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

The Influence of Therapy Enriched with the Erigo®Pro Table and Motor Imagery on the Body Balance of Patients After Stroke-A Randomized Observational Study

PURPOSE

Impaired balance leads to loss of function, e.g., the inability to walk safely. Therefore, restoring balance is a common goal of rehabilitation after a stroke. An innovative motor imaging and robotic device, the Erigo®Pro walking table, was used to improve balance in patients who had suffered an acute stroke.

MATERIALS AND METHODS

Sixty-six stroke patients in the acute phase with an average age of 64.85 ± 18.62 years were randomly assigned to one of three groups (22 subjects each) and treated with different therapies (conventional, conventional with Erigo®Pro, and conventional with Erigo®Pro enriched with motor imaging). The duration of therapy was two weeks. Patients were assessed before and after completion of therapy. The study used the trunk stability test and the Berg Balance Scale to assess balance, and the Riablo™ device to measure static balance. In addition, an assessment of the superficial tension of the transversus abdominis and multifidus muscles was performed. The clinical trial registration URL unique identifier was NCT06276075.

RESULTS

In each of the groups studied, the therapies applied resulted in significant improvement in functional assessment of trunk stability and balance (TCT < 0.001 and BBS < 0.001). The assessment of balance in the frontal (p = 0.023) and sagittal (p = 0.074) planes with the Riablo™ device confirmed the superiority of motor imaging-enhanced therapy at the level of a statistical trend. The tension of the transversus abdominis was higher at the second measurement (M = 14.41; SE = 3.31).

CONCLUSIONS

Motor imagery-enhanced therapy is most important, both for trunk stability and functional improvement of body balance parameters and for increasing transversus abdominis muscle tension.

Effect of Vibro-Tactile Stimulation Sequence and Support Surface Inclination on Gait and Balance Measures

The plantar surfaces of the feet are important for balance control during walking, specifically by allowing for the perception of pressure movements during stance. Background/Objectives: The current study aimed to perturb CoP movement perception in healthy individuals by applying vibrations to the soles of the feet in different stimulation sequences: a natural pattern that followed CoP movement (gait-like) and a perturbing pattern that did not follow the CoP (random) during walking. We hypothesized that the gait-like stimulation sequence would be similar to walking without any stimulation and therefore have no effect on balance measures and that the random sequence would negatively affect balance measures such as the anteroposterior (AP) and mediolateral (ML) margins of stability (MoSs) and foot placement area. Methods: Subjects walked at a level angle and 5.0 and 8.0 degrees of incline and with low visual conditions to increase reliance on tactile sensations from the feet. Results: No significant effect of the stimulation sequence was found at any incline, while there was a significant effect of incline. As the incline increased from level to 5 deg, subjects reduced their AP MoS measured at heel strikes from 4.36 ± 0.56 cm to 1.95 ± 1.07 cm and increased their foot placement area from 24.04 ± 11.13 cm2 to 38.98 ± 17.47 cm2. However, the AP MoS measured at midstance did not significantly change as the incline increased. Conclusions: The stimulation sequence had no effect on the dependent measures, but the subjects could still feel the vibrations on the plantar surfaces during walking; this implies that similar stimulation techniques could be a useful method for applying directive biofeedback without negatively impacting gait. Overall, this study demonstrates the detailed control of our tactile system and the adaptability of healthy individuals while walking with a perturbing stimulation.

Recent Advances and Developments in Injectable Conductive Polymer Gels for Bioelectronics

Soft matter bioelectronics represents an emerging and interdisciplinary research frontier aiming to harness the synergy between biology and electronics for advanced diagnostic and healthcare applications. In this context, a whole family of soft gels have been recently developed with self-healing ability and tunable biological mimetic features to act as a tissue-like space bridging the interface between the electronic device and dynamic biological fluids and body tissues. This review article provides a comprehensive overview of electroactive polymer gels, formed by noncovalent intermolecular interactions and dynamic covalent bonds, as injectable electroactive gels, covering their synthesis, characterization, and applications. First, hydrogels crafted from conducting polymers (poly(3,4-ethylene-dioxythiophene) (PEDOT), polyaniline (PANi), and polypyrrole (PPy))-based networks which are connected through physical interactions (e.g., hydrogen bonding, π-π stacking, hydrophobic interactions) or dynamic covalent bonds (e.g., imine bonds, Schiff-base, borate ester bonds) are addressed. Injectable hydrogels involving hybrid networks of polymers with conductive nanomaterials (i.e., graphene oxide, carbon nanotubes, metallic nanoparticles, etc.) are also discussed. Besides, it also delves into recent advancements in injectable ionic liquid-integrated gels (iongels) and deep eutectic solvent-integrated gels (eutectogels), which present promising avenues for future research. Finally, the current applications and future prospects of injectable electroactive polymer gels in cutting-edge bioelectronic applications ranging from tissue engineering to biosensing are outlined.

Plantar sensory stimulation and its impact on gait and lower limb motor function in individuals with stroke: A systematic review and meta-analysis

BACKGROUND

Stroke frequently leads to motor impairments, with almost half of the affected individuals experiencing diminished sensation, impacting their overall quality of life and autonomy. Rehabilitation efforts, however, often overlook somatosensory functions of the lower limbs. While plantar sensory stimulation activates receptors in the foot sole, its precise impact on the motor functions and gait of individuals with stroke is yet to be ascertained.

OBJECTIVES

This systematic review and meta-analysis aimed to examine the effects of sensory interventions on gait and lower limb motor function in individuals with stroke.

METHODS

We searched eight databases from inception to December 2023 for randomized controlled trials that investigated sensory interventions targeting gait or lower limb motor function in stroke patients. The primary outcomes included changes in gait and motor function, reported as standardized mean differences (SMD) and assessed heterogeneity (I2).

RESULTS

A total of [number] studies were included, covering different sensory modalities such as textured insoles, plantar vibration, and cognitive sensorimotor exercises. The interventions showed varying effectiveness, with plantar vibration therapy exhibiting a large effect size (SMD = 2.03 [1.13, 2.94]) for improving lower limb motor function, while textured insoles showed moderate effectiveness (SMD = 0.58 [0.24, 0.92]) with no heterogeneity (I2 = 0%). For gait, significant enhancement was seen with plantar vibration (SMD = 3.17 [2.05, 4.29]) and cognitive sensorimotor training (SMD = 2.85 [1.69, 4.02]). However, overall heterogeneity was moderate to high (I2 = 65% for motor function, 85% for gait), indicating variability across different studies and intervention types.

CONCLUSION

The findings of this review and meta-analysis suggest that plantar somatosensory stimulation has the potential to improve lower limb motor function and gait in people with stroke. However, to firmly establish its efficacy as a rehabilitative tool, larger-scale and high-quality studies are requisite.

Knee proprioception, muscle strength, and stability in Type 2 Diabetes Mellitus- A cross-sectional study

Background

The burgeoning prevalence of Type 2 Diabetes Mellitus (T2DM) has been linked to a spectrum of health complications, including those affecting the musculoskeletal system. Knee proprioception, muscle strength, and stability are essential for maintaining functional mobility and preventing falls, yet their relationship with T2DM is not fully elucidated.

Objectives

This study aimed to compare knee proprioception, muscle strength, and limits of stability (LOS) between individuals with T2DM and asymptomatic controls and to examine the moderating role of physical activity on these relationships.

Methods

In a cross-sectional design, 192 participants (96 with T2DM and 96 asymptomatic) underwent assessments for knee proprioception using a digital inclinometer, muscle strength via a handheld dynamometer, and LOS through dynamic posturography, graded as a percentage of maximum lean without losing balance.

Results

Our analysis revealed that individuals with T2DM demonstrated reduced knee muscle strength, with mean differences of 12.90 Nm (right) and 18.80 Nm (left) in 25° of flexion, and 25.78 Nm (right) and 26.36 Nm (left) in 40° of flexion, compared to asymptomatic controls. Proprioception errors were greater in the T2DM group (p < 0.001), with significant deficits noted in both knee 25° of flexion and 40° of flexion. Stability limits were also compromised, with the T2DM group displaying a decreased ability to maintain balance across all tested directions (p < 0.001). Physical activity emerged as a positive moderator, with higher activity levels correlating with improved muscle strength and stability.

Conclusion

T2DM significantly impairs musculoskeletal function, highlighting the need for integrated management strategies. The study underscores the importance of physical activity in mitigating T2DM-related musculoskeletal deterioration, suggesting that therapeutic interventions should include a focus on enhancing muscle strength and stability to improve the quality of life in this population.

Case report: New perspectives on gait initiation strategies from a case of full toes amputation in a professional mountain climber

Introduction

We studied the postural behaviour of a 52-year-old professional mountain climber who underwent bilateral amputation of all five toes after severe frostbite.

Methods

Two tasks were examined: static posturography (SP) and gait initiation (GI), both performed barefoot and with prosthetic shoes. During SP, the participant kept the upright stance for 30 s while an optoelectronic system with reflective markers recorded feet position and body sway, and two force plates measured the Center of Pressure (CoP) displacement and Ground Reaction Force (GRF) of each foot. During GI, the participant stood on the force plates for at least 10 s and then spontaneously started walking, while optoelectronic system was used to monitor heel-off events; wireless EMG probes recorded the anticipatory postural adjustments (APAs) in trunk and lower limb muscles.

Results

Compared to shod condition, during barefoot SP the participant showed a reduced anteroposterior (AP) and mediolateral (ML) extension of the Base of Support (BoS), and the whole-body CoP shifted about 7 mm more anteriorly, approaching the "safer" geometric center of the BoS. Despite this difference, the AP and ML ranges of CoP oscillations were similar in both conditions. In GI, the trunk dorsal muscles showed different APA patterns: when barefoot they were excitatory in the trailing and inhibitory in the leading side while they were bilaterally inhibitory when shod.

Discussion

In parallel to CoP shift toward a "safer" position in SP, in barefoot GI the body rotation toward the trailing side may reveal a more "cautious" approach; this also shows that different postural strategies may be adopted in GI by one and the same individual.

Relationship between Dynamic Balance and Physical Characteristics and Functions in Elite Lifesaving Athletes

Balance is important in lifesaving competitions. We aimed to investigate the relationship between dynamic balance and physical characteristics and functions in elite lifesavers by measuring the foot muscle cross-sectional area, ankle joint muscle strength, toe grasp strength, plantar superficial sensation, and dynamic balance (Y-balance test). In this observational study, we measured the foot muscle cross-sectional area, ankle dorsiflexion, plantar flexion, external flexion, isometric muscle strength, toe grasp strength, and superficial foot sensation of 15 adult lifesavers (12 males). The results show that toe grasp strength and ankle plantar flexion isometric muscle strength are particularly important for the dynamic balance of elite lifesavers working on sandy surfaces. Sand training improves intrinsic muscle strength and dynamic balance function. However, high training intensity may reduce plantar surface sensation; this needs to be verified through sand training interventions in the future.

Balancing act: Unraveling the link between muscle strength, proprioception, and stability in unilateral hip osteoarthritis

The objectives of this study are to compare hip muscle strength, hip joint proprioception, and functional balance between individuals with unilateral hip OA and asymptomatic individuals and to examine the relationships among these variables in the hip OA population. In a prospective cross-sectional study, 122 participants (unilateral Hip OA: n = 56, asymptomatic: n = 56) were assessed at the CAMS/KKU musculoskeletal Physical Therapy laboratory. Ethical standards were upheld throughout the research, with informed consent obtained. Hip muscle strength was measured using a hand-held dynamometer, hip joint proprioception with a digital inclinometer, and functional balance using the Berg Balance Scale (BBS) and Timed Up and Go (TUG) test. Hip OA individuals exhibited significantly lower muscle strength and proprioceptive accuracy, and poorer functional balance than controls (p < 0.003). Correlation analyses revealed a positive correlation between muscle strength and BBS scores (r = 0.38 to 0.42) and a negative correlation with TUG test times (r = -0.36 to -0.41). Hip joint reposition sense (JRS) in flexion showed a negative correlation with balance (r = -0.46), while JRS in abduction was positively correlated (r = 0.46). The study highlights the clinical importance of muscle strength and proprioception in functional balance among individuals with unilateral hip OA. The results support the incorporation of muscle strengthening and proprioceptive training in interventions to improve balance and mobility in this population.

Impact of five floor coverings on the orthostatic balance of healthy subjects

Plantar skin sensitivity contributes to the regulation of postural control and, therefore, changing the characteristics of the plantar support surface can modify this control. This study aimed at assessing the impact of five different floor coverings on the orthostatic balance in 48 healthy subjects. Static posturography was performed with eyes open or closed on a platform in a control condition (no covering) and with five different covering surfaces: foam, silicone, ethyl vinyl acetate, and two textured mats with small (height 2 mm) or large pimples (7 mm). The average velocity of center of pressure (CoP) displacement was the primary endpoint measure and ten other posturographic variables were assessed. Comfort and pain produced by the covering were also scored. In eyes open condition, the average velocity of CoP displacement was increased when subjects stood on the foam mat, the silicone mat, and especially the textured mat with large pimples. Several other posturographic variables showed significant changes with different types of floor coverings with eyes open. These changes were not correlated to the comfort or pain scores associated with the different surfaces. In contrast, no difference was observed compared to the control condition (no covering) with eyes closed. This study shows that adding smooth or textured floor covering can alter balance in eyes open condition. In eyes closed condition, although more disturbing for balance, healthy subjects achieved better postural adaptation, probably by mobilizing more of their proprioceptive resources. This posturographic examination procedure could, therefore, be used to assess "proprioceptive reserve" capacities in clinical practice.

The History and Future of Neuromusculoskeletal Biomechanics

The Executive Council of the International Society of Biomechanics has initiated and overseen the commemorations of the Society's 50th Anniversary in 2023. This included multiple series of lectures at the ninth World Congress of Biomechanics in 2022 and XXIXth Congress of the International Society of Biomechanics in 2023, all linked to special issues of International Society of Biomechanics' affiliated journals. This special issue of the Journal of Applied Biomechanics is dedicated to the biomechanics of the neuromusculoskeletal system. The reader is encouraged to explore this special issue which comprises 6 papers exploring the current state-of the-art, and future directions and roles for neuromusculoskeletal biomechanics. This editorial presents a very brief history of the science of the neuromusculoskeletal system's 4 main components: the central nervous system, musculotendon units, the musculoskeletal system, and joints, and how they biomechanically integrate to enable an understanding of the generation and control of human movement. This also entails a quick exploration of contemporary neuromusculoskeletal biomechanics and its future with new fields of application.

The 'Postural Rhythm' of the Ground Reaction Force during Upright Stance and Its Conversion to Body Sway-The Effect of Vision, Support Surface and Adaptation to Repeated Trials

The ground reaction force (GRF) recorded by a platform when a person stands upright lies at the interface between the neural networks controlling stance and the body sway deduced from centre of pressure (CoP) displacement. It can be decomposed into vertical (VGRF) and horizontal (HGRF) vectors. Few studies have addressed the modulation of the GRFs by the sensory conditions and their relationship with body sway. We reconsidered the features of the GRFs oscillations in healthy young subjects (n = 24) standing for 90 s, with the aim of characterising the possible effects of vision, support surface and adaptation to repeated trials, and the correspondence between HGRF and CoP time-series. We compared the frequency spectra of these variables with eyes open or closed on solid support surface (EOS, ECS) and on foam (EOF, ECF). All stance trials were repeated in a sequence of eight. Conditions were randomised across different days. The oscillations of the VGRF, HGRF and CoP differed between each other, as per the dominant frequency of their spectra (around 4 Hz, 0.8 Hz and <0.4 Hz, respectively) featuring a low-pass filter effect from VGRF to HGRF to CoP. GRF frequencies hardly changed as a function of the experimental conditions, including adaptation. CoP frequencies diminished to <0.2 Hz when vision was available on hard support surface. Amplitudes of both GRFs and CoP oscillations decreased in the order ECF > EOF > ECS ≈ EOS. Adaptation had no effect except in ECF condition. Specific rhythms of the GRFs do not transfer to the CoP frequency, whereas the magnitude of the forces acting on the ground ultimately determines body sway. The discrepancies in the time-series of the HGRF and CoP oscillations confirm that the body's oscillation mode cannot be dictated by the inverted pendulum model in any experimental conditions. The findings emphasise the robustness of the VGRF "postural rhythm" and its correspondence with the cortical theta rhythm, shed new insight on current principles of balance control and on understanding of upright stance in healthy and elderly people as well as on injury prevention and rehabilitation.

Vertical ground reaction force oscillation during standing on hard and compliant surfaces: The “postural rhythm”

When a person stands upright quietly, the position of the Centre of Mass (CoM), the vertical force acting on the ground and the geometrical configuration of body segments is accurately controlled around to the direction of gravity by multiple feedback mechanisms and by integrative brain centres that coordinate multi-joint movements. This is not always easy and the postural muscles continuously produce appropriate torques, recorded as ground reaction force by a force platform. We studied 23 young adults during a 90 s period, standing at ease on a hard (Solid) and on a compliant support (Foam) with eyes open (EO) and with eyes closed (EC), focusing on the vertical component of the ground reaction force (VGRF). Analysis of VGRF time series gave the amplitude of their rhythmic oscillations (the root mean square, RMS) and of their frequency spectrum. Sway Area and Path Length of the Centre of Pressure (CoP) were also calculated. VGRF RMS (as well as CoP sway measures) increased in the order EO Solid ≈ EC Solid < EO Foam < EC Foam. The VGRF frequency spectra featured prevailing frequencies around 4–5 Hz under all tested conditions, slightly higher on Solid than Foam support. Around that value, the VGRF frequencies varied in a larger range on hard than on compliant support. Sway Area and Path Length were inversely related to the prevailing VGRF frequency. Vision compared to no-vision decreased Sway Area and Path Length and VGRF RMS on Foam support. However, no significant effect of vision was found on VGRF mean frequency for either base of support condition. A description of the VGRF, at the interface between balance control mechanisms and sway of the CoP, can contribute information on how upright balance is maintained. Analysis of the frequency pattern of VGRF oscillations and its role in the maintenance of upright stance should complement the traditional measures of CoP excursions in the horizontal plane.

Incongruity of Geometric and Spectral Markers in the Assessment of Body Sway

Different measurements of body oscillations in the time or frequency domain are being employed as markers of gait and balance abnormalities. This study investigates basic relationships within and between geometric and spectral measures in a population of young adult subjects. Twenty healthy subjects stood with parallel feet on a force platform with and without a foam pad. Adaptation effects to prolonged stance were assessed by comparing the first and last of a series of eight successive trials. Centre of Foot Pressure (CoP) excursions were recorded with Eyes Closed (EC) and Open (EO) for 90s. Geometric measures (Sway Area, Path Length), standard deviation (SD) of the excursions, and spectral measure (mean power Spectrum Level and Median Frequency), along the medio-lateral (ML) and antero-posterior (AP) direction were computed. Sway Area was more strongly associated than Path Length with CoP SD and, consequently, with mean Spectrum Level for both ML and AP, and both visual and surface conditions. The squared-SD directly specified the mean power Spectrum Level of CoP excursions (ML and AP) in all conditions. Median Frequency was hardly related to Spectrum Level. Adaptation had a confounding effect, whereby equal values of Sway Area, Path Length, and Spectrum Level corresponded to different Median Frequency values. Mean Spectrum Level and SDs of the time series of CoP ML and AP excursions convey the same meaning and bear an acceptable correspondence with Sway Area values. Shifts in Median Frequency values represent important indications of neuromuscular control of stance and of the effects of vision, support conditions, and adaptation. The Romberg Quotient EC/EO for a given variable is contingent on the compliance of the base of support and adaptation, and different between Sway Area and Path Length, but similar between Sway Area and Spectrum Level (AP and ML). These measures must be taken with caution in clinical studies, and considered together in order to get a reliable indication of overall body sway, of modifications by sensory and standing condition, and of changes with ageing, medical conditions and rehabilitation treatment. However, distinct measures shed light on the discrete mechanisms and complex processes underpinning the maintenance of stance.

Increased 18F-FDG Uptake in the Axillary Lymph Nodes of the Vaccinated Side Associated with COVID-19 Vaccination

A 50-year-old female patient underwent (¹⁸fluorine-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) following modified radical mastectomy for cancer of the left breast. Ten days before the PET/CT, the coronavirus disease-2019 (COVID-19) vaccine was injected intramuscularly into the right deltoid muscle. Increased (¹⁸F-FDG uptake of maximum standardized uptake value (11.0) was observed in the lymph nodes of the right axilla, which had not been observed in the previous PET/CT. The size of the oval-shaped lymph nodes was up to approximately 11×9 mm; however, it was larger than that observed on the previous PET/CT. We contemplate that the increased (¹⁸F-FDG uptake was a reactive change in the lymph nodes associated with the COVID-19 vaccine.

Balance Adaptation While Standing on a Compliant Base Depends on the Current Sensory Condition in Healthy Young Adults

Background

Several investigations have addressed the process of balance adaptation to external perturbations. The adaptation during unperturbed stance has received little attention. Further, whether the current sensory conditions affect the adaptation rate has not been established. We have addressed the role of vision and haptic feedback on adaptation while standing on foam.

Methods

In 22 young subjects, the analysis of geometric (path length and sway area) and spectral variables (median frequency and mean level of both total spectrum and selected frequency windows) of the oscillation of the centre of feet pressure (CoP) identified the effects of vision, light-touch (LT) or both in the anteroposterior (AP) and mediolateral (ML) direction over 8 consecutive 90 s standing trials.

Results

Adaptation was obvious without vision (eyes closed; EC) and tenuous with vision (eyes open; EO). With trial repetition, path length and median frequency diminished with EC (p < 0.001) while sway area and mean level of the spectrum increased (p < 0.001). The low- and high-frequency range of the spectrum increased and decreased in AP and ML directions, respectively. Touch compared to no-touch enhanced the rate of increase of the low-frequency power (p < 0.05). Spectral differences in distinct sensory conditions persisted after adaptation.

Conclusion

Balance adaptation occurs during standing on foam. Adaptation leads to a progressive increase in the amplitude of the lowest frequencies of the spectrum and a concurrent decrease in the high-frequency range. Within this common behaviour, touch adds to its stabilising action a modest effect on the adaptation rate. Stabilisation is improved by favouring slow oscillations at the expense of sway minimisation. These findings are preliminary to investigations of balance problems in persons with sensory deficits, ageing, and peripheral or central nervous lesion.

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.

Specific Posture-Stabilising Effects of Vision and Touch Are Revealed by Distinct Changes of Body Oscillation Frequencies

We addressed postural instability during stance with eyes closed (EC) on a compliant surface in healthy young people. Spectral analysis of the centre of foot pressure oscillations was used to identify the effects of haptic information (light-touch, EC-LT), or vision (eyes open, EO), or both (EO-LT). Spectral median frequency was strongly reduced by EO and EO-LT, while spectral amplitude was reduced by all "stabilising" sensory conditions. Reduction in spectrum level by EO mainly appeared in the high-frequency range. Reduction by LT was much larger than that induced by the vision in the low-frequency range, less so in the high-frequency range. Touch and vision together produced a fall in spectral amplitude across all windows, more so in anteroposterior (AP) direction. Lowermost frequencies contributed poorly to geometric measures (sway path and area) for all sensory conditions. The same subjects participated in control experiments on a solid base of support. Median frequency and amplitude of the spectrum and geometric measures were largely smaller when standing on solid than on foam base but poorly affected by the sensory conditions. Frequency analysis but not geometric measures allowed to disclose unique tuning of the postural control mode by haptic and visual information. During standing on foam, the vision did not reduce low-frequency oscillations, while touch diminished the entire spectrum, except for the medium-high frequencies, as if sway reduction by touch would rely on rapid balance corrections. The combination of frequency analysis with sensory conditions is a promising approach to explore altered postural mechanisms and prospective interventions in subjects with central or peripheral nervous system disorders.