Recent research observations indicate that obesity is a significant independent predictor of cardiovascular disease (particularly coronary heart disease and stroke). Aside from the metabolic abnormalities, there are severe social and psychological consequences of obesity. It is clear that obesity is associated, to a large extent, with lifestyle. There is no single best way to treat obesity. In general, the lifestyle therapies include behavioral modification, nutritional adjustments, and exercise conditioning. In treating obesity, the major emphasis is particularly placed upon decreasing energy intake and, to a lesser extent, upon increasing energy expenditure. However, food restriction induces a decline in resting energy expenditure which is related to the decline in body mass. Numerous reports indicate that, although decreasing energy intake is undoubtedly the most obvious and effective way to reduce fat, it also induces a significant amount of fat-free tissue loss. Regular exercise is a significant variable to consider in understanding and treating obesity, since it is the principal discretionary component of energy expenditure. In particular, aerobic exercise definitely plays an important role in preventing obesity in most persons. This article reviews the importance of lifestyle behaviors such as regular exercise and proper diet for prevention and maintenance of chronic diseases, along with definitions of some important words and multidimensional information regarding the epidemiology of obesity. Strategies for weight reduction are discussed.
This study examined the effects of the head cooling on the sweat rates in 6 healthy female subjects at an ambient temperature of 28°C and a relative humidity of 60%. The exercising subjects wore protective clothing and a mask for pesticide. Head cooling was made by putting frozen gel strips on the parietal and the front head which were held by a net-bandage (with cooling). On separate days, the same experiments were made without head cooling (without cooling). The total weight of the frozen gel strips was 250 g. After the subjects rested for 15 min in a chair, they repeated three times the work/rest schedule of 15 min exercise on a bicycle ergometer (50 W) followed by 5 min rest. Frozen gel strips were put on the head just before the first exercise bout. Main results were summarized as follows : 1) The forearm sweat rate, heart rate and the changes in Tre from the initial level (ΔTre) were significantly lower “with cooling” than “without cooling”. 2) The amount of sweat adhered to the clothing ensemble was significantly lower “with cooling” than “without cooling”. 3) The changes in Tty from the initial level (ΔTty) tended to be clearly lower “with cooling” than “without cooling”. 4) Skin temperatures of the forehead and the cheek under a mask tended to be lower “with cooling” than “without cooling”. 5) Subjective. sensation ratings seemed to be improved in most subjects “with cooling”. Thus, it was concluded that head cooling seemed to be more effective in reducing thermal strain in working subjects wearing the protective clothing and a mask for pesticide at hot environments.
We compared thermoregulatory responses during night sleep between two kinds of pillow. One has special cool medium consisting of sodium sulfate and ceramic fiber (pillow A) and the other polyester padding (pillow B). The subjects wore 100% cotton thin pajamas with short sleeves and three-quarters trousers for summer use. They lay and slept in bed with cotton sleeping mat and cotton quilt between 10:30 p.m. and 6:30 a.m. in a bed room with an ambient temperature (Ta) of 27 ± 1°C and a relative humidity of 55 ± 5%, using either of the pillow A or pillow B. When they awoke, the subjects filled out a questionnaire on how well they slept during sleep. Main results were: 1) Rectal and forehead skin temperatures and heart rate were kept significantly lower in the pillow A during the latter half of the night sleep. 2) Palm and thigh skin temperatures were significantly higher mostly in the pillow A. 3) All the subjects regarded the pillow A better for deeper sleep. It was concluded that slight cooling of the head due to the pillow A during night sleep seemed to be of significance for deep sleep.
Changes in rectal temperature and metabolic rate were continuously monitored in men immersed in waterat 15, 20, 25, 30, and 35°C. The subjects (12 healthy male students) wore swimming suits while either resting or doing leg exercise (ΔM≈60 kcal·h-1·m-2≈70 W·m-2) for 1 h. At all water temperatures below 30°C, the metabolic rate increased but the rectal temperature fell continuously, resulting in hypothermia. The rate of fall in rectal temperature (cooling rate, CR, °C·h-1) was inversely proportional to water temperature (Tw, °C) according to the equation CR=3.818 - 0.109 Tw in resting subjects and CR=3.434 - 0.110 Tw in exercising subjects. At a given Tw the cooling rate was greater in resting than in exercising subjects and in lean than in obese subjects. From the relationships between the cooling rate and water temperature the duration of useful activity and the survival time were predicted for resting and exercising subjects of various fatness.
Fourteen young Japanese women were exposed to a dry-heat condition (Ta = 40°C, rh = 30%) both in winter and summer. During an exposure for 110 min, they were rested on a bicycle ergometer for 20 min, exercised with an intensity of 40% Vo2 max for 60 min and recovery for 30 min. Their rectal and skin temperatures, and heart rate were determined every minute. Total sweat loss and dripping sweat were recorded throughout the experiment by independent bed balances which connected to a computer processor with an accuracy of 1 g. Sweat capsule with filter paper was used to measure sodium concentration on the forearm and back sites. Rectal temperature was not significantly different between winter and summer. Mean skin temperature was significantly higher in summer than in winter during exercise while heart rate was significantly lower in summer than in winter. Sweat evaporation and dripping in summer showed a tendency to increase much more than these in winter, but there were not significantly different. Sweat sodium concentration were significantly lower in summer than that in winter. It was found that sweating responses were not influenced by seasonal variation during exercise in dry-heat except the sweat sodium concentration.
This paper describes a concept of how liquid cooling garments (LCG) can be automatically controlled by the objective physiological state. The technically controlled parameter was mean body temperature which was calculated from the measured rectal and mean skin temperature. This was motivated by the fact that mean body temperature is the basis for estimating body heat storage, a commonly used measure of thermal strain. Here the setpoint of mean body temperature was the individual value taken in a preceeding resting period and it was the task of the technical controller to keep the actual value of mean body temperature as close as possible to the setpoint. The most important tuning parameters of the controller were the weighting coefficients for rectal and mean skin temperature in the calculation for mean body temperature. The ratio of these two coefficients determined the degree of compensation for any rectal temperature shift by changing mean skin temperature. Test experiments were carried out (n=5) in which the controller was able to clamp mean body temperature to the setpoint thereby preventing heat storage. Although exercise rate (75 W) was the same, sweating and warm discomfort occurred in some cases due to the individual rectal temperature rise. Another source of discomfort were delays or paradoxical time courses of rectal temperature at the start or end of exercise which were responsible for a delayed onset of cooling or heating. To avoid these effects, the oxygen consumption signal, which is very fast and directly correlated to the exercise rate, was added to the control loop. Each increase of this parameter above its resting level lowered suit temperature. As heat storage should not be completely rejected by this new signal pathway, the controller for mean body temperature still remained active. The repetition of the experiments showed that the load error in the control loop was smaller and the comfort level in transient phases higher. For a further improvement of this concept it is recommended that the weighting coefficients be tuned to the individual requirements.
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