Significance: This study extends previous work by showing that visual biofeedback can have powerful effects on sitting balance, even with external support. Results from the different types of feedback conditions further our understanding of how the brain interprets visual biofeedback. Frequency-based results were similar to previous studies using different modalities and suggest participants interpret biofeedback through sensory addition as opposed to sensory substitution., Competing Interests: Declaration of Competing Interest There are no conflicts of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Recent work suggests that kinematics-based electrical stimulation may restore dynamic trunk stability following spinal cord injury. However, to ensure fatigue-resistant control, knowledge of the relation between body motion and the activity of relevant muscles during non-impaired, unstable sitting may be beneficial. Therefore, our objective was to quantify the spatial and temporal relationships between (1) characteristic angular kinematics (i.e., the kinematics characterizing trunk stabilization) and (2) trunk and upper leg muscle activity in unstable sitting as elicited via a wobble board. Wobble board motion and bilateral electromyograms from fourteen trunk and upper leg muscles were recorded in fifteen non-disabled participants (i.e., individuals with no history of neurological or musculoskeletal impairments or pain, gait or balance difficulties, or use of a walking aid) sitting on a wobble board. The relationship between wobble board tilt and the electromyograms was quantified using cross-correlation analysis. During unstable sitting, the trunk was stabilized through direction-specific activation of the trunk and upper leg muscles, preceding wobble board displacement by 110-230 ms. Direction-specific activation implies the presence of active neural control, while preceding activation may be needed to account for known torque generation time delays. Furthermore, the specific muscles activated for each direction of wobble board displacement suggest the use of stiffness control in the anterior-posterior, but not medial-lateral direction. Future work will use the gained insights in defining the muscle stimulation patterns of kinematics-based neuroprostheses that can restore trunk stability following impairment., 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 © 2020 Elsevier Ltd. All rights reserved.)

Faster trunk motions could be a strategy to prevent loss of balance and fall injuries due to unexpected perturbations. However, it is unclear how trunk sway velocities can be compensated during stepping in subjects with low back pain (LBP). The purpose of this study was to investigate lower limb reaction, swing, and step times, as well as trunk sway velocities at heel strike and toe-off, following repeated step perturbations between subjects with and without LBP. There were 30 subjects with LBP and 42 control subjects who were exposed to treadmill-induced perturbations at a velocity of 0.12 m/sec for 0.62 m. The treadmill-induced steps caused subjects to walk forward for 4.90 sec after the perturbation. The groups demonstrated significant interactions on the lower limb reaction times and on the number of repeated perturbations (F = 4.83, p = 0.03) due to a decreased step time at the first perturbation (t = 2.52, p = 0.01) in the LBP group. For the trunk sway velocities, the repeated perturbations demonstrated a significant interaction between groups (F = 4.65, p = 0.03). This adaptive trunk strategy for gait stability increased step times with repeated perturbations in the LBP group. The group interactions on the trunk sway velocities also indicated a possible somatosensory integration for step time adjustments to avoid potential fall hazards. This adaptive response with repeated step perturbations could result in compensatory trunk sway for gait stability., Competing Interests: Declaration of Competing Interest None of the authors has any financial or personal conflicts of interest in relation to the submission, other people, or any organizations., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Objective: Evaluate multisegmental postural sway after upper- vs lower-extremity manipulation., Methods: Participants were healthy volunteers (aged 21-40 years). Upper- or lower-extremity manipulations were delivered in a randomized crossover design. Postural assessments were made pre-post manipulation, in floor and rocker board conditions. Analysis included traditional balance measures of pathlength and range and sample entropy (SampEn) to examine the temporal structure of sway of the head, trunk, and surface., Results: No statistical changes in pathlength or sway range on the ground surface condition were observed. No increases in the amount of sway occurred in any condition. Chiropractic manipulation of either upper or lower extremities led to reductions in traditional measures of postural control on the rocker board. In the anteroposterior direction (sagittal plane), lower-extremity manipulation led to increased trunk SampEn while on the ground, and conversely a decreased SampEn while on the rocker board. In the mediolateral rocker board condition (frontal plane), manipulation elicited a change in SampEn that differed according to site of manipulation; upper-extremity manipulation increased SampEn, whereas lower-extremity manipulation reduced SampEn., Conclusion: Both upper- and lower-extremity manipulation influenced several measures of postural sway on both the ground and the rocker board. Lower-extremity manipulation improved the organization of sway at the trunk (anteroposterior direction) and the board (mediolateral direction). Given the reduction and reorganization of sway metrics seen in this study, we propose extending this line of research to the elderly who are at greatest risk of increased sway and falls., (Copyright © 2020. Published by Elsevier Inc.)

Background: Gait perturbations, occurring in any direction in daily life, may result in a fall. In fall prevention, gait perturbation training is a promising approach. Treadmill perturbations in anterior-posterior direction can easily be applied by accelerations or decelerations of the belt, but it is unknown whether training effects transfer to reactive recovery in medio-lateral direction. We aimed to evaluate the transfer and retention effects of gait training with treadmill perturbations in anterior-posterior direction to medio-lateral reactive recovery., Methods: 30 community dwelling older adults (>65 years) participated in this study. They were randomly assigned to a treadmill training session either with 16 anterior-posterior perturbations or with treadmill walking. The assessments contained a walking trial with 4 anterior-posterior and 4 medio-lateral perturbations. Deviations in trunk velocity from unperturbed walking were summed over the first three strides after perturbation as a measure of recovery., Findings: An exposure to gait perturbations during the baseline assessment led to significant improvement of recovery responses. For anterior-posterior perturbations, both groups showed better recovery immediately and 1-week post-intervention, and no group x time interaction was found.. For medio-lateral perturbations, both groups showed better recovery immediately and 1-week post-intervention, and again no group × time interaction., Interpretation: Baseline assessment with perturbations in anterior-posterior and medio-lateral directions caused significant improvements that were retained. Short-term training can be effective in dynamic stabilization of one's trunk, but our findings do not exclude that multi-directional perturbations may be needed., Competing Interests: Declaration of competing interest The first author is an early stage researcher, employed by Motek Medical BV. The position is funded the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 72157. Further, two authors are employed by Motek Medical BV and a device of this company was used for this experiment. Analysis of data was done by the first author, employed by Motek Medical BV, in collaboration with Vrije Universiteit Amsterdam., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Purpose : No previous study examined trunk control development in preterm infants. The present study examined the longitudinal development of segmental trunk control from 4 to 12 months of (corrected) age in preterm infants in comparison with full-term infants. Methods : Thirty-one preterm infants and 30 full-term infants were recruited. All infants were tested monthly using the Segmental Assessment of Trunk Control and the Alberta Infant Motor Scale at 4, 8 and 12 months of age. Results : Segmental trunk control development was significantly delayed in the preterm infants. Statistically significant positive correlations were found between trunk control status and gross motor skills. Conclusion : This was first study showing that segmental trunk control development was significantly different in preterm infants. Segmental trunk control and gross motor performance were coupled in young infants. A dual focus on training upright trunk control and specific motor skills may maximise therapy outcomes for infants with motor delay.

This study investigated effects of cognitive dual-task interference and task prioritization instructions on task performance and trunk control during a dynamic balance task in persons with and without recurrent low back pain (rLBP). First, we tested the hypothesis that those with rLBP rely more on cognitive resources than back-healthy controls, and therefore trunk kinematics would be altered under dual-task interference conditions. Then, we tested participants' ability to modulate task performance in accord with prioritization instructions. Persons with and without rLBP (n = 19/group) performed the Balance-Dexterity Task, which involved single-limb balance while compressing an unstable spring with the other limb, with and without a cognitive task engaging verbal working memory. Trunk coupling was quantified with the coefficient of determination (R 2 ) of an angle-angle plot of thorax-pelvis frontal plane motion. Task performance was quantified using variability of spring compression force and of cognitive task errors. Trunk coupling in the rLBP group was lower than that of the back-healthy control group in the single-task condition (p = 0.024) and increased in the dual-task condition (p = 0.006), abolishing the difference between groups. Significant main effects of task prioritization instruction on performance were observed with no differences between groups, indicating similar performance modulation. Cognitive task error variability decreased with a switch from a single- to dual-task condition, exposing an unexpected facilitation effect. We interpret these findings in the context of movement-specific reinvestment and action-specific perception theories as they pertain to cognitive contributions to posture and how the dual-task interference paradigm may influence those contributions.

Prevalence of gait impairments increases with age and is associated with mobility decline, fall risk and loss of independence. For geriatric patients, the risk of having gait disorders is even higher. Consequently, gait assessment in the clinics has become increasingly important. The purpose of the present study was to classify healthy young-middle aged, older adults and geriatric patients based on dynamic gait outcomes. Classification performance of three supervised machine learning methods was compared. From trunk 3D-accelerations of 239 subjects obtained during walking, 23 dynamic gait outcomes were calculated. Kernel Principal Component Analysis (KPCA) was applied for dimensionality reduction of the data for Support Vector Machine (SVM) classification. Random Forest (RF) and Artificial Neural Network (ANN) were applied to the 23 gait outcomes without prior data reduction. Classification accuracy of SVM was 89%, RF accuracy was 73%, and ANN accuracy was 90%. Gait outcomes that significantly contributed to classification included: Root Mean Square (Anterior-Posterior, Vertical), Cross Entropy (Medio-Lateral, Vertical), Lyapunov Exponent (Vertical), step regularity (Vertical) and gait speed. ANN is preferable due to the automated data reduction and significant gait outcome identification. For clinicians, these gait outcomes could be used for diagnosing subjects with mobility disabilities, fall risk and to monitor interventions.

Purpose: The intensity progression of core stabilization exercises (CSEs) is usually based on personal criteria rather than on objective parameters. To develop exercise progressions for four of the most common CSEs based on the postural control challenge imposed on the participants, and to analyze the effect of participants' sex and postural control level on these progressions., Methods: Seventy-six males and females performed five variations of front bridge, back bridge, side bridge and bird-dog exercises on two force platforms. The mean velocity of the center of pressure displacement was calculated to assess exercise intensity through the measurement of the participants' body sway (PBS)., Results: In general, long bridges produced higher PBS than short bridges, bridging with single leg support produced higher PBS than bridging with double leg support and bridging on a hemisphere ball produced higher PBS than bridging on the floor. The most difficult bridging variations were those performed on a hemisphere ball with single leg support. Regarding the bird-dog, two-point positions produced higher PBS than three-point positions and the positions performed on a hemisphere ball produced higher PBS than those performed on the floor., Conclusion: The CSE progressions obtained by males and females were very similar. However, the participants with high trunk control showed less significant differences between exercise variations than the participants with low trunk control, which shows the need to individualize the progressions according to the participants' training level. Overall, this study provides useful information to guide the prescription of CSE progressions in young physically active individuals.

Background: Appropriately responding to unexpected perturbations, such as a trip, is critical to sustain balance and avoid falling during walking., Research Question: How do arm motion and walking asymmetry affect postural stability when recovering from a trip perturbation?, Methods: Fifteen healthy young individuals, who had no experience with treadmill induced perturbations, participated in this study. The Computer-Assisted Rehabilitation Environment system (CAREN-Extended) was used to simulate unexpected perturbations while walking symmetrically and asymmetrically with various arm swings (normal, bound, released). Whole-body angular momentum (WBAM), peak trunk angular velocities, Center of Mass (COM), step width and stance time were analyzed before and when recovering from trip perturbations., Results: Participants were able to recover their postural stability within three strides following the sudden anterior-posterior trip perturbation. The perturbation increased peak trunk angular velocity, the COM excursion and WBAM but did not affect stance time and step width. The arm conditions had significant effects on peak trunk angular velocity, WBAM and step width during pre-perturbation. Walking conditions had a significant effect on all variables during pre-perturbation; however, post-perturbation showed significant effects only for peak trunk angular velocity, WBAM, and COM., Significance: Unexpected perturbation had effects on most of gait variables; nevertheless, participants fully recovered and adapted their gait pattern to sudden perturbations even without using their arms while walking symmetrically and asymmetrically. Arm movements could help young individuals recover after a perturbation but are not essential for perturbations of moderate magnitude. The effect of medial-lateral perturbations on gait still need to be investigated., Competing Interests: Declaration of Competing Interest The authors declare no conflicts of interest. This funding source had no involvement in: study design; data collection, analysis and interpretation of data; the writing of the report; or in the decision to submit the article for publication., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Key Points: Vestibulospinal reflexes participate in postural control. How this is achieved has not been investigated fully. We combined electrophysiological, neuroanatomical and imaging techniques to decipher the vestibulospinal network controlling the activation of back and limb muscles responsible for postural adjustments. We describe two distinct pathways activating either thoracic postural motoneurons alone or thoracic and lumbar motoneurons together, with the latter co-ordinating specifically hindlimb extensors and postural back muscles., Abstract: In vertebrates, trunk postural stabilization is known to rely mainly on direct vestibulospinal inputs on spinal axial motoneurons. However, a substantial role of central spinal commands ascending from lumbar segments is not excluded during active locomotion. In the adult Xenopus, a lumbar drive dramatically overwhelms the descending inputs onto thoracic postural motoneurons during swimming. Given that vestibulospinal fibres also project onto the lumbar segments that shelter the locomotor generators, we investigated whether such a lumbo-thoracic pathway may relay vestibular information and consequently, also be involved in the control of posture at rest. We show that thoracic postural motoneurons exhibit particular dendritic spatial organization allowing them to gather information from both sides of the cord. In response to passive head motion, these motoneurons display both early and delayed discharges, with the latter occurring in phase with ipsilateral hindlimb extensor bursts. We demonstrate that both vestibulospinal and lumbar ascending fibres converge onto postural motoneurons, and that thoracic motoneurons monosynaptically respond to the electrical stimulation of either pathway. Finally, we show that vestibulospinal fibres project to and activate lumbar interneurons with thoracic projections. Taken together, our results complete the scheme of the vestibulospinal control of posture by illustrating the existence of a novel, indirect pathway, which implicates lumbar interneurons relaying vestibular inputs to thoracic motoneurons, and participating in global body postural stabilization in the absence of active locomotion., (© 2019 The Authors. The Journal of Physiology © 2019 The Physiological Society.)

Objectives: People with cerebellar ataxia have few options to improve the standing stability they need for function. Strategic placement of light weights on the torso using the balance-based torso-weighting (BBTW) method has improved stability and reduced falls in people with multiple sclerosis, but has not been tested in cerebellar ataxia. We examined whether torso-weighting increased standing stability and/or functional movement in people with cerebellar ataxia., Methods: Ten people with cerebellar ataxia and 10 matched controls participated in this single-session quasi-experimental pilot study. People with ataxia performed the Scale for the Assessment and Rating of Ataxia (SARA) prior to clinical testing. All participants donned inertial sensors that recorded postural sway; stopwatches recorded duration for standing and mobility tasks. All participants stood for up to 30 s on firm and foam surfaces with eyes open then eyes closed, and performed the Timed Up and Go (TUG) test. Light weights (0.57-1.25 kg) were strategically applied to a vest-like garment. Paired t tests compared within-group differences with and without BBTW weights. Independent t tests assessed differences from controls. All t tests were one-tailed with alpha set at .05., Results: Duration of standing for people with ataxia was significantly longer with weighting (p = .004); all controls stood for the maximum time of 120 s with and without weights. More severe ataxia according to SARA was moderately correlated with greater improvement in standing duration with BBTW (Pearson r = .54). Tasks with more sensory challenges (eyes closed, standing on firm surface) showed less body sway with weighting. Duration for the TUG was unchanged by torso-weighting in people with ataxia., Conclusion: Strategic weighting improved standing stability but not movement speed in people with ataxia. BBTW has potential for improving stability and response to challenging sensory conditions in this population. Future studies should further examine gait stability measures along with movement speed., (© 2019 The Authors. Physiotherapy Research International published by John Wiley & Sons Ltd.)

Patients who require neurological rehabilitation often do not comply with conventional programs because they find the therapy uninteresting. As a result, specialized interactive video games have been designed to be more enjoyable than conventional therapy (CT) tasks. This study aimed to assess the trunk control and gait ability of patients with chronic stroke after participation in driving-based interactive video games (DBIVG). Participants included 24 chronic stroke patients allocated to an experimental group ( n  = 13, CT + DBIVG) or a control group ( n  = 11, CT + treadmill walking training). Both groups received CT five days/week; the experimental and control groups participated in DBIVG and treadmill walking training, respectively, three days/week for four weeks. The primary outcome of trunk control was measured by the trunk impairment scale (TISall) and TIS subscales, including static sitting balance (TISssb), dynamic sitting balance (TISdsb), and trunk co-ordination (TISco). Gait ability was measured by the dynamic gait index (DGI), timed walking test (TWT), and time up and go test (TUGT). Both groups demonstrated significant improvements in TISall, TISdsb, and TUGT results. The experimental group showed significantly greater improvement in TISssb, TISco, and DGI than the control group. Our findings indicate that DBIVG can improve trunk control and gait ability in patients with chronic stroke.

Prior work demonstrates that humans spontaneously synchronize their head and trunk kinematics to a broad range of driving frequencies of perceived mediolateral motion prescribed using optical flow. Using a closed-loop visuomotor error augmentation task in an immersive virtual environment, we sought to understand whether unifying visual with vestibular and somatosensory feedback is a control goal during human walking, at least in the context of head and trunk stabilization. We hypothesized that humans would minimize visual errors during walking - i.e., those between the visual perception of movement and actual movement of the trunk. We found that subjects did not minimize errors between the visual perception of movement and actual movement of the head and trunk. Rather, subjects increased mediolateral trunk range of motion in response to error-augmented optical flow with positive feedback gains. Our results are more consistent with our alternative hypothesis - that visual feedback can override other sensory modalities and independently compel adjustments in head and trunk position. Also, aftereffects following exposure to error-augmented optical flow included longer, narrower steps and reduced mediolateral postural sway, particularly in response to larger amplitude positive feedback gains. Our results allude to a recalibration of head and trunk stabilization toward more tightly regulated postural control following exposure to error-augmented visual feedback. Lasting reductions in mediolateral postural sway may have implications for using error-augmented optical flow to enhance the integrity of walking balance control through training, for example in older adults., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Background: Motor control dysfunction persisting during symptom remission in persons with recurrent low back pain (LBP) may contribute to the recurrence of pain., Objectives: To investigate trunk control in persons in remission from recurrent LBP and in back-healthy controls using a dynamic, internally driven balance task. No differences in task performance were expected between groups, but it was hypothesized that persons with recurrent LBP would exhibit greater trunk coupling, consistent with a trunk-stiffening strategy., Methods: In this cross-sectional controlled laboratory study, persons with and without recurrent LBP (n = 19 per group) completed the balance-dexterity task, which involved balancing on one limb in standing while compressing an unstable spring with the other. Task performance measures included center-of-pressure velocity under the stance limb and vertical force variability under the spring. Trunk coupling was quantified with the coefficient of determination ( R 2 ) of an angle-angle plot of thorax-pelvis frontal plane motion. Fine-wire and surface electromyography captured activations of paraspinals and abdominals., Results: There were no differences between groups for any task performance measure. The group in remission from recurrent LBP exhibited reduced trunk coupling, or more dissociated thorax and pelvis motion, compared to the healthy control group ( P = .024). Trunk coupling in this group was associated moderately with the lumbar multifidus-to-erector spinae activation ratio ( r = 0.618, P = .006) and weakly with the internal oblique-to-external oblique ratio ( r = 0.476, P = .046)., Conclusion: The balance-dexterity task is a submaximal, internally driven unstable balance task during which more dissociated trunk motion was observed in persons in remission from recurrent LBP. Findings underscore the task-dependent nature of trunk control research and assessment in persons with recurrent LBP. J Orthop Sports Phys Ther 2019;49(12):887-898. Epub 15 May 2019. doi:10.2519/jospt.2019.8756 .

Background: Trunk control is generally considered to be related to gross motor development. However, this assumption has not been validated with clinical data. This pilot study was the first of its kind to examine the longitudinal development of segmental trunk control and gross motor development from 4 to 12 months of age in typically developing full-term infants., Methods: A convenience cohort of 20 healthy full-term infants (mean gestation = 39.0 weeks, SD 1.2; mean birthweight = 2975.0 g, SD 297.0; males = 10) was recruited. All study infants were tested and scored monthly by independent assessors using the Segmental Assessment of Trunk Control and the Alberta Infant Motor Scale from 4 to 12 months of age., Results: A developmental trend of segmental trunk control was found in the infants. Static vertical upright trunk control developed prior to active and reactive control. Statistically significant correlations were found between trunk control status and gross motor development mainly in prone and sitting positions from 8 months of age onwards (all p < 0.004, Spearman's r ranged from 0.644 to 0.798)., Conclusions: This pilot study provides preliminary clinical evidence to support the inter-dependency between vertical upright trunk control and gross motor development in young infants, particularly as upright functional skills are gained. This suggests that a dual focus on training upright trunk control alongside gross motor skills could be of benefit in the treatment of infants with movement disorders.

Light Touch (LT) has been shown to reduce postural sway in a wide range of populations. While LT is believed to provide additional sensory information for balance modulation, the nature of this information and its specific effect on balance are yet unclear. In order to better understand LT and to potentially harness its advantages for a practical balance aid, we investigated the effect of LT as provided by a haptic robot. Postural sway during standing balance was reduced when the LT force (~ 1 N) applied to the high back area was dependent on the trunk velocity. Additional information on trunk position, provided through orthogonal vibrations, further reduced the sway position-metric of balance but did not further improve the velocity-metric of balance. Our results suggest that limited and noisy information on trunk velocity encoded in LT is sufficient to influence standing balance., Competing Interests: The authors have declared that no competing interests exist.

Fatigue arises during everyday activities, diminishes movement performance, and increases injury risk. Physical (PE) and cognitive exertion (CE) can induce similar feelings of fatigue, but it is not clear whether these also similarly affect movement performance. Therefore, this study examined the influence of PE and CE on anticipatory postural adjustments (APAs) of trunk muscles, which are feedforward mechanisms that contribute to motor control and controlled movement. Rapid arm movement tasks (RAM) were used to induce APAs of the trunk muscles prior and following three experimental conditions in 20 healthy adults: seated rest without exertion (NE), a combined isometric modified Biering-Sörensen and static abdominal curl to induce PE, and a modified incongruent Stroop colour-word task to induce CE. Fatigue was assessed using self-reported measures, and APA onset latencies of the trunk muscles with surface electromyography. Statistical analyses revealed that neither PE nor CE influence APAs of the trunk. Therefore, it is hypothesized that the influence of fatigue on movement performance might not be through altered motor control, but rather by reduced motivation. However, the possibility that fatigue might influence other mechanisms which contribute to trunk motor control, such as APA amplitude and variability, cannot be excluded and need further examination.

Context: Balance is important for injury prediction, prevention, and rehabilitation. Clinical measurement of higher level balance function such as hop landing is necessary. Currently, no method exists to quantify balance performance following hopping in the clinic., Objective: To quantify the sacral acceleration profile and test-retest reliability during hop landing., Participants: A total of 17 university undergraduates (age 27.6 [5.7] y, height 1.73 [0.11] m, weight 74.1 [13.9] kg)., Main Outcome Measure: A trunk-mounted accelerometer captured the acceleration profile following landing from hopping forward, medially, and laterally. The path length of the acceleration traces were computed to quantify balance following landing., Results: Moderate to excellent reliability (intraclass correlation coefficient .67-.93) for hop landing was established with low to moderate SEM (4%-16%) and minimal detectable change values (13%-44%) for each of the hop directions. Significant differences were determined in balance following hop landing from the different directions., Conclusion: The results suggest that hop landing balance can be quantified by trunk-mounted accelerometry.

Trunk control has been commonly studied via an unstable sitting paradigm, with the majority of analyses using angular kinematics-based, posturographic measures. However, considerable variability in the choice of kinematics exists. Furthermore, the kinematics capturing the completion of this task are unknown. The purpose of this study was to characterize the kinematics in unstable sitting by quantifying and comparing the angular motion of the base of support, pelvis, and trunk as elicited via a commonly used wobble board (WB) paradigm. WB, pelvis, and trunk motion was recorded in fifteen non-disabled participants sitting on a wobble board. Posturographic measures were calculated and compared between corresponding WB and pelvis, and between WB and trunk angles. The trunk was stabilized through relatively large WB motion, with the trunk adopting a quasi-static pose. For all measures, angles, and conditions, the WB measure values were significantly larger than their corresponding pelvis or trunk values. Our findings demonstrate that the WB-human system is stabilized by regulating WB motion. Future work utilizing an unstable sitting surface and kinematics-based analyses to investigate trunk control should include the analysis of base of support kinematics., (Copyright © 2019 IPEM. Published by Elsevier Ltd. All rights reserved.)

Background: Persons with unilateral lower-limb loss are at increased risk for developing chronic low back pain. Aberrant trunk and pelvis motor behavior secondary to lower-limb loss potentially alters trunk postural control and increases demands on the trunk musculature for stability. However, it is unclear whether trunk postural control is associated with the presence or chronicity of low back pain within this population., Research Question: Is there a potential role of impaired trunk postural control among persons with lower limb loss and chronic low back pain?, Methods: Two groups of males with unilateral lower-limb loss (n = 18 with chronic low back pain; n = 13 without pain) performed an unstable sitting task. Trunk postural control was characterized using traditional and non-linear measures derived from center-of-pressure time series, as well as trunk kinematics and the ratio of lumbar to thoracic erector spinae muscle activations., Results: Traditional and non-linear center-of-pressure measures and trunk muscle activation ratios were similar between groups, while participants with chronic low back pain demonstrated greater trunk motion and reduced local dynamic stability., Significance: Our results suggest that persons with both lower-limb loss and chronic low back pain exhibit impaired trunk postural control compared to those with limb loss but without pain. Aberrant trunk motor behavior may be a response to altered functional requirements of walking with a prosthesis. An inability to adequately control the trunk could lead to spinal instability and pain in the presence of repetitive exposure to aberrant motor behavior of these proximal structures during everyday activities., (Published by Elsevier B.V.)

Objectives: The aim of the study was to investigate (a) postural control, especially trunk and head control, in patients with unilateral vestibular hypofunction and healthy controls during walking on firm and foam surface and (b) the difference between the impact of left and right unilateral vestibular hypofunction, and correlation between trunk/head control and vestibular function in the patients., Design: Thirteen patients and 13 healthy controls were recruited. Vestibular function was examined based on the canal paresis value. Participants walked on a treadmill on firm and foam surface. Peak-to-peak trunk (Troll and Tpitch) and head roll and pitch angle (Hroll and Hpitch) were calculated as primary outcome measures., Results: In the unilateral vestibular hypofunction group but not healthy controls, Troll was significantly higher on foam than firm surface (P = 0.03). Tpitch was significantly higher on foam than firm surface in both groups (P = 0.02). Patients had significantly lower Hroll (P = 0.03) and Hpitch (P = 0.02) and lower head-trunk correlation in both medio-lateral (P = 0.05) and anteroposterior direction (P = 0.03) than those in the healthy control group., Conclusions: Patients with unilateral vestibular hypofunction seemed to rely more on lower limb somatosensory input for trunk control especially in the medio-lateral direction compared with healthy controls. Lower head sway and head-trunk correlation may suggest a more independent and successful head control strategy in patients.

This study evaluated the reactive biomechanical strategies associated with both upper- and lower-body (lead and trail limbs) following the first exposures to (un)expected stepdown at comfortable (1.22 ± 0.08 m/s) and fast (1.71 ± 0.11 m/s) walking velocities. Eleven healthy adults completed 34 trails per walking velocity over an 8-m, custom-built track with two forceplates embedded in its center. For the expected stepdown, the track was lowered by 0-, -10- and -20-cm from the site of the second forceplate, whereas the unexpected stepdown was created by camouflaging the second forceplate (-10-cm). Two-way repeated-measurement ANOVAs detected no velocity-related effects of stepdown on kinematic and kinetic parameters during lead limb stance-phase, and on the trail limb stepping kinematics. However, analyses of significant interactions revealed greater peak flexion angles across the trunk and the trail limb joints (hip, knee and ankle) in unexpected versus expected stepdown conditions at a faster walking velocity. The -10-cm unexpected stepdown (main effect) had a greater influence on locomotor behavior compared to expected conditions due mainly to the absence of predictive adjustments, reflected by a significant decrease in peak knee flexion, contact time and vertical impulse during stance-phase. Walking faster (main effect) was associated with an increase in hip peak flexion and net anteroposterior impulse, and a decrease in contact time and vertical impulse during stepdown. The trail limb, in response, swung forward faster, generating a larger and faster recovery step. However, such reactive stepping following unexpected stepdown was yet a sparse compensation for an unstable body configuration, assessed by significantly smaller step width and anteroposterior margin-of-stability at foot-contact in the first-recovery-step compared with expected conditions. These findings depict the impact of the expectedness of stepdown onset on modulation of global dynamic postural control for a successful accommodation of (un)expected surface elevation changes in young, healthy adults., (Crown Copyright © 2019. Published by Elsevier Ltd. All rights reserved.)

Background: Age-related changes, which include increased trunk and hip stiffness, negatively influence postural balance. While previous studies suggest no net-effect of trunk and hip stiffness on initial trip-recovery responses, no study to date has examined potential effects during the dynamic restabilisation phase following foot contact., Research Question: Does increased trunk and hip stiffness, in isolation from other ageing effects, negatively influence balance during the restabilisation phase of reactive stepping., Methods: Balance perturbations were applied using a tether-release paradigm, which required participants to react with a single-forward step. Sixteen young adults completed two blocks of testing: a baseline and an increased stiffness (corset) condition. Whole-body kinematics were utilized to estimate spatial step parameters, center of mass (COM), COM incongruity (peak - final position) and time to restabilisation, in anteroposterior (AP) and mediolateral (ML) directions., Results: In the corset condition, peak COM displacement was increased in both directions (p < 0.024), which drove reductions in minimum margins of stability (p < 0.032) as step width and length were unchanged (p > 0.233). Increased passive stiffness also increased the magnitude and variability of peak shear ground reaction force, COM incongruity, and time to restabilisation in the ML (but not AP) direction (p < 0.027)., Significance: In contrast to previous literature, increased stiffness resulted in greater peak COM displacement in both directions. Our results suggest increased trunk and hip stiffness have detrimental effects on dynamic stability following a reactive step, particularly in the ML direction. Observed increases in magnitude and variability of COM incongruity suggest the likelihood of a sufficiently large loss of ML stability - requiring additional steps - was increased by stiffening of the hips and trunk. The current findings suggest interventions aiming to mobilize the trunk and hips, in conjunction with strengthening, could improve balance and reduce the risk of falls., (Crown Copyright © 2019. Published by Elsevier B.V. All rights reserved.)

Background: Turning is a frequently performed, asymmetric task of daily living. The asymmetric nature makes turning challenging to perform while maintaining balance., Research Question: How do healthy individuals maintain dynamic balance, quantified as whole-body angular momentum, during a 90-degree turn compared to straight-line walking?, Methods: The kinematics of sixteen healthy individuals were tracked during walking in a straight-line and during left and right 90-degree turns at a comfortable pace. Whole-body and segment angular momenta were calculated and the relative contributions of the legs, arms, pelvis and head/trunk to whole-body angular momentum were evaluated., Results: Average whole-body angular momentum was different during turning compared to straight-line walking in all planes of motion. The initiation of a turn required generation of whole body angular momentum in all three planes of motion, which was counteracted at the end of the turn by a generation of angular momentum in the opposite direction in the frontal and sagittal planes. Transverse plane momentum was always directed in the turn direction. All segment groups, except for the inside leg, had a greater magnitude of angular momentum during turning compared to straight-line walking. The outside leg and head/trunk segments were the largest contributors to frontal and transverse plane whole-body angular momentum., Significance: Understanding how body segments contribute to maintaining balance during a 90-degree turn can be useful for designing rehabilitation paradigms for people who have difficulty turning or impaired balance., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Study Design: A multicenter cross-sectional study., Objectives: To clarify the relationship of trunk muscle mass with low back pain, spinal sagittal balance, and quality of life. Few reports have investigated the relationship of trunk muscle mass with lumbar spine function and spinal balance, and the clinical significance of trunk muscle mass remains unclear., Methods: Patients attending spinal outpatient clinics at 10 different medical institutions were enrolled in this study. Patient demographics, trunk muscle mass and appendicular skeletal muscle mass (ASM) measured by bioelectrical impedance analysis (BIA), body mass index (BMI), Charlson Comorbidity Index (CCI), the Oswestry Disability Index (ODI), visual analog scale (VAS) for low back pain, sagittal vertical axis (SVA), and EuroQol 5 Dimension (EQ5D) score were investigated. Multivariate nonlinear regression analysis was used to investigate the association of trunk muscle mass with the ODI, VAS score, SVA, and EQ5D score., Results: Of 2551 eligible patients, 1738 (mean age 70.2 ± 11.0 years; 781 men and 957 women) were enrolled. Trunk muscle mass was significantly correlated with the ODI, VAS score, SVA, and EQ5D score (P < 0.001) when adjusted for age, sex, BMI, ASM, CCI, and history of lumbar surgery. Patient deterioration was associated with a decrease in trunk muscle mass, and the deterioration accelerated from approximately 23 kg., Conclusions: Trunk muscle mass was significantly associated with the ODI, VAS score, SVA, and EQ5D score. Trunk muscle mass may assume an important role to elucidate and treat lumbar spinal dysfunction and spinal imbalance. These slides can be retrieved under Electronic Supplementary Material.

Background: Research has shown that postural perturbation training reduces falls. Trunk kinematics, at recovery step, are key outcome measures. Fall prevention training programs are being developed for routine clinical care. In these programs, the subject is positioned on a treadmill and subjected to forward and backward disturbances which simulate trips and slips. The patient wears a safety vest attached to an overhead harness to create a secure environment. Motion capture is used to measure trunk kinematics., Research Question: It is important to verify that trunk kinematics are independent of harness configuration. The purpose of this study was to compare the trunk flexion angle and angular velocity at recovery step after forward and backward disturbances on a treadmill measured by motion capture with the harness in both a fixed and free position., Methods: Ten healthy young adults (5/10 female, age: 29.2 ± 6.3 years, BMI: 24.2 ± 2.4) participated in this study. The subjects had retro-reflective markers placed on key anatomical landmarks to measure trunk kinematics. The participants experienced forward and backward disturbances, which incrementally increased in intensity until the harness clearly supported the subjects for three disturbances in both directions. The order of harness configurations was randomized across subjects and each subject participated in two consecutive rounds of disturbances, one round for each harness configuration. Equivalence testing was performed to demonstrate that the harness configurations were equivalent (α = 0.05)., Results and Significance: The Equivalence Test demonstrated that the trunk angle (TA) and angular velocity (TAV) were equivalent for the different harness configurations. The 95% Confidence Intervals (TA: [-2, 1], TAV: [-18, 16]) were within the equivalence interval (TA: [-3, 3], TAV: [-20, 20]) and the p-Values (TA: 0.008, TAV: 0.034) were less than alpha. Trunk kinematics are independent of overheard harness configurations during treadmill induced disturbances for clinical postural perturbation training., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Background: The proprioceptive system plays a role in the maintenance of postural control more than the visual and vestibular systems in ataxic patients with postural control disorders, but the relationship between trunk proprioception and postural control has not been sufficiently investigated yet. This relationship can provide a different perspective to the ataxia rehabilitation., Research Question: This study aimed to examine the relationship between trunk position sense and postural control in ataxic individuals by comparing them to healthy individuals., Methods: Twenty ataxic and 20 healthy individuals were included. The Sensory Organization Test, Limits of Stability Test, and Unilateral Stance Test in the Computerized Dynamic Posturography and Berg Balance Scale were used to evaluate postural control. The Baseline Digital Inclinometer (Norwalk, CA, USA) measured trunk position sense., Results: It was found that repositioning error degree of the trunk position sense was higher in ataxic individuals than in healthy individuals, including scores of clinical and objective tests in postural control evaluation: they were lower in ataxic individuals (p < 0.05). As a result, trunk position sense was associated with almost all evaluated parameters, including sensory integration, postural sway, limits of stability, and functional balance (p < 0.05)., Significance: The impairment of postural control, which is the most important cause of activity and participation limitations in ataxic patients, is not only affected by motor disorders, but by sensory disturbances. Our study demonstrated that impairment of the trunk position sense in ataxic individuals was higher than that of healthy individuals, and affected the different components of postural control., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Background: Patellofemoral pain syndrome (PFPS) is a common orthopedic problem with a high prevalence among young women. Patients with PFPS have altered trunk muscle activity, impaired postural control and greater displacement of the center of pressure (COP) while standing. Training in unstable sitting, by putting more emphasis on trunk sensory receptors, may improve trunk proprioception by minimizing the role of the lower extremities. The aim of this study was to compare trunk postural control in healthy persons and in patients with PFPS., Methods: Twenty-one women diagnosed with PFPS and 21 healthy women volunteered to participate in this cross-sectional study. The participants were asked to maintain trunk postural balance on an unstable sitting device, and COP indices of trunk postural control were compared between groups., Results: All COP indices (e.g., mean anterior-posterior and lateral COP displacement, mean COP velocity and mean area of COP displacement) were significantly increased in participants with PFPS in comparison to healthy controls (P < 0.001). The effect sizes of all the indices were greater than 0.80., Conclusions: Trunk postural control is impaired in patients with PFPS, and this finding has clinical implications for rehabilitation in patients with PFPS. Adding seated postural control training to conventional physical therapy management in patients with PFPS may have beneficial effects by emphasizing trunk proprioception while minimizing the role of the lower extremities., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Background: Trunk prevention training, which provides the basis of several conditioning training programs, is used in sports at professional and amateur levels, taking the specifications of the given sport and the age-related characteristics of the athletes into consideration., Objective: Our aim was to examine the strength and flexibility of muscles responsible for correct posture, the lumbar motor control ability and the posture of recruitment kayak-canoe athletes., Methods: Controlled, randomized examination with 103 persons (age: 15.1 ± 3.5 years), who were divided into two groups. Fifty were in the intervention group, who took part in the 6-month trunk prevention training program (height: 162.30 cm, body weight: 49.70 ± 10.32 kg), 53 in the control group (not performing trunk prevention training) (height: 158.24 cm, body weight: 51.45 ± 11.71 kg). The strength of core muscles was measured with Kraus-Weber test, muscle flexibility with Kempf-test, lumbar motor control ability with Sitting Forward Lean and Leg Lowering test and posture with photogrammetry test before and after the program., Results: Static strength of abdominal muscles (p< 0.001), superficial and deep dorsal muscles (p< 0.001), flexibility of knee extensors (p< 0.001), chest muscles (p< 0.001), the lumbar motor control ability (p< 0.001) and habitual posture (p< 0.001) significantly improved in the intervention group. The post-measurements in the intervention group were significantly (p< 0.001) better than in the control group., Conclusions: As a result of the trunk prevention training the strength of core stabilization muscles, the lumbar motor control ability and the posture also improved in case of recruitment athletes.

Background: Gait initiation is associated with changes in the steady state and experiencing an external perturbation during initiation of gait could further threaten balance stability., Research Question: The aim of the study was to investigate if changes in the symmetry of the perturbations affect patterns of muscle activity during gait initiation., Methods: Eleven young health participants were instructed to stand on the force platform and wait for the instruction of taking a right step, left step or stand still while experiencing a pendulum perturbation applied to the back of both shoulders (symmetric), back of the right shoulder (asymmetric) or no perturbations. Bilateral electromyographic activity (EMG) of dorsal and ventral muscles, moments of the pendulum release and perturbation impact, center of pressure (COP) displacements and pelvic movements were recorded and analyzed before and after the onset of the perturbation., Results: Taking the right/left step in presence of symmetric perturbation did not affect the temporal sequence of COP and pelvic movements. The onset of COP and pelvic movement occurred before the perturbation impact at the shoulder levels. The factors of step and perturbation did not significantly affect integrals of bilateral muscles at the pendulum release. After the pendulum release, ventral and dorsal EMG integrals of the trunk, thigh, and shank segments increased or decreased corresponding to the swing and stance leg. Changes in muscle activities were also associated with the symmetric or asymmetric perturbations before and after the perturbation impact., Significance: The outcome of the study provides information about strategies used to coordinate the activity of muscles while body perturbations are induced during gait initiation., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Introduction: Although the role of trunk exercises in the chronic phase of stroke is acknowledged, the addition of specific inpatient training in the subacute stage is a matter of debate and varies among centers. Recent new evidence suggests the question should be revisited., Objective: To assess the impact of the addition of specific trunk training to inpatient rehabilitation protocols after a recent stroke., Methods: A systematic review was performed assessing the impact of inpatient trunk training. The search was performed in LILACS, SciELO, PEDro, Cochrane, and NCBI PubMed databases for clinical trials published up to December 31st, 2017. The initial bibliographic research identified 3202 articles. After analyzing the titles, 19 abstracts were selected for detailed analysis. After application of the eligibility criteria, the final selection included nine studies. Outcome measurements from the same evaluation instruments were submitted to a meta-analysis to improve homogeneity (7 studies)., Results: All patients in the included studies were recruited less than three months after a stroke. Seven studies assessed trunk control using the Trunk Impairment Scale (TIS). There was a significant improvement in trunk control with a pooled increase in TIS score of 3.3 points from the baseline (CI95:2.54-4.06, p < 0.0001). Three studies assessed balance using the Brunel Balance Assessment (BBA) scale. There was also a significant improvement in balance with a pooled increase in BBA score of 2.7 points (CI95:1.5-4.03, p < 0.0001). The Berg Balance Scale was used for balance assessment in three studies. The meta-analysis of their results showed a pooled increase of 13.2 points (CI95:9.49-16.84, p < 0.0001). Weight transfer was evaluated in four studies using different methods. The addition of inpatient trunk exercises was associated with an improvement in the ability to transfer the trunk laterally in three studies., Conclusion: The introduction of trunk-based inpatient training protocols brings short-term benefits in trunk performance and balance in stroke patients.

Background: Although the Star Excursion Balance test (SEBT) has shown a good intrasession reliability, the intersession reliability of this test has not been deeply studied. Furthermore, there is an evident high influence of the lower limbs in the performance of the SEBT, so even if it has been used to measure core stability, it is possibly not the most suitable measurement., Objective: (1) To assess the absolute and relative between-session reliability of the SEBT and 2 novel variations of this test to assess trunk postural control while sitting, ie, the Star Excursion Sitting Test (SEST) and the Star Excursion Timing Test (SETT); and (2) to analyze the relationships between these 3 test scores., Design: Correlational and reliability test-retest study., Setting: Controlled laboratory environment., Participants: Twenty-seven physically active men (age: 24.54 ± 3.05 years)., Method: Relative and absolute reliability of the SEBT, SEST, and SETT were calculated through the intraclass correlation coefficient (ICC) and standard error of measurement (SEM), respectively. A Pearson correlation analysis was carried out between the variables of the 3 tests., Main Outcome Measures: Maximum normalized reach distances were assessed for different SEBT and SEST directions. In addition, composite indexes were calculated for SEBT, SEST, and SETT., Results: The SEBT (dominant leg: ICC = 0.87 [0.73-0.94], SEM = 2.12 [1.66-2.93]; nondominant leg: ICC = 0.74 [0.50-0.87], SEM = 3.23 [2.54-4.45]), SEST (ICC = 0.85 [0.68-0.92], SEM = 1.27 [1.03-1.80]), and SETT (ICC = 0.61 [0.30-0.80], SEM = 2.31 [1.82-3.17]) composite indexes showed moderate-to-high 1-month reliability. A learning effect was detected for some SEBT and SEST directions and for SEST and SETT composite indexes. No significant correlations were found between SEBT and its 2 variations (r ≤ .366; P > .05). A significant correlation was found between the SEST and SETT composite indexes (r = .520; P > .01)., Conclusions: SEBT, SEST, and SETT are reliable field protocols to measure postural control. However, whereas the SEBT assesses postural control in single-leg stance, SEST and SETT provide trunk postural control measures with lower influence of the lower-limbs., Level of Evidence: III., (Copyright © 2018 American Academy of Physical Medicine and Rehabilitation. Published by Elsevier Inc. All rights reserved.)

Clinicians frequently incorporate unstable sitting devices into training plans for improving proximal postural muscle control; however, the effect of unstable sitting conditions on postural adjustments during dynamic activities has not been fully explored. The aim of this study was to characterize early postural adjustments (EPAs) and anticipatory postural adjustments (APAs) under stable and unstable sitting conditions. Using a cross-sectional laboratory study design, 13 healthy college student volunteers used their dominant hand to reach forward and push a target under stable and unstable sitting conditions; subjects sat on an air-filled rubber cushion for the unstable condition. EPAs and APAs were quantified by recording muscle activation of the trunk and lower extremity muscles using electromyography (EMG). The center of pressure (COP) was measured using a force plate. The resulting EMG integral of the ipsilateral gastrocnemius muscle was larger during the EPA phase and smaller during the APA phase under unstable conditions (p = 0.014 and p = 0.041, respectively). COP amplitude in the anterior-posterior direction, path length, and velocity, was larger during the APA phase (p = 0.035, p = 0.023, and 0.023, respectively). This suggests greater distal muscle activation during EPAs in unstable sitting conditions, specifically in the ipsilateral gastrocnemius muscle. In addition, APAs adjusted by reducing the activity of the ipsilateral gastrocnemius muscle and increasing the anterior-posterior shift in the COP to compensate for the expected additional perturbation due to an unstable surface., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Objectives: Investigate the relationship of hip internal rotation (IR) and ankle dorsiflexion (DF) range of motion (ROM), trunk flexor, extensor, and lateral flexor muscle endurance with frontal plane knee projection angle (FPKPA) and Y-balance test (YBT)., Study Design: Cross-sectional study., Setting: Armed Force training site., Participants: 121 healthy male militaries with no history of musculoskeletal injury in the last 6 months., Main Outcomes: FPKPA was evaluated during single-leg squat. YBT was assessed on the anterior, posterolateral and posteromedial directions. Passive hip IR ROM and weight-bearing ankle DF ROM were measured with a digital inclinometer. Trunk muscle endurance was measured as the time the participant could hold the positions., Results: FPKPA was predicted by ankle DF ROM and hip IR ROM (r 2  = 0.340; P = 0.009). For YBT anterior, ankle DF ROM was the only predictor (r 2  = 0.32; P < 0.001); whereas trunk extensor endurance predicted YBT posterolateral (r 2  = 0.273; P < 0.001) and YBT posteromedial (r 2  = 0.033; P = 0.045)., Conclusion: The results suggest that increasing hip stiffness and ankle mobility might help to control dynamic knee alignment. In addition, the dynamic balance could be improved increasing ankle DF ROM and trunk extensor endurance., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Core stabilisation exercises are often promoted for purposes ranging from general fitness to high-performance athletics, and the prevention and rehabilitation of back troubles. These exercises, when performed properly, may have the potential to enhance torso postural awareness and control, yet the potential for achieving immediate gains has not been completely studied. Fourteen healthy young participants performed a single bout of non-fatiguing core stabilisation exercise that consisted of repeated sets of 2 isometric exercises, the side bridge and the four-point contralateral arm-and-leg extension. Seated postural control, using an unstable balance platform on top of a force plate, was assessed before and after exercise, including multiple time points within a 20-minute follow-up period. Nine standard postural control variables were calculated at each time point, including sway displacement and velocity ranges, root mean squares and cumulative path length. Statistical analysis showed that none of the postural control variables were significantly different at any time point following completion of core stabilisation exercise. Thus, we conclude that a single bout of acute core stabilisation exercise is insufficient to immediately improve seated trunk postural control in young healthy individuals.