Thermoregulation and Stress Hormone Recovery After Exercise Dehydration: Comparison of Rehydration Methods

Context:

Athletic trainers recommend and use a multitude of rehydration (REHY) methods with their patients. The REHY modality that most effectively facilitates recovery is unknown.

Objective:

To compare 5 common REHY methods for thermoregulatory and stress hormone recovery after exercise dehydration (EXDE) in trained participants.

Design:

Randomized, cross-over, controlled study.

Patients or Other Participants:

Twelve physically active, non–heat-acclimatized men (age = 23 ± 4 years, height = 180 ± 6 cm, mass = 81.3 ± 3.7 kg, V̇o₂max = 56.9 ± 4.4 mL·min⁻¹·kg⁻¹, body fat = 7.9% ± 3%) participated.

Intervention(s):

Participants completed 20-hour fluid restriction and 2-hour EXDE; they then received no fluid (NF) or REHY (half-normal saline) via ad libitum (AL), oral (OR), intravenous (IV), or combination IV and OR (IV + OR) routes for 30 minutes; and then were observed for another 30 minutes.

Main Outcome Measure(s):

Body mass, rectal temperature, 4-site mean weighted skin temperature, plasma stress hormone concentrations, and environmental symptoms questionnaire (ESQ) score.

Results:

Participants were hypohydrated (body mass −4.23% ± 0.22%) post-EXDE. Rectal temperature for the NF group was significantly greater than for the IV group (P = .023) at 30 minutes after beginning REHY (REHY30) and greater than OR, IV, and IV + OR (P ≤ .009) but not AL (P = .068) at REHY60. Mean weighted skin temperature during AL was less than during IV + OR at REHY5 (P = .019). The AL participants demonstrated increased plasma cortisol concentrations compared with IV + OR, independent of time (P = .015). No differences existed between catecholamine concentrations across treatments (P > .05). The ESQ score was increased at REHY60 for NF, AL, OR, and IV (P < .05) but not for IV + OR (P = .217). The NF ESQ score was greater than that of IV + OR at REHY60 (P = .012).

Conclusions:

Combination IV + OR REHY reduced body temperature to a greater degree than OR and AL REHY when compared with NF. Future studies addressing clinical implications are needed.Key Words: heat stress, heat illness, hypohydration

Key Points

• A combination of intravenous and oral fluid replacement after exercise dehydration reduced heat-related symptoms more than a single mode of rehydration.
• If intravenous fluid replacement is warranted, the addition of simultaneous oral rehydration seems to add benefit to an efficient recovery.

The importance of rehydration (REHY) after exercise dehydration (EXDE) is emphasized by the many physiologic systems affected by hypohydration. Many of the adverse effects of hypohydration can impair recovery or hamper future exercise performance.^1,2 The popular mantra surrounding REHY is that intravenous (IV) fluid is more rapid and advantageous to the athlete. Whether IV fluid administration is necessary in many instances can be questioned.³ Furthermore, it may not be ethical or legal in athletes without a significant medical reason.⁴Previous researchers^5–14 have identified that cardiovascular and thermoregulatory strain corresponds with greater body fluid losses. When blood volume is limited, evaporative sweat losses are impeded and overall heat dissipation decreases.^5,9,14–17 After EXDE, if dehydration is lasting, body temperature decreases at a slower rate, and this can delay recovery.⁴ Cellular metabolism remains elevated in conjunction with high temperatures, further complicating recovery.¹⁵ A delay in exercise recovery could have deleterious implications, hindering the benefits of exercise sessions or increasing the amount and duration of cellular stress.¹⁵ Finish-line medical tent staffs treat many patients after endurance races (triathlons, marathons, ultramarathons) for EXDE.³ The recovery time for these patients is the limiting factor in the number of patients that a tent staff can treat at once and should be expedited when possible.³Decreased water content and heat stress negatively affect cell function and integrity. Circulating catecholamine concentrations are typically used to quantify sympathetic stress.^18–22 Previous researchers who compared modes of REHY offer a glimpse of cellular recovery. These studies^18,19,21 demonstrate no appreciable differences between modes of REHY on cellular stress recovery. However, no previous authors have included trials during which participants consumed fluids as thirst dictated or combined oral (OR) and IV fluids.Comparisons of modes of REHY demonstrate the importance of fluid replacement after EXDE.^{18,19,21,23,24} A lack of REHY delays recovery and profoundly decreases subsequent exercise performance.⁴ When equal volumes of fluid are provided, IV and OR fluid administration are essentially the same.^19,21,23 No previous researchers have tested post-EXDE recovery facilitated by ad libitum (AL) consumption or a combination of IV and OR fluids. Therefore, the purpose of our study was to compare modes of REHY after heat stress and EXDE in recovery of body temperature and sympathetic stress hormone concentrations. We hypothesized that a combination trial, including simultaneous IV and OR fluids, would maximize the rate at which body temperature and hormone levels return to baseline.     

Renal Lithium Clearance during Dehydration and Rehydration with Water or 0.9% NaCl in the Rat

Male albino rats fed a diet containing lithium were dehydrated by 24 h of water deprivation and then rehydrated with demineralized water or 0.9 % NaCl. Renal lithium clearance decreased during rehydration with water. Rehydration with 0.9 % NaCl prevented the fall in the rate of urinary lithium elimination. The decrease in renal lithium clearance in the rats rehydrated with water was due to an increased fractional reabsorption of lithium in the renal tubules and was associated with a decrease in renal sodium clearance. The relationship between the renal elimination of sodium, potassium, and lithium during rehydration is discussed.     

Estimates of Radiation Doses and Cancer Risk from Food Intake in Korea

The aim of this study was to estimate internal radiation doses and lifetime cancer risk from food ingestion. Radiation doses from food intake were calculated using the Korea National Health and Nutrition Examination Survey and the measured radioactivity of ¹³⁴Cs, ¹³⁷Cs, and ¹³¹I from the Ministry of Food and Drug Safety in Korea. Total number of measured data was 8,496 (3,643 for agricultural products, 644 for livestock products, 43 for milk products, 3,193 for marine products, and 973 for processed food). Cancer risk was calculated by multiplying the estimated committed effective dose and the detriment adjusted nominal risk coefficients recommended by the International Commission on Radiation Protection. The lifetime committed effective doses from the daily diet are ranged 2.957-3.710 mSv. Excess lifetime cancer risks are 14.4-18.1, 0.4-0.5, and 1.8-2.3 per 100,000 for all solid cancers combined, thyroid cancer, and leukemia, respectively.     

The Opioid System and Food Intake: Homeostatic and Hedonic Mechanisms

Opioids are important in reward processes leading to addictive behavior such as self-administration of opioids and other drugs of abuse including nicotine and alcohol. Opioids are also involved in a broadly distributed neural network that regulates eating behavior, affecting both homeostatic and hedonic mechanisms. In this sense, opioids are particularly implicated in the modulation of highly palatable foods, and opioid antagonists attenuate both addictive drug taking and appetite for palatable food. Thus, craving for palatable food could be considered as a form of opioid-related addiction. There are three main families of opioid receptors (μ, κ, and δ) of which μ-receptors are most strongly implicated in reward. Administration of selective μ-agonists into the NAcc of rodents induces feeding even in satiated animals, while administration of μ-antagonists reduces food intake. Pharmacological studies also suggest a role for κ- and δ-opioid receptors. Preliminary data from transgenic knockout models suggest that mice lacking some of these receptors are resistant to high-fat diet-induced obesity. Copyright ? 2012 S. Karger GmbH, Freiburg.     

Neuroprotective Properties of Afobazole in Repeated Hemorrhagic Stroke Modeling in Aged Rats

Intraperitoneal administration of afobazole in a dose of 0.1 mg/kg over 2 weeks after repeated modeling of intracerebral post-traumatic hematoma reduces animal mortality, decreases motor coordination disturbances, and improves learning and memory processes in rats.     

Effect of Sucrose in Breakfast Items on Pleasantness and Food Intake in The Elderly

This study was designed to determine the differences between young and elderly people on the perceived intensity and pleasantness of sucrose in foods, in relation to their food intake. First, a group of 35 young subjects (mean age: 22 ± 2 years) and 29 elderly subjects (mean age: 79 ± 6 years) judged the intensity and the pleasantness of 5 series of breakfast items: orange lemonade, strawberry jam, strawberry yoghurt, chocolate paste, and grain porridge, each with 5 geometrically spaced sucrose concentration levels. On average, the elderly people had a lower slope of the sucrose psychophysical function. Optimal preferred sucrose concentrations were higher for the elderly compared to the young. The second phase in the study concerned the effects of the different optimal sucrose concentrations in foods on food intake. The second experiment dealt with 2 different optimal preferred sucrose concentrations (elderly vs. young subjects) in the food items: orange lemonade, strawberry and blueberry jam, and strawberry and blueberry yoghurt, served during breakfast. A group of 33 young people (mean age: 23 ± 2 years) and 25 elderly subjects (mean age: 82 ± 5 years) participated in a crossover study of 2 5-day (breakfast) treatments. Subjects ate ad lib from these foods and other items such as bread, coffee, and tea. The results showed that the sucrose concentration had no effect on the absolute amount consumed, although total energy intake of the breakfast increased with the higher sucrose foods. No clear difference was found in pleasantness between the 2 breakfasts with the different sucrose concentrations. These findings indicate that a flavor concentration evaluated as being most pleasant by the elderly with the help of small amounts of stimuli (in a lab setting) does not necessarily predict the pleasantness and the food intake behaviour in realistic settings.     

Detection of Food Intake from Swallowing Sequences by Supervised and Unsupervised Methods

Studies of food intake and ingestive behavior in free-living conditions most often rely on self-reporting-based methods that can be highly inaccurate. Methods of Monitoring of Ingestive Behavior (MIB) rely on objective measures derived from chewing and swallowing sequences and thus can be used for unbiased study of food intake with free-living conditions. Our previous study demonstrated accurate detection of food intake in simple models relying on observation of both chewing and swallowing. This article investigates methods that achieve comparable accuracy of food intake detection using only the time series of swallows and thus eliminating the need for the chewing sensor. The classification is performed for each individual swallow rather than for previously used time slices and thus will lead to higher accuracy in mass prediction models relying on counts of swallows. Performance of a group model based on a supervised method (SVM) is compared to performance of individual models based on an unsupervised method (K-means) with results indicating better performance of the unsupervised, self-adapting method. Overall, the results demonstrate that highly accurate detection of intake of foods with substantially different physical properties is possible by an unsupervised system that relies on the information provided by the swallowing alone.     

Variation in Intake of Sweet and Bitter Solutions by Inbred Strains of Golden Hamsters

Variation in intake of sweet and bitter solutions by inbred strains of laboratory mice has helped identify genes related to taste behaviors; but similar information is not available for golden hamsters (Mesocricetus auratus ), a species used much in taste research. Thus, 6-hour, 1-bottle intake by water-replete hamsters of 7 inbred strains was measured for water and 2 concentrations of sucrose, maltose, D-phenylalanine (D-Phe), and sodium saccharin, which are sweet; and quinine.HCl, L-phenylalanine (L-Phe), caffeine, and sucrose octaacetate (SOA), which are bitter to humans. Difference scores (DIF), calculated as solution intake minus mean baseline water intake (mL) for each animal, were evaluated by analysis of variance. Compared to ACN, CN, APA, APG, and CBN, five strains with similar DIF for all compounds, GN, an ancestral strain of ACNT, and ACNT preferred sucrose, caffeine, and SOA more strongly; ACNT also preferred saccharin and maltose more strongly and rejected quinine more strongly. Narrow sense heritabilities for the 6 compounds for which strain differences were revealed ranged from 0.31 to 0.57. Genetic correlations indicated the strain variations in intake of sucrose, saccharin, SOA, and caffeine were coupled; a statistical association with several possible interpretations. Intakes of the two amino acids, preferred D-Phe and aversive L-Phe, did not reveal strain differences, and heritability ranged from 0.13 to 0.23 for the two optical isomers. Thus, although, compared to mice, genetic variation in laboratory hamsters may be small, genetic differences that influence taste behaviors in existing strains may help identify relevant genes.     

NeuroFAST - the Integrated Neurobiology of Food Intake, Addiction and Stress

No abstract available.     

Energy Expenditure During Response-Dependent and Response-Independent Food Delivery in Rats

Two groups of rats received food on variable-interval schedules during S^D but not during S^Δ periods. Food delivery was contingent on running for Experimental subjects but independent of behavior for Controls. Contrary to predictions based on the energy maximization principle, Controls did not develop a more energy-efficient behavioral adaptation than Experimentals. The contingency of food delivery influenced the S^D/S^Δ distributions of running (AMB) and oxygen consumption (OC) but not their overall rates. Overall OC and AMB rates appear to have been determined by the similar levels of food deprivation and rates of food delivery to which both groups were submitted. AMB was found to be a less conspicuous determinant of energy expenditure than the rate of food delivery which, it is argued, influenced OC by eliciting high-energy consumatory activities. Although significant positive correlations between variations of heart rate (HR) and OC were observed in both groups, the HR/OC correlation was significantly weaker in the Control than in the Experimental group. This result is discussed in terms of the effects of the reinforcement contingencies on cardio-somatic control.     

Online Dietary Intake Estimation: Reproducibility and Validity of the Food4Me Food Frequency Questionnaire Against a 4-Day Weighed Food Record

Background

Advances in nutritional assessment are continuing to embrace developments in computer technology. The online Food4Me food frequency questionnaire (FFQ) was created as an electronic system for the collection of nutrient intake data. To ensure its accuracy in assessing both nutrient and food group intake, further validation against data obtained using a reliable, but independent, instrument and assessment of its reproducibility are required.

Objective

The aim was to assess the reproducibility and validity of the Food4Me FFQ against a 4-day weighed food record (WFR).

Methods

Reproducibility of the Food4Me FFQ was assessed using test-retest methodology by asking participants to complete the FFQ on 2 occasions 4 weeks apart. To assess the validity of the Food4Me FFQ against the 4-day WFR, half the participants were also asked to complete a 4-day WFR 1 week after the first administration of the Food4Me FFQ. Level of agreement between nutrient and food group intakes estimated by the repeated Food4Me FFQ and the Food4Me FFQ and 4-day WFR were evaluated using Bland-Altman methodology and classification into quartiles of daily intake. Crude unadjusted correlation coefficients were also calculated for nutrient and food group intakes.

Results

In total, 100 people participated in the assessment of reproducibility (mean age 32, SD 12 years), and 49 of these (mean age 27, SD 8 years) also took part in the assessment of validity. Crude unadjusted correlations for repeated Food4Me FFQ ranged from .65 (vitamin D) to .90 (alcohol). The mean cross-classification into “exact agreement plus adjacent” was 92% for both nutrient and food group intakes, and Bland-Altman plots showed good agreement for energy-adjusted macronutrient intakes. Agreement between the Food4Me FFQ and 4-day WFR varied, with crude unadjusted correlations ranging from .23 (vitamin D) to .65 (protein, % total energy) for nutrient intakes and .11 (soups, sauces and miscellaneous foods) to .73 (yogurts) for food group intake. The mean cross-classification into “exact agreement plus adjacent” was 80% and 78% for nutrient and food group intake, respectively. There were no significant differences between energy intakes estimated using the Food4Me FFQ and 4-day WFR, and Bland-Altman plots showed good agreement for both energy and energy-controlled nutrient intakes.

Conclusions

The results demonstrate that the online Food4Me FFQ is reproducible for assessing nutrient and food group intake and has moderate agreement with the 4-day WFR for assessing energy and energy-adjusted nutrient intakes. The Food4Me FFQ is a suitable online tool for assessing dietary intake in healthy adults.     

A Comparison of the Effects of Repeated Anaesthesia with Ether or Isoflurane in Rats

Ether anaesthesia has been used in rodents for routine blood sampling in toxicological studies for many years. Because of the highly flammable nature of ether and the inability to control the depth of anaesthesia, more suitable alternatives are needed. This study was conducted to compare data obtained using ether or isoflurane. Groups of male and female Sprague–Dawley rats, 5 weeks of age, were maintained on a normal diet for up to 25 weeks. Body weights were recorded during the study. Blood was sampled from the retro-orbital sinus under the different anaesthetics from the animals at 8, 12, 21 and from females only at 25 weeks of age for the analysis of standard haematology and biochemical parameters. These animals were killed at 25 weeks of age for histological examination. Body weights were unaffected. The major biochemical and haematological parameters were similar at the various time points with both types of anaesthetic. Minor variations, such as an increase in potassium and a reduction in glucose with isoflurane were seen, but there was no consistent trend. Examination of the liver, kidneys, heart and lungs did not reveal any changes that were considered to be associated with either anaesthetic. Blood was taken for prolactin analysis from a subgroup of animals at 12 weeks of age anaesthetised with ether or isoflurane, and from tail-bled animals without anaesthesia, these animals being killed at 17 weeks of age for histological examination. The level of prolactin at 12 weeks of age was reduced in the isoflurane group particularly in the males. This is considered to indicate that there was less stress. Based on these results, isoflurane is proposed as a suitable alternative to ether.     

大鼠心脏穿刺采血方法的改进

目的:介绍一种大鼠活体重复采血方法。方法:大鼠腹腔麻醉后,仰卧位沿剑突下斜行向上刺入2.5~3.0cm入心,抽血。60只大鼠,每间隔10天采血2.0ml,共4次。测定其Hb、RBC、WBC、Hct、ALT、AST、TP、BUN等指标,同时心脏切片行病理学检查。结果:采用本法进行大鼠心脏取血,成功率97.8%。各次标本的实验室指标均无显著性差异(P>0.05)。20只大鼠第4次采血后剖胸,未见胸腔脏器出血、粘连、血肿等并发症。心脏切片未见心肌组织学损伤。结论:该技术操作简便,定位准确,可重复采血,动物存活率高。尤其用于自身对照,可减少动物用量,提高实验准确性。