The electromyographic (EMG) activities of the back and thigh muscles while pedaling a bicycle ergometer at different load levels (300, 450, 600 and 750 kpm/min) and during walking and running at top speed up and down a staircase were investigated in children classified as physically less and more active than average. Each child underwent a battery of physical fitness tests to determine his physical fitness level relative to the national standard. Although the physiques of the inactive and active children did not differ, there were considerable differences between their back-lift, grip and knee-extension strengths, and the maximum anaerobic power, and 50-m dash performances of the two groups. The EMG data for each of the different tasks over selected periods (bicycle pedaling: 5 complete revolutions, staircase task: 5 stepping cycles) under different workload conditions were full-wave rectified and integrated (IEMG) . Under low workload conditions (ergometer tasks at 300 and 450 kpm/min and walking up and down stairs), the mean IEMG values (mIEMG) of all the muscles tested did not differ significantly in the inactive and active children. However, for all the higher workload tasks (pedaling at 600 kpm/min and running up and down stairs), the mIEMG values of the erector spinae muscles in the inactive children were significantly lower than those of the active children, and the difference increased gradually as the workload increased. This trend was even more marked when normalized mIEMG values were used. When the children ran up and down stairs at top speed, the inactive group had lower thigh, gluteus maximus and erector spinae muscle mIEMG values than the active group, and the difference between the normalized mIEMGs of the erector spinae muscles of the two groups showed a particularly strong statistical significance (P<0.01) when running both up and down stairs. As a similar trend was observed when the workload was maintained at a high level for the bicycle pedaling task, we concluded that at least part of the difference between the muscular activities of the two groups of children demonstrated when they carried out the running task was attributable to differences in the development of the muscle fibers and neuronal mechanisms of the erector spinae muscles.
In order to evaluate iron balance in the human body, we studied the effects of exercise on iron excretion in urine, sweat and feces. The subjects were five healthy male, college athletes. The daily intake of nutrients by the subjects was regulated by a prescribed diet (Calorie Mate, Ohtsuka), and the control measurements and the exercise measurements were performed within seven days. Excretion of iron in the urine during the exercise period was significantly higher than in the control period. The excretion of iron in the sweat was 1.076±0.118 mg, i. e, , about 70% of total iron physiologically excreted from the human body. The excretion of iron in the feces during the exercise period was significantly lower than during control period. Feces volume was positively correlated with energy expenditure and negatively correlated with the excretion of iron in the feces. Iron absorption during the exercise period was significantly higher than during the control period. These findings suggest that exercise stimulates not only iron excretion via urine and sweat, but iron absorption, and that iron balance remains positive in healthy male subjects who have normal iron status.
Deaths and morbidity due to heat disorders during physical activity were gleaned from newspaper reports between 1970 and 1990. The environmental temperatures (dry-bulb temperature and relative humidity) recorded at the closest meteorological observatory at the time of occurrence were used to calculate the wet-bulb temperature and WBGT (wet-bulb globe temperature), and the relationship between heat disorders and environmental temperature was analyzed. During the 21-year period, 108 cases of heat disorders (91 deaths and 477 casualties) were reported in newspapers. Of the 91 deaths, 9 were in females and 82 were in males, and mean ages were 23.3 years, females and 19.0 years, males. It was possible to record the environmental conditions at the time of the heat disorder in 99 cases. The results indicated that almost all disorders occurred at ranges higher than 25.5°C, dry-bulb temperature, and 20.0°C, wet-bulb temperature, 40% relative humidity, and 24.0°C, WBGT. The mean WBGT was 28°C at physiological intensities less than 12-RMR (Relative Metabolic Rate) and 25.8°C at RMR higher than 15. The seasonal distribution was from April to November. In cases observed in April, May and November, abrupt rises in WBGT in the 1.2-3.4°C range were observed on the day of occurrence in comparison with the previous day, suggesting that the degree of heat acclimatization is olso an important factor in preventing heat disorders.
Excess body fat has generally been considered to influence physical fitness and motor ability in obese boys. However, very few studies have been done on the relationships of percent body fat (%fat), body fat and fat-free mass with physical fitness and motor ability. The purpose of this study was to clarify the relationships between body composition and selected physical fitness and motor ability elements in obese boys. The subjects were three hundreds and five boys aged 12-14 years. Eighteen physical fitness and motor ability elements were tested and skinfold thickness was measured at six sites using an Eiken-type caliper. Impedance (Z) was measured using a tetrapolar bioelectrical impedance plethysmograph (Selco SIF-891) . Body density was calculated from the formula of Kim et al. Variables which represented muscular power and endurance were negatively affected by %fat, while muscular strength was positively related to %fat. Flexibility variables were found not to be affected by %fat. In order to further examine the effects of %fat on physical fitness and motor ability, the subjects were categorized into three groups according to %fat: lean= less than 12% (n=64), average=12-20% (n=192), and obese=greater than 20% (n=49) . The results of comparison among groups clearly indicated that the obese group was significantly poorer in muscular power and endurance but was better in muscular strength than the other groups. To analyze the factorial structure in obese boys, principal factor analysis was applied to the correlation matrix which was calculated with 18 variables, and then six factors were extracted. The differentiation and integration of factorial structure was investigated from the hierarchical factor model. Two factors (muscular power and speed, and flexibility) were extracted at a lower level of rotation. The body fat was found to be one important factor that affects many physical fitness and motor ability elements. The relationships between physical fitness, motor ability and degree of fatness seem to be rather complicated, and a great deal of data should be accumulated for analysis of influence of body fatness in the obese.
In the present study, we instiuted a long-term mild aerobic training program for older patients with hypertension and investigated its effects on serum lipids and lipoprotein concentrations. The intensity of exercise in mild aerobic training was adjusted to the lactate threshold level (LT), i, e., the level at which the blood lactate concentration began to increase nonlinearly with increasing work intensity. The training group (15 patients, 7 men and 8 women) and control group (15 patients, 7 men and 8 women) were 65-83 year-old patients with mean ages of 75.5±5.6 and 73.7±4.4 (mean±S.D), respectively, who had never exercised regularly up to that time. Treadmill training at the LT was carried out for 30min/day 3-6 times/week and continued for 9 months under the supervision of exercise physiology specialists. In the training group, LT speed significantly increased from 3.43±0.65 km/h to 3.73±0.67 km/h (9.0%) in men, and from 2.75±0.57 km/h to 3.05±0.61 km/h (11.8%) in women (both P<0.05) . HDL-c was significantly increased 9 months after training both in men (19.2%) and women (20.9%) (both P<0.05) . The TC/HDL-c ratio, an atherogenetic index, was significantly (P<0.05) decreased by training in women but not in men. The other serum lipid and lipoprotein profiles were unchanged in both men and women. In the control group, all serum lipid and lipoprotein profiles were unchanged in both men and women. The HDL-c level in the training group was higher than in the control group after 9 months in both men and women (both P<0.02) . The TC/HDL-c ratio in the training group was lower only in women (P<0.02) . There were no significant differences in other values between the training group and the control group in either men or women. These results suggest that mild aerobic training at the LT is an effective method of improving the level of serum HDL-c, the TC/HDL-c ratio and aerobic capacity in the older patients with hypertension.
This study was designed to evaluate the effect of exercise duration on the relation between sympathetic and adrenomedullary activities. Six trained subjects completed the following two exercise protocols ; six 2-min exercise sessions at 100% maximal O2uptake (VO2max) interspersed with 10-min recovery periods, and three 10-min exercise sessions at 80%VO2max interspersed with 10-min recovery periods. Plasma noradrenaline (NA), plasma adrenaline (A), NA/A ratio (NA/A), heart rate (HR), coefficient of variation of R-R intervals (CVRR) and blood lactate (La) were measured. With repetition of exercise sessions in both protocols, HR, NA and A gradually increased. CVRR rapidly decreased at the first exercise session and remained unchanged thereafter. NA/A increased by the first exercise session, but decreased by the following exercise sessions. NA in the second exercise session at 100%VO2max was significantly lower than that in the first. We conclude that, at the beginning of exercise, the increase of sympathetic activity is more dominant than that of adrenomedullary activity, whereas, with prolongation of exercise duration, the increase of adrenomedullary activity becomes more dominant than that of sympathetic activity,
A study was conducted to investigate the validity of bioelectrical impedance measurement (BIM) for determining changes in body composition during treatment of obesity with an exercise and diet regimen. Eleven obese women, aged 38-57 yr (44±6.0 yr), participated in a weight reduction study. Before and after the weight reduction period, body composition was measured by the deuterium oxide (D2O) dilution and BIM methods. For both methods, the correlation coefficients were of the same order of magnitude under both pre- and postregimen conditions. Mean weight reduction was 3.59±1.518 kg and loss of total body fat was estimated to be 4.8±1.72 kg by the D2O method and 2.5±1.14 kg by the BIM method. Thus the BIM method underestimated the change in body fat compared with the D2O method. Changes in resistance (R) and height squared divided by R were not significant at the p>0, 05 level. However, the mean change in fat-free mass (FFM) found by the D2O method was significantly greater than that found by the BIM method. Furthermore, there was no significant correlation between the changes in FFM estimated by the D2O and BIM methods. These results show that after weight reduction the BIM method overestimates body composition. It is concluded that the BIM method is not a valid approach for measuring the small changes in body composition that occur during treatment of obesity.
Using near-infrared spectroscopy, we monitored changes of oxygenated hemoglobin and myoglobin contents [oxy (Hb+Mb) ], deoxygenated hemoglobin and myoglobin contents [deoxy (Hb+Mb) ], and total hemoglobin and myoglobin contents [total (Hb+Mb) ] of the thigh muscle at rest and during incremental bicycle exercise and recovery in 10 healthy male volnuteers. Gas exchange parameters were also measured in breath-by-breath mode. The following results were obtained : 1) During low-intensity exercise (216 kpm/min), oxy (Hb+Mb) increased, while deoxy (Hb+Mb) and total (Hb+Mb) decreased. These changes are thought to reflect an increase in arterial blood flow to the exercising muscle and an increase in venous return. 2) During high-intensity exercise (above 972 kpm/min), oxy (Hb+Mb) decreased, while deoxy (Hb+Mb) increased. These findings probably reflect increased O2extraction. 3) Upon cessation of exercise, oxy (Hb+Mb) and total (Hb+Mb) increased, and deoxy (Hb+Mb) decreased abruptly. These changes probably reflect post-exercise hyperemia with decreased O2extraction. 4) Oxy (Hb+Mb) level at ventilatory threshold (VT) was the same as or higher than that of resting condition, indicating that VT occurs when the level of O2in the vessels of the thigh muscle is relatively high. 5) Spontaneous fluctuation of oxy (Hb+Mb) with frequency of 7-10 cycles/min was observed. This fluctuation was more marked during exercise than during rest or recovery. These findings suggest that the influence of increased blood flow and venous return on oxy (Hb+Mb), deoxy (Hb+Mb) and total (Hb+Mb) are greater than that of O2extraction during low intensity exercise, whereas the influence of O2extraction increases with exercise intensity. Near-infrared spectroscopy provides valuable information with regard to O2transport and O2extraction in the exercising muscle.