This study aims to clarify age-related changes of body composition structure in terms of the percentages of body fat and muscle (muscle mass/weight×100) in preschool children by using BMI. The subjects were 533 preschool children, comprising 260 boys and 273 girls. Regression analysis for BMI was performed and a regression polynomial of a proper order was determined. After examining the validity of the order in a regression polynomial for %Fat and muscle percentages for BMI, a regression polynomial evaluation chart was made up. After judging the degree of fat or muscle accumulation from BMI and the fat or muscle percentages for each age group of the boys and girls, a frequency distribution map of excessive development and underdevelopment of fat and muscle was drawn up and its age-related changes were examined. As a result, a complementary relationship was confirmed to exist between BMI and %Fat in preschool children. In contrast, an opposite relationship was found for BMI and muscle percentages. These results suggest that BMI can be used as an index of muscle percentages as well as %Fat. As a final result, the distribution composition map of fat and muscle percentages for BMI does not show changes with age from infancy in preschool boys as a whole, but it does show such changes in girls. It is inferred that preschool girls show, due to early maturity, earlier changes (fat decrease) toward an integrated child's body than do boys.
The aim of this study was to determine the effects of the single intake of a high-energy and high-fat meal, of that of a moderate-energy and high-carbohydrate meal, and of fasting, which are major global eating patterns involving the combination of various levels of energy and nutrients, on heart rate variability in healthy young males. Participants were assigned to three groups: the high-energy and high-fat meal group, the moderate-energy and high-carbohydrate meal group, and the fasting group (no meal) in a randomized crossover design. The R–R intervals were continuously recorded before and after meals. Physiological and psychological data were obtained before and 30, 60, 90, and 120 min after meal intake. The main results were: (1) decreased sympathetic modulation of the heart and increased parasympathetic modulation of the heart in the fasting group, indicated by an unchanged heart rate, a decreased lowfrequency/high-frequency ratio, and increased high-frequency power of heart rate variability in the fasting group; (2) cardiac sympathetic activation or parasympathetic withdrawal after the intake of either a high-energy and high-fat meal or a moderate-energy and high-carbohydrate meal, indicated by increases in the heart rate and the low-frequency/high-frequency ratio of heart rate variability, and a decrease in the high-frequency power of heart rate variability in both the high-energy and high-fat meal group and the moderate-energy and high-carbohydrate meal group; and (3) the high-energy and high-fat meal group and the moderate-energy and high-carbohydrate meal group showed similar movement in physiological and psychological measurements after the meal intake. In conclusion, the intake of the high-energy and high-fat meal and the moderate-energy and high-carbohydrate meal similarly activated sympathetic modulation of the heart, whereas fasting suppressed sympathetic modulation of the heart compared with the other two eating groups in healthy young males.
The purpose of this study was to assess the effect of low-frequency force steadiness practice in the plantar flexor muscles on postural sway during quiet standing. Healthy young 21 men (21±1 yrs) were randomly assigned to a practice group (n=14) and a nonexercising control group (n=7). Practice groups were divided by frequency of practice: 7 participants practiced once a week, and the other 7 twice a week, for 4 weeks. Steadiness practice required practice group to 5 sets of 60-s contraction at levels corresponding to 10% and 20% maximal voluntary contraction (MVC) in the plantar flexor muscles. The 4-week-long practice period reduced the force fluctuations (assessed as the standard deviation (SD) of the outputted force during steady isometric plantar flexion) and postural sway (assessed as SD of the center of mass velocity during quiet standing). However, these practice effects were not significantly affected by the practice frequencies (1 vs. 2 sessions per week) examined in this study. Further, a linear regression analysis revealed the association between prepractice postural sway and the relative change in postural sway by the practice (r=−0.904) in the practice group. These results suggest that the steadiness practice in plantar flexor muscles improves postural stability during quiet standing, even though the practice is low-frequency (once a week) and low-intensity (within 20% MVC). These practice effects are dependent on prepractice postural stability. Further, the present results have provided the functional significance of force fluctuation in lower limb muscles.
Recently, nonrestrictive and noninvasive sensing techniques to measure vital signs have been actively researched and developed. This study aimed to develop a prototype system to monitor cardiac activity using microwave radar without making contact with the body and without removing clothing—namely, a completely noncontact, remote monitoring system. In addition, heart rate and changes in heart rate variability (HRV) during simple mental arithmetic tasks were observed with the prototype system. The prototype system has a microwave Doppler radar antenna with 24 GHz frequency and approximately 7 mW output power. The experiments were conducted with seven subjects (23.00±0.82 years). We found that the prototype system captured heart rate and HRV precisely. The strong relationship between the heart rates during tasks (r=0.96), LF (cross-correlation=0.76), and LF/HF (cross-correlation=0.73) of HRV calculated from the prototype system and from electrocardiograph (ECG) measurements were confirmed. The proposed completely noncontact, remote method appears promising for future monitoring of cardiac activity as an indicator of changes in mental workload in workplaces.
Bright light at night improves the alertness of night workers. Melatonin suppression induced by light at night is, however, reported to be a possible risk factor for breast cancer. Short-wavelength light has a strong impact on melatonin suppression. A red-visor cap can cut the short-wavelength light from the upper visual field selectively with no adverse effects on visibility. The purpose of this study was to investigate the effects of a red-visor cap on light-induced melatonin suppression, performance, and sleepiness at night. Eleven healthy young male adults (mean age: 21.2±0.9 yr) volunteered to participate in this study. On the first day, the subjects spent time in dim light (<15 lx) from 20:00 to 03:00 to measure baseline data of nocturnal salivary melatonin concentration. On the second day, the subjects were exposed to light for four hours from 23:00 to 03:00 with a nonvisor cap (500 lx), red-visor cap (approx. 160 lx) and blue-visor cap (approx. 160 lx). Subjective sleepiness and performance of a psychomotor vigilance task (PVT) were also measured on the second day. Compared to salivary melatonin concentration under dim light, the decrease in melatonin concentration was significant in a nonvisor cap condition but was not significant in a red-visor cap condition. The percentages of melatonin suppression in the nonvisor cap and red-visor cap conditions at 4 hours after exposure to light were 52.6±22.4% and 7.7±3.3%, respectively. The red-visor cap had no adverse effect on performance of the PVT, brightness and visual comfort, though it tended to increase subjective sleepiness. These results suggest that a red-visor cap is effective in preventing melatonin suppression with no adverse effects on vigilance performance, brightness and visibility.
Frailty is a health problem that increases the probability of developing adverse health outcomes in the elderly. A frequently used way to operationalize frailty is the construction of a frailty index, which is built from the addition of several health deficits that describe biological aging. However, there is no consensus about the number of health deficits for building a frailty index and about which deficits must be chosen. This lack of a standardized frailty index is assumed to be an obstacle for the advancement of research on frailty. The focus of the present article is to propose a theoretically plausible alternative way of operationalizing frailty by means of frailty indexes composed of deficits selected at a local level. These deficits would therefore be different for each given population. This “anthropological approach” is on the opposite side from current trends in frailty research, which is characterized by the search for a standardized operational definition of frailty. The anthropological approach would generate more reliable data by taking into account the specificity of the population to be studied for selecting frailty deficits. In this approach, emotions, motives, and beliefs are as important to determine individuals' health vulnerability as chronic diseases and physical function. Physiological anthropologists are well positioned to contribute to research on frailty by carrying out studies on the selection of the best deficits to operationalize frailty in different populations, with different socio-cultural determinants of health, and living in different environmental life spaces.