ORCID Profile
0000-0001-5652-395X
Current Organisation
University of Southampton
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Publisher: Wiley
Date: 14-02-2014
DOI: 10.1111/SRT.12148
Abstract: In the absence of humidity receptors in human skin, the perception of skin wetness is considered a somatosensory experience resulting from the integration of temperature (particularly cold) and mechanical inputs. However, limited data are available on the role of the temperature sense. Wet and dry stimuli at 4°C and 8°C above local skin temperature were applied on the back of seven participants (age 21 ± 2 years) while skin temperature and conductance, thermal and wetness perceptions were recorded. Resting local skin temperature was always increased by the application of the stimuli (+0.5-+1.4°C). No effect of stimulus wetness was found on wetness perceptions (P > 0.05). The threshold (point '-2 slightly wet' on the wetness scale) to identify a clearly perceived wetness was never reached during any stimulations and participants did not perceive that some of the stimuli were wet. Overall, warm temperature stimuli suppressed the perception of skin wetness. We conclude that it is not the contact of the skin with moisture per se, but rather the integration of particular sensory inputs (amongst which coldness seems dominant) which drives the perception of skin wetness during the initial contact with a wet surface.
Publisher: American Physiological Society
Date: 04-2017
Abstract: Skin temperature detection thresholds have been used to measure human cold and warm sensitivity across the temperature continuum. They exhibit a sensory zone within which neither warm nor cold sensations prevail. This zone has been widely assumed to coincide with steady-state local skin temperatures between 32 and 34°C, but its underlying neurophysiology has been rarely investigated. In this study we employ two approaches to characterize the properties of sensory thermoneutrality, testing for each whether neutrality shifts along the temperature continuum depending on adaptation to a preceding thermal state. The focus is on local spots of skin on the palm. Ten participants (age: 30.3 ± 4.8 yr) underwent two experiments. Experiment 1 established the cold-to-warm inter-detection threshold range for the palm’s glabrous skin and its shift as a function of 3 starting skin temperatures (26, 31, or 36°C). For the same conditions, experiment 2 determined a thermally neutral zone centered around a thermally neutral point in which thermoreceptors’ activity is balanced. The zone was found to be narrow (~0.98 to ~1.33°C), moving with the starting skin temperature over the temperature span 27.5–34.9°C (Pearson r = 0.94 P 0.001). It falls within the cold-to-warm inter-threshold range (~2.25 to ~2.47°C) but is only half as wide. These findings provide the first quantitative analysis of the local sensory thermoneutral zone in humans, indicating that it does not occur only within a specific range of steady-state skin temperatures (i.e., it shifts across the temperature continuum) and that it differs from the inter-detection threshold range both quantitatively and qualitatively. These findings provide insight into thermoreception neurophysiology. NEW & NOTEWORTHY Contrary to a widespread concept in human thermoreception, we show that local sensory thermoneutrality is achievable outside the 32–34°C skin temperature range. We propose that sensory adaption underlies a new mechanism of temperature integration. Also, we have developed from vision research a new quantitative test addressing the balance in activity of cutaneous cold and warm thermoreceptors. This could have important clinical (assessment of somatosensory abnormalities in neurological disease) and applied (design of personal comfort systems) implications.
Publisher: American Physiological Society
Date: 03-2020
DOI: 10.1152/AJPREGU.00332.2019
Abstract: In contrast to other species, humans are believed to lack hygroreceptors for sensing skin wetness. Yet, the molecular basis of human hygrosensation is currently unknown, and it remains unclear whether we possess a receptor-mediated sensing mechanism for skin wetness. The aim of this study was to assess the role of the cutaneous cold-sensitive transient receptor potential melastatin-8 (TRPM8) channel as a molecular mediator of human hygrosensation. To this end, we exploited both the thermal and chemical activation of TRPM8-expressing cutaneous Aδ cold thermoreceptors, and we assessed wetness sensing in healthy young men in response to 1) dry skin cooling in the TRPM8 range of thermosensitivity and 2) application of the TRPM8 agonist menthol. Our results indicate that 1) independently of contact with moisture, a cold-dry stimulus in the TRPM8 range of activation induced wetness perceptions across 12 different body regions and those wetness perceptions varied across the body following regional differences in cold sensitivity and 2) independently of skin cooling, menthol-induced stimulation of TRPM8 triggered wetness perceptions that were greater than those induced by physical dry cooling and by contact with an aqueous cream containing actual moisture. For the first time, we show that the cutaneous cold-sensing TRPM8 channel plays the dual role of cold and wetness sensor in human skin and that this ion channel is a peripheral mediator of human skin wetness perception.
Publisher: Elsevier BV
Date: 09-2013
DOI: 10.1016/J.NEULET.2013.07.015
Abstract: Cold sensations are suggested as the primary inducer of the perception of skin wetness. However, limited data are available on the effects of skin cooling. Hence, we investigated the role of peripheral cold afferents in the perception of wetness. Six cold-dry stimuli (producing skin cooling rates in a range of 0.02-0.41°C/s) were applied on the forearm of 9 female participants. Skin temperature and conductance, thermal and wetness perception were recorded. Five out of 9 participants perceived wetness as a result of cold-dry stimuli with cooling rates in a range of 0.14-0.41°C/s, while 4 did not perceive skin wetness at all. Although skin cooling and cold sensations play a role in evoking the perception of wetness, these are not always of a primary importance and other sensory modalities (i.e. touch and vision), as well as the inter-in idual variability in thermal sensitivity, might be equally determinant in characterising this perception.
Publisher: Elsevier BV
Date: 10-2019
DOI: 10.1016/J.JTHERBIO.2019.102412
Abstract: Hygroreceptors are a type of humidity sensor that have been identified in several invertebrate classes including Insecta and Arachnida. While their structure has been well researched, the nature of the mechanisms behind their function is debated as being either mechanical, evaporative, or psychrometric in insects and potentially also olfactory in arachnids. There is evidence that can be used to support or oppose each of these concepts, which also invites the possibility of multiple unified mechanisms occurring together. The integration of multiple sensory modalities has also formed the foundation of wetness perception in humans, led by thermal and tactile cues with supplementary information from vision and sound. These inputs are integrated by a vast neural network in the brain, which also occurs on a smaller scale in insects and arachnids. It is possible that as cerebral capacity increased throughout human evolution, this facilitated a preferable system of wetness perception via multisensory integration and rendered hygroreceptors obsolete. While this cerebral development hypothesis is only speculative, it gives a framework for further investigation. Additional research needs to be conducted to correctly classify hygroreceptor types in invertebrates and their relative prevalence before evolutionary associations can be made with vertebrate species. This integratory premise also applies to the human system, as knowing the relative contribution and compounding effects of each sensory modality on wetness perception will aid the overall understanding of the system and help to uncover the evolutionary development pathways underpinning each sense.
Publisher: Elsevier BV
Date: 07-2023
Publisher: Termedia Sp. z.o.o.
Date: 09-2013
Abstract: The aim of this study was to investigate the effect of an increasing number of training hours of specific highintensity karate training on postural sway in preadolescent karate athletes. Seventy-four karatekas were randomly assigned to 1 of 2 groups: Karate Group (KG=37): age 10.29±1.68 yrs or Control Group (CG= 37): age 10.06±1.77 yrs. The KG performed two sessions per day for 1 week in total, while the CG performed only 3 sessions during the same period. The center-of-pressure length (COPL) and velocity (COPV) were recorded under four different experimental conditions: open eyes (EO), closed eyes (EC), open eyes monopodalic left (EOL), open eyes monopodalic right (EOR), pre as well as post training intervention. Post-c results indicated significant differences between the groups in the COPL p .001 an interaction of training type×time in the COPV (p .001) and an interaction of training type×time (p=0.020). The KG revealed an improvement in the COPL from pre to post-c under conditions of EO [-37.26% (p .001)], EC [-31.72% (p .001)], EOL [-27.27% (p .001)], EOR [-21.44% (p .001)], while CG revealed small adaptations in conditions of EO (3.16%), EC (0.93%), EOL (-3.03%), EOR (-0.97%). Furthermore, in the KG an improvement in the COPV from pre to post-c was observed in conditions of EO [-37.92% (p .001)], EC [-32.52% (p .001)], EOL [-29.11% (p .001)], EOR [-21.49% (p .001)]. In summary, one-week of high intensity karate training induced a significant improvement in static body balance in preadolescent karate athletes. Karate performance requires high-levels of both static and dynamic balance. Further research dealing with the effect of karate practice on dynamic body balance in young athletes is required.
Publisher: Wiley
Date: 13-06-2016
DOI: 10.1002/CPHY.C150040
Abstract: Undoubtedly, adjusting our thermoregulatory behavior represents the most effective mechanism to maintain thermal homeostasis and ensure survival in the erse thermal environments that we face on this planet. Remarkably, our thermal behavior is entirely dependent on the ability to detect variations in our internal (i.e., body) and external environment, via sensing changes in skin temperature and wetness. In the past 30 years, we have seen a significant expansion of our understanding of the molecular, neuroanatomical, and neurophysiological mechanisms that allow humans to sense temperature and humidity. The discovery of temperature‐activated ion channels which gate the generation of action potentials in thermosensitive neurons, along with the characterization of the spino‐thalamo‐cortical thermosensory pathway, and the development of neural models for the perception of skin wetness, are only some of the recent advances which have provided incredible insights on how biophysical changes in skin temperature and wetness are transduced into those neural signals which constitute the physiological substrate of skin thermal and wetness sensations. Understanding how afferent thermal inputs are integrated and how these contribute to behavioral and autonomic thermoregulatory responses under normal brain function is critical to determine how these mechanisms are disrupted in those neurological conditions, which see the concurrent presence of afferent thermosensory abnormalities and efferent thermoregulatory dysfunctions. Furthermore, advancing the knowledge on skin thermal and wetness sensations is crucial to support the development of neuroprosthetics. In light of the aforementioned text, this review will focus on the peripheral and central neurophysiological mechanisms underpinning skin thermal and wetness sensations in humans. © 2016 American Physiological Society. Compr Physiol 6:1279‐1294, 2016.
Publisher: Informa UK Limited
Date: 03-07-2018
Publisher: Wiley
Date: 26-12-2016
DOI: 10.1113/JP273052
Publisher: Elsevier BV
Date: 2020
Publisher: Informa UK Limited
Date: 28-02-2014
DOI: 10.1080/02640414.2014.889840
Abstract: The aim of this study was to investigate the effects of a single bout of whole-body vibration (WBV) on running gait. The running kinematic of sixteen male marathon runners was assessed on a treadmill at iso-efficiency speed after 10 min of WBV and SHAM (i.e. no WBV) conditions. A high-speed camera (210 Hz) was used for the video analysis and heart rate (HR) was also monitored. The following parameters were investigated: step length (SL), flight time (FT), step frequency (SF), contact time (CT), HR and the internal work (WINT). Full-within one-way analysis of variance (ANOVA) of the randomised crossover design indicated that when compared to SHAM conditions, WBV decreased the SL and the FT by ~4% (P < 0.0001) and ~7.2% (P < 0.001), respectively, and increased the SF ~4% (P < 0.0001) while the CT was not changed. This effect occurred during the first minute of running: the SL decreased ~3.5% (P < 0.001) and SF increased ~3.3% (P < 0.001). During the second minute the SL decreased ~1.2% (P = 0.017) and the SF increased ~1.1% (P = 0.02). From the third minute onwards, there was a return to the pre-vibration condition. The WINT was increased by ~4% (P < 0.0001) during the WBV condition. Ten minutes of WBV produced a significant alteration of the running kinematics during the first minutes post exposure. These results provide insights on the effects of WBV on the central components controlling muscle function.
Publisher: American Physiological Society
Date: 06-2015
Abstract: Humans sense the wetness of a wet surface through the somatosensory integration of thermal and tactile inputs generated by the interaction between skin and moisture. However, little is known on how wetness is sensed when moisture is produced via sweating. We tested the hypothesis that, in the absence of skin cooling, intermittent tactile cues, as coded by low-threshold skin mechanoreceptors, modulate the perception of sweat-induced skin wetness, independently of the level of physical wetness. Ten males (22 yr old) performed an incremental exercise protocol during two trials designed to induce the same physical skin wetness but to induce lower (TIGHT-FIT) and higher (LOOSE-FIT) wetness perception. In the TIGHT-FIT, a tight-fitting clothing ensemble limited intermittent skin-sweat-clothing tactile interactions. In the LOOSE-FIT, a loose-fitting ensemble allowed free skin-sweat-clothing interactions. Heart rate, core and skin temperature, galvanic skin conductance (GSC), and physical ( w body ) and perceived skin wetness were recorded. Exercise-induced sweat production and physical wetness increased significantly [GSC: 3.1 μS, SD 0.3 to 18.8 μS, SD 1.3, P 0.01 w body : 0.26 no-dimension units (nd), SD 0.02, to 0.92 nd, SD 0.01, P 0.01], with no differences between TIGHT-FIT and LOOSE-FIT ( P 0.05). However, the limited intermittent tactile inputs generated by the TIGHT-FIT ensemble reduced significantly whole-body and regional wetness perception ( P 0.01). This reduction was more pronounced when between 40 and 80% of the body was covered in sweat. We conclude that the central integration of intermittent mechanical interactions between skin, sweat, and clothing, as coded by low-threshold skin mechanoreceptors, significantly contributes to the ability to sense sweat-induced skin wetness.
Publisher: Elsevier BV
Date: 09-2016
DOI: 10.1016/J.CELLSIG.2016.05.010
Abstract: Deletions in the gene encoding signal-transducing inositol phospholipid-specific phospholipase C-γ2 (PLCγ2) are associated with the novel human hereditary disease PLAID (PLCγ2-associated antibody deficiency and immune dysregulation). PLAID is characterized by a rather puzzling concurrence of augmented and diminished functions of the immune system, such as cold urticaria triggered by only minimal decreases in temperature, autoimmunity, and immunodeficiency. Understanding of the functional effects of the genomic alterations at the level of the affected enzyme, PLCγ2, is currently lacking. PLCγ2 is critically involved in coupling various cell surface receptors to regulation of important functions of immune cells such as mast cells, B cells, monocytes/macrophages, and neutrophils. PLCγ2 is unique by carrying three Src (SH) and one split pleckstrin homology domain (spPH) between the two catalytic subdomains (spPHn-SH2n-SH2c-SH3-spPHc). Prevailing evidence suggests that activation of PLCγ2 is primarily due to loss of SH-region-mediated autoinhibition and/or enhanced plasma membrane translocation. Here, we show that the two PLAID PLCγ2 mutants lacking portions of the SH region are strongly (>100-fold), rapidly, and reversibly activated by cooling by only a few degrees. We found that the mechanism(s) underlying PLCγ2 PLAID mutant activation by cool temperatures is distinct from a mere loss of SH-region-mediated autoinhibition and dependent on both the integrity and the pliability of the spPH domain. The results suggest a new mechanism of PLCγ activation with unique thermodynamic features and assign a novel regulatory role to its spPH domain. Involvement of this mechanism in other human disease states associated with cooling such as exertional asthma and certain acute coronary events appears an intriguing possibility.
Publisher: American Physiological Society
Date: 05-2021
Abstract: The perception of wetness is a fundamental sensory experience which underpins many aspects of life, from homeostasis to enjoyable experiences. Although previous research has highlighted the importance of cold sensations in human wetness perception, the maximum sensitivity of our wetness sensing system remains to be established. This research presents a novel methodology, which for the first time, has quantified the high sensitivity of the human index fingerpad to wetness and its modulation by moisture temperature.
Publisher: Springer Science and Business Media LLC
Date: 21-11-2015
Publisher: American Physiological Society
Date: 11-2022
DOI: 10.1152/AJPREGU.00149.2022
Abstract: Skin wetness sensing is important for thermal stress resilience. In iduals with multiple sclerosis (MS) present greater vulnerability to thermal stress yet, it is unclear whether they present wetness-sensing abnormalities. We investigated the effects of MS on wetness sensing and their modulation with changes in mean skin temperature (T sk ). Twelve participants with MS [5 males (M)/7 females (F) 48.3 ± 10.8 yr Expanded Disability Status Scale (EDSS) range: 1–7] and 11 healthy controls (4 M/7 F 47.5 ± 11.3 yr) undertook three trials, during which they performed a quantitative sensory test with either a thermoneutral (30.9°C), warm (34.8°C), or cold (26.5°C) mean T sk . Participants reported on visual analog scales local wetness perceptions arising from the static and dynamic application of a cold-, neutral-, and warm-wet probe (1.32 cm 2 water content: 0.8 mL), to the index finger pad, forearm, and forehead. Data were analyzed for the group-level effect of MS, as well as for its in idual variability. Our results indicated that MS did not alter skin wetness sensitivity at a group level, across the skin sites and temperature tested, neither under normothermia nor under conditions of shifted thermal state. However, when taking an in idualized approach to profiling wetness-sensing abnormalities in MS, we found that 3 of the 12 participants with MS (i.e., 25% of the s le) presented a reduced wetness sensitivity on multiple skin sites and to different wet stimuli (i.e., cold, neutral, and warm wet). We conclude that some in iduals with MS may possess reduced wetness sensitivity however, this sensory symptom may vary greatly at an in idual level. Larger-scale studies are warranted to characterize the mechanisms underlying such in idual variability.
Publisher: Wiley
Date: 05-2020
DOI: 10.14814/PHY2.14425
Publisher: Elsevier BV
Date: 2014
DOI: 10.1016/J.NEUROSCIENCE.2013.11.019
Abstract: The central integration of thermal (i.e. cold) and mechanical (i.e. pressure) sensory afferents is suggested as to underpin the perception of skin wetness. However, the role of temperature and mechanical inputs, and their interaction, is still unclear. Also, it is unknown whether this intra-sensory interaction changes according to the activity performed or the environmental conditions. Hence, we investigated the role of peripheral cold afferents, and their interaction with tactile afferents, in the perception of local skin wetness during rest and exercise in thermo-neutral and warm environments. Six cold-dry stimuli, characterized by decreasing temperatures [i.e. -4, -8 and -15 °C below the local skin temperature (T(sk))] and by different mechanical pressures [i.e. low pressure (LP): 7 kPa high pressure (HP): 10 kPa], were applied on the back of 8 female participants (age 21 ± 1 years), while they were resting or cycling in 22 or 33 °C ambient temperature. Mean and local Tsk, thermal and wetness perceptions were recorded during the tests. Cold-dry stimuli produced drops in Tsk with cooling rates in a range of 0.06-0.4 °C/s. Colder stimuli resulted in increasing coldness and in stimuli being significantly more often perceived as wet, particularly when producing skin cooling rates of 0.18 °C/s and 0.35 °C/s. However, when stimuli were applied with HP, local wetness perceptions were significantly attenuated. Wetter perceptions were recorded during exercise in the warm environment. We conclude that thermal inputs from peripheral cutaneous afferents are critical in characterizing the perception of local skin wetness. However, the role of these inputs might be modulated by an intra-sensory interaction with the tactile afferents. These findings indicate that human sensory integration is remarkably multimodal.
Publisher: Elsevier
Date: 2018
Publisher: Elsevier BV
Date: 04-2015
DOI: 10.1016/J.JBMT.2014.11.019
Abstract: The aim of this study was to evaluate a new method to perform the one repetition maximum (1RM) bench press test, by combining previously validated predictive and practical procedures. Eight young male and 7 females participants, with no previous experience of resistance training, performed a first set of repetitions to fatigue (RTF) with a workload corresponding to ⅓ of their body mass (BM) for a maximum of 25 repetitions. Following a 5-min recovery period, a second set of RTF was performed with a workload corresponding to ½ of participants' BM. The number of repetitions performed in this set was then used to predict the workload to be used for the 1RM bench press test using Mayhew's equation. Oxygen consumption, heart rate and blood lactate were monitored before, during and after each 1RM attempt. A significant effect of gender was found on the maximum number of repetitions achieved during the RTF set performed with ½ of participants' BM (males: 25.0 ± 6.3 females: 11.0x± 10.6 t = 6.2 p < 0.001). The 1RM attempt performed with the workload predicted by Mayhew's equation resulted in females performing 1.2 ± 0.7 repetitions, while males performed 4.8 ± 1.9 repetitions. All participants reached their 1RM performance within 3 attempts, thus resulting in a maximum of 5 sets required to successfully perform the 1RM bench press test. We conclude that, by combining previously validated predictive equations with practical procedures (i.e. using a fraction of participants' BM to determine the workload for an RTF set), the new method we tested appeared safe, accurate (particularly in females) and time-effective in the practical evaluation of 1RM performance in inexperienced in iduals.
Publisher: American Physiological Society
Date: 15-10-2014
DOI: 10.1152/JAPPLPHYSIOL.00535.2014
Abstract: Sensing skin wetness is linked to inputs arising from cutaneous cold-sensitive afferents. As thermosensitivity to cold varies significantly across the torso, we investigated whether similar regional differences in wetness perception exist. We also investigated the regional differences in thermal pleasantness and whether these sensory patterns are influenced by ambient temperature. Sixteen males (20 ± 2 yr) underwent a quantitative sensory test under thermo-neutral [air temperature (T air ) = 22°C relative humidity (RH) = 50%] and warm conditions (T air = 33°C RH = 50%). Twelve regions of the torso were stimulated with a dry thermal probe (25 cm 2 ) with a temperature of 15°C below local skin temperature (T sk ). Variations in T sk , thermal, wetness, and pleasantness sensations were recorded. As a result of the same cold-dry stimulus, the skin-cooling response varied significantly by location ( P = 0.003). The lateral chest showed the greatest cooling (−5 ± 0.4°C), whereas the lower back showed the smallest (−1.9 ± 0.4°C). Thermal sensations varied significantly by location and independently from regional variations in skin cooling with colder sensations reported on the lateral abdomen and lower back. Similarly, the frequency of perceived skin wetness was significantly greater on the lateral and lower back as opposed to the medial chest. Overall wetness perception was slightly higher under warm conditions. Significantly more unpleasant sensations were recorded when the lateral abdomen and lateral and lower back were stimulated. We conclude that humans present regional differences in skin wetness perception across the torso, with a pattern similar to the regional differences in thermosensitivity to cold. These findings indicate the presence of a heterogeneous distribution of cold-sensitive thermo-afferent information.
Publisher: Wiley
Date: 02-06-2019
DOI: 10.1113/JP277928
Publisher: Wiley
Date: 29-10-2015
DOI: 10.1113/JP271507
Publisher: Wiley
Date: 12-12-2016
DOI: 10.1113/EP085955
Publisher: American Physiological Society
Date: 09-2018
DOI: 10.1152/JAPPLPHYSIOL.00158.2018
Abstract: The ability of hands and feet to convey skin thermal sensations is an important contributor to our experience of the surrounding world. Surprisingly, the detailed topographical distribution of warm and cold thermosensitivity across hands and feet has not been mapped, although sensitivity maps exist for touch and pain. Using a recently developed quantitative sensory test, we mapped warm and cold thermosensitivity of 103 skin sites over glabrous and hairy skin of hands and feet in male (M 30.2 ± 5.8 yr) and female (F 27.7 ± 5.1 yr) adults matched for body surface area (M: 1.77 ± 0.2 m 2 F: 1.64 ± 0.1 m 2 P = 0.155). Findings indicated that warm and cold thermosensitivity varies by fivefold across glabrous and hairy skin of hands and feet and that hands (warm/cold sensitivity: 1.25/2.14 vote/°C) are twice as sensitive as the feet (warm/cold sensitivity: 0.51/0.99 vote/°C). Opposite to what is known for touch and pain sensitivity, we observed a characteristic distal-to-proximal increase in thermosensitivity over both hairy and glabrous skin (i.e., from fingers and toes to body of hands and feet), and found that hairy skin is more sensitive than glabrous. Finally, we show that body surface area-matched men and women presented small differences in thermosensitivity and that these differences are constrained to glabrous skin only. Our high-density thermosensory micromapping provides the most detailed thermosensitivity maps of hands and feet in young adults available to date. These maps offer a window into peripheral and central mechanisms of thermosensory integration in humans and will help guide future developments in smart skin and sensory neuroprostheses, in wearable, energy-efficient personal comfort systems, and in sport and protective clothing. NEW & NOTEWORTHY We provide the most detailed thermosensitivity maps across glabrous and hairy skin of hands and feet in men and women available to date. Our maps show that thermosensitivity varies by fivefold across hands and feet, distal regions (e.g., fingers, toes) are less sensitive than proximal (e.g., palm, sole), hands are twice as sensitive as feet, and men and women present small thermosensitivity differences. These findings will help guide developments in sensory neuroprostheses, wearable comfort systems, and sport rotective clothing.
Publisher: American Physiological Society
Date: 12-2020
DOI: 10.1152/AJPREGU.00226.2020
Abstract: Many occupations and sports require high levels of manual dexterity under thermal stress and mental fatigue. Yet, multistressor studies remain scarce. We quantified the interactive effects of thermal stress and mental fatigue on manual dexterity. Seven males (21.1 ± 1.3 yr) underwent six separate 60-min trials characterized by a combination of three air temperatures (hot, 37°C neutral, 21°C cold, 7°C) and two mental fatigue states (MF, mental fatigue induced by a 35-min cognitive battery no-MF, no mental fatigue). Participants performed complex (O’Connor test) and simple (hand-tool test) manual tasks pre- and posttrial to determine stressor-induced performance changes. We monitored participants’ rectal temperature and hand skin temperature (T hand ) continuously and assessed the reaction time (hand-click test) and subjective mental fatigue (5-point scale). Thermal stress ( P 0.0001), but not mental fatigue ( P = 0.290), modulated T hand (heat, +3.3°C [95% CI: +0.2, +6.5] cold, −7.5°C [−10.7, −4.4]). Mental fatigue ( P = 0.021), but not thermal stress ( P = 0.646), slowed the reaction time (∼10%) and increased subjective fatigue. Thermal stress and mental fatigue had an interactive effect on the complex manual task ( P = 0.040), with cold-no-MF decreasing the performance by −22% [−39, −5], whereas neutral-MF, cold-MF, and heat-MF by −36% [−53, −19], −34% [−52, −17], and −36% [−53, −19], respectively. Only mental fatigue decreased the performance in the simple manual task (−30% [−43, −16] across all thermal conditions P = 0.002). Cold stress-induced impairments in complex manipulation increase with mental fatigue yet combined stressors’ effects are no greater than those of mental fatigue alone, which also impairs simple manipulation. Mental fatigue poses a greater challenge to manual dexterity than thermal stress.
Publisher: American Physiological Society
Date: 08-2015
Abstract: Although the ability to detect humidity (i.e., hygrosensation) represents an important sensory attribute in many animal species (including humans), the neurophysiological and molecular bases of such sensory ability remain largely unknown in many animals. Recently, Russell and colleagues (Russell J, Vidal-Gadea AG, Makay A, Lanam C, Pierce-Shimomura JT. Proc Natl Acad Sci USA 111: 8269–8274, 2014) provided for the first time neuromolecular evidence for the sensory integration of thermal and mechanical sensory cues which underpin the hygrosensation strategy of an animal (i.e., the free-living roundworm Caenorhabditis elegans) that lacks specific sensory organs for humidity detection (i.e., hygroreceptors). Due to the remarkable similarities in the hygrosensation transduction mechanisms used by hygroreceptor-provided (e.g., insects) and hygroreceptor-lacking species (e.g., roundworms and humans), the findings of Russell et al. highlight potentially universal mechanisms for humidity detection that could be shared across a wide range of species, including humans.
Publisher: American Physiological Society
Date: 2018
DOI: 10.1152/JAPPLPHYSIOL.00232.2017
Abstract: Elevating core temperature at rest causes increases in minute ventilation (V̇e), which lead to reductions in both arterial CO 2 partial pressure (hypocapnia) and cerebral blood flow. We tested the hypothesis that in resting heated humans this hypocapnia diminishes the ventilatory sensitivity to rising core temperature but does not explain a large portion of the decrease in cerebral blood flow. Fourteen healthy men were passively heated using hot-water immersion (41°C) combined with a water-perfused suit, which caused esophageal temperature (T es ) to reach 39°C. During heating in two separate trials, end-tidal CO 2 partial pressure decreased from the level before heating (39.4 ± 2.0 mmHg) to the end of heating (30.5 ± 6.3 mmHg) ( P = 0.005) in the Control trial. This decrease was prevented by breathing CO 2 -enriched air throughout the heating such that end-tidal CO 2 partial pressure did not differ between the beginning (39.8 ± 1.5 mmHg) and end (40.9 ± 2.7 mmHg) of heating ( P = 1.00). The sensitivity to rising T es (i.e., slope of the T es − V̇ E relation) did not differ between the Control and CO 2 -breathing trials (37.1 ± 43.1 vs. 16.5 ± 11.1 l·min −1 ·°C −1 , P = 0.31). In both trials, middle cerebral artery blood velocity (MCAV) decreased early during heating (all P 0.01), despite the absence of hyperventilation-induced hypocapnia. CO 2 breathing increased MCAV relative to Control at the end of heating ( P = 0.005) and explained 36.6% of the heat-induced reduction in MCAV. These results indicate that during passive heating at rest ventilatory sensitivity to rising core temperature is not suppressed by hypocapnia and that most of the decrease in cerebral blood flow occurs independently of hypocapnia. NEW & NOTEWORTHY Hyperthermia causes hyperventilation and concomitant hypocapnia and cerebral hypoperfusion. The last may underlie central fatigue. We are the first to demonstrate that hyperthermia-induced hyperventilation is not suppressed by the resultant hypocapnia and that hypocapnia explains only 36% of cerebral hypoperfusion elicited by hyperthermia. These new findings advance our understanding of the mechanisms controlling ventilation and cerebral blood flow during heat stress, which may be useful for developing interventions aimed at preventing central fatigue during hyperthermia.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 04-2018
Publisher: Informa UK Limited
Date: 03-02-2015
Publisher: American Physiological Society
Date: 03-2021
DOI: 10.1152/AJPREGU.00090.2020
Abstract: The purpose of this study is to determine whether thermoregulatory capacity is altered by multiple sclerosis (MS) during exercise in the heat. Sixteen MS participants (EDSS: 2.9 ± 0.9 47 ± 8 yr 77.6 ± 14.0 kg) and 14 healthy control (CON) participants (43 ± 11 yr 78.6 ± 17.0 kg) cycled at a heat production of 4 W·kg −1 for 60 min at 30°C, 30% relative humidity (RH) (Warm). A subset of eight MS (EDSS: 2.6 ± 0.5 44 ± 8 yr 82.3 ± 18.2 kg) and 8 CON (44 ± 12 yr 81.2 ± 21.1 kg) also exercised at 35°C, 30% RH (Hot). Rectal temperature (T re ), mean skin (T sk ) temperature, and local sweat rate (LSR) on the upper back (LSR back ) and forearm (LSR arm ) were measured. All CON, and only 9 of 16 and 7 of 8 MS participants completed 60 min of exercise in Warm and Hot trials, respectively. All MS participants who were unable to complete exercise stopped with a ΔT re between 0.2 and 0.5°C. The time to reach a ΔT re of 0.2°C was similar (MS: 28 ± 15 min, CON: 32 ± 18 min P = 0.51). For MS participants, completing 60-min of exercise in Warm, ΔT re ( P = 0.13), ΔT sk ( P = 0.45), LSR back ( P = 0.69), and LSR arm ( P = 0.54) was similar to CON, but ΔT b (body temperature) (MS: 0.16 ± 0.13°C, CON: 0.07 ± 0.06°C P = 0.02) and onset time (MS: 16 ± 10 min, CON: 8 ± 5 min P = 0.02) for sweating were greater in MS. Similarly, in Hot, ΔT re ( P = 0.52), ΔT sk ( P = 0.06), LSR back ( P = 0.59), and LSR arm ( P = 0.08) were similar, but ΔT b (MS: 0.19 ± 0.16°C, CON: 0.06 ± 0.04°C P = 0.04) and onset time (MS: 13 ± 7 min, CON: 6 ± 3 min P = 0.02) for sweating were greater in MS. Even at 35°C, a delayed sweating onset did not alter heat loss to sufficiently affect exercise-induced rises in core temperature. Heat intolerance with MS does not seem attributable to thermoregulatory impairments.
Publisher: American Physiological Society
Date: 03-2022
Abstract: Our skin often interacts with wet materials, yet how their physical properties influence our experience of wetness remains poorly understood. We evaluated wetness perception following naturalistic haptic interactions with materials varying in moisture content, friction, optical profiles, and heat transfer rates. We show that although mechanical parameters can influence wetness perception, their role is secondary to that of thermal factors. These findings expand our understanding of multisensory integration and could guide innovation in healthcare product design.
Publisher: Informa UK Limited
Date: 11-07-2014
DOI: 10.3109/00016489.2014.906749
Abstract: Posturographic tests can be used to assess and confirm the body's imbalance in subjects with whiplash injury. Further studies with larger cohorts are necessary to confirm this pilot study. To verify through a posturographic exam the qualitative and quantitative alterations of postural stability in subjects with previous cervical trauma in comparison with healthy subjects. A total of 42 subjects were analysed for the study 22 as the control group (NM) and 20 (WM) with a positive anamnesis of whiplash injury from 3 to 12 month from diagnosis through a force platform. Centre of pressure (CoP) movements of the two groups with their eyes open and closed were recorded. During the closed eye test, the subjects with cervical injuries displayed a significant increase in the anterior-posterior oscillation velocity (p < 0.05) compared with the control group, with a significant reduction (p < 0.01) of the ratio between the shifting length (SL) of CoP on the polygon support and the total envelope area (EA, mm(2)) of CoP movements in the polygon support (SL/EA-ratio, mm(-1)).
Publisher: American Physiological Society
Date: 04-2017
Abstract: Our perception of skin wetness is generated readily, yet humans have no known receptor (hygroreceptor) to signal this directly. It is easy to imagine the sensation of water running over our hands or the feel of rain on our skin. The synthetic sensation of wetness is thought to be produced from a combination of specific skin thermal and tactile inputs, registered through thermoreceptors and mechanoreceptors, respectively. The present review explores how thermal and tactile afference from the periphery can generate the percept of wetness centrally. We propose that the main signals include information about skin cooling, signaled primarily by thinly myelinated thermoreceptors, and rapid changes in touch, through fast-conducting, myelinated mechanoreceptors. Potential central sites for integration of these signals, and thus the perception of skin wetness, include the primary and secondary somatosensory cortices and the insula cortex. The interactions underlying these processes can also be modeled to aid in understanding and engineering the mechanisms. Furthermore, we discuss the role that sensing wetness could play in precision grip and the dexterous manipulation of objects. We expand on these lines of inquiry to the application of the knowledge in designing and creating skin sensory feedback in prosthetics. The addition of real-time, complex sensory signals would mark a significant advance in the use and incorporation of prosthetic body parts for utees in everyday life.
Publisher: Wiley
Date: 06-05-2015
DOI: 10.1111/SMS.12322
Abstract: We investigated the effects of mild evaporative cooling applied to the torso, before or during running in the heat. Nine male participants performed three trials: control-no cooling (CTR), pre-exercise cooling (PRE-COOL), and during-exercise cooling (COOL). Trials consisted of 10-min neutral exposure and 50-min heat exposure (30 °C 44% humidity), during which a 30-min running protocol (70% VO2max ) was performed. An evaporative cooling t-shirt was worn before the heat exposure (PRE-COOL) or 15 min after the exercise was started (COOL). PRE-COOL significantly lowered local skin temperature (Tsk ) (up to -5.3 ± 0.3 °C) (P < 0.001), mean Tsk (up to -2 ± 0.1 °C) (P < 0.001), sweat losses (-143 ± 40 g) (P = 0.002), and improved thermal comfort (P = 0.001). COOL suddenly lowered local Tsk (up to -3.8 ± 0.2 °C) (P < 0.001), mean Tsk (up to -1 ± 0.1 °C) (P < 0.001), heart rate (up to -11 ± 2 bpm) (P = 0.03), perceived exertion (P = 0.001), and improved thermal comfort (P = 0.001). We conclude that the mild evaporative cooling provided significant thermoregulatory benefits during exercise in the heat. However, the timing of application was critical in inducing different thermoregulatory responses. These findings provide novel insights on the thermoregulatory role of Tsk during exercise in the heat.
Publisher: Cold Spring Harbor Laboratory
Date: 18-08-2022
DOI: 10.1101/2022.08.18.504401
Abstract: Preliminary human studies show that reduced skin temperature minimises the risk of mechanically-induced skin damage. However, the mechanisms by which cooling enhances skin tolerance to pressure and shear remain poorly understood. We hypothesized that skin cooling below thermo-neutral conditions will decrease friction at the skin-material interface. To test our hypothesis, we measured the friction coefficient of a thermally pre-conditioned index finger sliding at a normal load (5N) across a plate maintained at three different temperatures (38, 24, and 16□). To quantify the temperature distribution of the skin tissue, we used 3D surface scanning and Optical Coherence Tomography to develop an anatomically-representative thermal model of the finger. Our data indicated that the sliding finger with thermally affected tissues (up to 8mm depth) experienced significantly (p .01) lower frictional forces at 16°C-plate temperature than at the 24°C [-23% (±19% SD)] and 38°C plate interactions [-35% (±11% SD)], respectively. This phenomenon occurred without changes in skin hydration during sliding. Accordingly, our experiments demonstrate thermal modulation of skin friction in the absence of skin-moisture effects. Our complementary experimental and theoretical results provide new insight into thermal modulation of skin friction that can be employed for developing thermal technologies to maintain skin integrity under mechanical loading.
Publisher: American Physiological Society
Date: 15-03-2016
DOI: 10.1152/JAPPLPHYSIOL.00906.2015
Abstract: We sought to determine 1) the influence of adiposity on thermoregulatory responses independently of the confounding biophysical factors of body mass and metabolic heat production (H prod ) and 2) whether differences in adiposity should be accounted for by prescribing an exercise intensity eliciting a fixed H prod per kilogram of lean body mass (LBM). Nine low (LO-BF) and nine high (HI-BF) body fat males matched in pairs for total body mass (TBM LO-BF: 88.7 ± 8.4 kg, HI-BF: 90.1 ± 7.9 kg P = 0.72), but with distinctly different percentage body fat (%BF LO-BF: 10.8 ± 3.6% HI-BF: 32.0 ± 5.6% P 0.001), cycled for 60 min at 28.1 ± 0.2°C, 26 ± 8% relative humidity (RH), at a target H prod of 1) 550 W (FHP trial) and 2) 7.5 W/kg LBM (LBM trial). Changes in rectal temperature (ΔT re ) and local sweat rate (LSR) were measured continuously while whole body sweat loss (WBSL) and net heat loss (H loss ) were estimated over 60 min. In the FHP trial, ΔT re (LO-BF: 0.66 ± 0.21°C, HI-BF: 0.87 ± 0.18°C P = 0.02) was greater in HI-BF, whereas mean LSR (LO-BF 0.52 ± 0.19, HI-BF 0.43 ± 0.15 mg·cm −2 ·min −1 P = 0.19), WBSL (LO-BF 586 ± 82 ml, HI-BF 559 ± 75 ml P = 0.47) and H loss (LO-BF 1,867 ± 208 kJ, HI-BF 1,826 ± 224 kJ P = 0.69) were all similar. In the LBM trial, ΔT re (LO-BF 0.82 ± 0.18°C, HI-BF 0.54 ± 0.19°C P 0.001), mean LSR (LO-BF 0.59 ± 0.20, HI-BF 0.38 ± 0.12 mg·cm −2 ·min −1 P = 0.04), WBSL (LO-BF 580 ± 106 ml, HI-BF 381 ± 68 ml P 0.001), and H loss (LO-BF 1,884 ± 277 kJ, HI-BF 1,341 ± 184 kJ P 0.001) were all greater at end-exercise in LO-BF. In conclusion, high %BF in iduals demonstrate a greater ΔT re independently of differences in mass and H prod , possibly due to a lower mean specific heat capacity or impaired sudomotor control. However, thermoregulatory responses of groups with different adiposity levels should not be compared using a fixed H prod in watts per kilogram lean body mass.
Publisher: American Physiological Society
Date: 15-09-2014
Abstract: Although the ability to sense skin wetness and humidity is critical for behavioral and autonomic adaptations, humans are not provided with specific skin receptors for sensing wetness. It has been proposed that we “learn” to perceive the wetness experienced when the skin is in contact with a wet surface or when sweat is produced through a multisensory integration of thermal and tactile inputs generated by the interaction between skin and moisture. However, the in idual roles of thermal and tactile cues and how these are integrated peripherally and centrally by our nervous system is still poorly understood. Here we tested the hypothesis that the central integration of coldness and mechanosensation, as subserved by peripheral A-nerve afferents, might be the primary neural process underpinning human wetness sensitivity. During a quantitative sensory test, we found that in iduals perceived warm-wet and neutral-wet stimuli as significantly less wet than cold-wet stimuli, although these were characterized by the same moisture content. Also, when cutaneous cold and tactile sensitivity was diminished by a selective reduction in the activity of A-nerve afferents, wetness perception was significantly reduced. Based on a concept of perceptual learning and Bayesian perceptual inference, we developed the first neurophysiological model of cutaneous wetness sensitivity centered on the multisensory integration of cold-sensitive and mechanosensitive skin afferents. Our results provide evidence for the existence of a specific information processing model that underpins the neural representation of a typical wet stimulus. These findings contribute to explaining how humans sense warm, neutral, and cold skin wetness.
Publisher: Elsevier BV
Date: 11-2023
Publisher: Elsevier BV
Date: 10-2023
Publisher: American Physiological Society
Date: 05-2018
Publisher: Wiley
Date: 23-05-2017
DOI: 10.1113/EP086320
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United States of America
Location: Italy
Location: United Kingdom of Great Britain and Northern Ireland
Start Date: 2017
End Date: 2021
Funder: Engineering and Physical Sciences Research Council
View Funded ActivityStart Date: 2011
End Date: 2014
Funder: Loughborough University
View Funded ActivityStart Date: 2015
End Date: 2015
Funder: Australian Education International, Australian Government
View Funded Activity