Physically trained and untrained preadolescent boys were examined experimentally for the effect of physical training on thermoregulatory responses to heat and cold. In summer they were asked to wear swimming pants and dip their legs up to the knees into water at 42.3°C for 60 minutes under given environmental conditions (30°C DB and 70% RH) . Then they were exposed to a given cold environment (18°C DB and 60% RH) in a resting posture for 60 minutes. Rectal and mean skin temperatures, total body sweat rate, puls rate, metabolism, etc, were measured. The pulse rate at rest was lower in those trained physically than in those untrained. The rectal temperature increased and decreased less remarkably during exposure to heat and cold, and the total body sweat rate to the increment of rectal temperature tended to be higher in those trained than in those untrained. The other variables measured during both cases of exposure failed to respond to physical training. These results suggested a possibility that physical training might be a means of improving the thermoregulation in preadolescents, although its effect might be inconsiderable.

As an index of bodily adaptation development for muscular exercise two groups of subjects (T-group, trained, and U-group, untrained) were studied under a fixed environmental condition. All the member of T-group responded with quicker rises in the sweat rate, as if their bodies anticipated and took measures against the impending rise of body temperature, and attained early at the individual steady levels, in moderate or low load exercise ; moreover their Cl losses in the sweat were remarkably low, thus effectively keeping the internal environment of the body (this time the ion concentration of the blood) less disturbed. Together with other findings, we infer that physical training sets our body more efficient in dealing with the excessive heat produced by muscular exertion.

The present study was designed to examine the thermoregulatory response to the alternate stress of heat and cold in relation to physical training. A heat stress was given as a 60-minute foot bath in water at 43°C in the air condition of 30°C DB and 60% RH, and a cold stress as a 60-minute exposure to an atmosphere of 20°C DB and 60% RH in summer and 17°C DB and 60% RH in winter. Two experimental conditions of four-hour exposure were set up by combining the hourly heat and cold stress alternately : Condition I was initiated with the heat stress and ended with the cold one, and condition II vice versa. In these conditions, both heat and cold stresses were given twice. In summer, as well as in winter, physical untrained and trained adult males in swimming pants were exposed to alternate heat and cold stress extending for four hours. Rectal and mean skin temperatures were taken every 5 minutes. A ten-minute metabolic rate was measured every 20 minutes during the exposure period. The effect of physical training was generally more remarkable in condition I than in condition II, and in summer than in winter. In condition I, the trained group had a smaller variation in rectal temperature and a smaller rate of variation from a resting value in energy consumption throughout the four-hour exposure than the untrained. The differences between the mean skin temperature in the last stage of the first exposure and that of the second tended to be smaller in the trained group than in the untrained. Reduced differences between these values were noticed in the untrained men after physical training. These results indicate that the effect of physical training was discernible on the thermal adaptability to the alternate stress of heat and cold. It was concluded that physical training generally promoted the acclimatization and enhanced tolerance capacity to heat and cold.

A study was performed to elucidate the effect of physical training on the cold tolerance in human beings. Physically well trained men (T group) and untrained ones (U group) were exposed to cold stress in summer and winter. Each subject was dressed in experimental clothes and exposed to 10°C DB for 60 minutes in both seasons. Moreover, he was exposed in the semi-nude to 20°C DB in summer and to 17°C DB in winter for 60 minutes. During the period of exposure to cold, rectal and mean skin temperatures and respiratory metabolic rate were measured. To confirm the training effect further, the untrained men were asked to follow an experimental training program of daily routine which consisted of about 7 km outdoor running for 40 consecutive days in July and August. Before and after the training, they were exposed to the same cold stress as in the aforementioned summer experiments and subjected to the same measurement. Resting metabolic rate was higher in the T group than in the U group. Although no significant group differences were shown in the metabolic rate during the period of exposure to cold, the rate of increase from the resting value was lower in the T group than in the U group. There were no group differences in rectal or mean skin temperature during this period. When the untrained men were subjected continually to physical training, the resting metabolic rate was higher and the rate of increase from the resting value during the period of exposure to cold lower after the training than before. It was concluded that physical training could be a means to increase the cold tolerance.

To study the age difference in sweating during muscular exercise, two series of experiments were conducted under constant climatic conditions (29 ± 1°C DB, 60 ± 5 % RH, 0.45±0.05 m/sec air flow) . In series A, 7 to 20 years old male subjects undertook 5-minute running or pedalling of a bicycle ergometer in various seasons. In this series of experiments, pectoral sweat volume, sweat chloride concentration, rectal and mean skin temperatures were in general determined every 5 minutes and, when necessary, the total body sweat volume was calculated from the body weight loss. In series B, the age difference in the sweating in relation to physical training was studied. Subjects, 3 to 20 years old received experimental physical training of 5-minute or 500m-running. Before and after the training, a work load of 3- or 5-minute outdoor running was assigned to them. Furthermore, before and after the training, 10 and 11 years old subjects were given a fixed mechanical work rate on a bicycle ergometer. In these experiments, most of the parameters described above were measured. In series A, age differences in sweating during exercise were noticed to be dependent on the intensity of work load between pre- and post-adolescents. When the work load was heavy enough to cause a rapid increase in rectal temperature, the sweat volume became significantly less, the mean skin temperature was far higher, and the sweat chloride concentration was remarkably smaller in the pre-adolescent subjects than in the post-adolescent ones. In series B, an age difference in the effect of physical training was also found on sweating during exercise. The effect of physical training on sweating in the pre-adolescent individuals was generally less significant than in adults and sometimes showed a different pattern from that of adults. From these results, it can be concluded that sweating in the pre-adolescents is less adaptive, particularly to continuous severe exercise and that physical training is less effective in them than in the post-adolescents.

Background/Aims: Metabolic dysfunction-associated steatotic liver disease (MASLD) was recently proposed as an alternative disease concept to nonalcoholic fatty liver disease (NAFLD). We aimed to investigate the prognosis of patients with biopsy-confirmed MASLD using data from a multicenter study. Methods: This was a sub-analysis of the Clinical Outcome Nonalcoholic Fatty Liver Disease (CLIONE) study that included 1,398 patients with NAFLD. Liver biopsy specimens were pathologically diagnosed and histologically scored using the NASH Clinical Research Network system, the FLIP algorithm, and the SAF score. Patients who met at least one cardiometabolic criterion were diagnosed with MASLD. Results: Approximately 99% of cases (n=1,381) were classified as MASLD. Patients with no cardiometabolic risk (n=17) had a significantly lower BMI than patients with MASLD (20.9 kg/m2 vs. 28.0 kg/m2, P<0.001), in addition to significantly lower levels of inflammation, ballooning, NAFLD activity score, and fibrosis stage based on liver histology. These 17 patients had a median follow-up of 5.9 years, equivalent to 115 person-years, with no deaths, liver-related events, cardiovascular events, or extrahepatic cancers. The results showed that the prognosis for pure MASLD was similar to that for the original CLIONE cohort, with 47 deaths and one patient who underwent orthotopic liver transplantation. The leading cause of death was extrahepatic cancer (n=10), while the leading causes of liver-related death were liver failure (n=9), hepatocellular carcinoma (n=8), and cholangiocarcinoma (n=4). Conclusions Approximately 99% of NAFLD cases were considered MASLD based on the 2023 liver disease nomenclature. The NAFLD-only group, which is not encompassed by MASLD, had a relatively mild histopathologic severity and a favorable prognosis. Consequently, the prognosis of MASLD is similar to that previously reported for NAFLD.