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Fall injuries often occur on extension ladders. The extendable fly section of an extension ladder is typically closer to the user than the base section, though this design is minimally justified. This study investigates the effects of reversing the fly on foot placement, frictional requirements, adverse stepping events (repositioning the foot or kicking the rung), and user preferences. Participant foot placement was farther posterior (rung contacted nearer to toes) in the traditional ladder compared to the reversed fly condition during descent, with farther anterior foot placements during ascent. The reversed configuration had similar friction requirements during early/mid stance and significantly lower frictional requirements during late stance. Increased friction requirements during late stance were associated with farther anterior foot placement and further plantar flexed foot orientation. The reversed fly had 5 adverse stepping events versus 22 that occurred in the traditional configuration. Users typically preferred the reversed fly. These results suggest that a reversed extension ladder configuration offers potential benefits in reducing fall-related injuries that should motivate future research and development work.

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Walking is unstable and requires active control. Foot placement is the primary strategy to maintain frontal-plane balance with contributions from lateral ankle torques, ankle push-off and trunk postural adjustments. Because these strategies interact, their individual contributions are difficult to study. Here, we used computational modelling to understand these individual contributions to frontal-plane walking balance control. A three-dimensional bipedal model was developed based on linear inverted pendulum dynamics. The model included controllers that implement the stabilization strategies seen in human walking. The control parameters were optimized to mimic human gait biomechanics for typical spatio-temporal parameters during steady-state walking and when perturbed by mediolateral ground shifts. Using the optimized model as a starting point, the contributions of each stabilization strategy were explored by progressively removing strategies. The lateral ankle and trunk strategies were more important than ankle push-off, with their removal causing up to 20% worse balance recovery compared with the full model, while removing ankle push-off led to minimal changes. Our results imply a potential benefit of preferentially training these strategies in populations with poor balance. Moreover, the proposed model could be used in future work to investigate how walking stability may be preserved in conditions reflective of injury or disease.

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Plantar shear stress may have an important role in the formation of a Diabetic Foot Ulcer, but its measurement is regarded as challenging and has limited research. This paper highlights the importance of anatomical specific shear sensor calibration and presents a feasibility study of a novel shear sensing system which has measured in-shoe shear stress from gait activity on both healthy and diabetic subjects. The sensing insole was based on a strain gauge array embedded in a silicone insole backed with a commercial normal pressure sensor. Sensor calibration factors were investigated using a custom mechanical test rig with indenter to exert both normal and shear forces. Indenter size and location were varied to investigate the importance of both loading area and position on measurement accuracy. The sensing insole, coupled with the calibration procedure, was tested one participant with diabetes and one healthy participant during two sessions of 15 minutes of treadmill walking. Calibration with different indenter areas (from 78.5 mm2 to 707 mm2) and different positions (up to 40 mm from sensor centre) showed variation in measurements of up to 80% and 90% respectively. Shear sensing results demonstrated high repeatability (>97%) and good accuracy (mean absolute error < ±18 kPa) in bench top mechanical tests and less than 21% variability within walking of 15-minutes duration. The results indicate the importance of mechanical coupling between embedded shear sensors and insole materials. It also highlights the importance of using an appropriate calibration method to ensure accurate shear stress measurement. The novel shear stress measurement system presented in this paper, demonstrates a viable method to measure accurate and repeatable in-shoe shear stress using the calibration procedure described. The validation and calibration methods outlined in this paper could be utilised as a standardised approach for the research community to develop and validate similar measurement technologies.

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Running jumps that depart the ground from two feet require momenta redirection upward from initial momenta that are primarily horizontal. It is not known how each leg generates backward and upward impulses from ground reaction forces to satisfy this mechanical objective when jumping to maximize height. We examined whole-body linear momentum control strategies during these two-foot running jumps by uncovering the roles of each leg in impulse generation. 3D motion capture and force plates were used to record 14 male basketball players performing two-foot running jumps towards an adjustable basketball hoop. Total ground contact phase started from the first leg ground contact and ended at takeoff and was divided into center of mass descent and ascent subphases. During the total ground contact phase, all participants generated significantly more upward impulse with the first leg and ten participants generated significantly more backward impulse with the first leg compared to the second leg. During the descent subphase, all participants generated significantly more upward and backward impulses with the first leg. During the ascent subphase, all but one participant generated significantly more backward impulse with the second leg. In addition to group-level statistics, participant-specific strategies were described. Overall, this study revealed the fundamental whole-body momentum control strategies used in two-foot running jumps and supports future research into optimal jump techniques and training interventions that respect the need to satisfy the mechanical objectives of the movement.

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Pressure-relieving footwear helps prevent foot ulcers in people with diabetes. The footwear design contributes to this effect and includes the insole top cover. We aimed to assess the offloading effect of materials commonly used as insole top cover. We measured 20 participants with diabetes and peripheral neuropathy for in-shoe peak pressures while walking in their prescribed footwear with the insole covered with eight different materials, tested in randomized order. Top covers were a 3 mm or 6 mm thick open or closed-cell foam or a 6 mm thick combination of open- and closed-cell foams. We re-assessed pressures after one month of using the top cover. Peak pressures were assessed per anatomical foot region and a region of interest (i.e., previous ulceration or high barefoot pressure). Walking comfort was assessed using a 10-point Likert scale. Mean peak pressure at the region of interest varied between 167 (SD:56) and 186 (SD:65) kPa across top covers (p < 0.001) and was significantly higher for the 3 mm thick PPT than for four of the seven 6 mm thick top covers. Across 6 mm thick top covers, only two showed a significant peak pressure difference between them. Over time, peak pressures changed non-significantly from -2.7 to +47.8 kPa across top cover conditions. Comfort ratings were 8.0 to 8.4 across top covers (p = 0.863). The 6 mm thick foams provided more pressure relief than the 3 mm thick foam during walking in high-risk people with diabetes. Between the 6 mm thick foams and over time, only small differences exist. The choice of which 6 mm thick insole top cover to use may be determined more by availability, durability, ease of use, costs, or hygienic properties than by superiority in pressure-relief capacity.

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An increase in plantar pressure and skin temperature is commonly associated with an increased risk of diabetic foot ulcers. However, the effect of insoles in reducing plantar temperature has not been commonly studied. The aim was to assess the effect of walking in insoles with different features on plantar temperature. Twenty-six (F/M:18/8) participants-13 with diabetes and 13 healthy, aged 55.67 ± 9.58 years-participated in this study. Skin temperature at seven plantar regions was measured using a thermal camera and reported as the difference between the temperature after walking with an insole for 20 m versus the baseline temperature. The mixed analyses of variance indicated substantial main effects for the Insole Condition, for both the right [Wilks' Lambda = 0.790, F(14, 492) = 4.393, p < 0.01, partial eta squared = 0.111] and left feet [Wilks' Lambda = 0.890, F(14, 492) = 2.103, p < 0.011, partial eta squared = 0.056]. The 2.5 mm-tall dimple insole was shown to be significantly more effective at reducing the temperature in the hallux and third met head regions compared to the 4 mm-tall dimple insole. The insoles showed to be significantly more effective in the diabetes group versus the healthy group, with large effect size for the right [Wilks' Lambda = 0.662, F(14, 492) = 8.037, p < 0.000, Partial eta-squared = 0.186] and left feet [Wilks' Lambda = 0.739, F(14, 492) = 5.727, p < 0.000, Partial eta-squared = 0.140]. This can have important practical implications for designing insoles with a view to decrease foot complications in people with diabetes.

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This study investigated the coactivation of plantar flexor and dorsiflexor muscles and oxygen uptake during running with forefoot and rearfoot strikes at 15 and 19 km/h. We included 16 male runners in this study. The participants ran each foot strike pattern for 5 min at 15 and 19 km/h on a treadmill. During the running, respiratory gas exchange data and surface electromyographic (EMG) activity of the medial gastrocnemius (MG), lateral gastrocnemius (LG), soleus, and tibialis anterior muscles of the right lower limb were continuously recorded. The indices of oxygen uptake, energy expenditure (EE), and muscle activation were calculated during the last 2 min in each condition. During the stance phase of running at 15 and 19 km/h, activation of the tibialis anterior and MG muscles was lower and higher, respectively, with forefoot strike than with rearfoot strike. The foot strike pattern did not influence the oxygen uptake. These results suggest that the foot strike pattern has no clear effect on the oxygen uptake when running at 15 and 19 km/h. However, forefoot strike leads to plantar flexion dominance during co-contraction of the tibialis anterior and MG muscles, which are an antagonist and agonist for plantar flexion, respectively, during the stance phase.

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Lameness is an important veterinary and welfare concern for giraffes in human care. To date, there is limited information on the objective weight-bearing characteristics of the foot in giraffes, making evidence-based decisions for foot care and lameness treatment subjective. Eleven young-adult reticulated giraffes (Giraffa camelopardalis reticulata; median age, 3.5 yr [range, 13 mon-13 yr]), with no clinical lameness or visible hoof overgrowth when viewed from standing, voluntarily walked across a commercially available pressure-sensitive walkway. Footfalls were analyzed for force, pressure, surface area, and impulse from each foot. The weight-bearing claw was also determined based on pressure in both the front and hind limbs. The data obtained suggest that the main weight-bearing claw is the lateral claw in both the forelimbs and the hind limbs the majority of the time, but is inconsistent. The forelimbs also had greater values for all biomechanical variables than the hind limbs. The higher force and pressure suggest that giraffe forelimbs are subjected to greater biomechanical stress than the hind limbs. The relative maximum force from front limbs to hind limbs was 59:41. For these clinically sound giraffes, the center of force was consistently located in the interdigital space approximately equidistant from the toe and heel correlating with the center of mass of the limb. Furthermore, foot strikes occurred in a heel-first pattern. A pressure-sensitive walkway was well tolerated by all animals in the study and may be used in future research to help further elucidate factors that contribute to lameness in giraffes.

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Purpose: This study aimed to evaluate professional footwear comfort, functionality and style as well as their relationships with the foot structure among nurses. Methods: We examined 120 clinical nurses aged 40-50 years, occupationally active, wearing specific type of foot-wear at work for a minimum of 7 h a day, for 5 days prior to the research. The study relied on the CQ-ST podoscope for measurements of foot. Perception of footwear comfort, functionality and style scales were also used in the research. The results were analysed with the use of Mann-Whitney U-test and Spearman's rank correlation. Results: Statistically significant negative associations were found between right and left foot length and overall comfort of footwear ( p = 0.045, p = 0.045) as well as between right and left foot width and arch height ( p = 0.015, p = 0.028). Heel angle positively correlated with safety ( p = 0.008, p = 0.050), ease of donning and doffing ( p = 0.001, p = 0.004), as well as shoe style ratings ( p = 0.047). Variables determining shoe comfort were positively correlated with most shoe functionality characteristics as well as with shoe style (p < 0.05). Conclusions: Tested medical footwear meets the requirements of nurses in terms of comfort, functionality and aesthetics, and the studied features of footwear can be a useful guideline for the selection of shoes for representatives of this professional group. These footwear can be an element of workwear, and even, in the case of women with transverse flat feet - an alternative to ordinary utility shoes. There is a need to consider different widths for the same length size in medical footwear designs.

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When designing footwear products, designers and kinesiologists usually factor in plantar surface pressure, motion capture data, and subjective comfort evaluations. However, these factors alone are not sufficient to guide the design of truly comfortable shoes. Pressure pain threshold (PPT) is a parameter that establishes a connection between psychological quantities and physical quantities. The purpose of this study was to construct a high-precision PPT map of the whole foot. Overall, 20 participants were included in this study, and an electronic, mechanical algometer was used to apply constant pressure to the participants' feet. A MATLAB graphical user interface was developed to simplify the data-collecting process and generate visual representations of the data. Finally, several high-precision unisex, different sex, and dominant side PPT maps were generated. The findings revealed that the foot dorsum area and the medial foot region exhibited the lowest PPTs (indicative of high sensitivity). Notably, the foot dorsum area near the toes displayed the highest pain sensitivity (indicative of the lowest PPT), while the plantar area demonstrated comparatively lower pain sensitivity. The heel area exhibited the lowest pain sensitivity. Simultaneously, the study observed that women's feet exhibited lower pain thresholds than men's. In the future, it is imperative to delve deeper into the correlation between short-term pain sensitivity and the daily, long-term exercise state, as well as other physiological data. This exploration will contribute to a more nuanced guide for footwear comfort design.

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Sarcopenia is an age-related syndrome characterized by the loss of skeletal muscle mass and function. Community screening, commonly used in early diagnosis, usually lacks features such as real-time monitoring, low cost, and convenience. This study introduces a promising approach to sarcopenia screening by dynamic plantar pressure monitoring. We propose a wearable flexible-printed piezoelectric sensing array incorporating barium titanate thin films. Utilizing a flexible printer, we fabricate the array with enhanced compressive strength and measurement range. Signal conversion circuits convert charge signals of the sensors into voltage signals, which are transmitted to a mobile phone via Bluetooth after processing. Through cyclic loading, we obtain the average voltage sensitivity (4.844 mV/kPa) of the sensing array. During a 6 m walk, the dynamic plantar pressure features of 51 recruited participants are extracted, including peak pressures for both sarcopenic and control participants before and after weight calibration. Statistical analysis discerns feature significance between groups, and five machine learning models are employed to screen for sarcopenia with the collected features. The results show that the features of dynamic plantar pressure have great potential in early screening of sarcopenia, and the Support Vector Machine model after feature selection achieves a high accuracy of 93.65%. By combining wearable sensors with machine learning techniques, this study aims to provide more convenient and effective sarcopenia screening methods for the elderly.

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The three Ground Reaction Force (GRF) components can be estimated using pressure insole sensors. In this paper, we compare the accuracy of estimating GRF components for both feet using six methods: three Deep Learning (DL) methods (Artificial Neural Network, Long Short-Term Memory, and Convolutional Neural Network) and three Supervised Machine Learning (SML) methods (Least Squares, Support Vector Regression, and Random Forest (RF)). Data were collected from nine subjects across six activities: normal and slow walking, static with and without carrying a load, and two Manual Material Handling activities. This study has two main contributions: first, the estimation of GRF components (Fx, Fy, and Fz) during the six activities, two of which have never been studied; second, the comparison of the accuracy of GRF component estimation between the six methods for each activity. RF provided the most accurate estimation for static situations, with mean RMSE values of RMSE_Fx = 1.65 N, RMSE_Fy = 1.35 N, and RMSE_Fz = 7.97 N for the mean absolute values measured by the force plate (reference) RMSE_Fx = 14.10 N, RMSE_Fy = 3.83 N, and RMSE_Fz = 397.45 N. In our study, we found that RF, an SML method, surpassed the experimented DL methods.

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Shoes affect the evolved biomechanics of the foot, potentially affecting running kinematics and kinetics that can in turn influence injury and performance. An important feature of conventional running shoes is heel height, whose effects on foot and ankle biomechanics remain understudied. Here, we investigate the effects of 6-26 mm increases in heel height on ankle dynamics in 8 rearfoot strike runners who ran barefoot and in minimal shoes with added heels. We predicted higher heels would lead to greater frontal plane ankle torques due to the increased vertical moment arm of the mediolateral ground reaction force. Surprisingly, the torque increased in minimal shoes with no heel elevation, but then decreased with further increases in heel height due to changes in foot posture. We also found that increasing heel height caused a large increase in the ankle plantarflexion velocity at heel strike, which we explain using a passive collision model. Our results highlight how running in minimal shoes may be significantly different from barefoot running due to complex interactions between proprioception and biomechanics that also permit runners to compensate for modifications to shoe design, more in the frontal than sagittal planes.

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BACKGROUND: Sprint skating is essential for competitive success in hockey. Previous studies have highlighted various measures of lower-body strength and power as key factors influencing sprint performance. However, while these studies have indicated a significant association between the ability to exert greater force and impulse into the ice surface, and the capacity to achieve faster sprint skating speeds, the direct relationship between these factors remains largely inferred. RESEARCH QUESTION: What are the relationships between insole plantar force variables, sprint skating performance, and their association with physical capacity measures, in national-level male hockey athletes? METHODS: Athletes (n=13) performed 25 m sprint skating trials with insole force sensors and completed: ankle dorsiflexion and hip abduction range-of-motion (ROM), countermovement jump (CMJ), seated single-leg jump, and 10-5 repeated-hop test (RHT) assessments. RESULTS: Relationships were assessed using Kendall's Tau rank correlations (τ), with significant relationships identified between mean relative weight acceptance impulse [WAI] and 0-5 m (τ=0.47) and total distance (τ=0.46) times. Additionally, significant associations were observed between mean relative WAI and: CMJ relative eccentric deceleration impulse (τ=0.44), CMJ eccentric peak velocity (τ=-0.46) and RHT concentric impulse (τ=-0.56). Finally, significant relationships were identified between mean relative PI for all strides and the 10-20 m split, with peak velocity (PV) (τ=-0.58 to -0.73); and between ankle dorsiflexion ROM and PV (τ=-0.57). SIGNIFICANCE: Athletes with faster initial acceleration and overall sprint performance times demonstrated lower relative WAI during their strides and employed a jump strategy that optimized concentric impulse with a rapid eccentric phase. To attain a high PV the athletes appeared to require a stride that maximized glide and minimized vertical force, with greater ankle dorsiflexion ROM potentially facilitating this.

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BACKGROUND: Multi-segment foot models (MFMs) provide a better understanding of the intricate biomechanics of the foot, yet it is unclear if they accurately differentiate foot type function during locomotion. RESEARCH QUESTION: We employed an MFM to detect subtle kinematic differences between foot types, including: pes cavus, neutrally aligned, and asymptomatic and symptomatic pes planus. The study investigates how variable the results of this MFM are and if it can detect kinematic differences between pathologic and non-pathologic foot types during the stance phase of gait. METHODS: Independently, three raters instrumented three subjects on three days to assess variability. In a separate cohort, each foot type was statically quantified for ten subjects per group. Each subject walked while instrumented with a four-segment foot model to assess static alignment and foot motion during the stance phase of gait. Statistical analysis performed with a linear mixed effects regression. RESULTS: Model variability was highest for between-day and lowest for between-rater, with all variability measures being within the true sample variance. Almost all static measures (radiographic, digital scan, and kinematic markers) differed significantly by foot type. Sagittal hindfoot to leg and forefoot to leg kinematics differed between foot types during late stance, as well as coronal hallux to forefoot range of motion. The MFM had low between-rater variability and may be suitable for multiple raters to apply to a single study sample without introducing significant error. The model, however, only detected a few dynamic differences, with the most dramatic being the hallux to forefoot coronal plane range of motion. SIGNIFICANCE: Results only somewhat aligned with previous work. It remains unclear if the MFM is sensitive enough to accurately detect different motion between foot types (pathologic and non-pathologic). A more accurate method of tracking foot bone motion (e.g., biplane fluoroscopy) may be needed to address this question.

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BACKGROUND: Short foot exercise (SFE) can be combined with dynamic functional tasks such as squats; however, it is unclear whether this combination increases intrinsic foot muscle activity. RESEARCH QUESTION: This study aimed to investigate and compare the abductor hallucis muscle (AbdH) activity during SFE in static and dynamic functional tasks. METHODS: The AbdH electromyography data of 17 healthy participants with and without SFE were analyzed during static tasks (sitting, double-leg standing, and single-leg standing) and dynamic tasks (double-leg squat, single-leg squat, split squat, and heel-raise). The static tasks were performed with SFE for 5 seconds, and the dynamic tasks were performed while performing SFE. AbdH activity with or without SFE during the task was compared using the Friedman and Wilcoxon signed-rank tests. RESULTS: AbdH activity was significantly greater in conditions with SFE than in those without SFE for all tasks (P < 0.01) except for heel-raise (P = 0.163). AbdH activity during SFE in single-leg standing was significantly higher than that in sitting, double-leg standing, and double-leg squats (P < 0.05). AbdH activity during SFE in the single-leg squat was also significantly greater than that in the sitting position (P = 0.024). No significant differences were found in any other between-task comparisons of AbdH activity during SFE. AbdH activity during tasks without SFE revealed significantly lower levels for sitting and double-leg standing compared to single-leg squat, split squat, and heel-raise (P < 0.001). Additionally, the activity in double-leg squat was significantly lower than in both single-leg squat and heel-raise (P < 0.05). SIGNIFICANCE: Combining dynamic tasks, except for the heel-raise task, with SFE can increase AbdH activity more than dynamic tasks without SFE. However, clinicians should note that combining dynamic tasks with the SFE may not increase AbdH activity compared to combining static tasks with the SFE.

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The human foot is a complex structure comprising 26 bones, whose coordinated movements facilitate proper deformation of the foot, ensuring stable and efficient locomotion. Despite their critical role, the kinematics of foot bones during movement remain largely unexplored, primarily due to the absence of non-invasive methods for measuring foot bone kinematics. This study addresses this gap by proposing a neural network model for estimating foot bone movements using surface markers. To establish a mapping between the positions and orientations of the foot bones and 41 skin markers attached on the human foot, computed tomography scans of the foot with the markers were obtained with eleven healthy adults and thirteen cadaver specimens in different foot postures. The neural network architecture comprises four layers, with input and output layers containing the 41 marker positions and the positions and orientations of the nine foot bones, respectively. The mean errors between estimated and true foot bone position and orientation were 0.5 mm and 0.6 degrees, respectively, indicating that the neural network can provide 3D kinematics of the foot bones with sufficient accuracy in a non-invasive manner, thereby contributing to a better understanding of foot function and the pathogenetic mechanisms underlying foot disorders.

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Overuse injuries are often caused by pronated foot and the associated abnormal lower-extremity kinematics during dynamic activities. Various patterns of foot kinematics are observed among individuals with pronated feet during dynamic activities, resulting in different dynamic kinematics of the proximal joint. This study aimed to identify the foot kinematic patterns during gait among individuals with pronated feet and evaluate the relationship between these foot kinematic patterns and the hip and knee kinematics. A three-dimensional motion capture system was used to collect data regarding the foot, knee, and hip kinematics during the stance phase of gait of 42 individuals with pronated feet. A hierarchical cluster analysis method was used to identify the optimal number of clusters based on the foot kinematics, including navicular height (NH) at initial contact and dynamic navicular drop (DND). The differences in the cluster and demographic variables were examined. One-dimensional statistical parametric mapping was used to evaluate the differences in the time histories of the NH, knee, and hip kinematics during the stance phase. Three subgroups were identified on the basis of the NH and DND: Cluster 1, moderate NH at initial contact and larger DND; Cluster 2, highest NH at initial contact and smaller DND; and Cluster 3, lowest NH at initial contact and smaller DND. The hip adduction angle of Cluster 1 was significantly higher than that of Cluster 3 from the 0% to 51% stance phases. Further longitudinal studies are needed to clarify the relationship between identified subgroups and the development of overuse injuries.

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The cold-induced vasodilation (CIVD) response of the human body to Arctic-like environments helps delay or prevent cold injuries to peripheral regions, such as the hands and feet. To more comprehensively predict the thermal responses of these body regions to cold stress, here we extended our previously developed and validated anatomically accurate three-dimensional whole-body thermoregulatory human model by incorporating a new phenomenological formulation of the CIVD mechanism. In this formulation, we modulated the cyclic vasodilation and vasoconstriction flow of warm blood from the body core to the peripheral regions solely by determining the heat-transfer exchange between the skin and the surrounding environment, and deactivated it when the core body temperature decreased to 36.5 °C. In total, we calibrated and validated the model using eight distinct studies involving 153 unique male subjects exposed to 10 diverse experimental conditions, including cold-air exposure of the whole body as well as air exposure and cold-water immersion of the hand or the foot. With CIVD incorporated, the model predictions generally yielded root mean square errors (RMSEs) of <3.0 °C for skin temperature, which represented a reduction of up to 3.6 °C compared to when we did not consider CIVD. Similarly, the incorporation of CIVD increased the fraction of predictions within two standard errors of the measured data by up to 63 %. The model predictions yielded RMSEs for core body temperature of <0.2 °C. The model can be used to provide guidelines to reduce the risk of cold-related injuries during prolonged exposures to very-cold environments.

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