Biomechanical and neurophysiological mechanisms related to postural control and efficiency of movement: a review

Balance, Gait, Functionality and Fall Occurrence in Adults and Older Adults with Type 2 Diabetes Mellitus and Associated Peripheral Neuropathy

BACKGROUND

Body balance is regulated by sensory information from the vestibular, visual and somatosensory systems, and changes in one or more of these sensory systems can trigger balance disorders. Individuals with type 2 Diabetes Mellitus (DM2) often present peripheral neuropathy, a condition that alters foot sensory information and can negatively influence balance and gait performance of these subjects.

OBJECTIVE

To evaluate and compare balance, gait, functionality and the occurrence of falls between individuals with and without a clinical diagnosis of DM2 with associated peripheral neuropathy.

METHODS

Cross-sectional study, which evaluated seventy individuals, thirty-five with and thirty-five without a clinical diagnosis of DM2, of both sexes and age range between 50 and 85 years, who were recruited from Basic Health Units of Serra Talhada, Pernambuco state, Brazil. The volunteers' balance was analyzed using the Berg Balance Scale, gait-related functional tasks were measured using the Dynamic Gait Index, functional mobility was assessed using the Timed Up and Go test and functionality was assessed using the Katz Index. The occurrence of falls was recorded by the volunteers' self-report.

RESULTS

Individuals with DM2 demonstrated the worst performance in balance (p = 0.000) and in gait-related functional tasks (p = 0.000), slower functional mobility (p = 0.000) and worse functionality (p = 0.016) compared to the group without DM2, demonstrating significant differences for all analyzed outcomes. A greater occurrence of falls was observed in individuals with DM2, compared to those without the disease (p = 0.019).

CONCLUSION

Individuals with DM2 demonstrated worse performance on balance, gait-related functional tasks, slower functional mobility and worse functionality compared to those without the disease. Individuals with DM2 had the highest occurrence of falls in this study.

Effect of short-term 10 Hz repeated transcranial magnetic stimulation on postural control ability in patients with mild hemiparesis in acute ischemic stroke: a single-blinded randomized controlled trial

Background

Previous studies have demonstrated that repetitive transcranial magnetic stimulation (rTMS) can improve postural control in subacute and chronic ischemic stroke, but further research is needed to investigate the effect of rTMS on acute ischemic stroke.

Objective

We compared the therapeutic effects of rTMS plus conventional rehabilitation and conventional rehabilitation on postural control in patients with mild hemiparesis in acute ischemic stroke.

Methods

Eighty-six patients with acute ischemic stroke were randomly assigned to either the experimental group or the control group within 1-7 days of onset. Patients in both groups received conventional rehabilitation for 2 weeks. Patients in the experimental group received rTMS treatments lasting for 2 weeks. Before and after the 2-week treatment, patients were assessed based on the Timed up and Go (TUG) test, Dual-Task Walking (DTW) test, Functional Ambulation Category (FAC), Tinetti Performance Oriented Mobility Assessment (POMA), gait kinematic parameters, Barthel Index (BI), Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), and National Institutes of Health Stroke Scale (NIHSS). Additionally, TUG and single-task gait velocity were assessed at 2 months after the start of treatment, and independent walking recovery was also followed up.

Results

After 2 weeks of treatment, compared to conventional rehabilitation, participants who underwent rTMS treatment plus conventional rehabilitation exhibited notable enhancements in TUG, FAC, POMA, and some gait parameters [single-task gait velocity, gait stride length, gait cadence, gait cycle]. Changes in cognitive function partially mediated the improvement in single-task gait velocity and gait stride length by rTMS plus conventional rehabilitation. Generalized Estimating Equation (GEE) analysis showed that the trend of improvement in single-task gait velocity over time was more pronounced in the experimental group than in the control group. The results of the Kaplan-Meier curve indicated a median gait recovery time of 90 days for patients in the experimental group and 100 days for the control group. Multifactorial Cox regression analyses showed that rTMS plus conventional rehabilitation promoted faster recovery of independent walking compared with conventional rehabilitation.

Conclusion

rTMS plus conventional rehabilitation outperformed conventional rehabilitation in improving postural control in patients with acute ischemic stroke. Improvements in cognitive function may serve as a mediating factor in the favorable treatment outcome of rTMS plus conventional rehabilitation for improving postural control.

Clinical trial registration

https://www.chictr.org.cn, identifier ChiCTR1900026225.

Postural Control and Neuromuscular Activation in 11-13-Year-Old Athletic Boy Swimmers

OBJECTIVE

This study compared postural control and neuromuscular activation in athletic swimmers (A-S) and non-athletic swimmers (N-A-S) in older children.

METHODS

Ten A-S and ten N-A-S underwent assessments of center of pressure (CoP) parameters under static and dynamic surfaces in two directions (dynamic mediolateral (DML) and dynamic anteroposterior (DAP)) in eyes-open (EO) and eyes-closed (EC) conditions, and electromyography (EMG) parameters under DAP and DML directions in EO and EC conditions.

RESULTS

Results showed that A-S demonstrated significantly superior postural control (p < 0.05), with smaller CoP area and lower CoP mean velocity compared with N-A-S, particularly in static with EC, DAP with EO and EC, and DML with EO conditions. A-S exhibited significantly larger neuromuscular activation amplitudes (p < 0.05), especially in the AP direction.

CONCLUSIONS

These findings suggested that athletic swimming training may enhance postural control and neuromuscular activation in 11-13-year-old children, emphasizing the potential benefits of incorporating swimming exercises in these children.

How virtual reality is impacting balance: An examination of postural stability

BACKGROUND

The interest in virtual reality (VR) applications has been on the rise in recent years. However, the impact of VR on postural stability remains unclear.

RESEARCH QUESTION

The study has two primary objectives: first, to compare postural stability in a 3D-immersed virtual reality environment (VE) and a real environment (RE), and second, to investigate the effect of positive and negative visual feedback, which are subconditions of VE on postural stability.

METHODS

The observational study recruited 20 healthy adults (10 male, 10 female, 22.8 ± 1.8 years) who underwent postural stability assessments in both RE and VE. In VE, participants received visual stimuli in three different ways: without visual feedback, with positive and negative visual feedback that they would consider themselves to be directed towards postural stability outcomes. The RE included two conditions: eyes open (EO) and eyes closed (EC). Postural stability was evaluated with sway velocity, sway area, and perimeter variables obtained from a force platform.

RESULTS

All postural stability variables were significantly lower in the RE than in the VE (p < 0.05). There was no significant difference between the VE and EC in terms of sway velocity and sway area (p > 0.05). The visual feedback in the VE did not affect participants' postural stability (p > 0.05). VE may cause an increase in postural sway variables compared to RE and postural requirements may be higher in VE compared to RE.

SIGNIFICANCE

This is the first and only study examining the effect of different visual feedback on postural stability in VE.

Movement efficiency in survivors of childhood acute lymphoblastic leukemia: a report from the St. Jude lifetime cohort study

PURPOSE

Movement efficiency, a measure of neuromuscular biomechanics, may be modified by physical activity. We aimed to assess the risk of and risk factors for low movement efficiency in survivors of childhood acute lymphoblastic leukemia (ALL).

METHODS

Participants underwent an assessment of activity energy expenditure (AEE) with actigraphy, and the gold standard doubly labeled water, where the differences between elimination rates of oxygen and hydrogen from body water are evaluated over a week. Movement efficiency was assessed using the raw residuals of a linear regression between AEEs from accelerometers and doubly labeled water. Elastic-net logistic regressions were used to identify demographic, treatment, and functional variables associated with movement efficiency.

RESULTS

The study cohort included 256 non-cancer controls and 302 ALL survivors (48% female), categorized as efficient (N = 24), normal (N = 245), or inefficient (N = 33) based on their movement efficiency. There was no difference in the odds for poor movement efficiency between survivors (n = 33, 10.9%) compared to controls (n = 23, 9.0%, odds ratio [OR]: 1.19, 95% confidence interval [CI]: 0.67, 2.10; p = 0.55). In survivors, neuropathy was associated with a higher risk of being inefficient compared to efficient (OR 4.30, 95% CI 1.03-17.96), while obesity (≥ 30 kg/m2) had a protective association (OR 0.18, 95% CI 0.04-0.87).

CONCLUSIONS

Neuropathy was associated with a higher risk of poor movement efficiency in survivors of childhood ALL.

IMPLICATIONS FOR CANCER SURVIVORS

These results further highlight impairments associated with treatment-induced neuropathy in survivors of childhood ALL.

Muscular Strategies for Correcting the Pelvic Position to Improve Posture-An Exploratory Study

The correction of postural weaknesses through the better positioning of the pelvis is an important approach in sports therapy and physiotherapy. The pelvic position in the sagittal plane is largely dependent on the muscular balance of the ventral and dorsal muscle groups. The aim of this exploratory study was to examine whether healthy persons use similar muscular activation patterns to correct their pelvic position or whether there are different motor strategies. The following muscles were recorded in 41 persons using surface electromyography (EMG): M. trapezius pars ascendens, M. erector spinae pars lumbalis, M. gluteus maximus, M. biceps femoris, M. rectus abdominis, and M. obliquus externus. The participants performed 10 voluntary pelvic movements (retroversion of the pelvis). The anterior pelvic tilt was measured videographically via marker points on the anterior and posterior superior iliac spine. The EMG data were further processed and normalized to the maximum voluntary contraction. A linear regression analysis was conducted to assess the relationship between changes in the pelvic tilt and muscle activities. Subsequently, a Ward clustering analysis was applied to detect potential muscle activation patterns. The differences between the clusters and the pelvic tilt were examined using ANOVA. Cluster analysis revealed the presence of four clusters with different muscle activation patterns in which the abdominal muscles and dorsal muscle groups were differently involved. However, the gluteus maximus muscle was involved in every activation pattern. It also had the strongest correlation with the changes in pelvic tilt. Different individual muscle patterns are used by different persons to correct pelvic posture, with the gluteus maximus muscle apparently playing the most important role. This can be important for therapy, as different muscle strategies should be trained depending on the individually preferred motor patterns.

Older adults with slow sit to stand times show reduced temporal precision of audio-visual integration

Sustained integration of sensory inputs over increased temporal delays is associated with reduced cognitive and physical functioning in older adults and adverse outcomes such as falls. Here, we explored the relationship between multisensory integration and a clinically relevant measure of balance/postural control; Sit-to-Stand Time, the efficiency with which an older adult can transition between a seated and a standing posture. We investigated whether temporal multisensory integration was associated with performance on the Five-Times Sit-to-Stand Test (FTSST) in a large sample of 2556 older adults (mean age = 63.62 years, SD = 7.50; 55% female) drawn from The Irish Longitudinal Study on Ageing (TILDA). K-means clustering was applied to FTSST data, yielding three clusters characterised by fast (mean = 10.88 s; n = 1122), medium (mean = 14.34 s; n = 1133) and slow (mean = 18.97 s; n = 301) sit-to-stand times. At wave 3 of TILDA, older adults participated in the Sound Induced Flash Illusion (SIFI), a measure of the precision of temporal audio-visual integration, which included three audio-visual stimulus onset asynchronies (SOAs): 70, 150 and 230 ms. Older adults with the slowest sit-to-stand times were more susceptible to the SIFI at the longest SOA (230 ms) compared to the shortest SOA (70 ms) relative to those with the fastest times (p = 0.02). Older adults who take longer to repeatedly transition from a seated to a standing posture exhibit an expanded temporal binding window for audio-visual events, supporting a link between multisensory perception and balance/postural control in ageing.

Unexpected running perturbations: Reliability and validity of a treadmill running protocol with analysis of provoked reflex activity in the lower extremities

Introduction

Balance is vital for human health and experiments have been conducted to measure the mechanisms of postural control, for example studying reflex responses to simulated perturbations. Such studies are frequent in walking but less common in running, and an understanding of reflex responses to trip-like disturbances could enhance our understanding of human gait and improve approaches to training and rehabilitation. Therefore, the primary aim of this study was to investigate the technical validity and reliability of a treadmill running protocol with perturbations. A further exploratory aim was to evaluate the associated neuromuscular reflex responses to the perturbations, in the lower limbs.

Methods

Twelve healthy participants completed a running protocol (9 km/h) test-retest (2 weeks apart), whereby 30 unilateral perturbations were executed via the treadmill belts (presets:2.0 m/s amplitude;150 ms delay (post-heel contact);100ms duration). Validity of the perturbations was assessed via mean ± SD comparison, percentage error calculation between the preset and recorded perturbation characteristics (PE%), and coefficient of variation (CV%). Test-retest reliability (TRV%) and Bland-Altman analysis (BLA; bias ± 1.96 * SD) was calculated for reliability. To measure reflex activity, electromyography (EMG) was applied in both legs. EMG amplitudes (root mean square normalized to unperturbed strides) and latencies [ms] were analysed descriptively.

Results

Left-side perturbation amplitude was 1.9 ± 0.1 m/s, delay 105 ± 2 ms, and duration 78 ± 1 ms. Right-side perturbation amplitude was 1.9 ± 0.1 m/s, delay 118 ± 2 ms, duration 78 ± 1 ms. PE% ranged from 5–30% for the recorded perturbations. CV% of the perturbations ranged from 19.5–76.8%. TRV% for the perturbations was 6.4–16.6%. BLA for the left was amplitude: 0.0 ± 0.3m/s, delay: 0 ± 17 ms, duration: 2 ± 13 ms, and for the right was amplitude: 0.1 ± 0.7, delay: 4 ± 40 ms, duration: 1 ± 35 ms. EMG amplitudes ranged from 175 ± 141%–454 ± 359% in both limbs. Latencies were 109 ± 12–116 ± 23 ms in the tibialis anterior, and 128 ± 49-157 ± 20 ms in the biceps femoris.

Discussion

Generally, this study indicated sufficient validity and reliability of the current setup considering the technical challenges and limitations, although the reliability of the right-sided perturbations could be questioned. The protocol provoked reflex responses in the lower extremities, especially in the leading leg. Acute neuromusculoskeletal adjustments to the perturbations could be studied and compared in clinical and healthy running populations, and the protocol could be utilised to monitor chronic adaptations to interventions over time.

The Effect of Additional Leg Supports in Control of Posture in Sitting

The objective of the study was to investigate the effect of leg supports on the anticipatory and compensatory postural adjustments of sitting subjects exposed to external perturbations in the anterior-posterior direction. Ten young participants received perturbations applied to the upper body while sitting on a stool with an anterior or posterior leg support and when using a footrest. Electromyographic activities of the trunk and leg muscles and center of pressure displacements were recorded and analyzed during the anticipatory and compensatory phases of postural control. Anticipatory activities were observed in the tibialis anterior, biceps femoris, and erector spinae muscles in the anterior leg support condition. Early onset of muscle activity was observed in the tibialis anterior, biceps femoris, rectus femoris, and erector spinae muscles in the posterior leg support condition compared to the feet support condition. Moreover, to maintain balance participants utilized co-contraction of muscles as the main mechanism of balance control in sitting regardless of the availability of the anterior or posterior leg support. There was no effect of a leg support on center of pressure displacements. The outcome of the study provides a background for future investigations of the effect of leg supports on control of balance in sitting when perturbed.

Effects of motor stimulation of the tibial nerve on corticospinal excitability of abductor hallucis and pelvic floor muscles

Introduction

Peripheral nerve stimulation can modulate the excitability of corticospinal pathways of muscles in the upper and lower limbs. Further, the pattern of peripheral nerve stimulation (continuous vs. intermittent) may be an important factor determining the modulation of this corticospinal excitability. The pelvic floor muscles (PFM) are crucial for maintaining urinary continence in humans, and share spinal segmental innervation with the tibial nerve. We explored the idea of whether the neuromodulatory effects of tibial nerve stimulation (TibNS) could induce effects on somatic pathways to the PFM. We evaluated the effects of two patterns of stimulation (intermittent vs. continuous) on corticospinal excitability of the PFM compared to its effect on the abductor hallucis (AH) muscle (which is directly innervated by the tibial nerve). We hypothesized that intermittent TibNS would increase, while continuous stimulation would decrease, the excitability of both AH and PFM.

Methods

Twenty able-bodied adults (20-33 years of age) enrolled in this study. TibNS was delivered either intermittently (1 ms pulses delivered at 30Hz with an on:off duty cycle of 600:400 ms, for 60 min), or continuously (1 ms pulses delivered at 30Hz for 36 min) just above the motor threshold of the AH. We randomized the order of the stimulation pattern and tested them on separate days. We used surface electromyography (EMG) to record motor-evoked responses (MEP) in the PFM and AH following transcranial magnetic stimulation (TMS). We generated stimulus-response (SR) curves to quantify the changes in peak-to-peak MEP amplitude relative to TMS intensity to assess changes in corticospinal excitability pre- and post-stimulation.

Results and Conclusion

We found that TibNS increased corticospinal excitability only to AH, with no effects in PFM. There was no difference in responses to continuous vs. intermittent stimulation. Our results indicate a lack of effect of TibNS on descending somatic pathways to the PFM, but further investigation is required to explore other stimulation parameters and whether neuromodulatory effects may be spinal in origin.

Sensorineural hearing loss imprint on postural control: A pediatric and adolescent innovative study

BACKGROUND

Sensorineural hearing loss is the most common type of permanent hearing impairment and results in postural control and motor deficits in children that may affect or delay all developmental indicators.

OBJECTIVE

The purpose of the study was to objectively investigate the consequences of sensorineural hearing loss concerning postural control in pediatrics.

METHODS

Forty students of both genders, ages ranging from 10 to 16 years, diagnosed with severe to profound sensorineural hearing loss, were selected from the Public School for the Deaf and Hard of Hearing in El-Minia district, Egypt. The outcome was assessed by HUMAC Balance System and Bruininks-Oseretsky Test (BOT-2) subtest (5) for balance.

RESULTS

Regarding HUMAC Balance System and subtest (5) of BOT-2, there was a statistically significant difference between the scores of study subgroups and the counterpart normal subgroups of the same age and gender where p-value equal 0.0035 or less.

CONCLUSION

The findings of this study suggest that children with sensorineural hearing loss have a defect in their postural control skills compared to normal children of the same gender and age groups according to HUMAC Balance System and Bruininks-Oseretsky scale.

Predicting the metabolic cost of exoskeleton-assisted squatting using foot pressure features and machine learning

Introduction: Recent studies found that wearable exoskeletons can reduce physical effort and fatigue during squatting. In particular, subject-specific assistance helped to significantly reduce physical effort, shown by reduced metabolic cost, using human-in-the-loop optimization of the exoskeleton parameters. However, measuring metabolic cost using respiratory data has limitations, such as long estimation times, presence of noise, and user discomfort. A recent study suggests that foot contact forces can address those challenges and be used as an alternative metric to the metabolic cost to personalize wearable robot assistance during walking. Methods: In this study, we propose that foot center of pressure (CoP) features can be used to estimate the metabolic cost of squatting using a machine learning method. Five subjects' foot pressure and metabolic cost data were collected as they performed squats with an ankle exoskeleton at different assistance conditions in our prior study. In this study, we extracted statistical features from the CoP squat trajectories and fed them as input to a random forest model, with the metabolic cost as the output. Results: The model predicted the metabolic cost with a mean error of 0.55 W/kg on unseen test data, with a high correlation (r = 0.89, p < 0.01) between the true and predicted cost. The features of the CoP trajectory in the medial-lateral direction of the foot (xCoP), which relate to ankle eversion-inversion, were found to be important and highly correlated with metabolic cost. Conclusion: Our findings indicate that increased ankle eversion (outward roll of the ankle), which reflects a suboptimal squatting strategy, results in higher metabolic cost. Higher ankle eversion has been linked with the etiology of chronic lower limb injuries. Hence, a CoP-based cost function in human-in-the-loop optimization could offer several advantages, such as reduced estimation time, injury risk mitigation, and better user comfort.

Mobile Brain Imaging to Examine Task-Related Cortical Correlates of Reactive Balance: A Systematic Review

This systematic review examined available findings on spatial and temporal characteristics of cortical activity in response to unpredicted mechanical perturbations. Secondly, this review investigated associations between cortical activity and behavioral/biomechanical measures. Databases were searched from 1980-2021 and a total of 35 cross-sectional studies (31 EEG and 4 fNIRS) were included. Majority of EEG studies assessed perturbation-evoked potentials (PEPs), whereas other studies assessed changes in cortical frequencies. Further, fNIRS studies assessed hemodynamic changes. The PEP-N1, commonly identified at sensorimotor areas, was most examined and was influenced by context prediction, perturbation magnitude, motor adaptation and age. Other PEPs were identified at frontal, parietal and sensorimotor areas and were influenced by task position. Further, changes in cortical frequencies were observed at prefrontal, sensorimotor and parietal areas and were influenced by task difficulty. Lastly, hemodynamic changes were observed at prefrontal and frontal areas and were influenced by task prediction. Limited studies reported associations between cortical and behavioral outcomes. This review provided evidence regarding the involvement of cerebral cortex for sensory processing of unpredicted perturbations, error-detection of expected versus actual postural state, and planning and execution of compensatory stepping responses. There is still limited evidence examining cortical activity during reactive balance tasks in populations with high fall-risk.

Electromyographic analysis of pelvic floor muscles during the execution of pelvic patterns of proprioceptive neuromuscular facilitation-concept: An observational study

OBJECTIVE

To assess the effect of pelvic patterns of proprioceptive neuromuscular facilitation (PNF-concept) on pelvic floor muscles (PFM) recruitment, as well as the electromyographic activity of muscles synergic to the pelvic floor in healthy women.

METHODS

Observational study conducted with 31 women aged between 18 and 35 years, with mean age of 23.3 ± 3.2 (22.1-24.4). PFM activity was monitored by surface electromyography during the combination of isotonics technique of four pelvic patterns of PNF-concept (i.e., anterior elevation, posterior depression, anterior depression, and posterior elevation). The electromyographic signal was analyzed using root mean square amplitude. Two-way repeated measures analysis of variance was performed to analyze differences in PFM activity between types of contraction (i.e., concentric, isometric, and eccentric) and the four pelvic patterns.

RESULTS

PFM activity did not differ among the four pelvic pattens. However, PFM activity was significantly different between the combination of isotonics technique and baseline, F(1.6, 48.2) = 71.5; p < 0.000, with a large effect size (partial ƞ² = 0.705). Concentric (22.4 µV ± 1.1), isometric (17.3 µV ± 0.6), and eccentric (15 µV ± 0.5) contractions of combination of isotonics technique increased PFM activity compared with baseline (10.8 µV ± 0.4) in all pelvic patterns. By analyzing the electromyographic activity of the muscles synergistic to the pelvic floor, there is effect of the interaction of the type of contraction, the pelvic pattern of the PNF concept, and the synergistic muscles on the myoelectric activity of the external anal sphincter, F(3.2, 96.5) = 5.6; p < 0.000, with a large magnitude of effect (partial ƞ² = 0.15). In the anterior elevation pattern, the muscles synergistic to the pelvic floor present synergy in phase with the PFM, and in the posterior patterns there was a decrease in the activity level of all synergistic muscles, without changing the activity level of the PFM.

CONCLUSION

PFM activity did not differ among the four pelvic patterns of PNF-concept. Nonetheless, the combination of isotonics technique showed a significant effect on PFM compared with baseline, with greater PFM activity during concentric contraction. Pelvic patterns of PNF-concept may be used to increase PFM recruitment in young healthy women.

Canine Mobility Maintenance and Promotion of a Healthy Lifestyle

This article highlights the recommendations and considerations for maintaining a healthy canine lifestyle. A key component of a healthy lifestyle is the enhancement and optimization of mobility. Mobility is essential in maintaining a high quality of life and involves the interplay of a dog's structure, posture, body condition score, physical exercise, and a healthy human-animal bond throughout a dog's lifetime.

Analysis of the Ability to Tolerate Body Balance Disturbance in Relation to Selected Changes in the Sagittal Plane of the Spine in Early School-Age Children

The study aimed to estimate the ability to tolerate body balance disturbance in relation to selected changes in the sagittal plane of the spine in early school-age children. The study involved 189 children with an average age of 8.3 ± 0.7 years (aged 7−10). The tests included an interview, clinical examination (measurement of body weight and height, assessment of the course of the spinous processes of the thoracic and lumbar vertebrae, assessment of the location of selected anatomical landmarks of the torso), and a physical examination in which the shape of the spine surface was examined with the use of the photogrammetric method and the moiré effect projection. Body balance disturbance tolerance skills (BBDTS) were measured with the rotational test (RT). In the rotational test, the results of body balance disturbance tolerance skills show a slight but statistically significant correlation with the bodyweight of the examined children (Rs = 0.35, p < 0.001). This relationship was also statistically significant in the groups by gender. Among the measured indicators of the curvature of the spine in the sagittal plane, the correlation with the RT test result was mostly related to the α angle and the value was Rs = 0.15 (p = 0.04). In the group of girls, this correlation was stronger and amounted to Rs = 0.26 (p = 0.015). Among other measured correlations, the dependence of variables such as the bodyweight of the subjects and the α angle was shown. In conclusion, increasing lumbar lordosis results in the deterioration of balance disturbance tolerance skills. As body weight increases, body balance disturbance tolerance skills decrease.

Detection of ataxia with hybrid convolutional neural network using static plantar pressure distribution model in patients with multiple sclerosis

OBJECTIVE

In this study, it is aimed to detect ataxia for Persons with Multiple Sclerosis (PwMS) through a deep learning-based approach using an image dataset containing static plantar pressure distribution. Here, an alternative and objective method will be proposed to assist physicians who diagnose PwMS in the early stages.

METHODS

A total of 406 static bipedal pressure distribution image data for 43 ataxic PwMS and 62 healthy individuals were used in the study. After preprocessing, these images were given as input to pre-trained deep learning models such as VGG16, VGG19, ResNet, DenseNet, MobileNet, and NasNetMobile. The data of each model is utilized to generate its feature vectors. Finally, feature vectors obtained from static pressure distribution images were classified by SVM (Support Vector Machine), K-NN (K-Nearest Neighbors), and ANN (Artificial Neural Network). In addition, a cross-validation method was used to examine the validity of the classifier.

RESULTS

The performance of the proposed models was evaluated with accuracy, sensitivity, specificity, and F1-measure criteria. The VGG19-SVM hybrid model showed the best performance with 95.12% acc, 94.91% sen, 95.31% spe, and 94.44% F1.

CONCLUSIONS

In this study, a specific and sensitive automatic test evaluation system was proposed for Ataxic syndromes using digital images to observe the motor skills of the subjects. Comparative results show that the proposed method can be applied in practice for ataxia that is clinically difficult to detect or not yet symptomatic. It can be defined using only static plantar pressure distribution in the early stage and it can be recommended as an assistant system to physicians in clinical practice.

The Refraction Assessment and the Electronic Trial Frame Measurement during Standing or Sitting Position Can Affect Postural Stability

Vision has been shown to influence body posture. The purpose of this study is to investigate the correlations between visual acuity and body postural control both in a standing and seated position. This cohort study included 37 patients examined using Adaptica’s (Italy) Kaleidos and VisionFit. Objective refraction was measured with Kaleidos both in a standing and seated position by the same operator and in the same environmental conditions. The parameters obtained with the device were binocular refraction, monocular refraction, pupil distance, pupil size, head tilt, gaze, phorias, and tropias. The results obtained were then subjectively tested using VisionFit: an electronic trial frame with phoropter functionalities. The study’s outcome revealed that the differences in the visual acuity parameters obtained in standing and seated positions were statistically significant; the Student’s t-test showed a p-value < 0.001 in all parameter averages. Automated refraction is widely being performed and postural control can affect the visual acuity parameters; therefore, it is relevant to consider the possibility of measuring in orthostatism. It might be appropriate to take into account the possibility of measuring in orthostatism and wearing trial frames in orthostatic conditions as well as walking freely around the room, looking outside of a window, sitting, and reading.

The Role of Walking Experience in the Emergence of Gait Harmony in Typically Developing Toddlers

The ability to walk without support usually develops in the first year of a typically developing toddler’s life and matures further in the following years. Mature walking is characterized by the correct timing of the different gait phases that make up a full gait cycle formed by stance, swing, and double support phases. The harmony of mature walking is given by a specific self-similar structure of the ratios between the durations of these phases (stride/stance, stance/swing, swing/double support), that in adults all converge to the golden ratio (phi, about 1.618). The aim of this longitudinal, prospective, experimental study was to investigate the evolution of this gait harmonic structure in the transition from supported to independent walking. In total, 27 children were recruited and recorded at various stages of locomotor development, ranging from neonatal stepping up to an independent walking experience of about six months. Differently from walking speed that progressively increased with age, the gait phase ratios started to converge to golden value only after the first independent steps, suggesting a relation to the maturation of the walking experience. The independent walking experience seems to represent a trigger for the evolution of a locomotor harmonic pattern in toddlers learning to walk.

Feasibility of a virtual reality-based exercise intervention and low-cost motion tracking method for estimation of motor proficiency in youth with autism spectrum disorder

Background

Motor impairment is widely acknowledged as a core feature in children with autism spectrum disorder (ASD), which can affect adaptive behavior and increase severity of symptoms. Low-cost motion capture and virtual reality (VR) game technologies hold a great deal of promise for providing personalized approaches to motor intervention in ASD. The present study explored the feasibility, acceptability and potential efficacy of a custom-designed VR game-based intervention (GaitWayXR™) for improving gross motor skills in youth with ASD.

Methods

Ten children and adolescents (10–17 years) completed six, 20-min VR-based motor training sessions over 2 weeks while whole-body movement was tracked with a low-cost motion capture system. We developed a methodology for using motion tracking data to quantify whole-body movement in terms of efficiency, synchrony and symmetry. We then studied the relationships of the above quantities with standardized measures of motor skill and cognitive flexibility.

Results

Our results supported our presumption that the VR intervention is safe, with no adverse events and very few minor to moderate side-effects, while a large proportion of parents said they would use the VR game at home, the most prohibitive reasons for adopting the system for home therapy were cost and space. Although there was little evidence of any benefits of the GaitWayXR™ intervention in improving gross motor skills, we showed several positive correlations between the standardized measures of gross motor skills in ASD and our measures of efficiency, symmetry and synchrony from low-cost motion capture.

Conclusions

These findings, though preliminary and limited by small sample size, suggest that low-cost motion capture of children with ASD is feasible with movement exercises in a VR-based game environment. Based on these preliminary findings, we recommend conducting larger-scale studies with methods for improving adherence to VR gaming interventions over longer periods.

An interventional exploratory study to assess the effect of footwear on postural stability and strategy during quiet standing

A stable quiet stance is achieved by controlling the relative position of the center of pressure and the vertical projection of the center of mass. The best postural performances include efficient strategies to mitigate external perturbations. Footwear impacts postural stability and strategy by affecting cutaneous proprioception and ankle proprioception in the case of heeled shoes. The purpose of this study was to quantify the effects of four common footwear conditions, i.e. barefoot, sports, flats, and heels, on postural stability and strategy during quiet standing of healthy young women. Postural stability and strategy were assessed overall and in the antero-posterior and medio-lateral directions using five parameters: total sway, average center of pressure (COP) velocity, α value computed using detrended fluctuation analysis, hip over ankle ranges of motion, and power of the COP time series. Significant differences with barefoot were consistently found when wearing heels, namely a decrease in postural sway and average COP velocity. Results seemed counter-intuitive as they indicate an apparent increase in postural stability when wearing heels. A deeper analysis revealed a more complex scheme. A potential tightening of the motion when wearing heels, combined with an increase of the neutral plantarflexion angle, shifts the postural strategy towards a predominant hip strategy. Finally, proprioception did not play a key role. This study highlighted the complexity of the multifactorial interactions between footwear characteristics and postural strategies. Additional work is needed to develop footwear that will enhance postural stability of populations at risk, such as pregnant women or the elderly.

Role of angular position of the seat in control of posture in response to external perturbation

Ability of the human body to regain balance after being externally perturbed is important in the maintenance of vertical posture. The goal of this study was to investigate trunk and leg muscle response to external perturbation while sitting on a stool with varying seat inclinations. Ten healthy subjects were required to receive a perturbation applied to the upper body while sitting on an adjustable stool with 0°, 10° forward or 10° backward inclination of the seat and without footrest and leg support. Electromyographic activities of the trunk and leg muscles and center of pressure displacements were recorded and analyzed during the anticipatory (APA) and compensatory (CPA) phases of postural control. APAs and CPAs were generated in response to an external perturbation. Delays in the onset of anticipatory muscle activity were seen when seated on the inclined seat compared to sitting on the horizontal seat (p < 0.05). To maintain balance after a perturbation, participants activated the trunk and thigh muscles, the activity of which was modulated to a greater degree than that of leg muscles. Moreover, they utilized co-contraction of muscles as the main mechanism of balance control in sitting. Furthermore, there was no effect of a seat inclination on COP displacements. The outcome provides a background for future investigations of the effect of seat inclination on control of balance in sitting.

Effects of resistance training on postural control in Parkinson's disease: a randomized controlled trial

BACKGROUND

Postural instability affects Parkinson's disease (PD) patients' postural control right from the early stages of the disease. The benefits of resistance training (RT) for balance and functional capacity have been described in the literature, but few studies have been conducted showing its effects on PD patients' postural control.

OBJECTIVE

To investigate the effects of a three-month RT intervention on static posturography (SP) measurements and clinical functional balance assessment among PD patients.

METHODS

Seventy-four patients were randomly assigned to a three-month RT intervention consisting of using weightlifting machines at a gym (gym group) or RT consisting of using free weights and elastic bands (freew group), or to a control group. The participants were evaluated at baseline, three months and six months. We evaluated changes of SP measurements under eyes-open, eyes-closed and dual-task conditions (primary endpoint), along with motor performance and balance effects by means of clinical scales, dynamic posturography and perceptions of quality of life (secondary endpoints).

RESULTS

There were no significant interactions in SP measurements among the groups. Unified Parkinson Disease Rating Scale (UPDRS-III) motor scores decreased in both RT groups (p<0.05). Better perceived quality of life for the mobility domain was reported in the gym group while functional balance scores improved in the freew group, which were maintained at the six-month follow-up (p<0.05).

CONCLUSIONS

This study was not able to detect changes in SP measurements following a three-month RT intervention. Both RT groups of PD patients showed improved motor performance, with positive balance effects in the freew group and better perceived quality of life in the gym group.

Gathering your 'sea legs': Extended durations in an offshore environment increases postural sway excursions

BACKGROUND

Mal de debarquement (MdD), or often called 'sea legs', is the perception of self-motion after exposure to passive movement such as being on a boat at sea. Previous studies highlight sensory re-organization difficulties and postural control impairments after disembarking from sea travel in experienced crew members. However, the impact of MdD in individuals with minimal offshore experience, defined as participating in less than 2 offshore excursions per year, has not been investigated.

RESEARCH QUESTION

Does exposure to boat motion while at sea alter static postural control after disembarking in individuals with minimal offshore experience?

METHODS

Healthy adults (n = 24) with minimal offshore experience had their static balance assessed on a force platform before (PRE) and after (POST) a 7-h deep sea fishing excursion. Static balance was tested in eyes open (EO), eyes closed (EC), eyes open on a foam surface (EOF), and eyes closed on a foam surface (ECF) conditions. Sway excursions, sway velocity and sway variability in the medial-lateral (ML) and anterior-posterior (AP) directions were computed and then compared PRE/POST using a paired t-test (p < 0.05).

RESULTS

Significant increases in ML sway excursion (p = 0.004), ML sway range (p < 0.001), ML sway variability (p < 0.001), AP sway excursion (p = 0.045), AP sway range (p = 0.020), and AP sway variability (p = 0.030) were observed at POST during EOF. Significant increases in ML sway excursion (p = 0.027), AP sway excursion (p = 0.020), and AP sway variability (p = 0.014) at POST were also observed during ECF. No differences were found in the EO condition (p > 0.05).

SIGNIFICANCE

Increases in postural sway excursion and variability were observed in individuals with minimal offshore experience after disembarking. Our findings suggest sensory re-organization difficulties in order to maintain an upright posture in challenging sensory conditions are dependent on vestibular and somatosensory inputs following exposure to boat motion at sea.

Prolonged Running Using Bionic Footwear Influences Lower Limb Biomechanics

The running biomechanics of unstable shoes have been well investigated, however, little is known about how traditional neutral shoes in combination with unstable design elements and scientifically (bionic) designed shoes influence prolonged running biomechanics. The purpose of this study was to investigate biomechanical changes for a typical 5 km run and how footwear technology may affect outcomes. Sixteen healthy male recreational heel strike runners participated in this study, and completed two prolonged running sessions (neutral shoe session and bionic shoe session), with 7 to 10 days interval between sessions. A two-way repeated-measures analysis of variance (ANOVA, shoe × time) was conducted to determine any differences in joint biomechanics. Main effects for shoe type were observed at the ankle, knee and hip joints during the stance phase. In particular, decreased range of motion (ROM) was observed using the bionic shoes for all three joints, and the joint moments also had significant changes except for the frontal plane of the hip. Main effects for time were also observed at the ankle, knee and hip joints. The ROM of the sagittal plane in the knee and hip decreased post-5 km running. The reduction of ankle dorsiflexion, hip flexion, hip adduction and hip internal rotation angles were observed post-5 km running, as well as the increase of ankle eversion and external rotation, knee adduction and internal rotation angles. The kinetics also exhibited significant differences between pre-5 km running and post-5 km running. The interaction effects only existed in the ROM of the hip sagittal plane, hip adduction angle and hip internal rotation angle. The results suggested that bionic shoes could be beneficial for strengthening muscle control, enhancing postural stability and proprioceptive ability. Footwear personalization could be a solution that benefits runners, reduces injury risk and improves running performance.

Bionic Footwear Effect to Lower Limb Locomotion in Biomechanical Analysis

Many scientific data have proven that regular wearing of high-heeled shoes adversely affects human health. Recent evidence suggested that bionic heels imitated hoofed animals have attracted widespread attention. However, few biomechanical studies have investigated the effects of bionic high-heeled footwear on the lower limbs. Accordingly, this study aimed to examine the impact of bionic high-heeled shoes (HHS) on the biomechanical characteristics of lower limbs by comparing kinematics and kinetics of walking in HHS and bionic flat-bottomed shoes (FBS). they find that when the subjects wore HHS, the loading is concentrated in the forefoot region for a much longer time. Couple with HHS lacks the cushioning effect of the complete sole, the sole has to rely only on plantar flexion and dorsiflexion of the ankle joint to cushion the impact force, which will undoubtedly increase the fatigue damage of the ankle joint. The unique split-toe structure balances the loading between the toes could reduce the risk of toes injury during walking. However, there are still risks of injury to the lower limbs of HHS, especially the ankle and knee joints.

Toe walking in children with cerebral palsy: a possible functional role for the plantar flexors

Equinus and toe walking are common locomotor disorders in children with cerebral palsy (CP) walking barefoot or with normal shoes. We hypothesized that, regardless of the type of footwear, the plantar flexors do not cause early equinus upon initial foot contact but decelerate ankle dorsiflexion during weight acceptance (WA). This latter action promoted by early flat-foot contact is hypothesized to be functional. Hence, we performed an instrumented gait analysis of 12 children with CP (Gross Motor Function Classification System class: I or II; mean age: 7.2 yr) and 11 age-matched typically developing children. The participants walked either barefoot, with unmodified footwear (4° positive-heel shoes), or with 10° negative-heel shoes (NHSs). In both groups, wearing NHSs was associated with greater ankle dorsiflexion upon initial foot contact, and greater tibialis anterior activity (but no difference in soleus activity) during the swing phase. However, the footwear condition did not influence the direction and amplitude of the first ankle movement during WA and the associated peak negative ankle power. Regardless of the footwear condition, the CP group displayed 1) early flattening of the foot and ample dorsiflexion (decelerated by the plantar flexors) during WA and 2) low tibialis anterior and soleus activities during the second half of the swing phase (contributing to passive equinus upon foot strike). In children with CP, the early action of plantar flexors (which typically decelerate the forward progression of the center of mass) may be a compensatory mechanism that contributes to the WA's role in controlling balance during gait.NEW & NOTEWORTHY Adaptation to walking in negative-heel shoes was similar in typically developing children and children with cerebral palsy: it featured ankle dorsiflexion upon initial contact, even though (in the latter group) the soleus was always spastic in a clinical examination. Hence, in children with cerebral palsy, the early deceleration of ankle dorsiflexion by the plantar flexors (promoted by early flattening of the foot, and regardless of the type of footwear) may have a functional role.

Neuromuscular performance of balance and posture control in childhood and adolescence

This study examined a potential age-dependency of both posture and stability (balance) control in children and adolescents in a healthy population. Body posture with open and closed eyes was examined for a total of 456 test persons (age 6.7–17.6 years. Posture parameters (posture index, upper body tilt, trunk tilt) were assessed in the sagittal plane. Additionally, the oscillation of the center of pressure with open and closed eyes was additionally analyzed in a sub-sample of 318 subjects.

Absolute values of stability control parameters changed significantly during childhood and adolescence for both boys (p = 0.005) and girls (p = 0.01). Relative changes of stability and posture parameters when closing the eyes did not change (p > 0.05) and were independent of age, gender or sports activity in healthy children and adolescents.

The shifting of the body segments towards each other, as a result of the loss of visual information, does not seem to be primarily responsible for the increase in COP fluctuation. This is a further indication that stability control and posture control are complex interdependent mechanisms whose interaction is not yet fully understood.

The Role of Footwear in the Pathogenesis of Hallux Valgus: A Proof-of-Concept Finite Element Analysis in Recent Humans and Homo naledi

Hallux valgus (HV), the bunion of the first metatarsophalangeal joint (MTPJ), bothers many adults. No consensus has been reached about the causes of HV, be it a hereditary, or acquired, or multifactorial disease. Nor has agreement been reached using MTPJ angle to assess HV based on X-ray because in most cases the assessment of MTPJ is not reliable as it depends on the posture during scanning. In this study, we assume that HV is predominately acquired and that shoe wearing per se is an important player in HV pathogenesis. To verify our hypothesis, a CT-based finite element (FE) model of the first MTPJ of fossil remains of bear-footed Homo naledi was created and compared to that of five contemporary shoe-wearing wrestlers (10 models from two scans at an interval of about 18 months) because Homo naledi's first MTPJ is an ideal model for non-shoe wearing with parallel sesamoid grooves. We developed the first MTPJ structure transformation method and created MTPJ joint capsule model for both Homo naledi and wrestlers. Constraint on the medial side of the first MTPJ capsule was set to simulate shoe-wearing conditions compared to the lack of medial constraint for barefooted conditions. Analysis of eight FE models of different angles for the first MTPJ of Homo naledi was performed by the first MTPJ transformation method and results showed that stress concentrated on the medial capsule of the first MTPJ in simulated shoe-wearing conditions, even at MTPJ angle of 0°. Increase in the first MTPJ angle further increased stress concentration on the medial side, and stress-growth relationship might reveal the causes of HV. We further developed a method to position the first MTPJ in wrestlers and created CT-based models at two time points. It was evident that the first MTPJ angle increased in all but one athlete, with a maximal increase of 4.03 degrees. This verifies our hypothesis that HV might be developed by wearing shoes. Further longitudinal studies with larger sample sizes are needed to additionally validate our results and determine the magnitude of the effects of shoe wearing on development and progression of HV.

Inter-trial phase coherence of visually evoked postural responses in virtual reality

Vision plays a central role in maintaining balance. When humans perceive their body as moving, they trigger counter movements. This results in body sway, which has typically been investigated by measuring the body’s center of pressure (COP). Here, we aimed to induce visually evoked postural responses (VEPR) by simulating self-motion in virtual reality (VR) using a sinusoidally oscillating “moving room” paradigm. Ten healthy subjects participated in the experiment. Stimulation consisted of a 3D-cloud of random dots, presented through a VR headset, which oscillated sinusoidally in the anterior–posterior direction at different frequencies. We used a force platform to measure subjects’ COP over time and quantified the resulting trajectory by wavelet analyses including inter-trial phase coherence (ITPC). Subjects exhibited significant coupling of their COP to the respective stimulus. Even when spectral analysis of postural sway showed only small responses in the expected frequency bands (power), ITPC revealed an almost constant strength of coupling to the stimulus within but also across subjects and presented frequencies. Remarkably, ITPC even revealed a strong phase coupling to stimulation at 1.5 Hz, which exceeds the frequency range that has generally been attributed to the coupling of human postural sway to an oscillatory visual scenery. These findings suggest phase-locking to be an essential feature of visuomotor control.

The feasibility of a split-belt instrumented treadmill running protocol with perturbations

Unexpected perturbations during locomotion can occur during daily life or sports performance. Adequate compensation for such perturbations is crucial in maintaining effective postural control. Studies utilising instrumented treadmills have previously validated perturbed walking protocols, however responses to perturbed running protocols remain less investigated. Therefore, the purpose of this study was to investigate the feasibility of a new instrumented treadmill-perturbed running protocol. Fifteen participants (age = 28 ± 3 years; height = 172 ± 9 cm; weight = 69 ± 10 kg; 60% female) completed an 8-minute running protocol at baseline velocity of 2.5 m/s (9 km/h), whilst 15 one-sided belt perturbations were applied (pre-set perturbation characteristics: 150 ms delay (post-heel contact); 2.0 m/s amplitude; 100 ms duration). Perturbation characteristics and EMG responses were recorded. Bland-Altman analysis (BLA) was employed (bias ± limits of agreement (LOA; bias ± 1.96*SD)) and intra-individual variability of repeated perturbations was assessed via Coefficients of Variation (CV) (mean ± SD). On average, 9.4 ± 2.2 of 15 intended perturbations were successful. Perturbation delay was 143 ± 10 ms, amplitude was 1.7 ± 0.2 m/s and duration was 69 ± 10 ms. BLA showed -7 ± 13 ms for delay, -0.3 ± 0.1 m/s for amplitude and -30 ± 10 ms for duration. CV showed variability of 19 ± 4.5% for delay, 58 ± 12% for amplitude and 30 ± 7% for duration. EMG RMS amplitudes of the legs and trunk ranged from 113 ± 25% to 332 ± 305% when compared to unperturbed gait. This study showed that the application of sudden perturbations during running can be achieved, though with increased variability across individuals. The perturbations with the above characteristics appear to have elicited a neuromuscular response during running.

Is virtual reality beneficial for dual-task gait training in patients with Parkinson's disease? A systematic review

This systematic review examined the evidence about the effects of virtual reality (VR) on dual-task gait training in Parkinson's disease (PD).

Lower limb joint motion and muscle force in treadmill and over-ground exercise

Background

Treadmill exercise is commonly used as an alternative to over-ground walking or running. Increasing evidence indicated the kinetics of treadmill exercise is different from that of over-ground. Biomechanics of treadmill or over-ground exercises have been investigated in terms of energy consumption, ground reaction force, and surface EMG signals. These indexes cannot accurately characterize the musculoskeletal loading, which directly contributes to tissue injuries. This study aimed to quantify the differences of lower limb joint angles and muscle forces in treadmills and over-ground exercises. 10 healthy volunteers were required to walk at 100 and 120 steps/min and run at 140 and 160 steps/min on treadmill and ground. The joint flexion angles were obtained from the motion capture experiments and were used to calculate the muscle forces with an inverse dynamic method.

Results

Hip, knee, and ankle joint motions of treadmill and over-ground conditions were similar in walking, yet different in running. Compared with over-ground running, joint motion ranges in treadmill running were smaller. They were also less affected by stride frequency. Maximum Gastrocnemius force was greater in treadmill walking, yet maximum Rectus femoris and Vastus forces were smaller. Maximum Gastrocnemius and Soleus forces were greater in treadmill running.

Conclusions

Treadmill exercise results in smoother joint kinematics. In terms of muscle force, treadmill exercise requires lower loading on knee extensor, yet higher loading on plantar flexor, especially on Gastrocnemius. The findings and the methodology can provide the basis for rehabilitation therapy customization and sophistic treadmill design.

Electronic supplementary material

The online version of this article (10.1186/s12938-019-0708-4) contains supplementary material, which is available to authorized users.

Contribution of vision and its age-related changes to postural stability in obstacle crossing during locomotion

BACKGROUND

Obstacle crossing requires sufficient toe clearance for trip and fall prevention for which postural stability is a prerequisite. It is thought that the upper visual field plays an important role in the maintenance of postural stability, but its influence and age-dependence have not been investigated yet.

RESEARCH QUESTION

What is the role of the visual fields in maintaining postural stability during crossing an obstacle in young and older adults?.

METHODS

This study included 14 young adults and 14 older adults. The participants, wearing an accelerometer and liquid crystal shutter goggles, were asked to cross an obstacle under the following three conditions (i) full vision; (ii) total visual field occlusion at two steps before the obstacle, and (iii) lower visual field occlusion at two steps before the obstacle. The root mean square ratio in the mediolateral direction (RMSR_ML) for the three sections (i.e., approach to the obstacle, lead limb crossing, and trail limb crossing), as well as the root mean square in the mediolateral direction (RMS_ML) for each section were calculated.

RESULTS

RMS_ML during lead limb crossing was significantly increased in older adults compared to young adults (p < 0.01). There was no significant main effect of visual condition and age group on RMSR_ML for the three steps.

SIGNIFICANCE

The study results suggest postural lateral instability in older adults with poor balance ability during lead limb crossing. Regardless of age, the peripheral visual information appears to contribute minimally to the maintenance of postural lateral stability at least from two steps before the obstacle, when the participants perceived the surrounding environment and the size of the obstacle while approaching it.

Acute Effects of Different Stretching Techniques on Lower Limb Kinematics, Kinetics and Muscle Activities during Vertical Jump

The purpose of this study was to examine the acute effects of different stretching techniques on performance and lower limb kinematics, kinetics and muscle activities during vertical jump in female aerobics athletes. 10 female college aerobics athletes participated in this study. Three-dimensional kinematic and kinetic data, as well as electromyography of rectus femoris, biceps femoris and gastrocnemius medialis were collected using Vicon motion analysis system, Kistler force plate and Wireless surface electromyographic system respectively during the test. No significant differences in jump height had been determined among these 3 warm-up methods. Hip peak flexion and internal rotation angles decreased significantly after BSM and peak adduction angle decreased significantly after SSM and BSM during landing. Knee peak flexion and internal rotation angles increased significantly after SSM and BSM during take-off. Also, BSM showed significantly greater peak flexion compared with SSM. Ankle peak plantarflexion angle increased significantly after BSM. In addition, BSM showed significantly greater improvement in the variation range than SSM except for the ankle int-external rotation. Existence of no significant differences in the peak value of vertical ground reaction force during take-off and landing phase had been determined among these 3 warm-up methods, and muscle activities of rectus femoris, biceps femoris and gastrocnemius medialis were likewise not significantly different. The results of this study suggest that it would be suitable for female aerobics athletes to perform ballistic stretching in warm-up in order to improve flexibility without decreasing the following vertical jumping event and may also reduce the risk of ankle sprain injury.

Do the center of mass strategies change with restricted vision during the sit-to-stand task?

BACKGROUND

The relationship between the visual sensory and center-of-mass characteristics during the sit-to-stand task is not well documented. Do the center of mass strategies change with restricted vision during the sit-to-stand task?

METHODS

The participants in this study were fifteen girls with congenital blindness (age (94.6 (5.6) months), mass (25.6 (2.0) kg), and height (1.3 (0.0) m)) and 30 healthy girls with no visual impairment who were divided randomly into two groups. The two experimental condition groups consisted of one in which the participants were assigned to keep their eyes open (age (95.8 (5.4) months), by mass (26.1 (5.1) kg), and by height (1.3 (0.0) m)) and the other in which the participants were assigned to keep their eyes closed (age (93.8 (0.0) months), by mass (24.2 (0.0) kg), and by height (1.1 (0.0) m)) for 20 min before the test. The center-of-mass displacement of the foot, leg, and thigh were calculated for dominance and non-dominance during the sit-to-stand performance at initiation, seat-off, and end events.

FINDINGS

Congenital blindness was associated with the non-dominant center-of-mass displacement of the foot increasing upwards during all events (initiation, p = 0.025; seat-off, p = 0.036; end, p = 0.034), as well the non-dominant center of mass of the foot moving anteriorly during the initiation point (p = 0.016). In addition, the center-of-mass displacements for the dominant and non-dominant feet (initiation, p = 0.006, and p = 0.016; seat-off, p = 0.006, and p = 0.014; end, p = 0.006, and p = 0.013, respectively) and legs (16.98%, p = 0.024, d = 0.95; and 17.88%, p = 0.032, d = 0.99, respectively) in the eyes-closed group shifted to a forward direction, and the center of mass of the non-dominant foot (initiation, p = 0.024; seat-off, p = 0.021; end, p = 0.012) moved significantly upwards. Furthermore, the whole body center of the mass velocity (anterior-posterior axis (initiation, p = 0.042; seat-off, p = 0.006; end, p = 0.005)) in the eyes-closed group was smaller than that in the eyes-open group.

INTERPRETATION

The findings show that the sit-to-stand center of the mass components in blind children may have clinical importance for the rehabilitation of these subjects.

The Determinants of the Preferred Walking Speed in Individuals with Obesity

BACKGROUND

The preferred walking speed (PWS), also known as the "spontaneous" or "self-selected" walking speed, is the speed normally used during daily living activities and may represent an appropriate exercise intensity for weight reduction programs aiming to enhance a more negative energy balance.

OBJECTIVES

The aim of this study was to examine, simultaneously, the energetics, mechanics, and perceived exertion determinants of PWS in individuals with obesity.

METHODS

Twenty-three adults with obesity (age 32.7 ± 6.8 years, body mass index 33.6 ± 2.6 kg/m2) were recruited. The participants performed 10 min of treadmill familiarization, and PWS was determined. Each subject performed six 5-min walking trials (PWS 0.56, 0.83, 1.11, 1.39, and 1.67 m/s). Gas exchanges were collected and analyzed to obtain the gross energy cost of walking (GCw), rated perceived exertion (RPE) was measured using a 6-20 Borg scale, and the external mechanical work (Wext) and the fraction of mechanical energy recovered by the pendular mechanism (Recovery) were computed using an instrumented treadmill. Second-order least-squares regression was used to calculate the optimal walking speed (OWS) of each variable.

RESULTS

No significant difference was found between PWS (1.28 ± 0.13 m/s) and OWS for GCw (1.28 ± 0.10 m/s), RPE cost of walking (1.38 ± 0.14 m/s), and Recovery (1.48 ± 0.27 m/s; p > 0.06 for all), but the PWS was significantly faster than the OWS for Wext (0.98 ± 0.56 m/s; p < 0.02). Multiple regression (r = 0.72; p = 0.003) showed that ∼52% of the variance in PWS was explained by Recovery, Wext, and height.

CONCLUSION

The main finding of this study was that obese adults may select their PWS in function of several competing demands, since this speed simultaneously minimizes pendular energy transduction, energy cost, and perceived exertion during walking. Moreover, recovery of mechanical work, external work, and height seem to be the major determinants of PWS in these individuals.

Examining the reliability, correlation, and validity of commonly used assessment tools to measure balance

OBJECTIVES

The Biodex SD Stability System has been shown to be a reliable assessment tool for postural stability. However, its ability to provide an accurate representation of balance has not been compared with functional performance measures such as the four-square step test (FSST) and timed-up-and-go test (TUG). The purpose of this study was to investigate reliability, internal consistency, and construct validity of FSST, TUG, and Biodex SD (limits of stability [LOS] and modified Clinical Test of Sensory Organization and Balance [m-CTSIB]).

METHODS

An observational reliability and validity study was conducted. A convenience sample of 105 healthy adults, 77 females and 28 males, mean age 24.5 years old (± 4.66 SD) performed balance assessments including the FSST, TUG, Biodex SD LOS, and m-CTSIB. For LOS, the overall percentage and test duration were recorded. For m-CTSIB, the overall Sway Index was recorded. Condition 1 of the m-CTSIB represented simple postural stability.

RESULTS

The Biodex SD LOS overall percentage, TUG, and FSST showed strong to excellent test-retest reliability (ICC [3, 1] = .83 [mean 1: 58.14, mean 2: 60.54], .88 [mean 1: 6.98 seconds, mean 2: 6.91 seconds], .92 [mean 1: 6.29 seconds, mean 2: 6.14 seconds], respectively), while the Biodex SD m-CTSIB overall percentage demonstrated strong test-retest reliability (ICC [3, 1] = .75 [mean 1: 1.18, mean 2: 1.18]). The LOS test duration showed moderate test-retest reliability (ICC [3, 1] = .58 [mean 1: 38.55 seconds, mean 2: 37.10 seconds]), while the m-CTSIB condition 1 showed poor test-retest reliability (ICC [3, 1] = .24 [mean 1: 0.63, mean 2: 0.66]). Weak construct validity was found between TUG, FSST, and Biodex SD measures of LOS and m-CTSIB (r values = -0.15-0.22).

CONCLUSION

It is suggested that clinicians use more than one measure to assess different aspects of a patient's balance deficits to better guide treatment and intervention.

Comparing functional dynamic normalization methods to maximal voluntary isometric contractions for lower limb EMG from walking, cycling and running

There is no consensus on the most appropriate method for normalizing an individual's electromyography (EMG) signals from walking, cycling and running in the same data collection. The aim of this study was to compare how the magnitude and repeatability of normalization values differ from three normalization methods and to compare their scaling effect in three moderate intensity activities. Three rounds of maximal voluntary isometric contractions (MVICs), sprint cycling and sprint running were performed to obtain normalization values for each method. EMG from five moderate intensity trials of walking, cycling and running were performed and normalized using each normalization value. Normalization values, coefficients of variation, and peak normalized EMG from the three moderate intensity activities were compared across normalization methods. Sprint running resulted in greater normalization values for 6/9 muscles. MVICs produced the lowest variance in 6/9 muscles. Comparing peak normalized signals of interest across normalization methods, there were significant differences in 6/9, 7/9 and 8/9 muscles for walking, cycling and running, respectively. When investigating a combination of walking, cycling and/or running EMG data, sprint running could be used for normalization, due to its simplicity and its ability to produce a larger normalization value, despite lower repeatability.

Targeted Athletic Training Improves the Neuromuscular Performance in Terms of Body Posture From Adolescence to Adulthood - Long-Term Study Over 6 Years

Poor posture in childhood and adolescence is held responsible for the occurrence of associated disorders in adult age. This study aimed to verify whether body posture in adolescence can be enhanced through the improvement of neuromuscular performance, attained by means of targeted strength, stretch, and body perception training, and whether any such improvement might also transition into adulthood. From a total of 84 volunteers, the posture development of 67 adolescents was checked annually between the age of 14 and 20 based on index values in three posture situations. 28 adolescents exercised twice a week for about 2 h up to the age of 18, 24 adolescents exercised continually up to the age of 20. Both groups practiced other additional sports for about 1.8 h/week. Fifteen persons served as a non-exercising control group, practicing optional sports of about 1.8 h/week until the age of 18, after that for 0.9 h/week. Group allocation was not random, but depended on the participants’ choice. A linear mixed model was used to analyze the development of posture indexes among the groups and over time and the possible influence of anthropometric parameters (weight, size), of optional athletic activity and of sedentary behavior. The post hoc pairwise comparison was performed applying the Scheffé test. The significance level was set at 0.05. The group that exercised continually (TR20) exhibited a significant posture parameter improvement in all posture situations from the 2nd year of exercising on. The group that terminated their training when reaching adulthood (TR18) retained some improvements, such as conscious straightening of the body posture. In other posture situations (habitual, closed eyes), their posture results declined again from age 18. The effect sizes determined were between η² = 0.12 and η² = 0.19 and represent moderate to strong effects. The control group did not exhibit any differences. Anthropometric parameters, additional athletic activities and sedentary behavior did not influence the posture parameters significantly. An additional athletic training of 2 h per week including elements for improved body perception seems to have the potential to improve body posture in symptom free male adolescents and young adults.

Analyzing the effect of an arch support functional insole on walking and jogging in young, healthy females

BACKGROUND AND OBJECTIVE

The aim of this study was to explore the effectiveness of arch support functional insoles to prevent metatarsalgia.

METHOD

Twenty-five healthy females participated in the study. A Vicon motion capture system was used to collect kinematics data of the lower limb. An AMTI force plate was used to record the vertical ground reaction force (GRF), and the Novel Pedar-X System was used to measure foot pressure while subjects wore normal insoles or functional insoles with an arch support during walking and jogging.

RESULTS

With the arch support functional insoles, the first metatarsal (FM) region's contact area was increased and the peak pressure and time-pressure integral of the FM and second and third metatarsal (SATM) were areas decreased. This suggests a lower risk of longitude stress injuries in these areas. The ankle dorsiflexion angle of jogging with the 'arch support functional insoles' (RF) and walking with the 'arch support functional insoles' (WF) were significantly increased at initial contact and the knee and hip flexion angle of RF and WF were reduced. The peak hip extension angle of WF and RF also declined. The vertical loading rate of RF was lower, which would be beneficial in reducing the risk of lower limb injuries during jogging.

CONCLUSIONS

The results demonstrate that arch support functional insoles can be used effectively to prevent and decrease pain and promote a suitable weight-bearing pattern in the foot for promoting the health of young females.

Detection of Infantile Movement Disorders in Video Data Using Deformable Part-Based Model

Movement analysis of infants' body parts is momentous for the early detection of various movement disorders such as cerebral palsy. Most existing techniques are either marker-based or use wearable sensors to analyze the movement disorders. Such techniques work well for adults, however they are not effective for infants as wearing such sensors or markers may cause discomfort to them, affecting their natural movements. This paper presents a method to help the clinicians for the early detection of movement disorders in infants. The proposed method is marker-less and does not use any wearable sensors which makes it ideal for the analysis of body parts movement in infants. The algorithm is based on the deformable part-based model to detect the body parts and track them in the subsequent frames of the video to encode the motion information. The proposed algorithm learns a model using a set of part filters and spatial relations between the body parts. In particular, it forms a mixture of part-filters for each body part to determine its orientation which is used to detect the parts and analyze their movements by tracking them in the temporal direction. The model is represented using a tree-structured graph and the learning process is carried out using the structured support vector machine. The proposed framework will assist the clinicians and the general practitioners in the early detection of infantile movement disorders. The performance evaluation of the proposed method is carried out on a large dataset and the results compared with the existing techniques demonstrate its effectiveness.

Short and Medium Latency Responses in Participants With Chronic Ankle Instability

CONTEXT

  The determinant role of medium latency responses (MLRs) during compensatory postural adjustments in postural stability and the lack of clarity about the mechanisms behind chronic ankle instability (CAI) sustain the hypothesis that these postural responses are impaired in this condition. However, to the best of our knowledge, no authors have assessed MLRs in patients with CAI; most of the research regarding compensatory postural adjustments has been directed at the timing of short latency responses (SLRs).

OBJECTIVE

  To evaluate bilateral compensatory postural responses, including SLRs and MLRs, in response to a unilateral simulated ankle-sprain mechanism in participants with CAI.

DESIGN

  Case-control study.

SETTING

  Laboratory.

PATIENTS OR OTHER PARTICIPANTS

  Twenty-four participants with CAI and 20 controls.

INTERVENTION(S)

  Bilateral electromyography of the peroneus longus (PL), peroneus brevis, tibialis anterior (TA), and soleus (SOL) muscles was collected during a unilateral sudden-inversion perturbation (30°).

MAIN OUTCOME MEASURE(S)

  Muscle-onset activations and magnitudes of SLRs and MLRs in the support and perturbed positions.

RESULTS

  Participants with CAI showed (1) later-onset activation of the TA and SOL in the uninjured limb and bilateral decreases in the magnitude of the TA MLR in the support position, (2) increased magnitude of the PL MLR in the uninjured limb in the support and perturbed positions, and (3) increased magnitude of the PL SLR and MLR in the injured limb in the perturbed position.

CONCLUSIONS

  Chronic ankle instability was associated with later TA and SOL activation in the uninjured limb and bilaterally decreased magnitude of the TA MLR in the support position.