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Background: This article discusses the current knowledge on the effects of heat stress on cognitive abilities. Whole-body hyperthermia (WBH) has a negative effect on mental performance. In this study, we investigated whether short-term whole-body immersion in water at 45°C (HWI-45°C), which induces a strong neurotransmitter and temperature flux without inducing whole-body hyperthermia, would impair mental performance in humans. Methods: Fourteen men (aged 25±6 years) were enrolled in this study and participated in three experiments: (i) a brief (5-min) immersion of the whole body in 37°C water (WI-37°C); (ii) a brief (5-min) immersion of the whole body in 45°C water (HWI-45°C); and (iii) a control trial in a thermoneutral condition at an ambient temperature of 24°C and 60% relative humidity. Before and after immersion, cognitive performance was tested. All tests were performed in a quiet and semi-darkened laboratory. Results: Baseline simple, 2-choice and procedural reaction time and percentage of correct answers did not differ significantly across all trials. 2-choice reaction time was reduced (i.e. faster reaction) only after immersion to 37°C water. Interestingly, only whole-body immersion to 45°C was a sufficient trigger to reduce procedural reaction time. Conclusion: young healthy men do not deteriorate in response to whole-body hot water immersion for a short duration. By contrast, we here show faster reaction time in procedural reaction task, which was the most difficult of the three to perform. Keywords: Heat stress, hot water immersion, cognitive performance.

Muscular atrophy is a mortality risk factor that happens with disuse, chronic disease, and aging. Recovery from atrophy requires changes in several cell types including muscle fibers, and satellite and immune cells. Here we show that Zfp697/ZNF697 is a damage-induced regulator of muscle regeneration, during which its expression is transiently elevated. Conversely, sustained Zfp697 expression in mouse muscle leads to a gene expression signature of chemokine secretion, immune cell recruitment, and extracellular matrix remodeling. Myofiber-specific Zfp697 ablation hinders the inflammatory and regenerative response to muscle injury, compromising functional recovery. We uncover Zfp697 as an essential interferon gamma mediator in muscle cells, interacting primarily with ncRNAs such as the pro-regenerative miR-206. In sum, we identify Zfp697 as an integrator of cell-cell communication necessary for tissue regeneration. ONE SENTENCE SUMMARY: Zfp697 is necessary for interferon gamma signaling and muscle regeneration.

Background: Noxious acute cold stimuli cause cold shock via the sympathetic nervous system. However, no studies have investigated respiratory “heat shock” in response to noxious acute heat stimuli (≥ 42 °C). Methods: In the present study, we examined whether short-duration whole-body immersion (for 5 min) in noxious hot water (45 °C) is a sufficient stimulus to induce a respiratory acute shock response. Results and conclusion: Our results indicate that short-duration whole-body immersion in noxious 45 °C water produces a significantly greater body temperature, heart rate, and perceptual and respiratory strain than immersion in innocuous warm 37 °C water (p < .05). The initial first minute of hot water immersion (HWI) at 45 °C (vs. immersion at 37 °C) caused a cardiorespiratory shock response, which manifested as acute hyperventilation, and increased ventilatory tidal volume, respiratory exchange ratio, and heart rate (p < .05). Adjustment to this initial respiratory heat shock response within the first minute of immersion was observed as compared with remaining HWI time (1–5 min). Intriguingly, the time-course kinetics of breathing frequency, oxygen uptake, and carbon dioxide washout did not differ between whole-body immersion at 37 °C and immersion at 45 °C, but were higher than in control thermoneutral conditions of an empty bath (p < .05). This may be because of events initiated not only by the water temperature but also by the change in the hydrostatic pressure acting upon the body when immersed in the water bath.

Inactivity is known to induce muscle weakness, and chronically increased levels of reactive oxygen species (ROS) are proposed to have a central causative role in this process. Intriguingly, high-intensity interval training (HIIT), which involves bursts of high ROS production, can have positive effects in pathological conditions with chronically increased ROS. Here, young male volunteers were exposed to 3 weeks of unloading of the dominant leg followed by 3 weeks of resistance training without (Ctrl group) or with the addition of all-out cycling HIIT. Changes in muscle thickness were assessed by ultrasonography, and contractile function was studied by measuring the torque during maximal voluntary contractions (MVC). The results show an ~6% decrease in vastus lateralis thickness after the unloading period, which was fully restored after the subsequent training period in both the Ctrl and HIIT groups. MVC torque was decreased by ~11% after the unloading period and recovered fully during the subsequent training period in both groups. All-out cycling performance was improved by the 3 weeks of HIIT. In conclusion, the decline in muscle size and function after 3 weeks of unloading was restored by 3 weeks of resistance training regardless of whether it was combined with HIIT.