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Since it has been demonstrated that spatial cognition can be affected in visually impaired children, training strategies that exploit the plasticity of the human brain should be early adopted. Here we developed and tested a new training protocol based on the reinforcement of audio-motor associations and thus supporting spatial development in visually impaired children. The study involved forty-four visually impaired children aged 6–17 years old assigned to an experimental (ABBI training) or a control (classical training) rehabilitation conditions. The experimental training group followed an intensive but entertaining rehabilitation for twelve weeks during which they performed ad-hoc developed audio-spatial exercises with the Audio Bracelet for Blind Interaction (ABBI). A battery of spatial tests administered before and after the training indicated that children significantly improved in almost all the spatial aspects considered, while the control group didn’t show any improvement. These results confirm that perceptual development in the case of blindness can be enhanced with naturally associated auditory feedbacks to body movements. Therefore the early introduction of a tailored audio-motor training could potentially prevent spatial developmental delays in visually impaired children.

OBJECTIVES: Widespread pressure hyperalgesia, facilitated temporal summation of pain (TSP), and impaired conditioned pain modulation (CPM) have been found in knee osteoarthritis (KOA) patients compared with controls and these parameters have further been suggested to be altered in the elderly. This study investigated the influence of age on pressure hyperalgesia, TSP, and CPM in patients with KOA and controls.METHODS: One-hundred-thirty-three severe KOA patients and 50 age and sex-matched asymptomatic controls were assessed by cuff algometry and handheld pressure algometry. Pain sensitivity was assessed around the head of the gastrocnemius muscle to identify mild pain detection (MPDT) and tolerance (PTT) threshold. TSP was assessed by visual analogue scale (VAS) scores of the pain evoked by 10 repetitive cuff stimulations. CPM was assessed as the difference in PTT before and during cuff-induced tonic arm pain. Pressure pain thresholds (PPTs) were assessed by handheld algometry at the tibialis anterior muscle. Two subgroups were analyzed in the age range below and above 65 years. Pearson correlations between age and pain parameters were applied.RESULTS: Patients demonstrated reduced MPDT, PTT and PPT (PDISCUSSION: Pressure hyperalgesia was affected by age whereas dynamic pain mechanisms such as TSP and CPM were unaffected suggesting that these parameters are robust for a larger age range and reliable for long-term follow up studies.

Research suggests that vision plays an important role in child's growth for building cognitive abilities necessary to process spatial information. Consequently, blindness in children affects the development of their spatial abilities. Here we present ABBI (Audio Bracelet for Blind Interaction), a wearable device that was developed to rehabilitate underdeveloped skills in visually impaired children. The core idea behind ABBI is to use the auditory modality to convey spatial information about the movement of the person's own body within the personal, peri-personal and extra-personal space. Specifically, it provides sources of sounds positioned on the main effectors/limbs (such as the wrists and feet) of persons with visual deficits. The ABBI system is composed of a small wearable custom-designed device with integrated audio system, motion sensors, and a Bluetooth low energy module to communicate with a smartphone. We discuss the importance of this device in terms of innovation, usability and highlight future studies aimed at rehabilitating the brain processes and functions involved in spatial cognition of children with visual disabilities through natural audio-motor associations.

This paper presents the process and results of a set of studies within the ABBI EU project, with the general aim to co-design wearable technology (an audio bracelet) together with visually impaired children, starting at a young age. The authors discuss user preferences related to sounds and tactile materials and present the results of a focus group with very young visually-impaired children under the age of 5, together with their parents. They find that multisensory feedback (visual, tactile/haptic, auditory) is useful and that preferences vary - also the drastic and potentially unpleasant sounds and materials may have a role. Further studies investigate the possibilities of using the ABBI wearable technology for social contexts and games. In a series of game workshops children with and without visual impairments created games with wearable technology employing very simple interactivity. The authors report the created games, and note that even with this simple interactivity it is possible to create fun, inclusive and rich socially co-located games.

Blind individuals are particularly dependent on their hearing for defining space. It has been found that both children and adults with visual impairments can struggle with complex spatial tasks that require a metric representation of space. Nonetheless the variability of methods employed to assess spatial abilities in absence of vision is wide, especially in the case of visually impaired children. For this reason, it would be necessary to define a battery of tests that appropriately assess different aspects of spatial perception and to investigate its reliability in order to provide a standard assessment of spatial abilities not only in experimental but also in clinical settings. The aim of this study is to determine the test-retest reliability of a battery of six spatial tasks (BSP, Blind Spatial Perception) and provide the first gold standard for assessing spatial cognition deficits in visually impaired children. Thirty visually impaired children aged 6-17 participated in two identical sessions, at a distance of 10 weeks, in which they performed six spatial tasks: auditory bisection, auditory localization, auditory distance discrimination, auditory reaching, proprioceptive reaching, and general mobility. Test-retest reliability was assessed using the test-retest scatter plots, intra-class correlation coefficient (ICC), and coefficient of variation (CV). The results showed good-to-excellent reliability for all six tests, with average ICC values ranging from 0.77 to 0.89 and average CV values ranging from 3.44% to 15.27%. In conclusion, the newly proposed battery (BSP) results as a reliable tool to identify spatial impairments in visually impaired children.

Purpose Delayed onset muscle soreness (DOMS) has been shown to induce changes in muscle activity during walking. The aim of this study was to elucidate whether DOMS also affects interlimb communication during walking by investigating its effect on short-latency crossed responses (SLCRs).Methods SLCRs were elicited in two recording sessions by electrically stimulating the tibial nerve of the ipsilateral leg, and quantified in the contralateral gastrocnemius muscle. The second recording session occurred 24–36 h after the participants (n = 11) performed eccentric exercises with the ipsilateral calf.Results DOMS caused a decreased magnitude of the spinally mediated component of the SLCR in the contralateral gas- trocnemius medialis.Conclusions The results of the current study provide insight on the relationship between pain and motor control. Muscle pain affects the spinal pathway mediating interlimb communication, which might result in a reduced ability to maintain dynamical stability during walking.

Blind football, or Football 5-a-side, is a very popular sport amongst visually impaired individuals (VI) worldwide. However, little is known regarding the movement patterns these players perform in sports actions. Therefore, the aim of this study was to determine whether visually impaired players present changes in their movement patterns in specific functional tasks compared with sighted amateur football players. Six VI and eight sighted amateur football players performed two functional tasks: (1) 5 m shuttle test and (2) 60 s ball passing against a wall. The sighted players performed the tests while fully sighted (SIG) as well as blindfolded (BFO). During both tasks, full-body kinematics was recorded using an inertial motion capture system. The maximal center-of-mass speed and turning center-of-mass speed were computed during the 5 m shuttle test. Foot resultant speed, bilateral arm speed, and trunk flexion were measured during the 60 s ball passing test. The results showed that VI players achieved lower maximal and turning speed compared to SIG players (p

Vision loss impairs the acquisition of some auditory, motor, and social skills, affecting the psychomotor, social and emotional development of blind people. Despite this, quantitative assessment methods of sensorimotor deficits in case of visual impairments are lacking. The goal of this work is to develop an optimized system for assessing spatial and motor impairments in visually impaired children. This system allows a better evaluation of a rehabilitative therapy with ABBI, the Audio Bracelet for Blind Interaction. It is an all-in-one tool, including a wireless and sensitized set of loudspeakers, controlled by a dedicated Android application on a smartphone. The aim of this innovative technological kit was to accelerate and facilitate assessment procedures for clinicians maintaining the same testing quality.

Objective Cutaneous hyperalgesia is prominent in the ultraviolet-B (UVB) model of inflammatory pain. This study investigated possible interactions between cutaneous and deep tissues hyperalgesia. Methods A total of 16 healthy volunteers participated in the study. Skin inflammation was induced unilaterally by UVB irradiation (three times of the individual minimal erythema dose) in square-shaped areas on the upper-trapezius and lower-back. Moderate delayed onset muscle soreness (DOMS) was induced bilaterally in the low-back by eccentric exercise. Cutaneous blood flow, mechanical thresholds, pressure pain thresholds (PPTs), temporal summation to repetitive pressure stimulation, and stimulus-response functions (SR curve) relating graded pressure stimulations and pain intensity were measured within and outside the irradiated areas, before and 24 hours after irradiation and eccentric muscle exercise. Results Compared with baseline (P < 0.05): the assessments 24 hours after irradiation demonstrated: 1) increased superficial blood flow inside and outside the irradiated areas and in the DOMS site; 2) reduced mechanical thresholds within the irradiated areas; 3) left-shifted SR curve function within and outside the irradiated areas; and 4) facilitated temporal summation of pain inside the irradiated areas and in the DOMS site. There was no significant influence of muscle hyperalgesia on skin measures in normal or UVB-inflamed skin. Conclusions Moderate degrees of muscle sensitization could not facilitate UVB-induced cutaneous mechanical sensitivity, whereas UVB-induced neurogenic inflammation is enhanced when the DOMS is present.

This paper presents the process and results of a set of studies within the ABBI EU project, with the general aim to co-design wearable technology (an audio bracelet) together with visually impaired children, starting at a young age. The authors discuss user preferences related to sounds and tactile materials and present the results of a focus group with very young visually-impaired children under the age of 5, together with their parents. They find that multisensory feedback (visual, tactile/haptic, auditory) is useful and that preferences vary - also the drastic and potentially unpleasant sounds and materials may have a role. Further studies investigate the possibilities of using the ABBI wearable technology for social contexts and games. In a series of game workshops children with and without visual impairments created games with wearable technology employing very simple interactivity. The authors report the created games, and note that even with this simple interactivity it is possible to create fun, inclusive and rich socially co-located games.

Studies have found that portions of space around our body are differently coded by our brain. Numerous works have investigated visual and auditory spatial representation, focusing mostly on the spatial representation of stimuli presented at head level, especially in the frontal space. Only few studies have investigated spatial representation around the entire body and its relationship with motor activity. Moreover, it is still not clear whether the space surrounding us is represented as a unitary dimension or whether it is split up into different portions, differently shaped by our senses and motor activity. To clarify these points, we investigated audio localization of dynamic and static sounds at different body levels. In order to understand the role of a motor action in auditory space representation, we asked subjects to localize sounds by pointing with the hand or the foot, or by giving a verbal answer. We found that the audio sound localization was different depending on the body part considered. Moreover, a different pattern of response was observed when subjects were asked to make actions with respect to the verbal responses. These results suggest that the audio space around our body is split in various spatial portions, which are perceived differently: front, back, around chest, and around foot, suggesting that these four areas could be differently modulated by our senses and our actions.

Blind individuals show impairments for auditory spatial skills that require complex spatial representation of the environment. We suggest that this is partially due to the egocentric frame of reference used by blind individuals. Here we investigate the possibility of reducing the mentioned auditory spatial impairments with an audio-motor training. Our hypothesis is that the association between a motor command and the corresponding movement's sensory feedback can provide an allocentric frame of reference and consequently help blind individuals in understanding complex spatial relationships. Subjects were required to localize the end point of a moving sound before and after either 2-min of audio-motor training or a complete rest. During the training, subjects were asked to move their hand, and consequently the sound source, to freely explore the space around the setup and the body. Both congenital blind (N = 20) and blindfolded healthy controls (N = 28) participated in the study. Results suggest that the audio-motor training was effective in improving space perception of blind individuals. The improvement was not observed in those subjects that did not perform the training. This study demonstrates that it is possible to recalibrate the auditory spatial representation in congenital blind individuals with a short audio-motor training and provides new insights for rehabilitation protocols in blind people.

Hyperalgesia in different musculoskeletal structures including bones is a major clinical problem. An experimental bone hyperalgesia model was developed in the present study. Hyperalgesia was induced by three different weights impacted on the shinbone in 16 healthy male and female subjects. The mechanical impact pain threshold (IPT) was measured as the height from which three weights (165, 330, and 660 g) should be dropped to elicit pain at the shinbone. Temporal summation of pain to repeated impact stimuli was assessed. All these stimuli caused bone hyperalgesia. The pressure pain threshold (PPT) was assessed by a computerized pressure algometer using two different probes (1.0 and 0.5 cm(2)). All parameters were recorded before (0), 24, 72, and 96 h after the initial stimulations. The IPTs were lowest 24 h after hyperalgesia induction for all three weights and the effect lasted up to 72 h (p0.05). The PPT obtained with the 1.0 cm(2) probe was significantly lower than the PPT obtained with the 0.5 cm(2) probe, regardless of the time. Females developed more pronounced hyperalgesia reflected in reduced IPTs and PPTs (p0.05). Temporal summation was significantly (p0.05) facilitated after induction of hyperalgesia with the strongest facilitation in males. The developed bone pain and hyperalgesia model may provide the basis for studying this fundamental mechanism of bone-related hyperalgesia and be used for profiling compounds developed for this target.

Different sensory systems interact to generate a representation of space and to navigate. Vision plays a critical role in the representation of space development. During navigation, vision is integrated with auditory and mobility cues. In blind individuals, visual experience is not available and navigation therefore lacks this important sensory signal. In blind individuals, compensatory mechanisms can be adopted to improve spatial and navigation skills. On the other hand, the limitations of these compensatory mechanisms are not completely clear. Both enhanced and impaired reliance on auditory cues in blind individuals have been reported. Here, we develop a new paradigm to test both auditory perception and navigation skills in blind and sighted individuals and to investigate the effect that visual experience has on the ability to reproduce simple and complex paths. During the navigation task, early blind, late blind and sighted individuals were required first to listen to an audio shape and then to recognize and reproduce it by walking. After each audio shape was presented, a static sound was played and the participants were asked to reach it. Movements were recorded with a motion tracking system. Our results show three main impairments specific to early blind individuals. The first is the tendency to compress the shapes reproduced during navigation. The second is the difficulty to recognize complex audio stimuli, and finally, the third is the difficulty in reproducing the desired shape: early blind participants occasionally reported perceiving a square but they actually reproduced a circle during the navigation task. We discuss these results in terms of compromised spatial reference frames due to lack of visual input during the early period of development.

The fundamental aspects of bone associated pain in humans are not fully understood. In this study pressure pain applied to the tibia bone was investigated experimentally in humans and by means of computer simulations. In humans, the pressure pain sensitivity and the relation between tissue indentation and pressure intensity were recorded by a computer-controlled pressure algometer with two different probe sizes (0.03 cm(2) and 1.0 cm(2)). The simulation-model was validated by the experimental pressure-indentation data and described tissue stress and strain distribution during pressure stimulation. Tissue stress and strain were extracted from the simulation models at the indentation equal to the pressure pain threshold. The pressure pain threshold was higher for the large compared with the small probe size (P

Considering that cortical plasticity is maximal in the child, why are the majority of technological devices available for visually impaired users meant for adults and not for children? Moreover, despite high technological advancements in recent years, why is there still no full user acceptance of existing sensory substitution devices? The goal of this review is to create a link between neuroscientists and engineers by opening a discussion about the direction that the development of technological devices for visually impaired people is taking. Firstly, we review works on spatial and social skills in children with visual impairments, showing that lack of vision is associated with other sensory and motor delays. Secondly, we present some of the technological solutions developed to date for visually impaired people. Doing this, we highlight the core features of these systems and discuss their limits. We also discuss the possible reasons behind the low adaptability in children.

BACKGROUNDS AND OBJECTIVES: Clinical observations indicate that cutaneous hyperalgesia may arise from pain located in deep structures. The objective of this study was to investigate whether combined sensitization of deep and superficial somatic tissues facilitates skin hyperalgesia.METHODS: The interaction between muscle and cutaneous hyperalgesia was investigated in 16 healthy volunteers. Skin sensitization was induced unilaterally on the same randomly selected part of the body by ultraviolet B (UVB) irradiation above the upper trapezius and low back muscles. The next day, muscle hyperalgesia was induced bilaterally in low back muscles by injections of nerve growth factor (NGF). Thus, 1 day after irradiation there was skin sensitization, whereas after 2 days both skin and muscle sensitizations were present. Cutaneous blood flow, pin-prick thresholds, pressure pain thresholds (PPTs), temporal summation to repetitive painful pressure stimulation, and stimulus-response functions of graded pressure stimulations and pain intensity were assessed within the irradiated skin area and in the surrounding area before and 1, 2 and 3 days after irradiation.RESULTS: Comparing baseline with 1 day after irradiation, UVB and UVB+NGF locations demonstrated: (1) Increased superficial blood flow inside the irradiated area (p < 0.01); (2) Reduced pin-prick (p < 0.01) and PPTs (p < 0.05) within the irradiated area and in the surrounding area; (3) Left-shifted pressure stimulus-response function within the irradiated area (p < 0.01); (4) Facilitated temporal summation inside the irradiated area (p < 0.01).CONCLUSIONS: Using skin and deep tissue pain sensitization models simultaneously, no significant synergistic effects were found within the 3-day investigation suggesting little integration between the two phenomena in this period.

The consequence of blindness on auditory spatial localization has been an interesting issue of research in the last decade providing mixed results. Enhanced auditory spatial skills in individuals with visual impairment have been reported by multiple studies, while some aspects of spatial hearing seem to be impaired in the absence of vision. In this study, the ability to encode the trajectory of a 2 dimensional sound motion, reproducing the complete movement, and reaching the correct end-point sound position, is evaluated in 12 early blind individuals, 8 late blind individuals, and 20 age-matched sighted blindfolded controls. Early blind individuals correctly determine the direction of the sound motion on the horizontal axis, but show a clear deficit in encoding the sound motion in the lower side of the plane. On the contrary, late blind individuals and blindfolded controls perform much better with no deficit in the lower side of the plane. In fact the mean localization error resulted 271 ± 10 mm for early blind individuals, 65 ± 4 mm for late blind individuals, and 68 ± 2 mm for sighted blindfolded controls.These results support the hypothesis that i) it exists a trade-off between the development of enhanced perceptual abilities and role of vision in the sound localization abilities of early blind individuals, and ii) the visual information is fundamental in calibrating some aspects of the representation of auditory space in the brain.

Chronic musculoskeletal pain is linked with sensitization, and standardized methods for assessment are needed. This study investigated (1) the test-retest reliability of computer-controlled cuff-pressure algometry (pain thresholds and temporal pain summation) on the arm and leg and (2) conditioned pain modulation (CPM) assessed by cuff algometry. The influences of age and gender were evaluated. On 2 different days, cuff pain threshold (cPPT), cuff pain tolerance (cPTT), and temporal summation of pain (TSP) by visual analog scale scores to 10 repeated cuff stimulations at cPTT intensity, as well as pressure pain threshold with handheld pressure algometry, were assessed in 136 healthy subjects. In one session, cuff pain sensitivity was also assessed before and after cold pressor-induced CPM. Good-to-excellent intraclass correlations (0.60-0.90) were demonstrated for manual and cuff algometry, and no systematic bias between sessions was found for cPPT, cPTT, and TSP on the leg and for cPTT and TSP on the arm. Cuff pressure pain threshold and cPTT were higher in men compared with women (P < 0.05). Middle-aged subjects had higher pressure pain threshold, but lower cPPT and cPTT, compared with younger subjects (P < 0.05). Temporal summation of pain was increased in women compared with men (P < 0.05). Cuff algometry was sensitive to CPM demonstrated as increased cPPT and cPTT and reduced TSP (P < 0.05). Reliability and sensitivity of computer-controlled cuff algometry for pain assessment is comparable with manual pressure algometry and constitutes a user-independent method for assessment of pain. Difference in age-related pain sensitivity between manual and cuff algometry should be further investigated.

This study was designed to assess the effectiveness of the Audio Bracelet for Blind Interaction (ABBI) system for improving mobility and spatial cognition in visually impaired children. The bracelet is worn on the wrist and the key feature is to provide an audio feedback about body movements to help visually impaired children to build a sense of space. Nine early blind children took part at this study. The study lasted 12 weeks. Once per week each child participated in a 45-minutes ABBI rehabilitation with trained professionals. He also had to use it one hour per day at home alone or with one relative. The mobility and spatial cognition abilities were measured before and after a 12-weeks rehabilitation program with three different tests. Results showed that the use of the Audio Bracelet for Blind Interaction allowed the early blind children to significantly improve their mobility and spatial abilities. Although an extended study including a larger number of participants is needed to confirm these data, the present results are encouraging. They do suggest that ABBI could be used for rehabilitate the sense of space in visually impaired children.

The ABBI (Audio Bracelet for Blind Interaction) device is designed for visually impaired and blind children to wear on the wrist and produce sound based on the movement of the arm through space. The primary function is to inform a child (or adult) about his/her own movements to aid spatial cognition rehabilitation. However, the device could also be worn by friends and family and be used to inform the visually impaired person of others' movement in the environment. In this paper, we describe an initial experiment that measured how well blindfolded sighted individuals could track a moving sound source in 2D horizontal space and then walk the same route to the same end position. Six sounds, including natural sounds, abstract sounds, Earcons and speech, were compared to identify which type of sound produced more accurate route recreation

Background and aims The ultraviolet-B (UVB) inflammatory model is a well-established model of inflammatory pain. This study investigated whether UVB-induced cutaneous inflammation would enhance pain responses from the underlying deep somatic areas. Methods Skin inflammation was induced, in 24 healthy volunteers, by UVB irradiation (three times of the individual minimal erythema UVB dose) in square-shaped areas on the forearm and lower back. Assessments of cutaneous blood flow, pin-prick thresholds, pressure pain thresholds and tolerance, stimulus–response functions relating graded pressure stimulations and pain intensity (visual analogue scale, VAS) were performed within and outside the irradiated area. Results Twenty-four hours after UVB irradiation, a significant increase in superficial blood flow in the irradiated skin area was demonstrated compared with baseline (P < 0.01) indicating that inflammation was induced. Compared with baseline, UVB irradiation significantly reduced the pin-prick thresholds, pressure pain thresholds and tolerance within and outside of the irradiated area (P < 0.05). The stimulus–response function was left-shifted compared with baseline both within and outside the irradiated area (P < 0.05) with a more pronounced left-shift within the irradiated area (P < 0.01). Application of topical anaesthesia 24h after irradiation in 5 subjects, both within and outside the irradiated area, could only increase the pin-prick thresholds outside the irradiated area. Conclusion The UVB irradiation of the skin not only provokes cutaneous primary and secondary hyper-algesia but also causes hyperalgesia to blunt pressure stimulations 24h after the UVB exposure. Implications The presented UVB model can be used as a translational model from animals into healthy subjects. This model can potentially be used to screen drug candidates with anti-inflammatory properties in early stages of drug development.

Temporal summation due to repeated pain stimulation of deep somatic structures is facilitated in chronic musculoskeletal pain. In this study, the relation between repeated pressure-induced pain and stress/strain distribution within the deep tissue was evaluated to understand whether tissue characteristics may change during repeated stimulation. This information is important for interpret the pain-evoked responses. The muscle pain intensity was recorded on a 10-cm visual analogue scale (VAS) during ten computer-controlled pressure stimulations (3-s interstimulus interval) at pain threshold intensity. The experimental data validated computer models describing the stress/strain time relationship in the deep tissue during pressure stimulation. VAS scores increased progressively with 2.5 ± 0.7 cm during the ten stimuli (P < 0.02) in contrast to the tissue indentation assessed by ultrasound, which was non-significantly changing leading to a mean of 3.4 ± 0.4 mm. The principal stress peaked in the skin was reduced to 16 % in the underlying muscle tissue and not different during the ten stimuli. The peak principal strain in adipose tissue was 0.12; in muscle tissue, it was 0.108 during the first stimulus and increased by 16 % in the tenth stimulus. In a model of a one-stimulus paradigm, it was found that a VAS increase of 2.5 cm required a 47 % increase in muscle strain. These findings show that the increase in muscle strain during repeated pressure stimulations is not sufficient to explain the VAS increase; the temporal summation of deep-tissue pain evoked by repetitive pressure stimulations is not likely to be fully explained by peripheral tissue changes.

Background/aims The ultraviolet B (UVB) inflammatory pain model is often used to induce a steady hyperalgesic area in human skin. UVB causes a well-described erythema, developing maximal response within about 24 h. The aim of the present study was to investigate if cutaneous UVB irradiation can influence both superficial and deep-tissue mechanical pain thresholds in the site of irradiation and in the surrounding area. Methods An area of 3 cm × 4 cm, located on the low back of 16 healthy volunteers, was irradiated by UVB (Medlight, Germany; 3xMED: Minimal Erythema Dose). The degree of inflammation was detected by measuring superficial blood flow before and after irradiation, inside and outside the stimulated area. Applying quantitative sensory assessments, mechanical pain threshold changes were detected one day after irradiation, within and outside of the irradiated area. Sensitivity to cutaneous mechanical stimuli was assessed using pin prick and deep-tissue pressure pain thresholds were evaluated on 12 spots (4 within and 8 outside, 1.5 cm distant from the irradiated area) by a computer-controlled pressure algometer (Aalborg University, Denmark; 1.0 cm2 flat probe, 0.5 cm2 flat probe and a V-shaped probe with a contact surface of 0.03 cm2). Results 24 h after exposure, the irradiated skin showed clear erythema with a boundary matching the irradiated area and a statistically significant increase in cutaneous blood flow (P < 0.001) compared with baseline assessment. Cutaneous pin prick pain thresholds and deep-tissue pressure pain thresholds (all probes) were significantly decreased inside and outside the irradiated area (P < 0.05). Conclusions Cutaneous UVB irradiation reduces mechanical pain thresholds to pin-prick and pressure stimulation which may indicate allodynic responses in both the skin and in deep-tissues. Expansion of the responses to areas outside the irradiated zone confirmed the presence of secondary hyperalgesia to mechanical stimuli.

Pressure algometry is used for assessment of pain sensitivity. In this study the relation between tissue characteristics and pressure pain thresholds was investigated.Three-dimensional finite-element computer-models were developed to simulate the tissue stress and strain distribution during pressure stimulation on muscles with different hardness (I, II, III, IV (hardest)) and subcutaneous adipose tissue thickness (normal and thicker). The computer model was validated based on data recorded by computer-controlled pressure-induced muscle pain in 8 and 16 partecipants, respectively.The experimental pressure-indentation curve fitted the outcome of the FE model (R0.73). Stress and strain were extracted from the models at a known painful pressure stimulation level. PPT and PPTO were not significantly different in subjects with normal and thick adipose tissue in accordance with the simulation model where the strain in muscle tissue was comparable in the two conditions. The strain in adipose tissue was larger in subjects with thick adipose tissue compared with normal adipose thickness. In relaxed muscle (hardness I) the principal strain peaked at 0.12 in the adipose tissue, was reduced to 0.07 in the muscle tissue and 0.05 in the harder muscle. Significantly higher PPT and PPTO were recorded in harder compared with softer muscles (P0.02).The pressure pain sensitivity of the deep layer is related to the amount of muscle strain, which is affected by the muscle hardness and the thickness of adipose tissue. This is clinically relevant as these two factors are not taken into consideration when pressure pain assessments are performed in clinical routine.

Objective: Pressure algometry is used for assessment of pain sensitivity. In this study the relation between tissue characteristics and pressure pain thresholds was investigated. Methods: Three-dimensional finite-element computer-models were developed to simulate the tissue stress and strain distribution during pressure stimulation on muscles with different hardness (1, II, III, IV (hardest)) and subcutaneous adipose tissue thickness (normal and thicker). The computer model was validated based on data recorded by computer-controlled pressure-induced muscle pain in 8 and 16 partecipants, respectively. Results: The experimental pressure-indentation curve fitted the outcome of the FE model (R 2 > 0.73). Stress and strain were extracted from the models at a known painful pressure stimulation level. PPT and PPTO were not significantly different in subjects with normal and thick adipose tissue in accordance with the simulation model where the strain in muscle tissue was comparable in the two conditions. The strain in adipose tissue was larger in subjects with thick adipose tissue compared with normal adipose thickness. In relaxed muscle (hardness 1) the principal strain peaked at 0.12 in the adipose tissue, was reduced to 0.07 in the muscle tissue and 0.05 in the harder muscle. Significantly higher PPT and PPTO were recorded in harder compared with softer muscles (P < 0.02). Discussion: The pressure pain sensitivity of the deep layer is related to the amount of muscle strain, which is affected by the muscle hardness and the thickness of adipose tissue. This is clinically relevant as these two factors are not taken into consideration when pressure pain assessments are performed in clinical routine.

Pressure algometry is broadly utilized to assess deep tissue sensitivity. In this study the relation between pressure-induced pain in humans and stress/strain distribution within the deep tissue was evaluated. A 3-dimensional finite-element computer model was utilized to describe stress/strain distribution in tissues of the lower leg during pressure stimulation. The computer model was validated based on data recorded by computer-controlled pressure-induced muscle pain in 6 subjects. An indentation of 7 mm was sore for all subjects and at this level data were extracted from each simulation. Simulations were performed with two probe designs (cylindrical and semispherical). The principal stress peaked in the skin and was decreased to about 10% in the underlying muscle tissue. The principal strain peaked in adipose tissue and was reduced in muscle tissue to 80%. The probe evoked a strain peak in adipose tissue at 0.12 (cylindrical) and 0.24 (semispherical); in muscle tissue 0.10 and 0.20 respectively. The shear strains were also reduced using the semispherical tip. The human pressure pain thresholds with the semispherical tip were significantly smaller compared with the flat probe (P