The purpose of this study was to examine the effects of a truss mattress upon sleep and bed climate. The truss mattress which has been designed to decrease the pressure and bed climate humidity was tested. Six healthy female volunteers with a mean age of 23.3 years, served as subjects. The experiment was carried out under two conditions: a truss mattress (T) and a futon (F) (Japanese bedding). The ambient temperature and relative humidity were controlled at 19-20°C, and RH 50-60% respectively. Sleep was monitored by an EEG machine and the rectal temperature, skin temperature and bed climate were also measured continuously. Subjective evaluations of bed and sleep were obtained before and after the recording sessions. No significant difference was observed in the sleep parameters and time spent in each sleep stage. Rectal temperature was significantly lower in T than F. Although there was no significant difference in bed climate over the T/F, the temperature under T/F was significantly higher in T. No significant difference was observed in subjective sleep evaluation. The subjective feeling of the mattress was significantly warmer in F than T before sleep. These results suggest that although T does not disturb the sleep parameters and the bed climate is maintained at the same level as with F, it may affect rectal temperature which can be due to low thermal insulation.
Several epidemiologic studies have shown the association between total leukocyte count and the risk of developing myocardial infarction. The purpose of this study was to assess the association between the total leukocyte and neutrophil counts and risk factors of ischemic heart disease in 1, 384 Japanese factory workers. Total leukocyte and neutrophil counts were significantly higher in current smokers than in non-smokers. Among current smokers, the total leukocyte and neutrophil counts were positively associated with the number of cigarettes smoked daily and the duration of cigarette smoking and alcohol consumption. Being independent of smoking habit, the total leukocyte and neutrophil counts were also related to several characteristics recorded at the physical examinations. The total leukocyte and neutrophil counts were positively associated with serum total cholesterol, serum triglyceride and hematocrit levels, and inversely associated with the serum HDL-cholesterol level. No significant associations of the total leukocyte or neutrophil counts were found with the red blood cell count and hemoglobin level. These results suggest that the total leukocyte and neutrophil counts may represent the metabolic condition with a high coronary risk among apparently healthy people.
Depth limitations to diving operation with air as the breathing gas are well known: air density, oxygen toxicity, nitrogen narcosis and requirement for decompression. The main objectives of our experiment were to assess the decompression, counterdiffusion and performance aspect of helium-nitrogen-oxygen excursions from nitrox saturation. The experiment was carried out in a wet diving stimulator with “igloo” attached to a 2-lock living chamber. Four subjects of two teams of 2 divers were saturated at 25 msw simulated depth in a nitrogen oxygen chamber environment for 8 days, during which period they performed 32 divers-excursions to 60 or 80 msw pressure. Excursion gas mix was trimix of 14.6% oxygen, 50% helium and 35.4% nitrogen, which gave a bottom oxygen partial pressure of 1.0 bars at 60 msw and 1.3 at 80 msw. Excursions were for 70 min at 60 msw with three 10-min work periods and 40 min at 80 msw with two 10-min work periods. Work was on a bicycle ergometer at a moderate level. We calculated the excursion decompression with M-Values based on methods of Hamilton (Hamilton et al., 1990). Staged decompression took 70 min for the 60 msw excursion and 98 min for 80 msw, with stops beginning at 34 or 43 msw respectively. After the second dive day bubbles were heard mainly in one diver but in three divers overall, to Spencer Grade III some times. No symptoms were reported. Saturation decompression using the Repex procedures began at 40 msw and was uneventful: Grade II and sometimes III bubbles persisted in 2 of the four divers until 24 hr after surfacing. We conclude that excursions with mixture rich in helium can be performed effectively to as deep as 80 msw using these procedures.
The present study was to determine the effects of bright light exposure during the daytime on core temperature rhythm. Eight female students participated as subjects. They were exposed to bright light of 5000 lux or dim light of 200 lux for 13 hours (06:30-19:30) for two consecutive days. Except the sleep period (22:30-06:30) and during the bright light exposure, light intensity was controlled at 200 lux. Rectal temperature data were collected every 10 min throughout the whole experimental period. The mean level of rectal temperature was not significantly different between the bright and the dim light conditions. However, the evening fall and the morning rise of rectal temperature were significantly greater in the bright light conditions on Day 2 compared to the dim. Furthermore, cosinor analysis showed that the acrophase of rectal temperature rhythm was earlier on Day 2 in the bright light conditions than the dim, and was significantly delayed on Day 2 compared to Day 1 in the dim light conditions. These results suggest that low intensity during the daytime for two consecutive days may induce a phase delay of core temperature rhythm rather than the bright light exposure at least in normally entrained female subjects.
The present study was designed to investigate the influences of aerobic training on the body composition, aerobic power and food intake of sedentary young females in relation to the initial levels of these variables. Thirty one untrained college females (age=19.8 ± 0.2 yr, stature=154.4 ± 0.8 cm, body mass=53.3 ± 1.2 kg, mean ± SEM) participated in an exercise regimen consisting of 40% of maximum oxygen uptake (VO2max) for 30 minutes per day on a bicycle ergometer 5 times a week in a training period of 12 weeks. Food consumption was ad libitum but the content of daily food intake was recorded accurately throughout the whole training period and analyzed weekly. The average body mass index (BMI) and fat mass relative to body mass (%FM), estimated from the data of skinfold thickness, decreased significantly after the 12 wk training. There were significant negative correlations between the relative changes (%Δs) and initial levels of both body mass (r=-0.447, p<0.05) and fat mass (r=-0.638, p<0.05), but the corresponding correlation for lean body mass (LBM) was not significant (r=0.186, p>0.05). While the energy intake during the training period did not differ significantly from that during the control period on the average, the %Δ value in energy intake between the two periods was negatively correlated to the energy intake during the control period (r=-0.604, p<0.05). In addition, there were low but significant negative correlations between both the initial levels of BMI and %FM and %Δ in energy intake; r=-0.413 (p<0.05) for BMI and r=-0.393 (p<0.05) for %FM. However, no significant correlations were found between %Δ in energy intake and those in body composition variables (r=0.116 to 0.237, p>0.05). On the average VO2max relative to body mass (VO2max/BM) increased significantly, but VO2max relative to LBM (VO2max/LBM) did not. However, not only VO2max/BM but also VO2max/LBM was negatively correlated to the initial level; r=-0.671 (p<0.05) for VO2max/BM and r=-0.625 for VO2max/LBM. Thus, the present results indicate that whether the body composition, food intake and aerobic power of sedentary young females can be modified by the exercise regimen eliciting 40% of VO2max depends on their initial levels.
Assessment of heat gain in man caused by solar radiation is one of the most important problems in research of the human heat balance outdoors. The purpose of the present study was to investigate a new method for estimation of solar heat income. Absorption of short wave radiation (direct, diffuse and reflected) was measured with an ellipsoid sensor representing a simple, physical model of man. Measurements were performed in climatic chamber with the use of an iodide CSI solar lamp. The absorbed quantity of solar radiation varied as a result of sun altitude as well as of a colour and insulation of fabric covering the ellipsoid sensor. The new coefficients derived from our investigations for estimating doses of absorbed solar radiation should be applicable for a standing man. They correlate better with mean skin temperature observed on subjects outdoor than previous results obtained based on a cylinder as an analogue model of man. The ellipsoid sensor covered by a black fabric absorbed about 6 times more of solar radiation than when covered by a white textile.
Exercise improves muscle insulin sensitivity and GLUT4 contents. We investigated the beneficial effects of swimming training on insulin sensitivity and genetic hypertension using stroke-prone hypertensive rats (SHRSP). We studied the relationship between genetic hypertension and insulin resistance in SHRSP and Wistar Kyoto rats (WKY) as a control. The systolic blood pressure of SHRSP was significantly reduced by 4-week swimming training (208.4 ± 6.8 mmHg vs. 187.2 ± 4.1 mmHg, p<0.05). The swimming training also resulted in an approximately 20% increase in the insulin-stimulated glucose transport activity (p<0.05) of soleus muscle strips and an approximately 3-fold increase in the plasma membrane GLUT4 protein expression (p<0.01) in SHRSP. However, basal and insulin-stimulated glucose transport activity and GLUT4 contents were not significantly different between WKY and SHRSP. There was no difference in insulin resistance in skeletal muscle of SHRSP as compared with WKY. Our results indicated swimming training exercise improved not only hypertension but also muscle insulin sensitivity and GLUT4 protein expression in SHRSP.
The direct measurement of true maximal oxygen uptake (VO2max) and oxygen uptake corresponding to anaerobic threshold (VO2AT) is not always practical, especially in middle age and older populations. Therefore, the purpose of this study was to develop a simple test that could accurately estimate cardiorespiratory fitness using a submaximal treadmill walking protocol for middle age, older, sedentary individuals and patients with chronic disease. Subjects for this study were 42 men (44.9 ± 15.7 years), which included 17 patients with coronary heart disease (57.0 ± 9.6 years). VO2peak and VO2AT were measured using a treadmill protocol (VO2peak; 38.4 ± 11.6 ml/kg/min, VO2AT; 22.9 ± 7.4 ml/kg/min). This simple test assessed the total distance covered in 12 minutes on the treadmill at an intensity corresponding to either 1) 11 on the Borg scale of ratings of perceived exertion (RPE11), 2) 13 on the Borg scale of ratings of perceived exertion (RPE13), or 3) “Optimal” by subjective judgment. The correlation coefficients between VO2peak or VO2AT and total distance at the three intensities (RPE11; 950 ± 100 m, RPE13; 1080 ± 140 m Optimal; 1050 ± 110 m) were statistically significant, ranging from 0.72 to 0.85. The test-retest reliability coefficient on 12 subjects was 0.98. The oxygen uptake (VO2) was measured during the three walk tests on 15 subjects. There were no significant changes in submaximal VO2 values from min 4 to min 12 (RPE11; 19.8 ± 4.7 ml/kg/min, RPE13; 24.1 ± 4.9 ml/kg/min, Optimal; 23.1 ± 4.8 ml/kg/min) in any of the three tests. Similarly, the three submaximal VO2 values did not differ from the VO2AT value (21.2 ± 8.3 ml/kg/min) obtained in the initial maximal test. These results suggest that the 12-min submaximal treadmill walk test (STWT) is a valid method for the assessment of Voub>2peak and VO2AT. Therefore, the STWT could be a useful performance test for evaluating cardiorespiratory fitness in middle age, older, sedentary individuals and patients with chronic disease.