Innovative air mattress for the prevention of pressure ulcers in neonates.

OBJECTIVE: Pressure ulcers (PUs) severely impact health outcomes in neonatal intensive care, with up to 28% prevalence and doubled mortality rates. Due to their only partially developed stratum corneum, neonates are highly susceptible to PUs because of a lack of adequate support surfaces. The occipital region of the head and hip are the main risk areas due to immobility and newborn body proportions. The main goal of the study was to investigate the impact of reduction in local pressure in these body areas by two air mattress designs and different filling states. METHOD: Two innovative air-filled mattress prototypes (prototype 1 and prototype 2), consisting of three different segments (head, trunk and feet regions), were developed to reduce local interface pressures by optimising pressure distribution, and were assessed with three air pressure filling states (0.2kPa, 0.4kPa and 0.6kPa). A baby doll was used to investigate pressure distribution and local pressure impact. It measured 51cm and the weight was modified to be 1.3kg, 2.3kg and 3.3kg, representing premature to term newborn weights, respectively. A specialised foam mattress and an unsupported surface were considered as controls. RESULTS: The interface pressures at the hip region for newborn models could be reduced by up to 41% with mattress prototype 1 and 49% with prototype 2 when filled with 0.2kPa air pressure. It was found that the size and the pressure inside air segments was crucial for interface pressure. CONCLUSION: Our results demonstrated that air mattresses achieved lower interface pressures compared to conventional support surfaces, and that the benefit of the air mattresses depended on their filling status. The importance of using innovative, segmented designs that were tailored to meet the specific needs of highly vulnerable paediatric patients was demonstrated.

Effects of alternating pressure patterns on sacral skin blood flow responses in people with spinal cord injury.

Alternating pressure support surface (APSS) is a common support surface for treating pressure injury in individuals with spinal cord injury (SCI). However, conflicting results on the effectiveness of APSS have been reported and may be associated with inappropriate configurations of APSS. The objectives of this study were to compare the different pressure amplitudes (75/5 mmHg [alternating between 75 and 5 mmHg] vs. 65/15 mmHg) and cycle periods (5 min [4 cycles] vs. 2.5 min [8 cycles]) of alternating pressure on sacral skin blood flow responses in 10 individuals with SCI. Sacral skin blood flow during and after loading of four alternating pressure protocols was assessed using laser Doppler flowmetry and was normalised to the value before loading (10-min baseline, 20-min loading and 10-min recovery). The results demonstrated that during the high-pressure phase, there was a significant difference between the 75/5 and 65/15 mmHg protocols (0.3658 ± 0.0688 for 75/5 mmHg and 0.1702 ± 0.0389 for 65/15 mmHg, p < 0.05); and during the low-pressure phase, there was a significant difference between the 75/5 and 65/15 mmHg protocols (1.7184 ± 0.262 for 75/5 mmHg and 0.5916 ± 0.1378 for 65/15 mmHg, p < 0.05). There were no differences between cycle periods in skin blood flow responses. No adverse events were reported. Our finding indicates that the pressure amplitude of alternating pressure is a significant factor affecting sacral skin blood flow responses. An appropriate configuration of alternating pressure is needed to effectively increase skin blood flow and tissue viability in individuals with SCI.

Prevention of pressure injuries using a non-motorised decompression air mattress: a non-interventional study.

OBJECTIVE: Prevention of pressure injuries (PI) is a public health issue. Among the preventive measures, the use of support surfaces adapted to the risk of PI occurrence is recommended. This study aimed to report the incidence of PIs in patients at medium-to-high risk of occurrence of PIs and using a new non-motorised automated decompression air mattress combined with other recommended PI prevention measures. METHOD: An observational, national, multicentre, prospective, non-comparative study, with a follow-up period of 35 days was conducted. Patients at medium-to-high risk of PIs and without PIs at baseline were included if they were lying on a specific non-powered automated decompression air mattress. The primary outcome was the percentage of patients who developed at least one category 2 or more severe PI of the sacrum, backbone or heel between day 0 and day 35. RESULTS: In total, 81 patients were included from four participating centres. There was one report of a patient with a PI that fitted within the definition of the primary outcome, meaning an incidence of 1.2% (95% confidence interval (CI) 0-6.7%). More than 80% of patients rated the overall comfort and the stability of the non-motorised automated decompression air mattress as satisfactory or very satisfactory. In more than 80% of cases, the healthcare teams found the use of the mattress to be easy or very easy. CONCLUSION: This study has shown that in combination with other preventive measures, the use of a specific non-motorised air mattress with automated decompression is associated with a low incidence of PIs in patients with medium-to-high risk of occurrence of PIs.

Center of pressure responses to unpredictable external perturbations indicate low accuracy in predicting fall risk in people with Parkinson's disease.

Falls are associated with impairment in postural control in people with Parkinson's disease (PwPD). We aimed to predict the fall risk through models combining postural responses with clinical and cognitive measures. Also, we compared the center of pressure (CoP) between PwPD fallers and non-fallers after unpredictable external perturbations. We expected that CoP parameters combined with clinical and cognitive measures would predict fall risk. Seventy-five individuals participated in the study. CoP parameters were measured during postural responses through five trials with unpredictable translations of the support-surface in posterior direction. Range and peak of CoP were analyzed in two periods: early and late responses. Time to peak (negative peak) and recovery time were analyzed regardless of the periods. Models included the CoP parameters in early (model 1), late responses (model 2), and temporal parameters (model 3). Clinical and cognitive measures were entered into all models. Twenty-nine participants fell at least once, and 46 PwPD did not fall during 12 months following the postural assessment. Range of CoP in late responses was associated with fall risk (p = .046). However, although statistically non-significant, this parameter indicated low accuracy in predicting fall risk (area under the curve = 0.58). Fallers presented a higher range of CoP in early responses than non-fallers (p = .033). In conclusion, although an association was observed between fall risk and range of CoP in late responses, this parameter indicated low accuracy in predicting fall risk in PwPD. Also, fallers demonstrate worse postural control during early responses after external perturbations than non-fallers, measured by CoP parameters.

Comparison of interface pressures on three operating table support surfaces during surgery.

AIM OF THE STUDY: To investigate the effect of support surface usage and positions on interface pressure during surgery. MATERIALS AND METHODS: This randomized controlled experimental study was conducted between October 2018 and June 2019. The study included patients who had planned surgery in supine and prone positions. The sample size was 72 patients. Patients were assigned to three groups (gel support surface, viscoelastic support surface and standard operating table) according to the determined randomization table. During the surgery, the pressure in the patients' body was recorded. The statistics program IBM SPSS Statistics 25.0 packaged software was used in the analyses of data. RESULTS: There was no statistically significant difference between the total body average interface pressure (mmHg) values between the supporting surfaces in the prone position. There was a statistically significant difference between the total body average interface pressure (mmHg) values between the support surfaces in the supine position, and the average interface pressure measured on the viscoelastic foam support surface was significantly lower than the gel support surface and the standard operating table. CONCLUSION: In the study, the use of viscoelastic foam support surface was found to be more effective than the use of a standard operating table and gel support surface. Viscoelastic foam support surface is recommended for patients at risk for pressure injury in the operating room.

Reductions in body sway responses to a rhythmic support surface tilt perturbation can be caused by other mechanisms than prediction.

Studies investigating balance control often use external perturbations to probe the system. These perturbations can be administered as randomized, pseudo-randomized, or predictable sequences. As predictability of a given perturbation can affect balance performance, the way those perturbations are constructed may affect the results of the experiments. In the present study, we hypothesized that subjects are able to adapt to short, rhythmic support surface tilt stimuli, but not to long pseudo-random stimuli. 19 subjects were standing with eyes closed on a servo-controlled platform tilting about the ankle joint axis. Pre and post to the learning intervention, pseudo-random tilt sequences were applied. For the learning phase, a rhythmic and easy-to-memorize 8-s long sequence was applied 75 times, where subjects were instructed to stand as still as possible. Body kinematics were measured and whole body center of mass sway was analyzed. Results showed reduced sway and less forward lean of the body across the learning phase. The sway reductions were similar for stimulus and non-stimulus frequencies. Surprisingly, for the pseudo-random sequences, comparable changes were found from pre- to post-tests. In summary, results confirmed that considerable adaptations exist when exposing subjects to an 8-s long rhythmic perturbation. No indications of predictions of the learning tilt sequence were found, since similar changes were also observed in response to pseudo-random sequences. We conclude that changes in body sway responses following 75 repetitions of an 8-s long rhythmic tilt sequence are due to adaptations in the dynamics of the control mechanism (presumably stiffness).

Effects of cycle periods and pressure amplitudes of alternating pressure on sacral skin blood flow responses.

BACKGROUND: There are no guidelines on selecting alternating pressure (AP) configurations on increasing sacral skin blood flow (SBF). AIM: The specific aims were to compare different cycle periods and pressure amplitudes of AP on sacral SBF responses in healthy people to establish the efficacy and safety of the protocols. METHODS: Two studies were tested, including the cycle period study (8 2.5-min vs 4 5-min protocols) and the pressure amplitude study (75/5 vs 65/15 mmHg protocols). Sacral SBF was measured using laser Doppler flowmetry (LDF) in 20 participants. AP loads were randomly applied using an indenter through the rigid LDF probe. Each protocol included a 10-min baseline, 20-min AP and 10-min recovery periods. A 30-min washout period was provided. The SBF response was normalized to the baseline SBF of each condition of each participant. RESULTS: For the cycle period study, the 4 5-min cycle protocol partially restored more SBF than the 8 2.5-min cycle protocol at the low-pressure phase (0.87 ± 0.04 vs 0.71 ± 0.03, p < 0.05) and at the high-pressure phase (0.25 ± 0.03 vs 0.19 ± 0.03, p < 0.05). For the pressure amplitude study, the 75/5 mmHg protocol partially restored more sacral SBF than the 65/15 mmHg protocol at the low-pressure phase (0.87 ± 0.1 vs 0.25 ± 0.03, p < 0.05) but not at the high-pressure phase (0.23 ± 0.02 vs 0.21 ± 0.02, non-significant). CONCLUSION: This study demonstrated that 1) a cycle period of 5 min was better than 2.5 min and 2) a pressure amplitude of 75/5 mmHg was better than 65/15 mmHg. The finding provides insights for selecting the AP configurations for increasing SBF.

An exploration of nursing home residents' experiences of a non-powered static air mattress overlay to prevent pressure ulcers.

Pressure ulcers are injuries to the skin and underlying tissue and are associated with a negative impact on well-being and health-related quality of life. This explorative, qualitative study aimed to explore the true meaning of elderly nursing home residents' perspectives and critical success factors when implementing a new non-powered static air mattress overlay to prevent pressure ulcers. Individual, loosely structured interviews were conductedin 12 nursing homes in Flanders, the Northern region of Belgium, a convenience sampling of 14 nursing home residents were selected based on the following eligibility criteria: high risk for pressure ulcer and/or with category 1 pressure ulcer, being bedbound and/or chair-bound, aged >65 years, and use of an alternating air pressure mattress previous to the application of the non-powered static air mattress overlay. Interviews were conducted in the participants' personal rooms between June 2017 and March 2018. Interviews included broad, open-ended questions, to invite and encourage participants to openly discuss their perspectives and experiences. Participants were interviewed once during the 14-day observation period between day 3 and day 14. All interviews were audio-recorded and fully transcribed by an experienced transcriber. Interviews were read several times to reveal emerging patterns and were marked with codes into NVivo 10 qualitative data analysis software. During the process, (sub) themes were discussed by the authors until a consensus was reached. Three main themes emerged from the analysis process: rest and sleep; mobility; and discomfort and pain associated with the use of the support surface. Themes were divided into multiple subthemes: motion, noise, sensation, repositioning, and transfer in and out of bed. Through interviews, critical success factors associated with the implementation were identified, including the lack of information and time needed to evaluate the functionality and effects of a new mattress overlay. Implementation of a non-powered static air mattress overlay to prevent pressure ulcers has a far-reaching impact on nursing home residents' experiences. This study provides insight into the true meaning of patients' perspectives by focusing on learning from the patients' experiences that provide valuable information for healthcare professionals and other stakeholders.

Pressure ulcer Cat. II-IV incidence on the CuroCell S.A.M. PRO powered reactive air support surface in a high-risk population: A multicentre cohort study in 12 Belgian nursing homes.

The primary objective was to study pressure ulcer (PU) category II-IV (including suspected deep tissue injury and unstageable PUs) cumulative incidence and PU incidence density, in a 30day observation period, associated with the use of the CuroCell S.A.M. PRO powered reactive air support surface in nursing home residents at risk for PU development. Secondary objectives were to study (a) PU category I cumulative incidence and PU incidence density and (b) user (caregivers and residents) experiences and perceptions of comfort associated with the use of the support surface under study. A multicentre cohort study was set up in 37 care units of 12 Belgian nursing homes. The sample consisted of 191 residents at risk of PU development (Braden score ≤ 17). The cumulative PU incidence was 4.7% (n = 9). The PU incidence density was 1.7/1000 observation days (9 PU/5370 days). The experience and perceptions of comfort analysis revealed that the CuroCell S.A.M. PRO powered reactive air support surface was comfortable for daily use. The mode of action and the quietness of the pump function had a positive impact on sleep quality. Patient comfort and sleep quality are essential criteria in the selection of a support surface.

Pressure ulcers: Prevention and management.

Prevention has been a primary goal of pressure ulcer research. Despite such efforts, pressure ulcers remain common in hospitals and in the community. Moreover, pressure ulcers often become chronic wounds that are difficult to treat and that tend to recur after healing. Especially given these challenges, dermatologists should have the knowledge and skills to implement pressure ulcer prevention strategies and to effectively treat pressure ulcers in their patients. This continuing medical education article focuses on pressure ulcer prevention and management, with an emphasis on the evidence for commonly accepted practices.

Vascular endothelial function is improved after active mattress use.

OBJECTIVE: Active mattresses are used to prevent, treat and relieve pressure ulcers (PU) by intermittent contact pressure/relief. However, no studies have directly assessed the vascular endothelial response to long-term active mattress use. This study investigated the hypothesis that eight weeks use of an active mattress would lead to improvements in vascular endothelial function in healthy participants. METHODS: Physiological parameters of baseline skin temperature (BskT), resting blood flow (RBF) and endothelial function as measured using post-occlusive reactive hyperaemia (PORH), were assessed at baseline (week 0); following eight weeks of sleeping on an active mattress, and after an eight week washout period (at week 16). RESULTS: We recruited 10 healthy participants (four male, age 52.7±8.5 years, six female age 51.8±17.5 years). Following active mattress use RBF, PORH and BskT at the hallux pulp increased by 336%, 197% and 3.5ºC, respectively. Mean values increased from 24.3±38.3 perfusion units to 106.0±100.3 perfusion units (p=0.021) and from 13,456±10,225 to 40,252±23,995 perfusion units x seconds (p=0.003) and from 22.9±2.5ºC to 26.4±1.9ºC (p<0.001), respectively. CONCLUSION: Active mattress use for eight weeks leads to significant improvements in RBF, PORH, and BskT. These results suggest that active mattress use can improve endothelial function. Future research is required to explore the potential of active mattress use in the treatment and management of diseases and conditions that would benefit from an improved endothelial function.

Dental occlusion and body balance: A question of environmental constraints?

BACKGROUND: In the past few years, growing interest was given to the relationship between the dental occlusion and the body balance. While most research focused on this relationship at static conditions, it is evident that the contribution of the sensory information for balance control is different depending on the environmental constraints. RESEARCH QUESTION: The aim of the present paper was to elucidate whether the stomatognathic system (SS) contributes differently on body balance regulation according to the presence of external disturbances. METHODS: Literature regarding the different sources involved in the proprioceptive information to the SS was reviewed. The influence of dental occlusion on balance control at different external environments was then explored. RESULTS: The main findings are: (a) a plausible evidence between the masticatory and cervical muscles can be described; (b) a reciprocal connection between the trigeminal and vestibular nuclei supports the influence of the SS on body balance; (c) traditionally, research involving the relationship between the SS and balance control has focused on strictly controlled situations, thus, ignoring the sensory reweighting which occurs depending on the external disturbances; and (d) the afferences of dental occlusion for balance control seem strengthened when more difficult conditions are present. CONCLUSION: Results of the present review suggest that afferent signals from dental occlusion effectively contribute to balance control when more external perturbations are present, that is unstable support surface, fatigue and tasks being performed. However, more studies are needed to elucidate the mechanisms by which dental occlusion may influence balance control focusing on different external environments.

Evaluation of comfort associated with the use of a robotic mattress with an interface pressure mapping system and automatic inner air-cell pressure adjustment function in healthy volunteers.

AIM OF THE STUDY: A robotic mattress equipped with an interface pressure mapping system and an automatic inner air-cell pressure adjustment function had been developed to aid in the management of pressure ulcers, but its effects on comfort remained unclear. The present study aimed to investigate whether use of the mattress with continuous, automatic, interface pressure mapping-based regulation of inner air-cell pressure (i.e., robotic mattress) improves comfort over that provided by body weight-based pressure regulation (traditional approach) in healthy volunteers. MATERIALS AND METHODS: A robotic mattress was used with two settings (i.e., interface pressure-vs. body weight-based regulation). First, 20 healthy volunteers were recruited, and the level of comfort, interface pressure distribution, body immersion, and tissue oxygenation were measured and compared between the two settings. RESULTS: The level of comfort (20.5 vs 47.5, p = 0.014), contact area (2263.9 vs 2145.2 cm2, p = 0.002), and body immersion for healthy participants were significantly larger when using the interface pressure-based setting. CONCLUSION: The robotic mattress provided improved comfort, which might be caused by increased contact area, and improved body immersion. The robotic mattress is expected to be effective both for managing pressure ulcers and increasing comfort.

Interface pressure mapping pilot study to select surfaces that effectively redistribute pediatric occipital pressure.

AIM: The aim of this pilot study was to better inform clinical decisions to prevent pediatric occipital pressure ulcers with quantitative data to choose an appropriate reactive support surface. MATERIALS: A commercially available capacitive pressure mapping system (XSENSOR, X3 Medical Seat System, Calgary, Canada) was used to evaluate a standard pediatric mattress and four commercially available pressure-redistributing support surfaces. METHODS: The pressure mapping system was validated for use in the pediatric population through studies on sensitivity, accuracy, creep, and repeatability. Then, a pilot pressure mapping study on healthy children under 6 years old (n = 22) was performed to determine interface pressure and pressure distribution between the occipital region of the skull and each surface: standard mattress, gel, foam, air and fluidized. RESULTS: The sensor was adequate to measure pressure generated by pediatric occipital loading, with 0.5-9% error in accuracy in the 25-95 mmHg range. The air surface had the lowest mean interface pressure (p < .005) and lowest peak pressure index (PPI), defined as the peak pressure averaged over four sensels, (p < .005). Mean interface pressure for mattress, foam, fluidized, gel, and air materials were 24.8 ± 4.42, 24.1 ± 1.89, 19.4 ± 3.25, 17.9 ± 3.10, and 14.2 ± 1.41 mmHg, respectively. The air surface also had the most homogenous pressure distribution, with the highest mean to PPI ratio (p < .005) and relatively high contact area compared to the other surfaces (p < .005). CONCLUSION: The air surface was the most effective pressure-redistributing material for pediatric occipital pressure as it had the lowest interface pressure and a homogeneous pressure distribution. This implies effective envelopment of the bony prominence of the occiput and increasing contact area to decrease peak pressure points.

Using an extreme bony prominence anatomical model to examine the influence of bed sheet materials and bed making methods on the distribution of pressure on the support surface.

Bed sheets generate high surface tension across the support surface and increase pressure to the body through a process known as the hammock effect. Using an anatomical model and a loading device characterized by extreme bony prominences, the present study compared pressure distributions on support surfaces across different bed making methods and bed sheet materials to determine the factors that influence pressure distribution. The model was placed on a pressure mapping system (CONFORMat; NITTA Corp., Osaka, Japan), and interface pressure was measured. Bed sheet elasticity and friction between the support surface and the bed sheets were also measured. For maximum interface pressure, the relative values of the following methods were higher than those of the control method, which did not use any bed sheets: cotton sheets with hospital corners (1.28, p = 0.02), polyester with no corners (1.29, p = 0.01), cotton with no corners (1.31, p = 0.003), and fitted polyester sheets (1.35, p = 0.002). Stepwise multiple regression analysis indicated that maximum interface pressure was negatively correlated with bed sheet elasticity (R(2) = 0.74). A statistically significant negative correlation was observed between maximum interface pressure and immersion depth, which was measured using the loading device (r = -0.40 and p = 0.04). We found that several combinations of bed making methods and bed sheet materials induced maximum interface pressures greater than those observed for the control method. Bed sheet materials influenced maximum interface pressure, and bed sheet elasticity was particularly important in reducing maximum interface pressure.

The effects of pilates mat exercise on the balance ability of elderly females.

[Purpose] The purpose of this study was to examine the effects of Pilates exercise on a mat and balance exercise on an unstable base of support for trunk stability on the balance ability of elderly females. [Subjects and Methods] Forty elderly women aged 65 or older were equally assigned to a Pilates mat exercise (PME) group and an unstable support surface exercise (USSE) group. They conducted exercise three times per week for 12 weeks for 40 minutes each time. In order to examine balance, sway length and the speed of the center of foot pressure were measured for one minute, and in order to examine dynamic balance, the Timed Up and Go (TUG) test was conducted. [Results] After the intervention, sway length, sway speed, and TUG significantly decreased in both groups. A comparison of sway speed after the intervention between the two groups revealed that the PME group showed larger decreases than the USSE group. [Conclusion] PME and USSE elicited significant effects on the static and dynamic balance of elderly female subjects, suggesting that those exercises are effective at enhancing the balance ability of this group of subjects. However, the Pilates mat exercise is regarded as being safer than exercise on an unstable base of support.

How Does Postural Control of Children with CP Deal with Manipulations on Base of Support and Support Surface? A Systematic Review.

AIMS: Systematically review literature addressing the effects of changes in base of support (BoS) configuration and characteristics of support surface (SS) on postural control of children with cerebral palsy (CP). METHODS: We conducted a tailored electronic database search in PubMed/Web of Science/SCOPUS/Embase. RESULTS: We identified 15 studies meeting inclusion criteria. CONCLUSION: The extant literature suggests that when children with CP experience changes in BoS and SS, they engage in fewer adaptive postural control responses than typically developing children. Documented response patterns of children with CP in the literature might guide the selection and development of rehabilitation strategies to appropriately facilitate or challenge postural control in children with CP.

Human body-sway steady-state responses to small amplitude tilts and translations of the support surface - Effects of superposition of the two stimuli.

BACKGROUND: For humans, control of upright standing posture is a prerequisite for many physical activities. Experimentally, this control is often challenged by the motion of the support surface presented as tilt or translation, or some combination thereof. In particular, we have investigated subjects balancing in situations where tilt and translation stimuli were presented in isolation and compared it to a situation where such stimuli occurred simultaneously. RESEARCH QUESTIONS: Is the human posture control system in the case of two or more superimposed external disturbances responding to these as if it were dealing with one disturbance? Or does it identify the disturbances individually and as such and respond to them specifically, as suggested in a current concept of disturbance-specific estimations and compensations? METHODS: We had healthy human subjects controlling their balancing of upright stance on a motion platform while we presented them with different combinations of pseudorandom support surface tilt and translation stimuli alone or in superposition (with peak-to-peak amplitude of 0.5° and 1° for tilt, and 0.8 cm and 1.5 cm for translation). In one set of trials they kept their eyes closed and in a second set open. Furthermore, a simulation was performed to qualitatively evaluate the impact of sensory non-linearities and joint stiffness modulation. RESULTS: We found that the experimental conditions 'eyes open' vs. 'eyes closed' always created significant differences (p < 0.05) between the frequency response functions. In contrast to this, with different combinations of the tilt and translation stimuli, significant differences between the responses were observed only in 5 cases over the 24 that have been tested. Significance The superposition of translation and tilt can be used to characterize the responses to both stimuli with one trial. When the amplitude of the stimuli is unbalanced (e.g. very small tilt superimposed with a larger translation) the effect of stiffness modulation can be studied.

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.

Arch index measurement method based on plantar distributed force.

In this paper, the solution method for foot arch index (FAI) based on plantar force measurement was proposed. The entire pelma (EP) was divided into three partitions: posterior heel (HP), lateral side of the sole (SL) and medial side of the sole (SM) according to the three-point support mechanics mechanism of the foot and ankle. A distributed force platform was established to obtain the mean positions of the center of pressure (CoP) trajectories on SL, SM, HP, and EP, which were defined as A, B, C, and O, respectively. Based on the principle that the arch height influences the distance from point O to the boundary of triangle ABC, the area ratio of triangle BOC to triangle ABC was defined as FAI. Arch height index (AHI) measurement of thirty participants by combined calipers was compared with FAI measurement of their right feet. The arches were classified based on AHI, and ANOVA was performed. The Pearson correlation coefficient between the FAI method and the AHI method is 0.79 (p＜0.0001). The Bland-Altman analysis showed good agreement. ANOVA indicated FAI was statistically significant (F = 18.81,p＜0.001), and there were statistical differences between groups. These results suggest that the proposed distributed force measurement method can provide support surface boundary (triangle ABC) information related to point O.