Remote ischemic preconditioning (RIPC) has been shown to minimize subsequent ischemia-reperfusion injury (IRI), whereas obesity has been suggested to attenuate the efficacy of RIPC in animal models. The primary objective of this study was to investigate the effect of a single bout of RIPC on the vascular and autonomic response after IRI in young obese men. A total of 16 healthy young men (8 obese and 8 normal weight) underwent two experimental trials: RIPC (three cycles of 5 min ischemia at 180 mmHg + 5 min reperfusion on the left thigh) and SHAM (the same RIPC cycles at resting diastolic pressure) following IRI (20 min ischemia at 180 mmHg + 20 min reperfusion on the right thigh). Heart rate variability (HRV), blood pressure (SBP/DBP), and cutaneous blood flow (CBF) were measured between baseline, post-RIPC/SHAM, and post-IRI. The results showed that RIPC significantly improved the LF/HF ratio (p = 0.027), SBP (p = 0.047), MAP (p = 0.049), CBF (p = 0.001), cutaneous vascular conductance (p = 0.003), vascular resistance (p = 0.001), and sympathetic reactivity (SBP: p = 0.039; MAP: p = 0.084) after IRI. However, obesity neither exaggerated the degree of IRI nor attenuated the conditioning effects on the measured outcomes. In conclusion, a single bout of RIPC is an effective means of suppressing subsequent IRI and obesity, at least in Asian young adult men, does not significantly attenuate the efficacy of RIPC.

Protective masks impose variable breathing resistance (BR) on the wearer and may adversely affect exercise performance, yet existing literature shows inconsistent results under different types of masks and metabolic demands. The present study was undertaken to determine whether added BR impairs cardiopulmonary function and aerobic performance during exercise. Sixteen young healthy men completed a graded exercise test on a cycle ergometer under the four conditions of BR using a customized breathing resistor at no breathing resistance (CON), 18.9 (BR1), 22.2 (BR2), and 29.9 Pa (BR3). The results showed that BR significantly elevates respiratory pressure (p < 0.001) and impairs ventilatory response to graded exercise (reduced V_E; p < 0.001) at a greater degree with an increased level of BR which caused mild to moderate exercise-induced hypoxemia (final mean SpO₂: CON = 95.6%, BR1 = 94.4%, BR2 = 91.6%, and BR3 = 90.6%; p < 0.001). Especially, such a marked reduction in SpO₂ was significantly correlated with maximal oxygen consumption at the volitional fatigue (r = 0.98, p < 0.001) together with exaggerated exertion and breathing discomfort (p < 0.001). In conclusion, added BR commonly experienced when wearing tight-fitting facemasks and/or respirators could significantly impair cardiopulmonary function and aerobic performance at a greater degree with an increasing level of BR.

PURPOSE: Despite the growing need for recreation and work in cold environments, which often involve high levels of physical activity and significant body heat loss, studies investigating the impact of exercise during repeated cold exposure on cold adaptation are lacking. Therefore, this study aimed to examine whether exercise during repeated cold exposure during winter influences thermoregulatory adaptation to cold.METHODS: Forty young male participants were recruited and classified into two groups: cold weather athletes (CA) who spent at least 10 hr per week training outdoors, and non-athletes (CON) who did not regularly exercise outdoors but were naturally exposed to cold during the winter season. Physiological and perceptual thermoregulatory responses were assessed before and after winter.RESULTS: After winter (December-February), both groups exhibited cold habituation features (p<.05; higher body temperature, blunted sympathetic response, and attenuated cold sensitivity), except for cold pain in the CA group. The cold-induced vasodilation (CIVD) response was enhanced in both groups (F=6.864, p=.034), as indicated by the higher temperature parameters of the fingers (Tmax, Tmean, and Tmin). However, the enhanced temperature response did not translate into improved manual dexterity following cold-water immersion (F=0.041, p=.841).CONCLUSIONS: Exercise during repeated cold exposure did not prevent overall thermoregulatory adaptation after winter. However, the CA group exhibited an attenuated habituation to cold pain, suggesting a potential area for future research on the effects of exercise on cold adaptation. Although the CIVD response improved, it did not result in better fine manual dexterity after cold immersion. These findings highlight the need for further studies of the biological advantages of CIVD.

PURPOSE: The primary objective of this study was to investigate the effects of local cold and heat stimuli on cutaneous thermal sensitivity and inter-threshold zone at rest and during exercise.METHODS: Cutaneous warm and cold thresholds were measured on two body regions (forehead and hand) in three types of local thermal stress environments (neutral, heat, cold) using a method of limit in sixteen young, healthy male subjects (25.44±2.28 years) at rest and during exercise.RESULTS: The results showed that the thermal inter-threshold zone was wider on the hand than on the forehead under thermal stress conditions at rest and during exercise. The thermal inter-threshold zone on both body regions widened with exercise (p<.05). Exercise significantly blunted both the warm and cold sensitivity in the forehead (p<.05), but only cold sensitivity in the hand (p<.05). Moreover, the thermal inter-threshold zone on both the forehead and hand became significantly wider when heat or cold stress was applied to the local body region (p<.001). In the forehead, warm and cold sensitivity were significantly blunted in both heat and cold stress environments (p<.05), whereas in the hard they were significantly blunted only in the heat stress environment (p<.01).CONCLUSIONS: In conclusion, the present study showed that the forehead is more sensitive to both warm and cold stimuli than the hand, regardless of thermal stress or exercise. Furthermore, the thermal inter-threshold zone on both the forehead and the hand widened with exercise and local thermal stimuli.