Foot anatomy specialization for postural sensation and control

The effect of foot somatosensory loss in postural control during Functional reach test in patients with diabetic polyneuropathy: A controlled study

BACKGROUND

In patients with diabetic polyneuropathy (DPN), differences in postural control due to losing the lower limb somatosensory information were reported. However, it is still unclear by which mechanisms the dynamic postural instability is caused.

OBJECTIVES

This study aimed to investigate postural control differences and neuromuscular adaptations resulting from foot somatosensory loss due to DPN.

METHODS

In this controlled cross-sectional study, fourteen DPN patients and fourteen healthy controls performed the Functional Reach Test (FRT) as a dynamic task. The postural control metrics were simultaneously measured using force plate, motion capture system, and surface electromyography (sEMG). The main metrics including reach length (FR), FR to height ratio (FR/H), displacement of CoM and CoP, moment arm (MA), and arch height ratio. Also, kinematic (range of motion of ankle, knee, and hip joints), and sEMG metrics (latencies and root mean square amplitudes of ankle and hallux muscles) were measured. To compare variables between groups, the independent sample T-test for (normally distributed) and the Mann-Whitney U test (non-normally distributed) were used.

RESULTS

The subjects' reach length (FR), FR to height ratio, absolute MA, and displacement of CoM were significantly shorter than controls, while displacement of CoP was not significant. Arch height ratio was found significantly lower in DPN patients. We observed that CoM was lagging CoP in patients (MA = + 0.89) while leading in controls (MA = -1.60). Although, the muscles of patients showed significantly earlier activation, root mean square sEMG amplitudes were found similar. Also, DPN patients showed significantly less hip flexion, knee extension, and ankle plantar flexion.

CONCLUSIONS

This study presented that decreasing range of motion at lower limbs' joints and deterioration in foot function caused poor performance at motor execution during FRT in DPN patients.

Spatiotemporal Evolution of Toddlers' Regional Foot Pressure Distribution and Center of Pressure at Antero-Posterior Axis During Learning of Standing

We investigated quiet stance of newly standing toddlers every three months (trimesters) of their second year of life. Their anteroposterior center-of-pressure (CoPx) velocity and centroidal frequency (CFREQ: 2.36 ± 0.10 to 1.50 ± 0.11 Hz) decreased over time. Besides, mean pressures revealed a potential role-sharing of foot regions in learning and control aspects of standing, with hindfoot carrying the highest (23.89 ± 6.47 kPa) pressure while forefoot the lowest (10.26 ± 2.51 kPa). The highest CFREQ of pressure signal was at midfoot. Through regional CoPx, forefoot has manifested the highest CFREQ (2.10 ± 0.40 Hz) and 90% power frequency (90%PF), whereas hindfoot presented the lowest (CFREQ: 1.80 ± 0.33 Hz). CFREQ and 90%PF of pressure and regional CoPx significantly decreased throughout the trimesters.

Magnitude of flat foot and its associated factors among school-aged children in Southern Ethiopia: an institution-based cross-sectional study

BACKGROUND

Flat foot, also known as pes planus, is a common condition among primary school children and is a leading cause of all clinical visits related to foot problems worldwide. It can cause skeletal problems and joint misalignment. This study aimed to assess the magnitude of flat foot and its associated factors among public primary school children.

METHODS

An institutional-based cross-sectional study was conducted on 1072 school children aged 11 to 18 years. A structured questionnaire was used for data collection and the footprints were used to calculate the plantar arch index. Data were entered into Epi data version 4.6, and analyzed by STATA version 15. Bivariable and multivariable binary logistic regressions were conducted. Adjusted odds ratios (AORs) with corresponding 95% confidence intervals (CIs) were calculated. Statistical significance was declared at a P-value < 0.05.

RESULT

Out of 1022 participants, 105(10.27%) 95%CI: 8.5-12) had a flat foot. Being male (AOR = 2; 95%CI:1.22-3.30), living in highland altitude (AOR = 8.83; 95% CI: 4.64-16.79), living in midland altitude (AOR = 3.32;95% CI:1.75-6.29), living in an urban area (AOR = 2.42;95% CI:1.15-5.09), insufficient physical activity (AOR = 8.78;95% CI: 4.42-12.3), wearing closed-toe shoes (AOR = 2.33;95%CI:1.27-4.28), obesity (AOR = 6.30;95% CI:3.31-11.9), and foot pain (AOR = 3.52;95%CI:2.08-6.27) had a higher likelihood of flat foot as compared to their counterparts.

CONCLUSION

One in every ten children had a flat foot. Altitude, residence, sex, physical activity, foot pain, body mass index, and type of footwear were found to be factors statistically associated with flat foot. Integrated interventions for children to have sufficient physical activity, wearing sandals, maintaining a healthy body mass index, and flatfoot screening and monitoring are recommended.

Difference in the recruitment of intrinsic foot muscles in the elderly under static and dynamic postural conditions

Background

The effect of foot, especially intrinsic muscles, on postural control and its related mechanisms remain unclear due to the complex structure. Therefore, this study aims to investigate the activation of intrinsic foot muscles in the elderly under static and dynamic postural tasks.

Methods

Twenty-one elderly participants were included to perform different postural tests (sensory organization test (SOT), motor control test (MCT), limit of stability test (LOS), and unilateral stance test) by a NeuroCom Balance Manager System. The participants were instructed to maintain postural stability under conditions with combined different sensory inputs (vision, vestibular, and proprioception) in SOT as well as conditions with translation disturbance in MCT, and to perform an active weight-shifting tasks in LOS. During these tasks, muscle activation were simultaneously acquired from intrinsic foot muscles (abductor halluces (AbH) and flexor digitorum brevis (FDB)) and ankle muscles (anterior tibialis, medial head of gastrocnemius, lateral head of gastrocnemius, and peroneus longus). The root-mean-square amplitude of these muscles in postural tasks was calculated and normalized with the EMG activity in unilateral stance task.

Results

The activation of intrinsic foot muscles significantly differed among different SOT tasks (p < 0.001). Post-hoc tests showed that compared with that under normal condition 1 without sensory interference, EMGs increased significantly under sensory disturbance (conditions 2-6). By contrast, compared with that under the single-sensory disturbed conditions (conditions 2-4; 2 for disturbed vision, 3 for disturbed vestibular sensation, 4 for disturbed proprioception), activation was significantly greater under the dual-sensory disturbed postural tasks (conditions 5 and 6; 5 for disturbed vision and proprioception, 6 for disturbed vestibular sensation and proprioception). In MCT, EMGs of foot muscles increased significantly under different translation speeds (p < 0.001). In LOS, moderate and significant correlations were found between muscle activations and postural stability parameters (AbH, r = 0. 355-0.636, p < 0.05; FDB, r = 0.336-0.622, p < 0.05).

Conclusion

Intrinsic foot muscles play a complementary role to regulate postural stability when disturbances occur. In addition, the recruitment magnitude of intrinsic foot muscles is positively correlated with the limit of stability, indicating their contribution to increasing the limits of stability in the elderly.

Emerging role of bone scintigraphy single-photon emission computed tomography/computed tomography in foot pain management

Foot and ankle joints being weight-bearing joints are commonly subjected to wear and tear and are prone to traumatic and other pathologies. Most of these foot and ankle pathologies present with pain. The diagnosis of pathology and localization of pain generators is difficult owing to the complex anatomy of the foot and similar clinical presentation. This makes the management of foot pain clinically challenging. Conventional anatomical imaging modalities are commonly employed for evaluation of any anatomical defect; however, these modalities often fail to describe the functional significance of the anatomical lesions, especially in presence of multiple lesions which is common in ankle and foot; however, hybrid single-photon emission computed tomography/computed tomography (SPECT/CT) by virtue of its dual modalities, that is, highly sensitive functional imaging and highly specific anatomical imaging can serve as a problem-solving tool in patient management. This review attempts to describe the role of hybrid SPECT/CT in overcoming the limitation of conventional imaging and describes its potential application in the management of foot and ankle pain.

Three-Dimensional Analysis of the Windlass Mechanism Using Weightbearing Computed Tomography in Healthy Volunteers

BACKGROUND

The windlass mechanism (WM) increases the longitudinal arch of the foot via tension of the plantar aponeurosis during dorsiflexion of the metatarsophalangeal (MTP) joint. The purpose of this study was to perform a 3-dimensional evaluation of the displacement of each joint and the height of the navicular during dorsiflexion of the first MTP joint by using weightbearing computed tomography (CT).

METHODS

Participants were 6 men and 8 women with 23 healthy feet. CT of the foot with a load equivalent to the participant's body weight was performed. The first MTP joint was in the neutral position and dorsiflexed 30 degrees. Between the conditions, we measured the (1) rotation of each bone, (2) rotation of the distal bone with respect to the proximal bone at each joint, and (3) height of the navicular.

RESULTS

With respect to the tibia, the calcaneus was at 0.8 ± 0.7 degrees dorsiflexion and 1.4 ± 0.9 degrees inversion, while the talus was at 2.0 ± 1.2 degrees dorsiflexion and 0.1 ± 0.8 degrees eversion. The navicular was at 1.3 ± 1.2 degrees dorsiflexion and 3.2 ± 2.1 degrees inversion, whereas the medial cuneiform was at 0.3 ± 0.6 degrees plantarflexion and 1.3 ± 1.1 degrees inversion. At the talonavicular joint, the navicular was at 0.7 ± 1.3 degrees plantarflexion, whereas at the cuneonavicular joint, the medial cuneiform bone was at 1.4 ± 1.4 degrees plantarflexion. The height of the navicular increased by 1.1 ± 0.6 mm.

CONCLUSION

We 3-dimensionally confirmed the dynamics of WM and found that the calcaneus, navicular, and medial cuneiform moved in all 3 planes. The results suggest that the cuneonavicular joint has the greatest movement among the joints. We believe that these findings will help to elucidate the pathogenesis of WM-related diseases and lead to advances in treatments for pathologies involving the longitudinal arch.

LEVEL OF EVIDENCE

Level IV, case series.

The Rehabilitation Program Improves Balance Control in Children with Excessive Body Weight and Flat Feet by Activating the Intrinsic Muscles of the Foot: A Preliminary Study

BACKGROUND

determining the appropriate rehabilitation protocol is essential to influence the correction of flat feet, e.g., by activating the intrinsic muscles of the foot. Therefore, this study aimed to determine the impact of the exercises activating the intrinsic foot muscles for postural control in children with flat feet, with normal and excessive body weight.

METHODS

Fifty-four children aged 7 to 12 were enrolled in the research. Forty-five children were qualified for the final evaluation. Each child in the experimental group was demonstrated an appropriate technique for performing a short foot exercise without compensation by extrinsic muscle. The participants then performed a supervised short foot training session once a week and on other days of the week under the supervision of caregivers for 6 weeks. Flat feet were scored on the foot posture index scale. A postural test was evaluated with a Biodex balance system SD. Statistical significance in the foot posture index scale and postural test were evaluated using an analysis of variance (ANOVA) with Tukey's post-hoc test.

RESULTS

according to the six indices of the foot posture index scale, five indicators showed statistically significant improvement after rehabilitation. At the 8-12 platform mobility level, it was revealed that the excessive body weight group had significant improvements in the overall stability index and medio-lateral stability index, with eyes closed.

CONCLUSION

our results indicate that a 6-week rehabilitation program based on the activation of the intrinsic muscles of the foot resulted in an improvement in the foot position. This, in turn, affected balance control, especially in children with excess body weight in conditions of closed eyes.

Integrating ankle and hip strategies for the stabilization of upright standing: An intermittent control model

Even in unperturbed upright standing of healthy young adults, body sway involves concurrent oscillations of ankle and hip joints, thus suggesting to using biomechanical models with at least two degrees of freedom, namely, a double inverted pendulum (DIP) framework. However, in a previous study, it was demonstrated that the observed coordinated ankle-hip patterns do not necessarily require the independent active control of the two joints but can be explained by a simpler hybrid control system, with a single active component (intermittent, delayed sensory feedback of the ongoing sway) applied to the ankle joint and a passive component (stiffness control) applied to the hip joint. In particular, the proposed active component was based on the internal representation of a virtual inverted pendulum (VIP) that links the ankle to the current position of the global center of mass (CoM). This hybrid control system, which can also be described as an ankle strategy, is consistent with the known kinematics of the DIP and, in particular, with the anti-phase correlation of the acceleration profiles of the two joints. The purpose of this study is to extend the hybrid control model in order to apply to both the ankle and hip strategy, clarifying as well the rationale of mixed strategies. The extension consists of applying the hybrid control scheme to both joints: a passive stiffness component and an active intermittent component, based on the same feedback signals derived from the common VIP but with independent parameter gains for the two joints. Thus, the hip gains are null in the pure ankle strategy, the ankle gains are null in the pure hip strategy, and both ankle and hip gains are specifically tuned in mixed strategies. The simulation of such an extended model shows that it can reproduce both strategies; moreover, the pure ankle strategy is more robust than the hip strategy, because the range of variation (RoV) of the intermittent control gains is larger in the former case than in the latter, and the pure ankle strategy is also more energy efficient. Generally, the simulations suggest that there is no advantage to employ mixed strategies, except in borderline situations in which the control gains are just outside the RoV that provides stable control for either pure strategy: in this case, a stable mixed strategy can emerge from the combination of two marginally unstable pure strategies.

Influence of pregnancy related anthropometric changes on plantar pressure distribution during gait—A follow-up study

Background

As foot constitutes the base of support for the whole body, the pregnancy-related anthropometric changes can result in adaptive plantar pressure alterations. The present study aimed to investigate how pregnancy affects foot loading pattern in gait, and if it is related to body adjustments to growing foetus that occur in the course of pregnancy.

Methods

A prospective longitudinal study included 30 women. Three experimental sessions in accordance with the same procedure were carried out in the first, second and third trimesters of pregnancy. First, the anthropometric measures of the body mass and waist circumference were taken. Then walking trials at a self-selected speed along a ~6-m walkway were registered with the FreeMED force platform (Sensor Medica, Italy). Vertical foot pressure was recorded by the force plate located in the middle of the walkway.

Findings

The correlation of individual foot loading parameters across different trimesters was relatively high. Nevertheless, our results revealed a longitudinal foot arch flattening with the strongest effect in late pregnancy (P = 0.01). The anthropometric characteristics also influenced the foot loading pattern depending on the phase of pregnancy. In particular, arch flattening correlated with the body mass in all trimesters (r≥0.44, P≤0.006) while the medial-lateral loading index correlated only in the first (r = 0.45, P = 0.005) and second (r = 0.36, P = 0.03) trimesters. Waist circumference changes significantly influenced dynamic arch flattening but only in the late pregnancy (r≥0.46, P≤0.004). In the third trimester, a small though significant increase in the right foot angle was observed (P = 0.01).

Interpretation

The findings provided the characteristics of the relative foot areas loading throughout pregnancy. Growing abdominal size increases the risk of medial arch flattening, which can result in less stable gait. The observed increase in foot angle in late pregnancy may constitute a strategy to enhance gait stability.

Effectiveness of the Mat Pilates on the postural control, plantar pressure and plantar arch of school children: A randomized clinical trial

OBJECTIVE

To evaluate the effectiveness of Mat Pilates on postural control, plantar pressure and plantar arch (ALM) in schoolchildren.

DESIGN AND SETTING

The study was a randomized clinical trial, developed at the Early Childhood Education Institute, Londrina-PR. The participants were randomly assigned to groups: Pilates Group (PG) and Control Group (CG). Patients in the CG did not perform extra physical activity (Interventions).

PARTICIPANTS

43 children (eight to 12 years), no prior knowledge of the Pilates method, and no exercise training in the last six months.

INTERVENTION

The exercise program was based on the Mat Pilates method, twice weekly, 50 min each, 28 sessions.

OUTCOME MEASURES

Static balance (force platform), dynamic balance (the Reach Test), ALM (plantigraphy) and plantar pressure (baropodometry). The assessors were blinded to the allocation of participants.

RESULTS

Three children were excluded before randomization and 40 were randomized (PG n: 20; CG n:20).12 children were excluded during the protocol (PG n:7; CG n:5) and included in the intention to treat analysis. No significant difference between groups was observed for static and dynamic balance and ALM measures. There was a significant difference in the following outcomes for the PG: the plantar pressure on the right hemibody forefoot between pre-test 38.70 ± 14.38 and post-test 42.65 ± 15.63 (ES = 0.66; SRM = 0.50). The plantar pressure on the right hemibody rearfoot between pre-test 61.10 ± 14.18 and post-test 56.85 ± 19.39 (ES = 0.68; SRM = 0.53). No adverse or harmful events were reported in any group.

CONCLUSION

There were no differences in static and dynamic postural control and ALM between PG and CG. However, children GP showed improvement in some results of plantar pressure in relation CG.

CLINICAL TRIAL REGISTRATION NUMBER

Brazilian Registry of Clinical Trials (REBEC) (N_ RBR-8t5p7d).

Adjustments in the Range of Angular Motion during Walking after Amputation of the Toes: A Case Report

The forefoot plays an important role in providing body support and propulsion during walking. We investigated the effect of forefoot dysfunction on the gait pattern of a young adult with partial bilateral amputation of the toes. We measured our participant’s gait kinematics during barefoot and shod overground walking and analysed time-distance and joint range of motion (RoM) parameters against a group of healthy adults. Forefoot dysfunction gait is improved by footwear and walking experience; however, this improvement was still remarkably different (exceeded 95% CI) when compared to healthy gait at matching walking speed. Compared to healthy gait, walking barefoot had a slower speed and a 30% reduction in ankle and knee joint RoM, but a larger hip RoM. Shod gait resulted in a remarkable increase in ankle RoM and walking speed compared to barefoot gait. These results are consistent with the important role of the forefoot (tarsals and metatarsophalangeal joints) and suggest that footwear can facilitate gait function following toe amputation.

A Study on the Contribution of Medial and Lateral Longitudinal Foot Arch to Human Gait

This study aimed to investigate the contribution of medial longitudinal arch and lateral longitudinal arch in human gait and to study the correlation between foot features and gait characteristics. The foot arch plays a significant role in human movements, and understanding its contribution to spatiotemporal gait parameters is vital in predicting and rectifying gait patterns. To serve the objectives, the study developed a new foot feature measurement system and measured the foot features and spatiotemporal gait parameters of 17 young healthy subjects without any foot structure abnormality. The foot-feature parameters were measured under three movement conditions which were sitting, standing, and one-leg standing conditions. The spatiotemporal gait parameters were measured at three speeds which were fast, preferred, and slow speeds. The correlation study showed that medial longitudinal arch characteristics were found to be associated with temporal gait parameters while lateral longitudinal arch characteristics were found to be associated with spatial gait parameters. The developed system not only eases the burden of manual measuring but also secures accuracy of the collected data. Inviting variety of subjects including athletes and people with abnormal foot structures would extend the scope of this study in the future. The findings of this study break new ground in the field of the foot- and gait-related research work.Clinical Relevance-This study demonstrated that the medial longitudinal arch and lateral longitudinal arch characteristics were related to the temporal and spatial gait parameters, respectively. These underlying findings can be applied to investigate relationships between foot abnormality and gait characteristics.

Overpressure on fingertips prevents state estimation of the pen grip force and movement accuracy

We tested the hypothesis that the inability to move a pen accurately in a graphic task is partly due to a decrease of afferent somatosensory information resulting from overpressure on the tactile receptors of the fingers holding the pen. To disentangle the depressed somatosensory origin from an altered motor command, we compared a condition in which the participant actively produces pressure on the pen (active grip) with a condition in which pressure is passively applied (passive grip, no grip-related motor command). We expected that the response of the somatosensory cortex to electric stimulation of the wrist's tactile nerve (i.e., SEP) would be greater in the natural pen grip (baseline condition) than in the two overpressure conditions (actively or passively induced). Fifteen adults were required to trace a geometrical shape in the three grip conditions. The SEP amplitude was not significantly different between the baseline and both overpressure conditions. However, behavioral results showed that drawing accuracy is impaired when the pressure on the pen is increased (passively or actively). Cortical source analyses revealed that the activity of the superior parietal areas (SPL) increased in both overpressure conditions. Our findings suggest that the SPL is critical for sensorimotor integration, by maintaining an internal representation of pen holding. These cortical changes might witness the impaired updating of the finger-pen interaction force for such drawing actions under visual guidance.

Are foot deformity and plantar sensitivity impairment associated with physical function of community-dwelling older adults?

BACKGROUND

Foot deformities are highly prevalent in older adults and negatively impact their mobility and quality of life. However, the association between foot problems and physical function is still unclear.

OBJECTIVE

To investigate whether structural foot deformities and plantar tactile sensitivity are associated with lower extremity physical function impairment in community-dwelling older adults.

METHODS

We included 200 men and women aged 60 years and older from a community-based program. The foot assessment included toe deformities and calluses inspection and evaluation of plantar tactile sensitivity using monofilaments. The Short Physical Performance Battery (SPPB) was used to assess lower extremity physical function. We conducted a multivariate logistic regression analysis to investigate the association between foot problems and lower extremity physical function.

RESULTS

Hallux valgus was the most prevalent deformity among older adults. Those participants with reduced plantar tactile sensitivity (OR= 2.77; 95% CI: 1.38, 5.55) and a hallux valgus (OR= 2.23; 95% CI: 1.10, 4.52) were more likely to present poor lower extremity physical function.

CONCLUSION

Hallux valgus and impaired plantar sensitivity were associated with reduced lower extremity physical function in older adults. Further studies are necessary to identify this causality and to what extent management of these foot problems can improve general mobility and quality of life of older adults.

Foot Problems in Patients in Acute Care: A Point-Prevalence Survey

PURPOSE

Determine the prevalence of foot problems in an inpatient population and to describe demographic data, comorbid conditions, and type of footwear worn.

DESIGN

Observational point-prevalence cross-sectional design.

SUBJECTS AND SETTING

The study setting was a 722-bed licensed hospital in Western Australia. A convenience sampling was used to include adults hospitalized in the study setting during the period of data collection.

METHODS

A subset of foot questions, guided by a literature review, and input from foot, wound, diabetes, and psychometric researchers and clinicians, was incorporated into the hospital point-prevalence survey conducted annually for nursing safety and quality. Trained nurses collected data during the 1-day survey. Data were analyzed using descriptive statistics and 2-tailed tests; associations between study variables were analyzed.

RESULTS

Two hundred twenty-one patients participated in the survey; a majority (n = 193, 87%) self-reported at least 1 foot problem. More than half (n = 124) reported 3 foot problems and nearly one-third (n = 67) had 5 or more foot problems. Thick nails, damaged nails, and calluses and corns were the most frequently occurring foot problems. Older participants were more likely to have certain foot problems such as calluses and thick nails. Eleven (5%) participants were admitted to the hospital for a foot-related condition.

CONCLUSION

The majority of foot problems in our study were found to be minor and not the primary admitting diagnosis. However, even minor foot problems can pose a risk of worsening, especially in high-risk populations such as those with diabetes. Thus, detection is critical in overall patient assessment, and nurses play a critical role in assessment and management of minor foot problems through the delivery of skin and nail care and through collaboration with other professionals who provide specialized foot care.

The rise of the longitudinal arch when sitting, standing, and walking: Contributions of the windlass mechanism

The original windlass mechanism describes a one-to-one coupling between metatarsal joint dorsiflexion and medial longitudinal arch rise. The description assumes a sufficiently stiff plantar aponeurosis and absence of foot muscle activity. However, recent research calls for a broader interpretation of the windlass mechanism that accounts for an extensible plantar aponeurosis and active foot muscles. In this study, we investigate the rise of the arch in response to toe dorsiflexion when sitting, standing, and walking to discuss the windlass mechanism’s contributions in static and dynamic load scenarios. 3D motion analysis allowed a kinematic investigation of the rise and drop of the arch relative to the extent of toe dorsiflexion. The results suggest that static windlass effects poorly predict the relationship between arch dynamics and metatarsophalangeal joint motion during dynamic load scenarios, such as walking. We were able to show that toe dorsiflexion resulted in an immediate rise of the longitudinal arch during sitting and standing. In contrast, a decrease in arch height was observed during walking, despite toe dorsiflexion at the beginning of the push-off phase. Further, the longitudinal arch rose almost linearly with toe dorsiflexion in the static loading scenarios, while the dynamic load scenario revealed an exponential rise of the arch. In addition to that, the rate of change in arch height relative to toe motion was significantly lower when sitting and standing compared to walking. Finally, and most surprisingly, arch rise was found to correlate with toe dorsiflexion only in the dynamic loading scenario. These results challenge the traditional perspective of the windlass mechanism as the dominating source of foot rigidity for push-off against the ground during bipedal walking. It seems plausible that other mechanisms besides the windlass act to raise the foot arch.

Learned Overweight Internal Model Can Be Activated to Maintain Equilibrium When Tactile Cues Are Uncertain: Evidence From Cortical and Behavioral Approaches

Human adaptive behavior in sensorimotor control is aimed to increase the confidence in feedforward mechanisms when sensory afferents are uncertain. It is thought that these feedforward mechanisms rely on predictions from internal models. We investigate whether the brain uses an internal model of physical laws (gravitational and inertial forces) to help estimate body equilibrium when tactile inputs from the foot sole are depressed by carrying extra weight. As direct experimental evidence for such a model is limited, we used Judoka athletes thought to have built up internal models of external loads (i.e., opponent weight management) as compared with Non-Athlete participants and Dancers (highly skilled in balance control). Using electroencephalography, we first (experiment 1) tested the hypothesis that the influence of tactile inputs was amplified by descending cortical efferent signals. We compared the amplitude of P1N1 somatosensory cortical potential evoked by electrical stimulation of the foot sole in participants standing still with their eyes closed. We showed smaller P1N1 amplitudes in the Load compared to No Load conditions in both Non-Athletes and Dancers. This decrease neural response to tactile stimulation was associated with greater postural oscillations. By contrast in the Judoka's group, the neural early response to tactile stimulation was unregulated in the Load condition. This suggests that the brain can selectively increase the functional gain of sensory inputs, during challenging equilibrium tasks when tactile inputs were mechanically depressed by wearing a weighted vest. In Judokas, the activation of regions such as the right posterior inferior parietal cortex (PPC) as early as the P1N1 is likely the source of the neural responses being maintained similar in both Load and No Load conditions. An overweight internal model stored in the right PPC known to be involved in maintaining a coherent representation of one's body in space can optimize predictive mechanisms in situations with high balance constraints (Experiment 2). This hypothesis has been confirmed by showing that postural reaction evoked by a translation of the support surface on which participants were standing wearing extra-weight was improved in Judokas.

Added body mass alters plantar shear stresses, postural control, and gait kinetics: Implications for obesity

Context

Obesity is a growing global health concern. The increased body mass and altered mass distribution associated with obesity may be related to increases in plantar shear that putatively leads to physical functional deficits. Therefore, measurement of plantar shear may provide unique insights on the effects of body mass and body distribution on physical function or performance.

Purpose

1) To investigate the effects of body mass and distribution on plantar shear. 2) To examine how altered plantar shear influences postural control and gait kinetics.

Hypothesis

1) a weighted vest forward distributed (FV) would shift the center of pressure (CoP) location forward during standing compared with a weighted vest evenly distributed (EV), 2) FV would increase plantar shear spreading forces more than EV during standing, 3) FV would increase postural sway during standing while EV would not, and 4) FV would elicit greater compensatory changes during walking than EV.

Methods

Twenty healthy young males participated in four different tests: 1) static test (for measuring plantar shear and CoP location without acceleration, 2) bilateral-foot standing postural control test, 3) single-foot standing postural test, and 4) walking test. All tests were executed in three different weight conditions: 1) unweighted (NV), 2) EV with 20% added body mass, and 3) FV, also with 20% added body mass. Plantar shear stresses were measured using a pressure/shear device, and several shear and postural control metrics were extracted. Repeated measures ANOVAs with Holms post hoc test were used to compare each metric among the three conditions (α = 0.05).

Results

FV and EV increased both AP and ML plantar shear forces compared to NV. FV shifted CoP forward in single-foot trials. FV and EV showed decreased CoP range and velocity and increased Time-to-Boundary (TTB) during postural control compared to NV. EV and FV showed increased breaking impulse and propulsive impulse compared to NV. In addition, EV showed even greater impulses than FV. While EV increased ML plantar shear spreading force, FV increased AP plantar shear spreading force during walking.

Conclusion

Added body mass increases plantar shear spreading forces. Body mass distribution had greater effects during dynamic tasks. In addition, healthy young individuals seem to quickly adapt to external stimuli to control postural stability. However, as this is a first step study, follow-up studies are necessary to further support the clinical role of plantar shear in other populations such as elderly and individuals with obesity or diabetes.

Cutaneous and muscular afferents from the foot and sensory fusion processing: Physiology and pathology in neuropathies

The foot-sole cutaneous receptors (section 2), their function in stance control (sway minimisation, exploratory role) (2.1), and the modulation of their effects by gait pattern and intended behaviour (2.2) are reviewed. Experimental manipulations (anaesthesia, temperature) (2.3 and 2.4) have shown that information from foot sole has widespread influence on balance. Foot-sole stimulation (2.5) appears to be a promising approach for rehabilitation. Proprioceptive information (3) has a pre-eminent role in balance and gait. Reflex responses to balance perturbations are produced by both leg and foot muscle stretch (3.1) and show complex interactions with skin input at both spinal and supra-spinal levels (3.2), where sensory feedback is modulated by posture, locomotion and vision. Other muscles, notably of neck and trunk, contribute to kinaesthesia and sense of orientation in space (3.3). The effects of age-related decline of afferent input are variable under different foot-contact and visual conditions (3.4). Muscle force diminishes with age and sarcopenia, affecting intrinsic foot muscles relaying relevant feedback (3.5). In neuropathy (4), reduction in cutaneous sensation accompanies the diminished density of viable receptors (4.1). Loss of foot-sole input goes along with large-fibre dysfunction in intrinsic foot muscles. Diabetic patients have an elevated risk of falling, and vision and vestibular compensation strategies may be inadequate (4.2). From Charcot-Marie-Tooth 1A disease (4.3) we have become aware of the role of spindle group II fibres and of the anatomical feet conditions in balance control. Lastly (5) we touch on the effects of nerve stimulation onto cortical and spinal excitability, which may participate in plasticity processes, and on exercise interventions to reduce the impact of neuropathy.

Biomineralization at fluid interfaces

Biomineralization is of paramount importance for life on Earth. The delicate balance of physicochemical interactions at the interface between organic and inorganic matter during all stages of biomineralization resembles an extremely high complexity. The coordination of this sophisticated biological machinery and physicochemical scenarios is certainly a wonderful show of nature. Understanding of the biomineralization processes is still far from complete. The recent advances in biomineralization research from the Colloid and Interface Science perspective are reviewed herein. The synergy between this two fields of research is demonstrated. The unique opportunities offered by purposefully designed fluid interfaces, mainly Langmuir monolayers are presented. Biomedical applications of biomineral-based nanostructures are discussed, showing their improved biocompatibility and on-demand delivery features. A brief guide to the array of state-of-the-art experimental techniques for unraveling the mechanisms of biomineralization using fluid interfaces is included. In summary, the fruitful and exciting crossroad between Colloid and Interface Science with Biomineralization is exhibited.

Immediate Effects of Plantar Vibration on Fall Risk and Postural Stability in Stroke Patients: A Randomized Controlled Trial

BACKGROUND

Local vibration can improve balance problems of individuals with stroke when applied to the plantar region.

AIMS

This study aimed to determine the immediate effect of local vibration applied to the plantar region on fall risk and postural stability in patients with stroke.

STUDY DESIGN

Randomized controlled study.

METHODS

30 patients (23 male,7 female) with stroke were randomized to either vibration (n = 15; 58.47 ± 8.23 years) or control (n = 15; 58.27 ± 9.50 years) groups. Before and after the intervention, the patients were evaluated using a Biodex Balance System. Local vibration was applied to the plantar region of two feet in the supine position using a vibration device for a total of 15 min to the individuals in the vibration group. While the patients in the placebo group were in the supine position, the device was brought into contact and no vibration was applied to the plantar region of two feet for 15 min.

RESULTS

While significant improvements were observed in the postural stability and fall risk of the vibration group (p < 0.05), no significant change was observed in the placebo group (p > 0.05). Furthermore, significant improvements occurred in the SD values of the postural stability expressing postural oscillation in the vibration group (p < 0.05).

CONCLUSION

As a result of local vibration applied to the plantar region, immediate (within 5 min) significant improvements in postural stability and fall risk values were detected.

Plantar Myofascial Mobilization: Plantar Area, Functional Mobility, and Balance in Elderly Women: A Randomized Clinical Trial

OBJECTIVE

The purpose of this study was to evaluate the effects of plantar myofascial mobilization (PMM) on the plantar area, balance, and functional mobility of elderly women.

METHODS

In this randomized, single-blind, placebo-controlled clinical trial, elderly women with maintained independent orthostatism were recruited from the community and randomly separated into a PMM group (MG = 15), a placebo group (PG = 13), or a control group (control group = 14). Vigorous PMM and soft PMM were performed in the MG and PG, respectively, for 5 days with a rest day between each. The measures of plantar area, single leg stance test with open eye and closed eye, and timed up-and-go test were performed pre-PMM, immediately post-PMM, and on the last day of the protocol. The control group only underwent evaluation before and on the last day of the protocol. The sample size was calculated, and, for quantitative variables, a mixed analysis of variance was used for repeated measurements (split plot), followed by the Bonferroni post hoc test. The results were analyzed in 2 ways: 3 groups at 2 moments (pre, last day), and 2 groups at 3 moments (pre, post, last day).

RESULTS

Forty-two elderly women with mean age of 69.03 ± 3.32 years were included in the study. The vigorous MMP showed a statistically significant increase in the plantar area of the right foot (3 groups: P = .49) and single leg stance test with open eye time (2 groups: P = .002; 3 groups: P = .001), and a decrease in the timed up-and-go time (2 groups: P = .04; 3 groups: P = .0001).

CONCLUSION

The vigorous PMM showed increases of the plantar area and promoted beneficial effects on functional mobility and body balance.

Relationships between Foot Morphology and Foot Muscle Strength in Healthy Adults

The purpose of this study was to investigate if measurements of foot morphology in sitting and standing positions can predict foot muscle strength. Twenty-six healthy male adults were recruited, and their foot morphology and foot muscle strength were measured. Foot morphological variables, toe flexor strength, and metatarsophalangeal joint flexor strength were measured by using a digital caliper, Ailitech-AFG500 dynameter and metatarsophalangeal joint flexor strength tester, respectively. Partial correlation and multivariate stepwise regression were used to explore the relationships between foot morphology and toe/metatarsophalangeal joint strength. Results adjusted by age and body mass index were as follows: (1) truncated foot length in sitting and standing positions and foot width in standing position were positively correlated with the flexor strength of the first toe; (2) foot length, foot width, and truncated foot length in both positions were positively related to the flexor strength of the other toes; (3) arch height index in sitting position and differences in navicular height were negatively associated with the flexor strength of the other toes; (4) differences in foot width were negatively associated with metatarsophalangeal joint flexor strength; and (5) the multivariate stepwise regression model showed that truncated foot length in sitting position, navicular height in standing position, differences in navicular height, foot width in sitting position, and differences in foot width were significantly correlated with toe/metatarsophalangeal joint flexor strength. Simple measurements of foot morphological characteristics can effectively predict foot muscle strength. Preliminary findings provided practical implications for the improvement of the foot ability by making specific foot muscle training sessions in professional sports and by compensating the predicted muscle strength defects to prevent foot injury.

Pelvic movements during walking throughout gestation - the relationship between morphology and kinematic parameters

BACKGROUND

Many researchers emphasize adaptations following pregnancy. Our purpose was to get more insight into how morphology interacts with the pelvic walking pattern - the segment most prone to the adaptation following altered body demands.

METHODS

Thirty women were enrolled. Three experimental sessions were arranged according to the same protocol in the first, second and third trimesters of pregnancy. First, the anthropometric measures were taken, then walking trials at a self-selected speed were registered. At the end of the experimental session the subjects were asked to fill out a questionnaire on pain.

FINDINGS

The sagittal plane pelvic range of motion (RoM) significantly increased throughout pregnancy. There were significant positive correlations between pelvic anthropometric dimensions and pelvic tilt and rotation primarily in the third trimester of pregnancy. Significant positive correlations were found between pelvic RoM and thigh circumference. Indicators associated with body mass increase were positively correlated with pelvic obliquity in the second trimester and pelvic tilt and rotation in late pregnancy. It is also worth noting that the individual differences were not related to back pain and that the reported correlations were observed in some but not in all trimesters.

INTERPRETATION

Morphological changes following the fetus growth induced increased pelvic tilt and rotation, however, pelvis movements were not associated with back pain. Overall, the results highlight correlations between morphology and pelvis kinematic patterns in some but not in all trimesters.

Ankle muscles activation and postural stability with Star Excursion Balance Test in healthy individuals

INTRODUCTION

The ankle joint, a part of the kinetic chain of the lower limb, plays a significant role in the maintenance of postural stability during bipedal and unipedal balancing activities. This study aimed to evaluate the neuromuscular control of the ankle joint and the postural stability while executing the Star Excursion Balance Test (SEBT), by recording the EMG activity of the extrinsic ankle musculature and the displacement of the center of pressure (CoP).

METHODS

The EMG activity of the tibialis anterior (TA), the peroneus brevis (PB) and the medial and lateral gastrocnemius (GM, GL), along with the anteroposterior and mediolateral displacements (APd and MLd) of CoP as well as the plantar pressure distribution of the supportive lower limb were recorded during reaching to the eight directions of SEBT in 29 healthy, physically active college students (15 males and 14 females; mean ± SD of age 25.6 ± 4.5 yrs.; height: 172.5 ± 8.2 cm; body weight: 67.7 ± 13.6 kg; and BMI: 22.6 ± 2.9 kg/m²).

RESULTS

The tibialis anterior muscle demonstrated the greatest EMG activity during SEBT, followed by the PB, GL and GM muscles. The increased EMG activity of TA and PB during the execution of all posterior-oriented and lateral directions coincided with a decreased APd of CoP and increased reaching distances. The opposite occurred during the execution of all the anterior-oriented and medial directions. The differences among the directions of SEBT regarding the EMG activity of GL, GM and the mediolateral displacement of CoP were, in general, not significant.

CONCLUSIONS

The neuromuscular control of the ankle joint and the associated postural stability during SEBT was highly depended upon the activation level of TA and PB, which should be considered by clinicians and sports specialists when using this test for screening and/or rehabilitation purposes.

The Validity of an Oculus Rift to Assess Postural Changes During Balance Tasks

OBJECTIVE

To investigate whether shifts in head position, measured via an Oculus Rift head-mounted display (HMD), is a valid measure of whole-body postural stability.

BACKGROUND

The inverted single-link pendulum model of balance suggests shifts in whole-body center of mass can be estimated from individual body segments. However, whether head position describes postural stability such as center-of-pressure (COP) remains unclear.

METHOD

Participants (N = 10) performed six conditions while wearing an HMD and performing a previously validated virtual reality (VR)-based balance assessment. COP was recorded with a Wii Balance Board force plate (WBB), while an HMD recorded linear and angular head displacement. Visual input was presented in the HMD (stable scene, dark scene, or dynamic scene) and somatosensory information (with or without foam) was varied across each condition. The HMD time series data were compared with the criterion-measure WBB.

RESULTS

Significant correlations were found between COP measures (standard deviation, range, sway area, velocity) and head-centered angular and linear displacements (roll, pitch, mediolateral and anteroposterior directions).

CONCLUSIONS

The Oculus Rift HMD shows promise as a measure of postural stability without additional posturography equipment. These findings support the application of VR HMD technology for assessment of postural stability across a variety of challenging conditions.

APPLICATION

The human factors and ergonomic benefit of such an approach is in its portability, low cost, and widespread availability for clinic and home-based investigation of postural disturbances. Fall injury affects millions of people annually, so assessment of fall risk and treatment of the underlying causes has enormous public health benefit.

Thickness, cross-sectional area, and stiffness of intrinsic foot muscles affect performance in single-leg stance balance tests in healthy sedentary young females

The purpose of this study was to investigate the effect of thickness, cross-sectional area and stiffness of intrinsic foot muscles on performance in single-leg stance balance tasks in healthy sedentary young females. This study included a total of 40 healthy sedentary young females between the ages of 19 and 35 years. Single-leg stance balance assessments were carried out using Biodex Balance Systems (Biodex Medical Systems, Shirley, NY, USA). Performance in the single-leg stance balance tests was assessed using the overall stability index (OSI), mediolateral stability index (MLSI) and the anteroposterior stability index (APSI). Lower scores indicated better postural stability. Stiffness, thickness and cross-sectional area measurements of the abductor hallucis (AbH), flexor digitorum brevis (FDB) and flexor hallucis brevis (FHB) muscles were performed using an ultrasonography device. Larger AbH and FHB muscles were correlated with higher OSI, APSI, and MLSI (r = 0.31-0.46, p < 0.05), whereas larger FDB muscle was correlated with higher OSI and MLSI (r = 0.28-0.38, p < 0.05). Higher stiffness of the AbH and FHB muscles were correlated with lower OSI, APSI, and MLSI (r = -0.32 to 0.58, p < 0.05), but stiffness of the FDB muscle was not significantly correlated with OSI, APSI, and MLSI (r = 0.03-0.22, p ˃ 0.05). These results suggest that larger AbH, FDB and FHB muscles are related to reduced performance in single-leg stance balance tests, whereas higher AbH and FHB stiffness are related to better performance in single-leg stance balance tests in healthy sedentary young females.

Feet deformities and their close association with postural stability deficits in children aged 10-15 years

BACKGROUND

Children and young people make up an age group most vulnerable to falls. Various stability disorders may become instrumental in sustaining more frequent falls and resultant fractures. Correct morphological structure impacts overall efficiency of the foot, as well as offers significant diagnostic potential. Even minor foot disorders may affect the entire bio kinematic chain, also impacting the foot's motility. Structural alterations within a foot may also impair balance in the standing position, and contribute to more frequent injuries. The study aimed to assess the relationship between feet deformities and postural stability deficits in schoolchildren prone to sustain accidental falls.

METHODS

The study involved 200 children (101 girls and 99 boys) aged 10-15 years, randomly selected from primary schools. A 2D podoscan was used to assess the plantar part of the foot, while stabilometric examination was aided by the FreeMed dynamometric platform.

RESULTS

Correlation between respective variables was reflected by Spearman's rank coefficient. The subjects' age negatively correlated with the COP range of movement along the Y axis, and the COP surface area, while their BMI negatively correlated with the COP trajectory's length. Step regression analysis indicated that the width of the left foot, the left foot Wejsflog index, the left foot Clark's angle, the hallux valgus angle were the essential predictors of stabilometric variables in girls. In boys, though, predictive value was associated with Clarke's angle of the left and right foot, Wejsflog index of the right foot, and the width of both the left and right foot.

CONCLUSIONS

There is a statistically significant correlation between morphological variables of the foot and postural stability. When assessing the key variables of the foot and their interrelationship with postural stability, the Clarke's angle, Wejsflog index, hallux valgus angle, and foot width, should be granted due prominence in the girls. As regards the boys, the following variables were established as predictive in assessing postural stability: Clarke's angle, Wejsflog index, and foot width.

The Relationship Between Foot Feature Parameters and Postural Stability in Healthy Subjects

OBJECTIVE

Little has been explored about the disparate contribution of medial longitudinal arch (MLA) and lateral longitudinal arch (LLA) to human gait and postural stability. This study aims to investigate the correlation of foot feature parameters including both MLA and LLA with postural stability.

METHOD

Thirteen young and healthy subjects participated in this study. The newly developed FFMS extracted foot feature parameters in nonweight-bearing (NWB) and weight-bearing (WB) conditions along with postural stability parameters in single-leg-standing (SLS) condition. A bivariate correlation analysis was carried out to investigate the correlation between the foot characteristics and the postural stability parameters.

RESULTS

The foot length and width showed negative correlation with center of pressure (CoP) distance in medio-lateral (ML) and total direction, whereas the foot length in NWB and WB conditions, and the foot width in WB condition showed positive correlation with CoP distance in anterior-posterior (AP) direction. The height of the LLA curve and the area of the MLA were correlated with the postural stability parameters in AP direction. The ratios of the LLA height and area showed moderate correlation with the CoP distance in ML direction and total direction.

CONCLUSION

The size of a foot, such as the length and width, is correlated with postural stability. Whereas the MLA features are associated with postural stability in AP direction, the LLA features are associated with that in ML and total direction.

APPLICATION

The findings suggest that the roles and contributions of the MLA and LLA features in and to the postural control are different.

Less Than One Millimeter Under the Great Toe is Enough to Change Balance Ability in Elite Women Handball Players

Team handball is a complex intermittent sport game, which requires several motor abilities and effective postural control. Objective evaluation of stabilometric variables may be interesting to assess and improve functional parameters by postural control management. The purpose of the study was to evaluate the effects of a small additional thickness placed under the great toe (TUGT) on the Centre of Pressure (CoP) parameters in elite women handball players. Fourteen elite women handball players voluntarily participated in this study. Two conditions were compared: TUGT 0 (control) and TUGT 0.8 mm; four variables were computed from the CoP displacements. A paired T-test was performed for each variable. This study concludes that a low focal additional thickness placed under both great toes has an effect on the CoP measures used to assess postural control during an unperturbed stance. These results suggest that a low TUGT could contribute to a change in balance ability, and may be of clinical interest. This brings new perspectives in the management of athletes to prevent injury risk and optimize performance.

The effect of medial longitudinal arch height and medial longitudinal arch support insoles on postural balance in perimenopausal women

Background/aim

Changes in balance and postural control have been reported during the perimenopausal period. We investigated the effect of medial longitudinal arch height and medial arch support insoles on postural sway and balance in middle-aged perimenopausal women.

Materials and methods

29 women with normal arches and 29 women with low arches were included in the study. The foot arches of the participants were determined using the arch height index. The static balance index (SBI) measured by Kinesthetic Ability Trainer 3000 and functional reach test were used to evaluate postural balance. Measurements were obtained from all participants with and without medial arch support insoles.

Results

The SBI-total scores without the insoles were found to be significantly higher in the lower arch group than in the normal arch group. SBI-total, SBI-anteroposterior, and SBI-mediolateral scores significantly improved in the low arch group in the presence of insoles, whereas the usage of insoles resulted in no difference in the normal arch group. In the presence of insoles, the reach distances to left and right sides increased in both groups, while the forward functional reach distances decreased.

Conclusion

Medial longitudinal arch height and medial arch support insoles affect the balance parameters in perimenopausal women.

Assessing Plantar Sensation in the Foot Using the Foot Roughness Discrimination Test (FoRDT): A Reliability and Validity Study in Stroke

BACKGROUND

The plantar foot represents a sensory dynamometric map and is essential for balance and gait control. Sensory impairments are common, yet often difficult to quantify in neurological conditions, particularly stroke. A functionally oriented and quantifiable assessment, the Foot Roughness Discrimination Test (FoRDT), was developed to address these shortcomings.

OBJECTIVE

To evaluate inter- and intrarater reliability, convergent and discriminant validity of the FoRDT.

DESIGN

Test-retest design.

SETTING

Hospital outpatient.

PARTICIPANTS

Thirty-two people with stroke (mean age 70 years) at least 3 months after stroke, and 32 healthy, age-matched controls (mean age 70).

MAIN OUTCOME MEASURES

Roughness discrimination thresholds were quantified utilizing acrylic foot plates, laser cut to produce graded spatial gratings. Stroke participants were tested on three occasions, and by two different raters. Inter- and intrarater reliability and agreement were evaluated with Intraclass Correlation Coefficients and Bland-Altman plots. Convergent validity was evaluated through Spearman rank correlation coefficients (rho) between the FoRDT and the Erasmus modified Nottingham Sensory Assessment (EmNSA).

RESULTS

Intra- and interrater reliability and agreement were excellent (ICC =0.86 [95% CI 0.72-0.92] and 0.90 [95% CI 0.76-0.96]). Discriminant validity was demonstrated through significant differences in FoRDT between stroke and control participants (P < .001). Stroke fallers had statistically significant higher FoRDT scores compared with nonfallers (P = .01). Convergent validity was demonstrated through significant and strong correlations (rho) with the Erasmus MC Nottingham Sensory Assessment (r = .69, P < .01). Receiver operator characteristic curve analysis indicated the novel test to have excellent sensitivity and specificity in predicting the presence of self-reported sensory impairments. Functional Reach test significantly correlated with FoRDT (r = .62, P < .01) whereas measures of postural sway and gait speed did not (r = .16-.26, P > .05).

CONCLUSIONS

This simple and functionally oriented test of plantar sensation is reliable, valid, and clinically feasible for use in an ambulatory, chronic stroke and older population. It offers clinicians and researchers a sensitive and robust sensory measure and may further support the evaluation of rehabilitation targeting foot sensation.

LEVEL OF EVIDENCE

III.

Quiet standing: The Single Inverted Pendulum model is not so bad after all

In the study of balance and postural control the (Single) Inverted Pendulum model (SIP) has been taken for a long time as an acceptable paradigm, with the implicit assumption that only ankle rotations are relevant for describing and explaining sway movements. However, more recent kinematic analysis of quiet standing revealed that hip motion cannot be neglected at all and that ankle-hip oscillatory patterns are characterized by complex in-phase and anti-phase interactions, suggesting that the SIP model should be substituted by a DIP (Double Inverted Pendulum) model. It was also suggested that DIP control could be characterized as a kind of optimal bi-axial active controller whose goal is minimizing the acceleration of the global CoM (Center of Mass). We propose here an alternative where active feedback control is applied in an intermittent manner only to the ankle joint, whereas the hip joint is stabilized by a passive stiffness mechanism. The active control impulses are delivered to the ankle joint as a function of the delayed state vector (tilt rotation angle + tilt rotational speed) of a Virtual Inverted Pendulum (VIP), namely a pendulum that links the ankle to the CoM, embedded in the real DIP. Simulations of such DIP/VIP model, with the hybrid control mechanism, show that it can reproduce the in-phase/anti-phase interaction patterns of the two joints described by several experimental studies. Moreover, the simulations demonstrate that the DIP/VIP model can also reproduce the measured minimization of the CoM acceleration, as an indirect biomechanical consequence of the dynamic interaction between the active control of the ankle joint and the passive control of the hip joint. We suggest that although the SIP model is literally false, because it ignores the ankle-hip coordination, it is functionally correct and practically acceptable for experimental studies that focus on the postural oscillations of the CoM.

Supplementary Motor Area and Superior Parietal Lobule Restore Sensory Facilitation Prior to Stepping When a Decrease of Afferent Inputs Occurs

The weighting of the sensory inputs is not uniform during movement preparation and execution. For instance, a transient increase in the transmission to the cortical level of cutaneous input ~700 ms was observed before participants initiated a step forward. The sensory facilitation occurred at a time when feet cutaneous information is critical for setting the forces to be exerted onto the ground to shift the center of mass toward the supporting side prior to foot-off. Despite clear evidence of task-dependent modulation of the early somatosensory signal transmission, the neural mechanisms are mainly unknown. One hypothesis suggests that during movement preparation the premotor cortex and specifically the supplementary motor area (SMA) can be the source of an efferent signal that facilitates the somatosensory processes irrespectively of the amount of sensory inputs arriving at the somatosensory areas. Here, we depressed mechanically the plantar sole cutaneous transmission by increasing pressure under the feet by adding an extra body weight to test whether the task-dependent modulation is present during step preparation. Results showed upregulation of the neural response to tactile stimulation in the extra-weight condition during the stepping preparation whereas depressed neural response was still observed in standing condition. Source localization indicated the SMA and to a lesser extent the superior parietal lobule (SPL) areas as the likely origin of the response modulation. Upregulating cutaneous inputs (when mechanically depressed) at an early stage by efferent signals from the motor system could be an attempt to restore the level of sensory afferents to make it suitable for setting the anticipatory adjustments prior to step initiation.

Influence of rearfoot alignment on static and dynamic postural stability

Background/Aims:

It has been postulated that foot alignment affects postural stability. However, previous studies reported contradicting results regarding the association between foot alignment and postural stability.

Methods:

A total of 216 healthy participants aged 15 to 24 years were recruited. Their rearfoot alignment was measured in non-weight bearing and weight-bearing positions. Their static balance was assessed using Balance Error Scoring System and dynamic balance by Star Excursion Balance Test. The relationship between the data obtained were analysed using SPSS version 22 software.

Findings:

A Pearson correlation with a 95% confidence interval reported that there was: (i) no significant difference in the rearfoot alignment between both genders; (ii) no significant relationship between the rearfoot alignment measured in prone lying and unilateral stance position; (iii) a weak negative correlation between the rearfoot alignment measured in prone lying position to dynamic balance on medial, posterior, lateral, anterolateral and posteromedial direction; (iv) no significant relationship between the rearfoot alignment measured in unilateral stance position to both static and dynamic postural balance.

Conclusions:

Rearfoot alignment measured in non-weight bearing position plays some role in postural stability and therefore should be considered in sports rehabilitation. However, this can be overlooked in rehabilitation for individuals whose postural stability is not the primary concern.

Firing properties of muscle spindles supplying the intrinsic foot muscles of humans in unloaded and freestanding conditions

We recently developed an approach for recording from muscle spindles in the intrinsic muscles of the foot in freestanding humans by inserting a tungsten microelectrode into the posterior tibial nerve behind the medial malleolus of the ankle. Here we characterize the behavior of muscle spindles in the small muscles of the foot in 1) seated subjects with the leg horizontal and the foot naturally plantarflexed and 2) standing subjects. In the first study, recordings were made from 26 muscle spindle afferents located within flexor digiti minimi brevis ( n = 4), abductor digiti minimi ( n = 3), quadratus plantae ( n = 3), plantar interossei ( n = 4), flexor digitorum brevis ( n = 3), dorsal interossei ( n = 2), and lumbricals ( n = 2), with one each supplying abductor hallucis, adductor hallucis, and flexor hallucis brevis. The identity of another two muscle afferents was unknown. The majority of the units were silent at rest, only seven (27%) being spontaneously active. Because of the anatomic constraints of the foot, some spindles supplying muscles acting on the toes responded to movements of one or more digits. In the second study, 12 muscle spindle afferents were examined during standing. The ongoing discharge of eight spindle afferents covaried with changes in the center of pressure during postural sway. We conclude that the majority of spindle endings in the small muscles of the foot are silent at rest, which may allow them to encode changes in conformation of the foot when it is loaded during standing. Moreover, these muscle spindle afferents can provide useful proprioceptive information during standing and postural sway. NEW & NOTEWORTHY We have characterized the firing properties of muscle spindles in the intrinsic muscles of the human foot for the first time. The majority of the spindle endings are silent in seated subjects, and most fire tonically during standing, their discharge covarying with center of pressure during postural sway. We conclude that spindle endings in the intrinsic muscles of the foot provide useful proprioceptive information during free standing.

Foot typology, body weight distribution, and postural stability of adolescent elite soccer players: A 3-year longitudinal study

Objective

The unique foot morphology and distinctive functions facilitate complex tasks and strategies such as standing, walking, and running. In those weight-bearing activities, postural stability (PS) plays an important role. Correlations among foot type, PS, and other musculoskeletal problems that increase sport injury risk are known. However, long-term associations among the foot type, the PS, and body weight (BW) distribution are lacking. Thus, the purpose of this study was to longitudinally identify changes in foot morphology, PS, and symmetry in BW distribution during adolescence among elite male soccer players.

Methods

Thirty-five Czech elite male soccer players (age, 15.49 ± 0.61 years; BW, 64.11 ± 6.16 kg; body height, 174.62 ± 5.71 cm) underwent foot type, PS, and BW distribution measurements during 3 consecutive years (T1, T2, T3). The Chippaux-Smirak index (CSI), BW distribution, and centre of pressure (COP) displacement (total traveled way [TTW]) of each player for the preferred (PL) and non-preferred leg (NL) were acquired. Repeated-measures analysis of variance (RM ANOVA), Bonferroni´s post hoc tests, and partial eta-squared (η_p²) coefficient were used for investigating the effect of time on selected variables and effect size evaluation.

Results

Statistically significant effect of time on CSI values (PL: F_2,68 = 5.08, p < 0.01, η_p² = 0.13 and NL: F_2,68 = 10.87, p < 0.01, η_p² = 0.24) and COP displacement values (PL: F_2,68 = 5.07, p <0.01, η_p² = 0.13; NL: F_2,68 = 3.53, p <0.05, η_p² = 0.09) for both legs over 3-years period was identified. Furthermore, the Bonferroni´s post hoc analysis revealed a significant improvement of PS values in the PL (TTW_T1 = 1617.11 ± 520.22 mm vs. TTW_T2 = 1405.29 ± 462.76, p < 0.05; and between TTW_T1 = 1617.11 ± 520.22 mm vs. TTW_T3 = 1370.46 ± 373.94, p < 0.05). Only BW distribution parameter showed no significant differences, although slightly improved over time.

Conclusions

We observed changes in foot typology, PS, and BW distribution in young elite male soccer players during 3 consecutive years. Results demonstrated that changes in PS and body weight distribution under the high-load sport conditions during adolescence may improve with aging, except for foot morphology. Therefore, foot morphology should be carefully monitored to minimize sport injury risk in professional young soccer players during adolescence. Further research is necessary to determine more clear associations between these parameters, soccer-related injuries, and sport performances.

Vestibular-Evoked Responses Indicate a Functional Role for Intrinsic Foot Muscles During Standing Balance

Maintaining standing balance involves multisensory processing and integration to produce dynamic motor responses. Electrical vestibular stimulation (EVS) delivered over the mastoid processes can be used to explore the vestibular control of balance. The purpose of this study was to determine whether intrinsic foot muscles exhibit vestibular-evoked balance responses and to characterize the traits associated with these responses. Electromyography (EMG) of the abductor hallucis (AH), abductor digiti minimi (ADM) and medial gastrocnemius (MG) and anterior-posterior (AP) forces were sampled while quietly standing participants were subjected to a random continuous EVS signal (peak-to-peak amplitude = ±3 mA). The relationship between EVS input and motor output was characterized in both the frequency (coherence) and time (cumulant density) domains. When head orientation was rotated in yaw from left to right, the biphasic cumulant density function was inverted for all muscle (EVS-EMG) and whole-body (EVS-AP forces) balance responses. When vision was occluded, the EVS-EMG and EVS-AP forces coherence function amplitude increased at low frequencies (<2 Hz) and was accompanied by a heightened medium-latency peak amplitude for all muscles as well as the whole-body balance response (AP forces) compared to when static visual cues were present. The enhanced coherence amplitudes at lower frequencies may highlight a mechanism for the increase in postural sway from vision to occluded vision. The current findings indicate that the vestibular control of standing balance can be represented by the intrinsic foot muscles and implicate a postural role for these muscles in modulating quiet standing.

Human Postural Control

From ancient Greece to nowadays, research on posture control was guided and shaped by many concepts. Equilibrium control is often considered part of postural control. However, two different levels have become increasingly apparent in the postural control system, one level sets a distribution of tonic muscle activity (“posture”) and the other is assigned to compensate for internal or external perturbations (“equilibrium”). While the two levels are inherently interrelated, both neurophysiological and functional considerations point toward distinct neuromuscular underpinnings. Disturbances of muscle tone may in turn affect movement performance. The unique structure, specialization and properties of skeletal muscles should also be taken into account for understanding important peripheral contributors to postural regulation. Here, we will consider the neuromechanical basis of habitual posture and various concepts that were rather influential in many experimental studies and mathematical models of human posture control.

Detection of surface-EMG activity from the extensor digitorum brevis muscle in healthy children walking

OBJECTIVE

The purpose of the study was the assessment of activation patterns of the extensor digitorum brevis (EDB) muscle in healthy children, during walking at self-selected speed and cadence.

APPROACH

To this end, statistical gait analysis was performed on surface electromyographic (sEMG) signals of the EDB, in a large number (hundreds) of strides per subject. sEMG data from the tibialis anterior (TA) and gastrocnemius lateralis (GL) were also investigated for comparative purposes.

MAIN RESULTS

Results from 23 healthy children showed a large variability in the number of muscle activations, occurrence frequency, and onset-offset instants across considered strides. The assessment of different modalities of muscle activation allowed the identification of a single activity pattern, common to all the modalities and we were able to characterize the behavior of the EDB during the gait of healthy children. The pattern of EDB activity centered in two main regions of the gait cycle: in the second half of the stance phase (detected in 100% of subjects) and in the final swing phase (50%). Comparison with the TA and GL regions of activity suggested that the EDB and TA worked mainly as antagonist muscles for the ankle joint, while the EDB and GL did not oppose each other in action, but acted in synergy for the control of the ankle joint during walking.

SIGNIFICANCE

The 'Normality' pattern for the EDB activity reported here represents the first attempt to develop a reference for dynamic sEMG of the EDB in healthy children, enabling us to include the physiological variability of the phenomenon. Present results could be useful for discriminating physiological and pathological behavior in children and for deepening the maturation of the gait.

Foot and Ankle Joint Biomechanical Adaptations to an Unpredictable Coronally Uneven Surface

Coronally uneven terrain, a common yet challenging feature encountered in daily ambulation, exposes individuals to an increased risk of falling. The foot-ankle complex may adapt to improve balance on uneven terrains, a recovery strategy which may be more challenging in patients with foot-ankle pathologies. A multisegment foot model (MSFM) was used to study the biomechanical adaptations of the foot and ankle joints during a step on a visually obscured, coronally uneven surface. Kinematic, kinetic and in-shoe pressure data were collected as ten participants walked on an instrumented walkway with a surface randomly positioned ±15 deg or 0 deg in the coronal plane. Coronally uneven surfaces altered hindfoot–tibia loading, with more conformation to the surface in early than late stance. Distinct loading changes occurred for the forefoot–hindfoot joint in early and late stance, despite smaller surface conformations. Hindfoot–tibia power at opposite heel contact (@OHC) was generated and increased on both uneven surfaces, whereas forefoot–hindfoot power was absorbed and remained consistent across surfaces. Push-off work increased for the hindfoot–tibia joint on the everted surface and for the forefoot–hindfoot joint on the inverted surface. Net work across joints was generated for both uneven surfaces, while absorbed on flat terrain. The partial decoupling and joint-specific biomechanical adaptations on uneven surfaces suggest that multi-articulating interventions such as prosthetic devices and arthroplasty may improve ambulation for mobility-impaired individuals on coronally uneven terrain.

The Bobath concept - a model to illustrate clinical practice

Background and purpose: The model of Bobath clinical practice provides a framework identifying the unique aspects of the Bobath concept in terms of contemporary neurological rehabilitation. The utilisation of a framework to illustrate the clinical application of the Bobath concept provides the basis for a common understanding with respect to Bobath clinical practice, education, and research. The development process culminating in the model of Bobath clinical practice is described. Case description: The use of the model in clinical practice is illustrated using two cases: a client with a chronic incomplete spinal cord injury and a client with a stroke. Discussion: This article describes the clinical application of the Bobath concept in terms of the integration of posture and movement with respect to the quality of task performance, applying the Model of Bobath Clinical Practice. Facilitation, a key aspect of Bobath clinical practice, was utilised to positively affect motor control and perception in two clients with impairment-related movement problems due to neurological pathology and associated activity limitations and participation restrictions - the outcome measures used to reflect the individual clinical presentation. Implications for Rehabilitation The model of Bobath clinical practice provides a framework identifying the unique aspects of the Bobath-concept. The model of Bobath clinical practice provides the basis for a common understanding with respect to Bobath clinical practice, education, and research. The clinical application of the Bobath-concept highlights the integration of posture and movement with respect to the quality of task performance. Facilitation, a key aspect of Bobath clinical practice, positively affects motor control, and perception.

Foot Placement Characteristics and Plantar Pressure Distribution Patterns during Stepping on Ground in Neonates

Stepping on ground can be evoked in human neonates, though it is rather irregular and stereotyped heel-to-toe roll-over pattern is lacking. Such investigations can provide insights into the role of contact- or load-related proprioceptive feedback during early development of locomotion. However, the detailed characteristics of foot placements and their association with motor patterns are still incompletely documented. We elicited stepping in 33 neonates supported on a table. Unilateral limb kinematics, bilateral plantar pressure distribution and EMG activity from up to 11 ipsilateral leg muscles were recorded. Foot placement characteristics in neonates showed a wide variation. In ~25% of steps, the swinging foot stepped onto the contralateral foot due to generally small step width. In the remaining steps with separate foot placements, the stance phase could start with forefoot (28%), midfoot (47%), or heel (25%) touchdowns. Despite forefoot or heel initial contacts, the kinematic and loading patterns markedly differed relatively to toe-walking or adult-like two-peaked vertical force profile. Furthermore, while the general stepping parameters (cycle duration, step length, range of motion of proximal joints) were similar, the initial foot contact was consistently associated with specific center-of-pressure excursion, range of motion in the ankle joint, and the center-of-activity of extensor muscles (being shifted by ~5% of cycle toward the end of stance in the "heel" relative to "forefoot" condition). In sum, we found a variety of footfall patterns in conjunction with associated changes in motor patterns. These findings suggest the potential contribution of load-related proprioceptive feedback and/or the expression of variations in the locomotor program already during early manifestations of stepping on ground in human babies.

Feet deformities are correlated with impaired balance and postural stability in seniors over 75

Objective

Understanding the factors and mechanisms that determine balance in seniors appears vital in terms of their self-reliance and overall safety. The study aimed to determine the relationship between the features of feet structure and the indicators of postural stability in the elderly.

Methods

The study group comprised 80 seniors (41F, 39M; aged 75–85 years). CQ-ST podoscope and the CQ-Stab 2P two-platform posturograph were used as primary research tools. The data were analyzed based on Spearman’s rank correlation and forward stepwise regression.

Results

Analysis of forward stepwise regression identified the left foot length in females and Clarke’s angle of the left foot in men as significant and independent predictors of postural up to 30% of the variance of dependent variables.

Conclusions

Longer feet provide older women with better stability, whereas in men, the lowering of the longitudinal arch results in postural deterioration. In the elderly, the left lower limb shows greater activity in the stabilizing processes in the standing position than the right one. In gerontological rehabilitation special attention should be paid to the individually tailored, gender-specific treatment, with a view to enhancing overall safety and quality of seniors’ lives.

Recent Developments in the Treatment of Ankle and Subtalar Instability

It was nearly a centenary ago that severe ankle sprain was recognized as an injury of the ankle ligament(s). With the recent technological advances and tools in imaging and surgical procedures, the management of ankle sprains - including subtalar injuries - has drastically improved. The repair or reconstruction of ankle ligaments is getting more anatomical and less invasive than previously. More specifically, ligamentous reconstruction with tendon graft has been the gold standard in the management of severely damaged ligament, however, it does not reproduce the original ultrastructure of the ankle ligaments. The anatomical ligament structure of a ligament comprises a ligament with enthesis at both ends and the structure should also exhibit proprioceptive function. To date, it remains impossible to reconstruct a functionally intact and anatomical ligament. Cooperation of the regenerative medicine and surgical technology in expected to improve reconstructions of the ankle ligament, however, we need more time to develop a technology in reproducing the ideal ligament complex.

Age- and sex-associated morphological variations of metatarsal torsional patterns in humans

It has been demonstrated that the torsional patterns of the metatarsal heads are associated with the presence or absence of the medial longitudinal arch in hominoid feet. The relatively untwisted second metatarsal is unique in humans, but that of the African apes is much more inverted, suggesting that the torsion of the second metatarsal might represent the overall shape and flatness of the foot. Some clinical studies have recently argued that the onset of foot pathologies such as hallux valgus might be related to the torsional pattern of the metatarsals. However, to date, no studies have systematically investigated the morphological variations of the torsional patterns of human metatarsals. In this study, therefore, the aim was to clarify the age- and sex-associated variations in the torsional patterns of human metatarsals using three-dimensional computed tomography. The torsion angles of the five metatarsals were calculated by defining the dorsopalmar vector of the metatarsal base and the vector corresponding to the rotational axis of the metatarsal head. The present result demonstrated that the second metatarsals of females were significantly more inverted with increasing age. Flat foot is known to be most common in elderly women. Whether there is a cause-effect relationship between second metatarsal torsion and flattening of the medial longitudinal arch has yet to be answered, but this study suggested that torsion of the second metatarsal might possibly be used as an indicator for the early diagnosis of flat foot and associated foot pathologies. Clin. Anat. 30:1058-1063, 2017. © 2017 Wiley Periodicals, Inc.