Effect Of Cold Acclimatization Research Articles

Effect of cold acclimatization on exercise economy in the cold

We sought to determine if cold acclimatized men display higher economy (i.e. lower oxygen consumption at a given workload) during graded cycle ergometry in the cold (5°C). After completing a familiarization trial 1 week prior, five cold weather athletes (CWA) and eight physically active men (NON) underwent graded exercise tests to volitional fatigue in 5°C. The protocol always started at 60 W and increased by 20 W each minute. Oxygen consumption (VO(2)), respiration rate (RR), tidal volume (TV), and respiratory exchange ratio (RER) were determined via open circuit spirometry. Individuals were matched for body size and minutes of weekly physical activity. Repeated measures analyses of variance were conducted across time (workload) and cold acclimatization was entered as a between subjects factor. VO(2) peak was not different between groups but CWA had lower VO(2) at 60 and 240 W. CWA also had lower RR at 180 and 260 W as well as lower RER at 240 and 260 W. At submaximal workloads, cold acclimatized men have higher exercise economy than non-acclimatized men. This could have implications for those who work in this context.

Sciatic nerve monoaminergic system response to cold acclimatization in Muscovy duckling.

The effect of cold acclimatization on the monoamines in duckling sciatic nerve was studied. In thermoneutral (TN) ducklings, the high dopamine (DA) to norepinephrine (NE) ratios in the right (R, 0.14) or in the left (L, 0.20) sciatic nerves at 6 weeks of age suggests the presence of non-precursor specific dopaminergic pools. DA, DOPAC (3, 4-dihydroxyphenylacetic acid) levels and the ratio DA to NE were similar in cold-acclimated (CA) and TN ducklings sciatic nerves. Moreover, serotonin and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) remained unchanged in the sciatic nerve, indicating that this system is not affected with cold exposure. The contents of NE were higher (R = +44.46%; L = +43.73%) in sciatic nerve of CA than in TN ducklings. The results indicate that noradrenergic systems in the ducklings sciatic nerve are markedly affected by cold exposure. Interestingly, chronic exposure to cold failed to alter the dopaminergic and the serotonergic system in duckling sciatic nerve.

Studies on Prevention of cold Injuries

Studied were carried out to find out suitable measures for prevention of cold injuries. These includes methods to screen out individuals who are more prone to cold injuries; and to evaluate the effect of cold acclimatization and use of certain drugs and vitamins in its prevention. Studies were also conduced to evaluate the peripheral vascular response to cold on a group of young men who suffered from cold injury at high altitude. Experiments on monkeys have shown that the animals with higher peripheral vascular response under local cold stress are better protected against frost bite. Cold acclimatization also was found to be effective in raising these responses and thereby lessening the degree of injury, in experimental animals. Role of certain drugs and vitamins were tried in animals.

Effect of cold acclimatization on cardiac function during acute cold stress in rats: L. Mathew, W. Selvamurty, Y.B.M. Rao and H.S. Nayar. Defence Institute of Physiology and Allied Sciences, Delhi Cantt-10, India

Effect of cold acclimatization on cardiac function during acute cold stress in rats: L. Mathew, W. Selvamurty, Y.B.M. Rao and H.S. Nayar. Defence Institute of Physiology and Allied Sciences, Delhi Cantt-10, India

Seasonal changes in thermogenesis, organ weights, and body composition in the white-footed mouse,Peromyscus leucopus.

1. Seasonal adjustments in wild-caughtPeromyscus leucopus include autumn increases in basal metabolic, nonshivering thermogenesis, and interscapular brown fat and decreases in weights of gonads, liver, adrenal glands, and total lipid. Body weight and nonextractable dry weight do not change. 2. Basal metabolic rate, nonshivering thermogenesis, and interscapular brown fat increase following initial cold exposure in mid-September and are maintained at similar levels through January. 3. There is a positive correlation between nonshivering thermogenesis and interscapular brown fat, and negative correlations for both nonshivering thermogenesis and interscapular brown fat with body weight. 4. These seasonal changes in wild-caughtP. leucopus are compared with laboratory studies on the effects of chronic exposure to differences in temperature and photoperiod on these characters. It is concluded that disparities between the effects of cold acclimatization and cold acclimation could result from the influence of additional environmental cues, such as photoperiod, in cold acclimatized mice.

PULMONARY FUNCTION DURING NOREPINEPHRINE-INDUCED CALORIGENESIS IN COLD-ACCLIMATIZED RATS.

The effects of cold acclimatization on pulmonary function during norepinephrine-induced calorigenesis were studied. Norepinephrine resulted in a marked increase (85%) in the pulmonary minute volume in both the warm- and cold-acclimatized rats. This increase in the warm-acclimatized rats was accomplished entirely by increasing the respiratory rate, whereas in the cold-acclimatized rats, the increase in pulmonary minute volume was achieved for the most part by increasing the tidal volume with a slight increase in respiratory rate. Cold acclimatization was associated with a greater “efficiency of oxygen extraction” before, during, and after the infusion of norepinephrine. pulmonary minute volume; respiratory rate; oxygen extraction Submitted on December 6, 1962

Effects of cold acclimatization on liver di- and triphosphopyridine nucleotide.

The levels of oxidized and reduced di- and triphosphopyridine nucleotide were measured in liver tissue from rats that had been exposed to cold (4 ± 1 C) for 1 month. These animals exhibited about 65% more reduced and total triphosphopyridine nucleotides than control animals maintained at an ambient temperature of 25 ± 1 C. The significance of these alterations to the efficiency of oxidative phosphorylation is discussed.

Effect of cold acclimatization on plasma electrolyte levels.

Plasma from control (26℃) and cold acclimatized (5℃) rats was assayed for sodium, potassium, calcium, magnesium, chloride and phosphate. Significant increases were found in the levels of sodium and...

Cardiovascular response to hypothermia: effect of cold acclimatization.

The cardiovascular response to hypothermia was studied in dogs which had been exposed continuously to sub-zero arctic temperatures for a period of 1–4 weeks. All dogs exposed in this fashion showed a significantly lower terminal rectal temperature than unexposed control dogs. In addition, the incidence of ventricular fibrillation was reduced in direct proportion to the exposure period. Acclimatization to cold appeared complete in dogs exposed for a period of 4 weeks. In this group of animals, the frequency of ventricular fibrillation was reduced to 9% as compared to an incidence of 96% in the control dogs. The process of acclimatization occurred with extreme rapidity. Dogs which were deemed fully acclimatized, became deacclimatized after 5 days in a warm environment. Both the frequency of ventricular fibrillation and the mean terminal rectal temperature of this group were the same as that in the control unexposed group.