The purpose of the present study was to evaluate the different behavior of forearm blood flow (FBF) during intermittent isometric handgrip (IIHG, 6 seconds contraction +6 seconds relaxation) in a thermo-neutral versus a hot environment. Six healthy men performed three times of 5-minute period IIHG at three different work loads (10%, 20% and 30% MVC). The IIHG was performed with the right hand. The experiments of IIHG were performed at two different air temperatures (25°C and 40°C, RH: 50%), and an experiment without work was also carried out at 40°C (RH: 50%). The physiological responses measured involved heart rate (HR), cardiac output (CO), mean arterial blood pressure (MBP), FBF, and skin blood flow (SBF). HR, CO and SBF showed higher values during IIHG at 40°C than at 25°C. MBP had a tendency to increase with the intensity of work load at both 25°C and 40°C. Since intramuscular pressure might increase during contraction periods at 20% MVC and 30% MVC at 25'C, FBF was significantly higher during relaxation periods than during contraction periods. FBF showed similar values between contraction and relaxation periods at lO% MVC at both temperatures. The present study suggested that FBF was sufficient for active muscles during IIHG at 10% MVC. FBF of contraction periods was close to that of relaxation periods at 40'C due to the modulation of the sympathetic outflow to the muscles and/or the decreased efficiency of the muscle pump. It was suggested that FBF showed different behaviors during IIHG at 25'C versus at 40°C.
This paper is aimed to investigate which part of the body should be uncovered by clothing for the heat stress to be lessened under the influence of an ambient temperature increase from 32°C to 40°C. Two types of clothing were used as experimental garmentss: one was turtle necklined sports jacket with short sleeves and short pants (HALF) and the other was open round necklined sports jackets with long sleeves and short pants (OPEN). Both types of clothing were made of 100%vinyl. Uncovered area was same between HALF and OPEN. Five males volunteered as subjects. The subjects wearing either HALF or OPEN sat quietly in a bioclimatic chamber for 160 min, where ambient temper-ature (Ta) was gradually increased from 32°C to 40°C by 2°C every 30 min with a relative humidity of 40%. Thermophysiological parameters such as esophageal temperature (Tes), tympanic temperature (Tty), Iocal sweat rate, skin temperatures at 11 sites and evaporation were continuously measured. Main findings are as follows: 1) Tty was kept lower significantly in HALF than in OPEN during warm exposure. 2) An increase of local sweat rate was significantly lower in HALF. 3) Skin temperature at abdomen region was kept lower significantly in HALF, reflecting lower core tempera-ture in HALF. It is concluded that HALF seems more beneficial than OPEN in reducing heat strain during warm exposure, due to more effective cooling by evaporation from the uncovered forearms (HALF) than from the uncovered upper trunk (OPEN).
The effccts of ingestion of fructose (F), as well as of arginine (A) and citric acid(C)on both carbohydrate metabolism and lipid metabolism during prolonged exercise in seven distance runners on treadmill running were investigated by comparing it with those of glucose+arginine+citric acid (GAC) and placebo. With the values of the plasma glucose, though FAC as well as placebo contrastively indicated almost a flat distribution. GAC increased from 30 min rest before the exercise (i.e., the time for 500 ml intake of GAC) to the beginning of the exercise. The plasma glucose for GAC showed significantly higher values (138±22mg/dl) than that for FAC or placebo, whose values were 102±l8 mg/dl and 93±8mg/dl, respectively. The plasma glucose for GAC was likely to decrease gradually as the exercise progressed more. At the end of exercise, however, the plasma glucose for FAC indicated significantly higher values (100±12 mg/dl) than that for GAC, whose values were 89±12 mg/dl. Though the serum free fatty acid showed upward tendencies of values in all cases of FAC, placebo, and GAC as the exercise progressed, no significant difference of the values in those cases was observed (the following values were drawn at the end of the exercise; FAC:655±185, μEq/1, placebo:603:±289, μEq/1, GAC:485±140 μEq/1). The serum insulin for GAC represented higher values (39.5± 23.1 μU/ml) at the beginning ofthe exercise than that for FAC or placebo at that time (12.3±4.8 μU/ml and l0.4±11.1 μU/ml), but was more likely to decrease as the exercise progressed more. In addition, with the respiratory exchange ratio during exercise, no significant difference of the values in these cases was observed. The results of this study suggest that the ingestion of fructose in distance runners before and during prolonged exercise should be continuously supplied as a source of energy without lipolysis inhibition.
The validity of the visceral fat evaluation based on B-mode ultrasonography was tested on 30 healthy young women (mean age 19.6 years). The mass of visceral fat (VFM) was estimated by subtracting the subcutaneous fat mass (SFM) from the total body fat mass. The SFM was calculated as the sum of segmental subcutaneous fat mass determined from the surface area and mean thickness of adipose tissue in six body seg-ments (face and neck, upper arm, forearm, thigh, Iower leg, and trunk). Reproducibility of the determination of VFM by the repeated measures of SFM and total fat mass was sufficiently high with the difference of 5.0. Serial cross-sectional areas of visceral adipose tissue (VATarea) were measured by magnetic resonance imag-ing (MRI) at three different positions of the trunk (at umbilicus and at 3.5 cm upper and lower positions). The VFM correlated significantly to each VATarea (r= 0.75 to r=0.78, P0.01). The present findings suggest that the VFM can be determined with the use of B-mode ultrasonography for the clinical assessment and field surveys.
Themoregulatory responses were compared at an ambient temperature of 30°C and a relative humidity of 50% between two kinds of protective clothing for pesticide spraying. One was made of nylon with wet coating polyurethane (A) and another was made of cotton with water repellent finish (B). The clothing ensemble was composed of a short-sleeved cotton shirt, long cotton underpants, cotton socks, shoes and the protective clothing. Five young female adults served as subjects. They took a rest with protective clothing ensemble for 15 min and then walked on a motor-driven treadmill (80m/min, 5% uphill grade) for 40 min, followed by 20-min rest. The increase of forearm sweat rate was higher in clothing A than in clothing B in 4 out of 5 subjects, although the average values were not significantly different. The total sweat rate of the whole body was also significantly larger in clothing A. Mean skin temperature and local skin temperatures in the arm, the chest and the thigh were significantly higher in clothing A than in clothing B. Clothing microclimate humidity was significantly higher in clothing A, while clothing microclimate temperature tended to be higher in clothing A. Individual observations about thermal, humidity and comfort sensation disclosed that the sensation was improved as a whole in clothing B. Local sweat rate was linearly related to mean body temperature and the regression line for clothing A was located above that for clothing B in 4 out of 5 subjects. Thus, it was concluded that the new cotton protective clothing with water proof finishing (clothing B) was improved in terms of subjective voting and reduction of heat strain compared with the protective clothing consisting of nylon with wet coating polyurethane (clothing A).
We evaluated changes in body temperature, heart rate, and oxygen uptake during arm cranking exercise (20 watts, 30 min) in an artificial climate room at a temperature of about 25°C or 35°C (relative humidity, about 50%) in 5 patients with paraplegics due to spinal cord injury (SCI). The tympanic temperature (Tty) was significantly higher from rest to recovery at 35°C than at 25'C. The mean Tty after 10 minutes of rest was 36.68°C ±0.396 (mean±SD) at a room temperature of 25°C and 37.25°C±0.253 at 35°C, showing a difference of about 0.5°C. This difference was maintained during exercise and recovery. The Tty at the end of exercise was higher than that at the start of exercise by 0.66°C± 0.218 (mean±SD) at 25°C and by 0.59°C±0.210 at 35°C. The skin temperature (Tsk) in each measurement area (the head, arm, chest, thigh, shin, and calf) was significantly higher at 35°C. Oxygen uptake did not differ between 25°C and 35°C. The heart rate was significantly higher at 35°C than at 25°C during rest and at the start of exercise but did not differ during exercise and recovery. Thus, mild - moderate exercise in this study did not cause marked changes such as increases in body temperature and heart rate that affect biological function in SCI. Mild-moderate exercise within 30 minutes may be possible at a temperature of 25 - 35°C and a relative humidity of 50% or less in SCI patients. However, attention should be paid to such matters as the supply of drinking water.
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