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Biomedical subjects

E Kamon

Publications and source records attributed to E Kamon.

At least 19 recordsLinked to original sources
PubMed1986

A simple exercise test for the prediction of relative heat tolerance.

A medical screening exercise test is presented which accurately predicts relative heat tolerance during work in very hot environments. The test consisted of 15-20 min of exercise at a standard absolute intensity of about 600 kcal/hr (140W) with the subject wearing a vapor-barrier suit. Five minutes after the subject exercised, recovery heart rate was measured. When this heart rate is used, a physiological limit (+/- approximately 5 min) can be predicted with 95% confidence for the most intense work-heat conditions found in nuclear power stations. In addition, site health and safety personnel can establish qualification criteria for work on hot jobs, based on the test results. The test as developed can be performed in an office environment with the use of a minimum of equipment by personnel with minimal expertise and training. Total maximal test duration is about 20-25 min per person and only heart rate need be monitored (simple pulse palpation will suffice). Test modality is adaptable to any ergometer, the most readily available and least expensive of which is bench-stepping. It is recommended that this test be available for use for those persons who, based upon routine medical examination or past history, are suspected of being relatively heat intolerant.

Adolescent↗
PubMed1986

Readdressing personal cooling with ice.

An ice-based system of personal, non-restrictive cooling of workers exposed to high temperature work environments in nuclear power plants was evaluated. The garments were designed to be worn under the protective clothing donned for penetration into radiation areas. The cooling system consisted of direct body contact with small packets of frozen water enclosed in the pockets of a shirt in high ambient temperatures (55 degrees C) and moderate metabolic heat production (200-300 kcal/hr). Mean exposure time without cooling (control) was 52 min for workloads demanding 200 kcal/hr energy expenditure. A long garment with 7.2 kg of frozen water (LFWG) increased mean exposure time over the control by 242% (163% for the same garment with 6.2 kg of frozen water). A short version garment with 3.8 kg of frozen water (SFWG) increased the stay time by 115%. In field observations, the LFWG with 6.2 kg of frozen water improved stay time by 125%. The leveling off of the body temperatures and heart rates during the work both in the laboratory and in the field confirmed a reduction of heat strain associated with the use of these garments. Calculated heat balance equations of heat uptake by the ice predicted these results very closely. It was concluded that direct body contact with frozen water provided predictable adequate body cooling for the work and ambient conditions investigated in this study.

Adult↗
PubMed1984

Comparative physiological responses of normotensive and essentially hypertensive men to exercise in the heat.

Six essentially hypertensive men (average resting arterial pressure of 150/97 mm Hg) and eight normotensive controls (average resting arterial pressure of 115/73 mm Hg) were tested during 1 h of dynamic leg exercise in a warm environment. The groups were well matched for age, VO2 max, body surface area, weight, and body fat. Environmental conditions were 38 degrees C dry-bulb, 28 degrees C wet-bulb; exercise intensity was approximately 40% VO2 max (85-90 W). There were no significant intergroup differences in core or mean skin temperatures, calculated heat exchange variables, heart, or sweat rates. Blood pressure differences between the groups were maintained (P less than 0.01). The hypertensive group responded with a significantly lower stroke index (P less than 0.01) and cardiac index (P less than 0.01), and a decreased slope of the rise in forearm blood flow (P less than 0.01) due to an higher vascular resistance (P less than 0.01). The combined heat load (M + R + C) presented was not sufficient to override the hypertensives' higher cutaneous vasoconstrictor tone. However, on a practical basis, the hypertensives were able to tolerate exercise in the heat as well as their normotensive counterparts.

Adult↗
PubMed1984

Effect of mild essential hypertension on control of forearm blood flow during exercise in the heat.

Six essential hypertensive (resting mean arterial pressure, MAP greater than 110 mmHg) and eight normotensive (resting MAP less than 95 mmHg) men, aged 30-58 yr, were tested during 1 h of dynamic leg exercise in the heat. Environmental conditions were fixed at 38 degrees C dry-bulb temperature and 28 degrees C wet-bulb temperature; exercise intensity was preset to approximate 40% of each subject's maximal aerobic capacity (actual range 38-43%). Forearm blood flow (FBF) was measured by impedance plethysmography. The intergroup difference in arterial pressure was maintained but not increased or decreased during exercise in the heat. FBF increased in both groups, but the increase was significantly less for the hypertensive subjects. FBF showed a significant linear correlation (different from 0) with core temperature in seven of eight control subjects but in none of the hypertensive subjects. The magnitude of FBF increase was inversely proportional to resting MAP (r = -0.89). It was concluded that essential hypertensive subjects respond to exercise in the heat with a diminished FBF response related to an alteration in control relative to central (core temperature) influences. This may be due to an imbalance between thermal and nonthermal (baroreflex) mechanisms controlling cutaneous blood flow.

Adult↗
PubMed1983

A comparison of peak and constant angle torque-velocity curves in fast and slow-twitch populations.

Peak and constant angle torque-velocity (T-V) curves were measured on a group of fast-twitch (FT, n = 10) and slow-twitch (ST, n = 6) subjects using a Cybex dynamometer. The T-V curve was plotted from 10 randomly assigned velocities ranging from 0.52 to 5.24 rad s-1 (30 to 300 degrees s-1). Each subject was tested four times with at least 24 h between testing sessions. Torque-velocity curves were plotted from the peak torque generated throughout the range of motion and from torque produced at a constant angle (150 degrees). When all subjects were combined into a single group, no significant difference existed between the normalized T-V curves even though they differed significantly in absolute amounts. When subjects were grouped according to muscle fiber type the T-V curves produced from constant angle torque differed significantly while those generated from peak torque did not. This finding suggests that T-V curves generated from peak torque are not as sensitive to influences produced by muscle fiber type as those curves generated from constant angle torque.

Adult↗
PubMed1983

Single breath cardiac output--enhanced sampling and analysis techniques.

The single breath method for measuring cardiac output (Q) was enhanced using new computer sampling and analysis techniques. The carbon dioxide (CO2) elimination rate was measured breath by breath using computer integration of expired flow rate and CO2 concentration. The concentration of CO2 in the arterial blood was determined from the CO2 partial pressure at the end of a normal breath. The concentration of CO2 in mixed venous blood was determined with a modification of the single breath method. The variability and relative accuracy of measurement of cardiac output were evaluated using four healthy men who exercised at three work rates from 0.5 L X min-1 (rest) to 2 L X min-1 oxygen consumption (VO2). Repeatability of measurements was assessed by making repeated measurements on one subject at a steady state exercise work rate. The coefficients of variation for repeated measurements made at 0.5 L X min-1 (rest), 1.0 L X min-1 VO2, and 2.0 L X min VO2 were 18.2, 10.5% and 8.8%, respectively. Regression lines relating cardiac output and oxygen consumption from three separate studies, employing the direct Fick method, and the described method were all similar. The probability of a successful breathing maneuver was increased to nearly 100%. Success was defined as a linear regression correlation coefficient (r2), relating instantaneous exchange ratio and CO2 during the breathing maneuver, of greater than 0.9.

Adult↗
PubMed1983

The oxygen cost of an escape from an underground coal mine.

Six 27- to 63-year-old coal miners performed an "escape" maneuver from an underground mine along a passageway that required walking and running erect or stooped, duck walking and crawling. The miners traveled at different speeds, for each mode of locomotion. The minute pulmonary ventilation (VE), O2 uptake (VO2) and heart rate (HR), recorded continuously on a magnetic tape via lightweight meters carried on the miners' waists, indicated similar average and peak values for all modes of locomotion. The mean VE, VO2 (L X min1, STPD) and HR (b X min1) were, respectively, 49, 1.63 and 143 for the average values, and 52, 1.92 and 161 for the peak values. Compared to the aerobic capacity obtained during graded treadmill test to exhaustion, the average effort of the "escape" was performed at 64% and the peak effort at 70% of the miners aerobic capacity for an "escape" time of 58 minutes.

Adult↗
PubMed1982

Responses of menstrual women, amenorrheal women, and men to exercise in a hot, dry environment.

Rectal (Tre) and mean skin temperatures, heart rate (fc) and sweat rate (Msw) during exercise in a hot, dry environment were compared among four menstrual women (both before and after ovulation), four amenorrheal women and four men, all with similar aerobic capacities. Progesterone and estrogen were compared in a pair of monozygotic twins (one menstrual and one amenorrheal) who participated in the study. Before acclimation, subjects were given a heat-stress test (HST) consisting of treadmill walking at 25%-30% VO2 max in a hot, dry environment (Tdb/Twb = 48/25 degrees C) until Tre reached 39 degrees C or fc reached 160 beat . min-1. Subjects were then acclimated to the dry heat with conventional acclimation procedures. After acclimation, subjects were given a HST which continued for 3 h. Before acclimation Tre and fc increased more rapidly in the women, with the men. Following acclimation all subjects maintained similar Tre, fc, and sweat rates. There were no differences between the exercise/heat-stress responses of the preovulatory menstrual women, postovulatory menstrual women, and amenorrheal women. Although the estrogen concentrations were normal in the menstrual twin, her progesterone concentrations were significantly depressed. Both hormones were depressed in the amenorrheal twin. Following acclimation thermoregulatory function in dry heat did not differ between the sexes when fitness level was similar. Neither were there any differences in thermoregulation between the pre- and postovulatory phases of the menstrual cycle or between the menstrual and amenorrheal women.

Acclimatization↗
PubMed1982

Dynamic and static lifting capacity and muscular strength of steelmill workers.

Dynamic and static strength measurements were compared respectively to maximal actual lifting and to a static lifting strength of 228 male steelmill workers. The strength tests were reasonably correlated with the lifting measurements. The dynamic strength test was the simplest, the least time consuming, revealing one to one ratio with the maximal actual lift and was not perceived as an exerting maneuver. Therefore, when matching between the job and a worker is desirable, it is suggested to use the dynamic strength test as a predictor for lifting capacity.

Adult↗
PubMed1981

Effective heat strain index using pocket computer.

An effective heat strain index (EHSI) using a hand calculator with memory is suggested for on-site evaluation of prevailing hot ambient conditions. The inputs to the programmed calculator include dry-bulb, wet-bulb and globe temperatures, and estimates of metabolism and air movements. The index is based on a program for calculation of the total heat balance and on the efficiency of sweating. The display of information on the ambient conditions EHSI display is one of following: no strain; low strain; high strain; or time limits of exposure.

Body Temperature↗
PubMed1981

Physiological responses to resistance breathing during short and prolonged exercise.

Respirators which impose a resistance to breathing may cause a limitation in maximum exercise intensity. This limitation is of particular concern when respirators are used in emergency situations requiring high levels of exercise intensity. Many studies have defined the limitations of exercise intensity imposed by breathing resistance as the point where the subject feels "uncomfortable". Perhaps of greater importance is the true physiological limit. Using motivated subjects, the physiological limits of exercise intensity and related respiratory responses resistances of 11, 16, 25, 40, and 57 cm H2O pressure at a flow rate of 120 L.min-1 exercise limits were 72, 72, 79, 60, and 54 percent of maximum aerobic capacity (% VO2 max) for the short term and 58, 60, 49, 43, and 35% VO2max for the prolonged exercise (1 hour). The presence of significant external resistance to breathing was found to influence the traditional relationship between exercise intensity and duration.

Adult↗
PubMed1981

Responses to dry heat of men and women with similar aerobic capacities.

Four men and four women with similar VO2max (56.33 +/- 4.05 and 54.08 +/- 4.27 ml.kg-1.min-1, respectively) exercised up to 3 h at 30% VO2max during heat stress tests (HST) before and after acclimation to dry heat [dry-bulb temperature (Tdb)/wet-bulb temperature (Twb) = 48/25 degrees C]. Rectal (Tre), tympanic sweat on the chest (msw), and total sweat rate (Msw) were recorded. There were no differences in the responses of the women between phases of the menstrual cycle. Tre, Tty, Tsk, and Tdb at the onset of sweating were similar in both sexes before and after acclimation. The nonacclimated men had significantly higher Msw and slower rise in Tre as compared to the nonacclimated women. Following acclimation these differences were no longer evident. Acclimation produced an increase in Msw in both sexes that was characterized by an increase in sweating sensitivity (delta msw/delta Tre). It was concluded that sex alone does not determine responses to heat stress. Consideration should also be given to the relative cardiovascular strain, state of acclimation, and the ambient conditions.

Acclimatization↗