An exploratory study of structural and microvascular changes in the skin following electrical shaving using optical coherence topography.

BACKGROUND: Consumer products such as electrical shavers exert a combination of dynamic loading in the form of pressure and shear on the skin. This mechanical stimulus can lead to discomfort and skin tissue responses characterised as "Skin Sensitivity". To minimise discomfort following shaving, there is a need to establish specific stimulus-response relationships using advanced tools such as optical coherence tomography (OCT). OBJECTIVE: To explore the spatial and temporal changes in skin morphology and microvascular function following an electrical shaving stimulus. METHODS: Ten healthy male volunteers were recruited. The study included a 60-s electrical shaving stimulus on the forearm, cheek and neck. Skin parameters were recorded at baseline, 20 min post stimulus and 24 h post stimulus. Structural and dynamic skin parameters were estimated using OCT, while transepidermal water loss (TEWL) was recorded to provide reference values for skin barrier function. RESULTS: At baseline, six of the eight parameters revealed statistically significant differences between the forearm and the facial sites, while only surface roughness (Rq) and reflectivity were statistically different (p < 0.05) between the cheek and neck. At 20 min post shaving, there was a significant increase in the TEWL values accompanied by increased blood perfusion, with varying magnitude of change dependent on the anatomical site. Recovery characteristics were observed 24 h post stimulus with most parameters returning to basal values, highlighting the transient influence of the stimulus. CONCLUSIONS: OCT parameters revealed spatial and temporal differences in the skin tissue response to electrical shaving. This approach could inform shaver design and prevent skin sensitivity.

Quantifying skin sensitivity caused by mechanical insults: A review.

BACKGROUND: Skin sensitivity (SS) is a commonly occurring response to a range of stimuli, including environmental conditions (e.g., sun exposure), chemical irritants (e.g., soaps and cosmetics), and mechanical forces (e.g., while shaving). From both industry and academia, many efforts have been taken to quantify the characteristics of SS in a standardised manner, but the study is hindered by the lack of an objective definition. METHODS: A review of the scientific literature regarding different parameters attributed to the loss of skin integrity and linked with exhibition of SS was conducted. Articles included were screened for mechanical stimulation of the skin, with objective quantification of tissue responses using biophysical or imaging techniques. Additionally, studies where cohorts of SS and non-SS individuals were reported have been critiqued. RESULTS: The findings identified that the structure and function of the stratum corneum and its effective barrier properties are closely associated with SS. Thus, an array of skin tissue responses has been selected for characterization of SS due to mechanical stimuli, including: transepidermal water loss, hydration, redness, temperature, and sebum index. Additionally, certain imaging tools allow quantification of the superficial skin layers, providing structural characteristics underlying SS. CONCLUSION: This review proposes a multimodal approach for identification of SS, providing a means to characterise skin tissue responses objectively. Optical coherence tomography (OCT) has been suggested as a suitable tool for dermatological research with clinical applications. Such an approach would enhance the knowledge underlying the multifactorial nature of SS and aid the development of personalised solutions in medical and consumer devices.

Asymmetrical loading during non-visual navigation.

Since previous studies showed that loading influences posture and gait, the aim of the present study was to determine the effect of asymmetrical loading on locomotion. The following questions were posed: is there a habituation to asymmetrical loading and what is the effect of immediate unloading? Nine healthy subjects (4 males and 5 females) were tested. They had to memorize visually a triangle drawn on the floor and then to walk clockwise and counterclockwise along it in darkness and blindfolded under the following conditions: baseline, loading of right shoulder with 20% of the body weight, after 30 min of habituation to the weight, and immediately after unloading. The turns in degrees around the angles and the distance of the path in cm were measured. The present study demonstrated that asymmetrical loading, which leads to changes in the somatosensory afferentation, affects the human locomotor pattern. There is a habituation effect as well as an unloading effect. There was also a difference between the changes in clockwise and counterclockwise locomotion. Several hypotheses are discussed to explain the results obtained under all conditions.

Spatial rotational orientation ability in standing children with cerebral palsy.

This study quantified perception and reorientation ability after passive horizontal rotations in thirteen children with cerebral palsy (CP). They stood barefoot on a platform in front of a fixed reference point (static posture task, SPT) and were then blindfolded and passively rotated with six velocity profiles (maximum angular velocity: 57°/s; rotation amplitudes: ±90°, ±180° and ±360°). After the perturbation, the blindfolded children were asked to point to the fixed reference point with their preferred hand (pointing task, PT) and to step back to the initial position on the stationary platform (reorientation task, RT). In order to gain further insight into rotational attitude, the results were comparatively examined with body segment rotations determined using standardized gait analysis (gait task, GT). The kinematic evaluations were conducted using an optoelectronic system: for SPT, PT and RT we confined the analysis, in the horizontal plane, to the head and upper pointing arm of the subject and to the platform; for GT a full body analysis was performed. When CP children were passively rotated towards their more affected side, they overestimated the imposed angle in PT but under-reproduced it in RT. A higher variability emerged in left-hemiplegic children, confirming that the spatial disorganization is predominantly related to right brain lesion. Patients tended to rotate in GT towards the more affected side while in RT they showed an opposite trend.

Vestibular and proprioceptive estimation of imposed rotation and spatial updating in standing subjects.

The aim of the study was to evaluate in standing subjects their perception of whole-body rotation and spatial updating, and to determine whether the brain uses mainly angular velocity or rotational duration to re-orient the body. Ten healthy blindfolded adults stood barefoot on a horizontal rotating platform. Participants had to maintain their balance while being passively rotated by a platform through 45°, 90°, 135°, 180° and 360°, clockwise (CW) and counter-clockwise (CCW). At the end of platform rotation, participants had to give their estimation of the angle. They then had to actively reproduce it in the opposite direction. Three different conditions were applied: one which involved different peak cosinusoidal angular velocity profiles (18°/s, 35°/s, 53°/s, 71°/s and 141°/s) at constant duration of stimulus (4 s); one which involved different stimulus durations (1.25 s, 2.5 s, 3.75 s, 5 s and 10 s) at constant peak velocity (57°/s); and one where subjects had to reproduce a specific angle without prior stimulus imposed by the platform. In the reproduction phase, results show overestimation of stimulus from -180° to 180° in all three conditions; however, ±360° rotations were underestimated only in the first two conditions. Comparing stimulus perception and reproduction, the perceived angle corresponded to that reproduced in the range from -180° to 180°; however, ±360° angles were correctly perceived but inaccurately reproduced. Thus, the interconnection between movement and information via the vestibular/proprioceptive systems is essential to evaluate the body position in space; however, the spatial errors show the key importance of sight in correcting the errors caused by the cue integration.

Reach-to-grasp interjoint coordination for moving object in children with hemiplegia.

OBJECTIVE: To evaluate interjoint coordination in children with hemiplegia as they reach to grasp objects, in both static and dynamic conditions. An ad hoc robotic device was used to study the dynamic condition. DESIGN: Observational study. PATIENTS: Six children with hemiplegia and 6 young adults. METHODS: Kinematics of the trunk and arm were studied using an optoelectronic system. In the dynamic condition the target object, a cup, was moved by the robotic device along clockwise and counterclockwise circular trajectories. RESULTS: Two main strategies were used to study the onset and offset of shoulder and elbow movements and their maximum velocities. The hand velocity profile was bell-shaped in the static condition and compatible with ramp movements for the more affected side in the dynamic condition. The time to object contact was higher for the more affected side in the dynamic condition. The temporal coordination index illustrated an immature and less flexible behaviour in children's reaching in all the examined conditions. CONCLUSION: Study of the hand velocity profiles, the time to object contact and the temporal coordination index highlighted, first, the dependence of upper limb interjoint coordination on task, context, residual resources and individual solution, and secondly, the sensory-motor deficit characteristics of the children's more affected side during dynamic reaching, raising the prospect of a promising training context in children with hemiplegia.