Heat acclimation enhances the cold-induced vasodilation response (original) (raw)
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Enhancement of the finger cold-induced vasodilation response with exercise training
European journal of …, 2010
Cold-induced vasodilatation (CIVD) is a cyclical increase in finger temperature that has been suggested to provide cryoprotective function during cold exposures. Physical fitness has been suggested as a potential factor that could affect CIVD response, possibly via central (increased cardiac output, decreased sympathetic nerve activity) and/or peripheral (increased microcirculation) cardiovascular and neural adaptations to exercise training. Therefore, the purpose of this study was to investigate the effect of endurance exercise training on the CIVD response. Eighteen healthy males trained 1 h d -1 on a cycle ergometer at 50% of peak power output, 5 days week -1 for 4-weeks. Pre, Mid, Post, and 10 days after the cessation of training and on separate days, subjects performed an incremental exercise test to exhaustion ðV Á O 2peak Þ; and a 30-min hand immersion in 8°C water to examine their CIVD response. The exercise-training regimen significantly increased V Á O 2peak (Pre: 46.0 ± 5.9, Mid: 52.5 ± 5.7, Post: 52.1 ± 6.2, After: 52.6 ± 7.6 ml kg -1 min -1 ; P \ 0.001). There was a significant increase in average finger skin temperature (Pre: 11.9 ± 2.4, After: 13.5 ± 2.5°C; P \ 0.05), the number of waves (Pre:
The Effect of a Sleep High–Train Low Regimen on the Finger Cold-Induced Vasodilation Response
Amon, Mojca, Michail E. Keramidas, Stylianos N. Kounalakis, Igor B. Mekjavic. The effect of a sleep high-train low regimen on the finger cold-induced vasodilation response. High Alt. Med. Biol. 13:32-39.-The present study evaluated the effect of a sleep high-train low regimen on the finger cold-induced vasodilation (CIVD) response. Seventeen healthy males were assigned to either a control (CON; n = 9) or experimental (EXP; n = 8) group. Each group participated in a 28-day aerobic training program of daily 1-h exercise (50% of peak power output). During the training period, the EXP group slept at a simulated altitude of 2800 meters (week 1) to 3400 m (week 4) above sea level. Normoxic (CIVD NOR ; CON and EXP groups) and hypoxic (CIVD HYPO ; F I O 2 = 0.12; EXP group only) CIVD characteristics were assessed before and after the training period during a 30-min immersion of the hand in 8°C water. After the intervention, the EXP group had increased average finger skin temperature (CIVD NOR : + 0.5°C; CIVD HYPO : + 0.5°C), number of waves (CIVD NOR : + 0.5; CIVD HYPO : + 0.6), and CIVD amplitude (CIVD NOR : + 1.5°C; CIVD HYPO : + 3°C) in both CIVD tests ( p < 0.05). In contrast, the CON group had an increase in only the CIVD amplitude ( + 0.5°C; p < 0.05). Thus, the enhancement of aerobic performance combined with altitude acclimatization achieved with the sleep high-train low regimen contributed to an improved finger CIVD response during cold-water hand immersion in both normoxic and hypoxic conditions.
Enhancement of cold-induced vasodilatation following acclimatization to altitude
European Journal of Applied Physiology, 2008
The present study evaluated the eVect of highaltitude acclimatisation on the cold-induced vasodilatation (CIVD) response. A group of highly trained mountaineers (N = 9; Alpinists) were tested before and after a 3 week high-altitude Himalayan expedition (altitude ranging from 3,985 to 6,828 m). A control group (N = 7) with no mountaineering experience was tested at the same time points. During each test, subjects Wrst immersed their hand to the styloid process in 37°C water for 5 min and then in 10°C water for 30 min. Upon completion of the hand immersion, the same procedure was repeated for the foot. Skin temperature of the pads of all immersed digits was measured throughout the immersion and for 10 min following the immersion. In the Alpinists, a signiWcant increase in amplitude of CIVD and absolute maximum Wnger skin temperature during immersion was observed in the hand post-expedition. For the foot, peak time of CIVD was signiWcantly shorter in the Alpinist group, and there were signiWcant increases in minimum and maximum toe skin temperature during CIVD, mean toe skin temperature during immersion, absolute minimum and maximum toe skin temperature during immersion, and absolute amplitude during immersion. The results demonstrate a signiWcant enhancement of the CIVD response as a consequence of a brief high altitude acclimatisation, and that these changes were especially prominent in the toes.
Military Medicine, 2017
Introduction: Warfighters often train and conduct operations in cold environments. Specifically, military trainees and divers that are repeatedly exposed to cold water may experience inadvertent cold acclimatization, which results in body heat retention. These same warfighters can quickly switch between environments (cold to hot or hot to cold) given the nature of their work. This may present a risk of early onset of hyperthermia when cold-acclimatized warfighters are subsequently exposed to physiological insults that increase body temperature, such as exercise and heat stress. However, there is currently no evidence that suggests this is the case. The purpose of this work, therefore, is to determine what impact, if any, repeated immersion in cold water has on subsequent exercise in the heat. Materials and Methods: Twelve healthy subjects (values in mean ± SD: age, 25.6 ± 5.2 years; height, 174.0 ± 8.9 cm; weight, 75.6 ± 13.1 kg) voluntarily provided written informed consent in accordance with the San Diego State University Institutional Review Board. They first completed 120 minutes of moderate treadmill walking in 40°C and 40% relative humidity. During this trial, subjects' physiological and perceptual responses were recorded. Twenty-four hours later, subjects began a cold acclimation protocol, which consisted of seven, 90-minute immersions in cold water (10°C, water level to chest). Each immersion was also separated by 24 hours. Subjects then repeated a subsequent trial of exercise in the heat 24 hours after the final immersion of the cold acclimation protocol. Results: Results from cold acclimation revealed no change in core temperature, a decrease in skin temperature, and attenuated shivering and lactate responses, which supports a successful insulative-hypothermic cold acclimation response. This type of cold acclimation response primarily results in heat retention with associated energy conservation. Findings for heat trials (pre-cold acclimation and post-cold acclimation) revealed no differences between trials for all measurements, suggesting that cold acclimation did not influence physiological or perceptual responses during exercise in the heat. Conclusion: Our findings indicate that military divers or trainees that are frequently exposed to cold water, and hence have the ability to experience cold acclimatization, will likely not be at greater risk of increased thermal strain when subsequently exposed to physical activity in hot environments. In this study, no physiological or perceptual differences were observed between trials before and after cold acclimation, suggesting that cold acclimation does not present a greater hyperthermia risk during subsequent exercise in the heat.
Effect of body temperature on cold induced vasodilation
European journal of …, 2008
Cold-induced vasodilation (CIVD) is an acute increase in peripheral blood flow observed during cold exposures. It is hypothesized to protect against cold injuries, yet despite continuous research it remains an unexplained phenomenon. Contrary to the traditionally held view, we propose that CIVD is a thermoregulatory reflex mechanism contributing to heat loss. Ten adults (4 females; 23.8 +/- 2.0 years) randomly underwent three 130-min exposures to -20 degrees C incorporating a 10-min moderate exercise period at the 65th min, while wearing a liquid conditioning garment (LCG) and military arctic clothing. In the pre-warming condition, rectal temperature was increased by 0.5 degrees C via the LCG before the cold exposure. In the warming condition, participants regulated the LCG throughout the cold exposure to subjective comfort. In the control condition, the LCG was worn but was not operated either before or during the cold exposure. Results demonstrated that the majority of CIVD occurred during the warming condition when the thermometrically-estimated mean body temperature (T (b)) was at its highest. A thermoregulatory pattern was identified whereby CIVD occurred soon after T (b) increased past a threshold (approximately 36.65 degrees C in warming and pre-warming; approximately 36.4 degrees C in control). When CIVD occurred, T (b) was reduced and CIVD ceased when T (b) fell below the threshold. These findings were independent of extremity temperature since CIVD episodes occurred at a large range of finger temperatures (7.2-33.5 degrees C). These observations were statistically confirmed by auto-regressive integrated moving average analysis (t = 9.602, P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001). We conclude that CIVD is triggered by increased T (b) supporting the hypothesis that CIVD is a thermoregulatory mechanism contributing to heat loss.
American journal of physiology. Regulatory, integrative and comparative physiology, 2017
Adaptations to heat and hypoxia are typically studied in isolation, but are often encountered in combination. Whether the adaptive response to multiple stressors affords the same response as when examined in isolation is unclear. We examined: i) the influence of overnight moderate normobaric hypoxia on the time course and magnitude of adaption to daily heat exposure; ii) whether heat acclimation (HA) was ergogenic and if this was influenced by an additional hypoxic-stimulus. Eight males (V̇O2max=58.5[8.3] mL·kg(-1)·min(-1)) undertook two 11-day HA programmes (balanced-crossover design), once with overnight normobaric hypoxia (8[1] h per night; 10 nights; FIO2=0.156; SpO2=91[2]% [HAHyp]) and once without (HACon). Days 1, 6, 11 were exercise-heat stress tests (HST [40°C, 50% RH]); days 2-5 and 7-10 were isothermal-strain (target rectal temperature [Tre] ~38.5°C), exercise-heat sessions. A graded exercise test and 30-minute cycle trial were undertaken pre, post and 14-days after HA in ...
Eur J Appl Physiol, 2008
Cold-induced vasodilatation (CIVD) is proposed to be a protective response to prevent cold injuries in the extremities during cold exposure, but the laboratorybased trainability of CIVD responses in the hand remains equivocal. Therefore, we investigated the thermal response across the Wngers with repeated local cold exposure of the whole hand, along with the transferability of acclimation to the Wngers of the contralateral hand. Nine healthy subjects immersed their right hand up to the styloid process in 8°C water for 30 min daily for 13 days. The left hand was immersed on days 1 and 13. Skin temperature was recorded on the pads of the Wve Wngertips and the dorsal surface of the hand. The presence of CIVD, deWned as an increase in Wnger skin temperature of 0.5°C at any time during cooling, occurred in 98.5% of the 585 (9 subjects £ 5 sites £ 13 trials) measurements. Seven distinct patterns of thermal responses were evident, including plateaus in Wnger temperature and superimposed waves. The number (N) of CIVD waves decreased in all digits of the right hand over the acclimation period (P = 0.02), from average (SD) values ranging from 2.7 (1.7) to 3 (1.4) in diVerent digits on day 1, to 1.9 (0.9) and 2.2 (0.7) on day 13. Average (SD) Wnger skin temperature (T avg ) ranged from 11.8 (1.4)°C in Wnger 5 to 12.7 (2.8)°C in Wnger 3 on day 1, and then decreased signiWcantly (P < 0.001) over the course of the training immersions, attaining values ranging from 10.8 (0.9)°C in Wnger 4 to 10.9 (0.9)°C in Wnger 2 on day 13. In the contralateral hand, N was reduced from 2.5 to 1.5 (P < 0.01) and T avg by »2°C (P < 0.01). No changes were observed in thermal sensation or comfort of the hand over the acclimation. We conclude that, under conditions of whole-hand immersion in cold water, CIVD is not trainable and may lead to systemic attenuation of thermal responses to local cooling.
International Archives of Occupational and Environmental Health, 2012
Purpose Differences among individuals concerning susceptibility to local cold injury following acute cold exposure may be related to function of the autonomic nervous system. We hypothesized that there are differences in heart rate variability (HRV) between individuals with normal or more pronounced vasoconstriction following cold exposure and that there is an adaptation related to prolonged cold exposure in autonomic nervous system response to cold stimuli. Methods Seventy-seven young men performed a cold provocation test, where HRV was recorded during cold hand immersion and recovery. Forty-three subjects were reexamined 15 months later, with many months of cold weather training between the tests. Subjects were analyzed as 'slow' and 'normal' rewarmers according to their thermographic rewarming pattern. Results For the 'pre-training' test, before cold climate exposure, normal rewarmers had higher power for low-frequency (P LF) and high-frequency (P HF) HRV components during the cold provocation test (ANOVA for groups: p = 0.04 and p = 0.005, respectively). There was an approximately 25 % higher P HF at the start in normal rewarmers, in the logarithmic scale. Low frequency-tohigh frequency ratio (P LF /P HF) showed lower levels for normal rewarmers (ANOVA for groups: p = 0.04). During the 'post-training' cold provocation test, both groups lacked the marked increase in heart rate that occurred during cold exposure at the 'pre-training' setting. After cold acclimatization (post-training), normal rewarmers showed lower resting power values for the low-frequency and high-frequency HRV components. After winter training, the slow rewarmers showed reduced low-frequency power for some of the cold provocation measurements but not all (average total P LF , ANOVA p = 0.05), which was not present before winter training. Conclusions These HRV results support the conclusion that cold adaptation occurred in both groups. We conclude that further prospective study is needed to determine whether cold adaptation provides protection to subjects at higher risk for cold injury, that is, slow rewarmers.