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Biomedical subjects

A Magazanik

Publications and source records attributed to A Magazanik.

At least 37 records · Page 2Linked to original sources
PubMed1980

A comparison of various methods for the determination of VO2max.

Previous studies have shown that true maximal oxygen uptake (VO2max) obtained by means of cycle ergometer and step test are lower than the VO2max measured during uphill treadmill running. The predicted VO2max measured by ergometer was even lower. Four different methods for the determination of VO2max within the same group of examinees were compared: True VO2max by treadmill, ergometer, step test, and predicted VO2max (Astrand-Rhyming). This study was performed on 15 healthy non-professional sportsmen. They underwent progressive test protocols on alternating days and the results were as follows -- VO2max expressed in ml O2 kg BW/min (mean +/- SD): treadmill running 63.8 +/- 4.7; ergometer cycling 60.2 +/- 5.6; step test 59.6 +/-5.2 and predicted VO2max 59.9 +/- 6.9. The VO2max as determined by uphill treadmill running was significantly higher than with the other methods. No significant difference was found between true VO2max determined by the ergometer and step test. However, step test and properly executed Astrand-Rhyming test again proved to be reliable and deviate from the treadmill test by only 6%. Maximal heart rate was significantly higher in the treadmill and step tests than in the direct ergometer test.

Adult↗
PubMed1980

Dynamic changes in acid base balance during heatstroke in dogs.

The dynamic changes in acid base balance and respiratory metabolism during the development of heatstroke in dogs were studied. Three groups of five unanesthetized dogs each were exposed to different climatic conditions while at rest: A) 24 degrees C, 50% relative humidity (RH); B) 35 degrees C, 35% RH, and C) 45 degrees C , 25% RH. These conditions were maintained for 4 h or until the dogs collapsed. The heatstroke dogs were cooled in tap water bathes and were observed for another 4 h. Dogs of groups A and B did not show any notable changes in rectal temperature (Tre) and acid base balance. All dogs in group C developed heatstroke. Their peak mean Tre (44.1 degrees C) was reached after a mean of 111 min of exposure, with respiratory alkalosis followed by increasingly severe metabolic acidosis above Tre of 42 degrees C. At peak Tre mean arterial pH was 7.26. Acidosis increased (pHa = 7.17) following cooling, as panting subsided. At Tre above 42 degrees C blood lactate increased and bicarbonate decreased significantly, attaining mean values of 58 mg% and 8 mEq/l, respectively. Bicarbonate changes correlated linearly with lactate changes. During recovery lactate decreased and blood pH increased approximating normal by the end of the experiment. The results illustrate the body's ability to spontaneously correct arterial pH without therapeutic means.

Acid-Base Equilibrium↗
PubMed1980

Orthostatic responses in heat tolerant and intolerant subjects compared by three different methods.

The orthostatic responses of 10 heat tolerant and five intolerant subjects were evaluated by three different test methods--standing, head-up tilt (HUT), and head-up tilt after prolonged exercise (HUTPE)--in a hot environment of 40 degrees C, 40% RH. No difference was found within the normal group between responses in the standing and HUT test. In the HUTPE test, orthostatic responses were inadequate and 5 of 10 subjects fainted. The heat intolerant subjects reacted to all three tests similarly to the normal group, though their heart rate was higher and 3 out of 5 fainted at an earlier phase in the HUTPE test.

Adult↗
PubMed1980

Tap water, an efficient method for cooling heatstroke victims--a model in dogs.

Forty experimentally heatstroke dogs were cooled by immersion in water at temperatures varying from 1-25 degrees C. At all water temperatures, cooling occurred at a much slower rate in comatose dogs in conscious ones. Dogs cooled in tap water (15-16 degrees C) had the same cooling rate as those cooled in ice water (1-3 degrees C). At water temperatures above 18 degrees C, cooling rates were considerably decreased. Since tap water cooled as efficiently as ice water, its use may prove the method of choice for human heatstroke victims. Its advantages are ready availability, simplicity of use, and its failure to cause shivering.

Animals↗
PubMed1979

Heat intolerance in former heatstroke patients.

Nine young men who had suffered from heatstroke on previous occasions (heat-intolerant subjects) and 10 young volunteers (control subjects) were examined to determine their physiologic responses to exercise in temperate (23 degrees C) and hot environments (40 degrees C). The tests included an orthostatic test, work loads of 40 W and 80 W, and oxygen consumption (Vo2) determination. Although all the control subjects completed the exercise under severe heat load (3 h), none of the heat-intolerant subjects succeeded in completing this test due to high rectal temperatures and high heart rates. Sweat rates were similar in both groups, with Vo2 slightly higher in the control subjects. Orthostatic responses were similar in each group. The results suggest that inefficient thermoregulation, possibly due to decreased heat conductance from core to periphery, contributes to heat intolerance in former heatstroke patients.

Adult↗
PubMed1978

Cold-induced profuse sweating on back and chest. A new genetic entity?

Two sisters whose parents shared a grandfather had cold-induced sweating. Since childhood they had sweated profusely from the back and chest when exposed to environmental temperatures of 18 degrees to 7 degrees C. They had additional abnormalities--e.g., high palate and inability fully to extend the elbows--which neither their parents nor their sibs shared. The cold-induced sweating, which could not be stopped by a beta-adrenergic blocking agent, was abolished by postganglionic blockade with atropine sulphate. This indicates the possibility of a peripheral mechanism.

Administration, Oral↗
PubMed1978

Optimal back-pack load for short distance hiking.

Twenty young men marched 6 and 12 km with a well-fitted back-pack load of 30 or 35 kg. Each subject served as his own control. No significant increase in mean heart rate, rectal temperature, or decrease in mean VO2 max and serum levels of glucose and muscle enzymes were recorded in the groups marching 6 km with 30 and 35 kg. Significant differences in the increases in mean heart rate, the decreases in VO2 max and the changes in blood glucose were noted between the two groups carrying 30 and 35 kg for 12 km. These significant differences were also supported by the subjective feelings of the volunteers. The present study shows the optimal back-pack load for healthy young men, marching at 6 km/hr on a paved level road to be 30 kg for 12 km and 35 kg for 6 km without considering the task too difficult and with no significant decrease in VO2 max. The results are relevant to hiking, rescue assignments, and military missions.

Adolescent↗
PubMed1978

Maximal oxygen uptake, heat tolerance and rectal temperature.

To determine the relation of rectal temperature (Tre) to Vo2max and heat tolerance, eight untrained, eight trained and five heat acclimated subjects (respective means +/- SE for Vo2max in ml/kg.min of 37.5 +/- 1.6; 55.7 +/- 1.5; and 54.5 +/- 3.2) were tested in 3 conditions: 60 min of exercise at a fixed load of 35 W at room temperature of 23 degrees C; 60 min of exercise at 35% Vo2max also at 23 degrees C, and 3-hr of exercise in heat (40 degrees C DB, 30 degrees C WB). The heat-acclimated group showed the best heat tolerance, while the untrained group showed the poorest responses in heat. Exercise at 35 W resulted in higher heart rates shown by the untrained, compared with the other subjects, while equilibrium Tre were 37.6, 37.9, and 38.2 degrees C, in the heat-acclimated, trained and untrained groups, respectively, with corresponding differences for resting Tre (36.7, 36.9, and 37.1 degrees C). During exercise at 35% Vo2max, the heat-acclimated group showed lower Tre than the trained group despite working at the same relative loads. Tre during exercise at 35 W at 23 degrees C correlated r = -70 with Vo2max and r = 0.80 with Tre during exercise in heat. These results show that Vo2max accounts for only part of the variability which determines the level of Tre in cool conditions with heat acclimatization accounting for the remainder of this relationship.

Acclimatization↗
PubMed1977

Prediction of heat tolerance from heart rate and rectal temperature in a temperate environment.

To determine if heat tolerance could be predicted from responses to exercise in temperature conditions, 51 young men performed 15 min of bench stepping at an average work load of 80 W at 23 degrees C. On the following day they attempted to perform 3 h of bench stepping at 40 W in heat (39.3 degrees C dry bulb, 30.3 degrees C wet bulb). Of these subjects, 4 were heat intolerant, judged by previous heat stroke episodes during field marches, 12 were heat acclimated, and 35 were unacclimated. The heat-intolerant subjects showed the highest heart rates (HR) and rectal temperatures (Tre) at 23 degrees C and in heat, and the acclimated subjects showed the lowest corresponding values. HR and Tre in each environment were combined into a single score, from 10, indicating the poorest responses, to 100, indicating the best responses. These scores at 23 degrees C when correlated with the corresponding scores in heat resulted in a linear correlation coefficient of r = 0.94 with a standard error of estimate of 8.6%. Scores of the heat-intolerant subjects were below 35, and those of the acclimated subjects were between 70 and 100. Thus heat tolerance can accurately be predicted for HR and Tre responses to exercise at room temperature.

Acclimatization↗
PubMed1977

Responses to temperate, cold, and hot environments and the effect of physical training.

Ten young men underwent several tests before and after a training program: a bicycle ergometer test and 60 min of moderate exercise performed at a temperate 24 degrees C; the same work load performed in heat (40.0 degrees C DB, 30.4 degrees C WB) for 3 h; and cold (10 degrees C) exposure for 60 min. Training consisted of 13 1-h sessions of hard, strenuous, and exhaustive work performed in temperate conditions four times a week. Training resulted in substantial decreases in heart rate and rectal temperature responses to exercise in temperate, minor increases in hot, and no significant changes in cold conditions. Subjects who showed good responses to heat, also showed good responses at 24 degrees C, and poor compensatory responses to cold, which were indicated by relatively low heat production and rectal temperature values, and relatively high body heat loss and extremities temperature values. Subjects who showed poor heat tolerance also showed poor responses in temperate and good compensatory responses in cold conditions. Positive correlation coefficients were found between rectal temperatures in the three environments, and between heart rate and sweat rate responses in temperate and hot conditions. The results indicated that moderately severe training causes minor tolerance improvements in heat and no changes in cold, and that responses in temperate, cold, and hot environments are interdependent.

Acclimatization↗
PubMed1977

Exercise and heat orthostatism and the effect of heat acclimation and physical fitness.

Twelve trained and 16 untrained young men were administered five orthostatic tests while leaning upright against a wall, for 20 min--before exercise; after 60 min of exercise at a load of 40 W; after 15 min of exercise at a load of 80 W; after a Vo2 max test, and after 3 h of exercise at a load of 40 W in heat (39.4 degrees C DB, 30.3 degrees C WB). Eight of the untrained subjects were retested in the five orthostatic tests after 8 d of heat acclimation. The number of fainters in the orthostatic tests administered before exercise, after exercise at 40 W and 80 W, and after exercise in heat, were 3, 4, 6, and 13, respectively. There were no fainting episodes after the Vo2 max tests. Orthostatic responses in the different conditions were partially related. The trained subjects showed substantially better responses than the untrained ones (10% vs. 25% of fainting episodes), and heat acclimation resulted in marked improvement in orthostatism (decrease to 5% faintings). The results show that Vo2 max and heat tolerance account for most of the variability which determines orthostatic tolerance.

Acclimatization↗
PubMed1976

Human chorionic gonadotropin stimulation of Leydig cell function in puberty. Comparison of testosterone response in plasma and urine.

The plasma and urinary testosterone response to one i.m. injection of 5,000 IU human chorionic gonadotropin (HCG) was tested in 45 children and adolescents of several diagnostic entities: testosterone was measured before the injection and on the second, fourth and sixth days thereafter. It was found that there was a better correlation between the testosterone concentrations and the different pubertal stages than between testosterone concentration and either chronological or skeletal age. In the children with normal pubertal development, there was a slight rise in basal testosterone concentration with the progression of the pubertal stages. HCG caused a rise in plasma and urinary testosterone: this response was more marked in pubertal stages 4 and 5. The urinary response was variable whereas the changes in plasma testosterone concentration were more constant. In children and adolescents with primary or secondary hypogonadism, the basal levels of testosterone were low or undetectable and there was only a slight response to the single dose of HCG. It was concluded that a single i.m. injection of 5,000 IU HCG and the determination of plasma testosterone before, and two and four days after injection is a useful screening test for Leydig cell function.

Adolescent↗
PubMed1976

Sweat studies in hyperhidrosis palmaris and plantaris. A survey of 60 patients before and after cervical sympathectomy.

60 patients suffering from excessive sweating in the hands underwent cervical sympathectomy. At follow-up 1-7 years after operation the hands were dry in 55. No differences in electrolyte concentrations were found in the sweat from palms, arms, or body prior to and after the surgical intervention. Similarly no differences were found in electrolyte concentrations between healthy subjects and hyperhidrotics. Palmar sweat was hypertonic in comparison to arm or body sweat. The Na and K sweat concentrations were: palmar 50 +/- 20 and 16 +/- 7 mEq/1; arm 30 +/- 11 and 8 +/- 2 mEq/1; and body 21 +/- 20 and 4 +/- 3 mEq/1, respectively. Na/K ratio was: palmar 3.2; arms 3.6 and body 5.8. Total sweat loss prior to the operation was 5.7 +/- 4.2 g/kg BW/h; afterwards it was 5.9 +/- 4 g/kg BW/h. These equal sweat rates were associated with compensatory sweating in areas of the body not affected prior to the operation.

Adolescent↗