Individualized analysis of skin thermosensory thresholds and sensitivity in heat-sensitive people with multiple sclerosis

Human temperature regulation under heat stress in health, disease, and injury

The human body constantly exchanges heat with the environment. Temperature regulation is a homeostatic feedback control system that ensures deep body temperature is maintained within narrow limits despite wide variations in environmental conditions and activity-related elevations in metabolic heat production. Extensive research has been performed to study the physiological regulation of deep body temperature. This review focuses on healthy and disordered human temperature regulation during heat stress. Central to this discussion is the notion that various morphological features, intrinsic factors, diseases, and injuries independently and interactively influence deep body temperature during exercise and/or exposure to hot ambient temperatures. The first sections review fundamental aspects of the human heat stress response, including the biophysical principles governing heat balance and the autonomic control of heat loss thermoeffectors. Next, we discuss the effects of different intrinsic factors (morphology, heat adaptation, biological sex, and age), diseases (neurological, cardiovascular, metabolic, and genetic), and injuries (spinal cord injury, deep burns, and heat stroke), with emphasis on the mechanisms by which these factors enhance or disturb the regulation of deep body temperature during heat stress. We conclude with key unanswered questions in this field of research.

Thermophysiological aspects of wearable robotics: Challenges and opportunities

Technological advancements in the last two decades have enabled development of a variety of mechanically supporting wearable robots (i.e. exoskeletons) that are transitioning to practice in medical and industrial settings. The feedback from industry and recent controlled studies is highlighting thermal discomfort as a major reason for the disuse of the devices and a substantial barrier to their long-term adoption. Furthermore, a brief overview of the devices and their intended applications reveals that many of the potential users are likely to face thermal comfort issues because of either high exertion or medically related high heat sensitivity. The aim of this review is to discuss these emerging thermal challenges and opportunities surrounding wearable robots. This review discusses mechanisms, potential solutions, and a platform for systematically measuring heat transfer inhibition caused by wearing of an exoskeleton. Lastly, the potential for substantial metabolic rate reduction provided by exoskeletons to reduce worker thermal strain in warm-to-hot conditions is also considered.

High-density thermal sensitivity of the hand under different thermal states and stimulus intensities

Understanding how the human body senses small-scale heating and cooling stimuli can help researchers evaluate thermal comfort effects and health risks of thermal stimulus combinations under complex thermal exposure. Two experiments measured high-density thermal sensitivity on the hand to investigate whether the initial thermal states and stimulus intensities affect thermal sensitivity. After pilot tests, a 23°C cold-water bath and a 41°C hot-water bath were applied to create initial states deviating from thermal neutrality. The whole hand and part of the wrist with all test spots were immersed for 1 min and dried by a towel. Results showed that cold sensitivity and warmth sensitivity have a linear relationship with each other, but 16 of 20 subjects (80%) were more sensitive to cooling than to heating. The 1-min water-bath treatment significantly reduced hand thermal sensitivity. Compared with a thermally neutral state, a cold-water bath and hot-water bath reduced cold sensitivity by 22% and 61%, respectively, and reduced warmth sensitivity by 47% and 51%, respectively. Under a thermally neutral state, the perceptible thresholds for cooling and heating stimuli were -1.3°C and +1.8°C, respectively. Comfortable stimulating temperature ranges were 24°C-30°C for cooling and 34°C-39°C for heating. Thermal sensitivity differences among stimulus intensities were small, but differences among test spots and subjects were significant.