1) Children's data (10-18 years old) of back strength, height, grip strength and running long jump from data book of Japan Education Ministry (1964-1981) were analyzed. Back strength was mainly studied and was compared with other data (grip strength etc.) . The groups with high average values for back strength at 10-14 years old did not necessarily show high values for back strength at 17 years old, or vice versa. Values for back strength at 10-14 years old were not significantly correlated with those at 17 years old.
2) Using the data from data book mentioned above, tension of deep back muscle (FMUS) was calculated based on kinetic models (FMUS. I, II, III) . Calculated FMUS values were 3-5 times larger than measured back strength values at each age.
3) Relative change of back strength and FMUS in 1964-1981 were compared. All values for back strength were lower than those for FMUS except in 1967. During the late 1960th and the 1970th, average back strength values gradully decreased, but the decrease of FMUS was less obvious than that of back strength.
4) Based on the data of 422 children (7-12 years old, male and femele), values of diaphragm area were approximated with some assumptions, and then FMUS values were calculated. FMUS values calculated by approximate diaphragm area were significantly larger than those calculated by constant diaphragm area (465 cm2) .
The figure for getting FMUS values easily was offered to avoid troublesome calculation. This consists of two graphs, and one can read FMUS values with reasonable precision. Parameters needed for getting FMUS values are sexuality, height, body weight and back strength.

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We have developed the new dynamometer to measure twist strength of upper limbs that was not investigated sufficiently before. This dynamometer can measure both twisting hold strength and torque at a time. Therefore, it can be applied to motion analysis at demonstrating muscle strength. Both development curve of the age group's average of the average hold strength of left and right hand { (LH⋅HS+RH⋅HS) /2} and the average twisting hold strength of left and right hand { (LF⋅HS+RF⋅HS) /2} showed the peak of development in man's thirties and in woman's twenties-thirties and then marked depreciation gradually with ageing. The average torque of forward twisting of left hand and that of right hand { (LF⋅T+RF⋅T) /2} showed the same tendency in respect of the peak of development too, but woman's curve showed the peak in twenties different from that in man and then didn't mark depreciation remarkably. From the analysis with respect to twisting motion by the subjects of right handedness, we have recognized that the twisting hold strength of right hand by the action of left or right forward twisting (LF·RH·HS, RF·RH·HS) is greater than that of left hand (LF·LH·HS, RF·LH·HS), the torque of forward twisting of left hand (LF·T) is greater than that of right hand (RF·T) and that the hand of back twisting supports the grip-torque dynamometer from the result of EMG. Therefore, we can understand that the stronger torque is generated by the motion of forward twisting of left hand which can support stronger than by that of right hand. But we have recognized too that the average hold strength and the average torque correlate to one another closely. Therefor, we can understand that it requires the stronger hold strength to generate the higher torque.

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Boys and girls of elementary school (1 st, 3 rd and 6 th-grades), junior high school (2 nd-grade) and senior high school (2 nd-grade) were tested for 2 days to examine the reliability of grip strength, back strength, arm strength and leg strength.
The following results were obtained:
1. When elementary school boys performed three trials of these four items, over half boys recorded maximal value up to the second trial.
2. The reliability of tests applied to the left and right sides (grip strength, arm strength and leg strength) was not different each other.
3. In boys and girls attending elementary, junior- and senior high schools the reliability of grip strength was highest and the next was back strength.
4. Grip strength had statistically significant relationship to the other three items. Thus grip strength is considered to be the representative of four strength tests for growing boys and girls.

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To examine the variation in the knee extension force and the integrated electromyogram from rectus femoris, medial vastus and lateral vastus muscles with the knee joint angle in growing children, measurements were conducted in 61 school boys aged from 7 to 12 years old. Anthropometric measurements were also done on the body height, the lower limb length, and so on. Results obtained were as follows.
1) Ratio of the lower limb length comparing with the body height increased with the grade.
2) Maximal force at each joint angle in each grade was shifted peak from 70°to 90°with the grade.
3) The pattern of the integrated surface electromyogram from rectus femoris, medial vastus or lateral vastus muscle at each joint angle was the same in all of the grade. The integrated electromyogram at the maximal voluntary contraction was maximal at 45°of the knee joint angle in the rectus femoris muscle, at 110°in the medial vastus and at 90°in the lateral vastus muscle.

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The purpose of this study was to investigate the optimal starting period of muscle power training during growth. Thirty-three Wistar strain male rats were used and classified into four groups, control group, 3T group started a training at 3 weeks after birth (weaning period), 8T group started a training at 8 weeks after birth (puberty period) and 13T group started a training at 13 weeks after birth (beginning of mature period) . Each training group was subjected to a power sprint training till 23 weeks after birth (mature period) .
The results were summarlized as follows;
1) Hypertrophy and increase of contractile properties in muscle were not seen in each training group.
2) Muscle glycogen contents increased significantly in 3T group (p<0.05) and in 8T, 13T group (p<0.01) .
3) Muscle fiber area increased significantly in 8T group only.
4) Phosphofructokinase activity in muscle increased significantly in 8T group only.
These results suggest that 8 weeks after birth, the puberty period may be the most effective starting period of power sprint training during growth in rats.

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Development and aging of muscular strength of 1, 056 male and 460 female subjects in varied ages were studied for the purpose of obtaining basic data necessary for examining the ability of evacuation in emergency.
In adition to the conventional measurements of muscular strength such as grip strength, back strength and distance of Sargent jump, new strength measures like horizontal push, horizontal pull and lifting strength which were considered as some part of characteristic of ability of evacuation in emergency were measured by newly developed apparatuses.
Back strength showed the largest strength measure among them followed by lifting strength, horigontal pull, horizontal push and grip strength in that order, however ratios of one strength measure to other strength measures were kept almost constant regardless of subjects' ages.
Proportions of each measured value to their peak value were calculated and approxi-mated by biquadratic equation the curve of which corresponded to aging curve of ratio to the peak value. Most of the aging curves of ratio to the peak value of different strength measures were found to be similar except for the curve of distance of Sargent jump. The aging curve representing each product of distance of Sargent jump and subject's body weight fairly well agreed with other aging curves as it was.
For practical use, application of conventional strength measures, grip strength for example, to the assessment of muscular strength as a characteristic of ability of evacuation in emergency was considered to be significant.

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Within the brain stem of the cat, two locomotor centers have already been identified: one is the subthalamic locomotor region (SLR) and the other mesencephalic locomotor region (MLR) . Anatomically, the SLR and the MLR corresponds to the lateral hypothalamic area and the nucleus cuneiformis, respectively. The SLR presumably controls“volitional”aspects of locomotion while the MLR controls“automatic”aspects of it such as interlimb coordination. In a precollicular-postmammillary decerebrate cat, repetitive microstimulation of the MLR evoked locomotion on a moving treadmill.
In addition to these locomotor centers, midpontine neuronal structures which subserve“setting”and“resetting”of postural muscle tone have recently been identified in the same preparation. Repetitive microstimulation of the dorsal part and the ventral part of the midpontine tegmentum along the midline evoked long-lasting suppression and augmentation of postural muscle tone, respectively. Paired stimulation of the MLR with the dorsal part changed the pattern of MLR evoked locomotion from well coordinated four-legged locomotion to hindlimb stepping, and from stepping to total suppression of locomotor movements with a substantial decrease in postural muscle tone. In contrast, paired stimulation of the MLR with the ventral part changed the locomotor pattern from total suppression to hindlimb stepping, from stepping to locomotion, and even from locomotion to a gallop, by increasing the level of postural muscle tone in a graded manner. Stimulation of the ventral part alone at a higher stimulus intensity evoked spastic locomotor movements associated with a substantial increase in extensor muscle tone.
During spontaneous locomotion in an intact, unrestrained cat, stimulation of the dorsal part of the midpontine tegmentum evoked a series of postural changes. Within a few seconds from the beginning of stimulation, the cat ceased to walk but maintained a standing posture with a locomotor figure. With continuation of this stimulation, it squatted and then lay down on the floor in a sequential manner. The cat continued to keep its last posture for several minutes even after termination of the stimulation. Stimulation of the ventral part of the midpontine tegmentum evoked almost an opposite series of postural changes. Within a few seconds from the beginning of stimulation, the cat changed from a lying to a squatting posture, and then started to walk during continuation of this stimulation. The cat was always“alerted”by the stimulation and“oriented”, raising its head and looking around before the initiation of locomotion.
All these results suggest that the“locomotor”control system and“postural”control system share common neuronal structures within the brain stem and the spinal cord. Possible functions of these neuronal structures of the midpontine tegmentum are discussed in relation to the“volitional”and “automatic”control aspects of posture and locomotion.

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Muscle strength per unit muscle area related to age was investigated in normal 131 males and 127 females, 7 to 18 years of age. A cybex machine was used to measure the isometric muscle strength of elbow flexion and extension, knee flexion and extension, respectively. The cross-sectional muscle area of extensor and flexor at right upper arm and thigh were determined by using ultrasonic apparatus. The muscle area in male increased with age from 7 years to 17 or 18 years. Females showed increment in muscle area from 7 to 12 years for elbow flexor muscle, and from 7 to 16 years for another muscles. Muscle strength in both males and females increased with age from 7 to 16 or 17 years. Muscle strength per unit muscle area tended to increase with age in males from 7 to 12 years, and in girls 7 to 9 years except for elbow extension. The strength per area under 12 years of age for males and 9 years of age for females except for elbow extension were significantly lower than that of the above age. There were little differences in the strength per unit area with age among males from 13 to 18 years and females from 10 to 18 years, respectively. These results indicate that under 12 years for boys and 9 years for girls the increment in muscle area with age is not accompanied with the development of muscle function.

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The active and passive grip strength, repeated grip strength, back lift strength, leg press, vertical jump and back extension were measured for 220 boys and 205 girls in the primary school to examine the similarity and difference between back lift strength and grip strength. The results were as follows;
1) The strength of large muscle groups such as back lift strength and leg press in boys were significantly higher than in girls, but no differences were found in the strength of smaller muscle group like a grip strength.
2) Higher increment rate of the passive grip strength to the active strength was found in younger grade of primary school children. They might possess a lower level of contractile force-integrating ability than older ones.
3) No significant differences between boys and girls and among each grade were found in the decrement rate of repeated grip strength and no sigficant relationship between the decrement rate and maximum grip strength.
4) Significant relationship was observed between back lift strength and active or passive grip strength, and the correlation coefficients with the passive strength were lower than the active strength.
5) Significant relationship was observed between back lift strength and vertical jump and back extension in all grade of primary school girls and lower grade of the boys.

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There have been an apparent trend in the decline of back-lift strength of young people during recent years. The purpose of this study was to investigate the cause-effect relationship of such a trend using young peoples and university students. In order to examine the characteristics of activities in the lumber back muscles during various physical activities, the surface electromyography (EMG) was obtained from the trapezius, latissimus dorsi, and elector spinae muscles for individuals with poor back-lift strength (5 male children and 4 university male students) and individuals with relatively strong back-lift strength (5 male children and 2 male university students) . The children with poor back-lift strength had significantly less EMG activities in both the trapezius and elector spinae muscles during the measurement of back-lift strength using a dynamometer than the strong back-lift strength children. The former children also had a less EMG activities in elector spinae muscle and a greater EMG activities in trapezius muscle during cycling the bicycle elgometer. Such a trend became more distinct when the load was increased. The university students with poor back-lift strength had a less EMG activity in the elector spinae muscle during the measurement of back-lift strength than those with strong back-lift strength. During running, there was not a distinct difference in the EMG activities of the muscles in the back between the poor and strong strength students. However, as the running speed increased, a greater EMG activity in the trapezius muscle or the latissimus dorsi muscle were observed for the poor back-lift strength students than the stronger back-lift strength students.
These results indicated that the individuals with poor back-lift strength relied more on the upper portion of the back muscle group than the lower portion of the back muscle group during both static and dynamic activities, suggesting that the trend in the decline of back-lift strength of children and students was due to a lack of opportunity to use the lower back muscles in the daily physical activities.

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The peak (dPower/dt), the maximum value of dPower/dt calculated by differentiation of ventricular power with respect to time, is verified from the physiological studies to be quite useful index indicating the ventricular contractility independent of the pre- and afterloads. However, the index has the disadvantage in the clinical application that it can not be measured by a non-invasive method. In the present study, peak (dPower/dt) could successfully be determined in a non-invasive manner as the product of aortic flow as measured with an ultrasonic pulsed Doppler flowmeter and brachial blood pressure as measured with cuff in the new apparatus. Involved in this study were 21 children, 52 adults with normal cardiac performance and 11 adult patients with coronary artery disease. The measurement of the index was successfully carried out in 28 of 61 adults and especially 16 of 21 children. The results of the study are summarized as follows:
1. Power waveform is similar to blood flow waveform and is little influenced by blood pressure waveform.
2, Peak (dPower/dt) can be determined as product of peak rate of change of aortic flow (peak (dF/dt) ) and mean brachial blood pressure without resorting to measurement of blood pressure waveform.
3. Peak (dPower/dt) was found significantly lower in cases having an ejection fraction less than 50% (93.5 J/sec²) than in those showing an ejection fraction of above 50% (145.3 J/sec²) (p<0.001) .
4. Peak (dPower/dt) normalized with body surface area was not significantly different from 8 years old children (80.2 J/sec²/m²) and 21-34 years old adults (88.0 J/sec²/m²) . According to this index, the cardiac contractility of 8 yearus old children seemed to reach the adult level.
From these findings it is concluded that the non-invasive method of determining a cardiologic parameter, peak (dPower/dt), as an index of cardiac contractility provides a means of salient clinical value.

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Long term physical training is known to cause a change of cardiac functions and this effect is observed at various levels of the heart (from whole heart to subcellular level), although its mechanism is not fully understood. It is reported that cardiac hypertrophy and decreased heart rate can be observed as effects of long term physical training, but change of the catecholamine content in heart tissue induced by training is controversial.
In the present experiment, long schedule of short daily swimming episodes was employed to observe the effect of mild physical training on cardiac functions of rats in the growing stage. We measured body weight, heart weight, heart rate under light anesthesia, variation of R-R-interval of electrocardiogram, and catecholamine contents in cardiac muscle.
1) Wister rats were divided into 2 groups 3 weeks after birth. One group rats was kept sedentary in cages, and the other group was required to free swim in a tank containing water at 30°C. At the beginning of the programme, swimming time was 10 min. Swimming was applied 5 days a week for up to 14 weeks, and swimming time was gradually increased to 30 min.
2) Body weight of rats in the trained group was significantly less than that of the controls, and the heart weight to body weight ratio in the trained rats was significantly higher than in the controls.
3) In the exercised rats, the R-R interval of the ECG was longer than that of the controls, and there was a tendency for the variation of R-R interval in the trained group to be larger than that of the controls.
4) At 10 and 17 weeks, rats from each group were sacrificed after or without a 30 min test swim for measurement of catecholamine content of the ventricular muscle. One time swimming for 30 min increased dopamine content, but did not change norepinephrine content except for the trained group at 10 weeks. There was no significant difference in cardiac catecholamine contents in the rested state of the control and trained groups at 10 and 17 weeks.
5) Results were interpreted as follows: One time swimming for 30 min influences the activity of the autonomic nervous system innervating the heart, and catecholamine metabolism at nerve terminals of the sympathetic nervous system. Long term mild swimming does not cause permanent change of catecholamine contents, and the low heart rate in the trained group cannot be soley explained by the decreased activity of the sympathetic nervous system.

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The purpose of this clinical investigation is to analyse the growth of the ventricular volumes and the changes of indices of cardiac performance during infancy and childhood. The materials were composed of 129 healthy infants and children (4 months to 13 years of age), who had a history of Kawasaki disease and without any evidence of coronary artery lesion. All the cases underwent cardiac catheterization and cineangiography under sedation. Volumes of the left and right ventricles were calculated by integration methods in tow frames for end-diastole and end-systole from biplane cineangiograms. Left ventricular mass was calculated in 120 infants and children by Rackley's method.
All the volumes and masses were deviled by body surface area in order to normalize the crude values for infants and children of different size. The mean values of left ventricular end-diastolic volume index (LVEDVI), right ventricular end-diastolic volume index (RVEDVI) and stroke index (SI) for each age were less in the younger children than those in the older children, and abrupt stepwise increase was observed at 1 year, 6 years and 10-11 years of age in the values of LVEDVI, RVEDVI and SI.
The infants and chidren were divided into four groups according to age (under 1 year, 1 to 5 years, 6 to 10 years and more than 11 years) . The values of LVEDVI, RVEDVI, SI and LVmass index were less in the younger age groups than those in the older age groups, and the difference of each age groups was statistically significant. The value of left ventricular ejection fraction (LVEF) was less in the youngest group (under 1 year) than those in the another groups (p<0.01) . The value for right ventricular ejection fraction (RVEF) was not significantly different in the age groups. End-systolic pressure-volume ratio was normalized with left ventricular mass (LVESP/ (LVESV/LVmass) ) . This normalized ratio was the lowest in the youngest group (under 1 year) and the highest in the oldest group (more than 11 years) .
As mentioned before, abrupt stepwise increase was observed in the“normal”values of LVEDVI, RVEDVI and SI in infancts and children. The explanation of this fact may be difficult at present. By the evidence of the normalized end-systolic pressure-volume ratio, it can be said that the contractility of the left ventricle in“healthy”infants and children was increased according to age. The reason why the value of LVEF was less in the youngest group than those in the another groups can be attributed to the lower contrac-tility in the youngest group. A possible factor that the value of RVEF was not significantly different between the youngest group and the another groups is; because the right ventricle works under higher pressure during fetal and neonatal period, then the right ventricular performance developed already in infancy.

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In order to characterize the neural control of the circulation in an organism undergoing a rapid somatic growth, we compared the arterial baroreceptor reflex in two groups of male Wistar rats anesthetized with urethane. The first group consisted of 36 rats of 6-7 weeks old, known to exhibit the greatest rate of increase of the body weight during the life span, whereas the second group consisted of 30 full-grown rats of 20-22 weeks old. When arterial pressure was controlled by phenylephrine or nitroglycerin, the reflex change in renal nerve activity was elicited over the arterial pressure range 15-30 mmHg lower than that of full-grown rats. The difference was attributable partly, but not exclusively, to the lower operating range of arterial baroreceptors in the former groups. Although no difference was observed between the two groups with respect to the reflex fall in arterial pressure in response to graded electrical stimulation of the aortic nerve, the accompanying bradycardia was significantly smaller in 6-7 weeks old rats primarily due to the difference in the vagally mediated component of the reflex response. In conclusion, the arterial baroreceptor reflex of growing rats, as compared to full-grown counterparts, is characterized by deviation of the operating range of arterial baroreceptors as well as the arterial baroreceptor reflex itself to lower arterial pressure range and poor development of the vagally mediated reflex bradycardia.

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Orthostatic Disregulation (OD, a kind of dysautonomia) is a syndrome which indicates disfunction of vessel contraction reflex during static standing. OD patients often show some symptoms of fainting, dizziness, headache and the like or syncope when they are holding orthostatic posture. OD is more recognized especially in preadolescence and adolescence periods (9-15 yrs.) . Brück & Oltmann (1957), Okuni (1958) etc, have reported details about OD.
The purpose of this study was to obtain and discuss details relating to recent appearance of OD, physique, growth characteristics, cardio-vascular functions and physical fitness on OD children by the questionnaire method and some experiments.
2, 227 children in elementary and junior high school in Yokohama and Kamakura cities as sub jectswere first screened by the questionnaire. And 165 subjects out of 2, 227 were at random selected for data on Schellong standing test, passive head-up tilt and distance running.
The value of 9-29%, which was the ratio of false OD (+) appearance by the questionnaire method in this study, was recognized higher than the value of 5-20% by previous studies'. Physique on false OD (+) children was somewhat lean in comparison with the normal. And they had more height increase than the normal.
In physical fitness, distance running, 50 m dash, broad jump, ball throw, chinning exercise and back pull-over tests, OD children were inferior than the normal.
A concrete datum in syncope for standing was got in this study. When an OD child exhibited syncope, systolic blood pressure became 78 mmHg (rest 120-130 mmHg) and heart rate became 76 beats per minute (standing before syncope 100-110 beats per minute) . T wave in II, _aV_F and P wave in II, III (depression, negative waves etc.) of ECG varied from resting ECG. Judging from these data about ECG and blood pressure on standing test, passive head-up tilt, it was indicated that a reflex system of vessel contraction on OD child didn't work well, and that the heart of OD child was much stressed by gravity in orthostatic posture and changing posture than the normal.
In addition, a fact was proven that false OD (+) children (39.1% boys and 48.2% girls) didn't like sports and physical activities comparing with the normal (16.4% boys and 23.5% girls), It was statistically significant. Therefore, it is estimated that there is a relationship between appearance of OD and physical activities in daily life.

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For the purpose to clarify whether physical training during the peak height velocity period of growth can accelerate the development of aerobic power and cardiorespiratory function, we determined the anaerobic threshold, VO₂ (AT) and maximaum O₂ uptake, VO₂ (MAX) together with cardiac output and several parameters indicating respiratory function in 16 boys. Stroke volume (SV), heart rate (HR) and cardiac output (Q) were measured continuously by using an automated impedance cardiograph. This apparatus can print out the above parameters once every 10 to 20 cardiac cycles in analog or digital form. An ensemble averaging technique was applied to improve the signal to noise ratio of the impedance signal during exercise. Minute ventialttion (V_E), O₂ uptake (VO₂), CO₂ output (VCO₂), end-tidal CO₂ tension (P_ETCO₂) and respiratory quotient were simultaneously measured breath by breath. The subjects were classified into two groups, the one trained group (T) and the other control group (C) . The boys included in T were 16 yrs and were engaged in the systematic training of Judo since 4 to 8 years ago. The boys of C were of the same age and were received no systematic physical training. The body weight of T was greater than C by 24%. The exercise was performed using a bicycle ergometer of which load was increased in step by 10 W every 30 sec. The measurement was terminated when VO₂ reached a plateau. AT was determined later on the record adopting the criteria proposed by Wasserman et al. i. e., the time point when V_E/VO₂ increased dominantly with constan V_E/VCO₂. At lest, SV, V_E and VO₂ were greater in T by 24, 20 and 36%, respectively. There was no significant difference in Q. At AT, the above parameter were greater in T than C by 36, 43 and 31%. At VO₂ (MAX), SV, Q, V_E, and VO₂ were larger in T by 56, 42, 34, and 27%. The difference between C and T was however disappeared when the parameters were normalized on body weight. There were significant correlations between body weight and either of VO₂ (AT) or VO₂ (MAX) . The same held true between the maximum value of SV and the above aerobic parameters. It was concluded that Judo training during the growth period enhances the muscle mass primarily, and the aerobic power is developed so as to match the increased mascle mass. The development of cardiac function is a major determinant for anaerobic threshold and maximum O₂ uptake.

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In this study the effects of endurance exercise on cardiorespiratory functions and performance in developing age were exemined in 12 year old boys. Sujects were consisted of 11 boys who had been participating in training for soccer more than 2 hours a day for 6 days per week (S) and 10 non-participating boys for control (C) . Maximal oxygen uptake (Vo₂max), maximal heart rate (HRmax) and maximal cardiac output (Qmax) by acetylnerebreathing method were measured on the exercise on a treadmill. Five minute run was also administered.
Significant differences were found in Vo₂max (p<0.05), values of which were 2.13±0.07 1⋅min^-1 for S. and 1.86±0.08 1⋅min^-1 for C., respectively, and in Qmax (p<0.001), values of which were 17.9±1.41⋅min^-1 for S. and 12.4+0.71⋅min^-1 for C. G., respectively. There were no significant differences in HRmax and V_E between both groups. Values of stroke volume and V_E/Vo₂max were significantly higher for S.. Performances on 5 minute-run were 1164 m for S. and 1083 m for C, which showed significant difference (p<0.01) . Significant correlationship (r=0.746, p<0.001) was obtained between Vo₂max and Qmax. It was also found that the higher Vo₂max was, the higher Qmax was attaind.

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The relationships between running performances (200 m running time and 5-min run) and VO₂max, Lactate Threshold (LT), or percent fat were investigated on 11-12-year old boys. Subjects were 21 control boys (group C) and 21 soccer boys (group S) . Mean 200 m running time in group S was significantly better than that in group C. Mean distance of 5-min run in group S was significantly longer than that in group C. No significant difference was found between mean running speed of 5-min run and mean speed at exhaustion in LT experiment. In group C, 200 m running time correlated significantly with VO₂max. In group S, faster runners showed higher peak post 200 m run lactate concentration. 5-min run correlated significantly with VO₂max for group C, group S and all subjects combined. LT correlated significantly with 200 m running time and 5-min run. No significant relation was found between running petformances and percent fat. It is suggested that VO₂max and LT determine, in part, boy's running performances, but percent fat do not.

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The influence of daily physical exercise on oxygen utilizing capacity of working muscle investigated by means of measureing lactate threshold (LT) during progressive treadmill running from the comparison between soccer group (S group: N=12, 11.9±0.1 years of age) and control group (C group ; N=14, 11.8±0.1 years of age) . LT₁ was determined as the point where blood lactate concentration (La) increased from rest level, and LT₂ was determined by the gradient, La/VO₂. body weight^-1 (2 mM/10 ml. kg^-1, min^-1) .
LT₁ and LT₂ in S group were significantly higher than those in C group expressed with absolute and relative values of VO₂ (1. min^-1, ml. kg^-1. min^-1, % VO₂max) . No significant differences in La, ventilation responses, and heart rate at the point of LT₁ and LT₂ were observed between S and C group, La showed slight decrease and was kept at lower level in S group with increase of VO₂, compared with C group. On the contrary, La in C group began to increase at lower level of VO₂. From our previous longitudinal study of LT in non-athletic children, we observed that LT shifted to lower level with growth. It was sugesed that La curve of S group, such shift had not occurred. Differences of these patterns in VO₂ and La between athletic children and non-athletic children were similar to those observed in adults athletes and non-athletes.
In conclusion it was supposed that sufficient daily physical training in 10-12 year of age might increase oxygen utilizing capacity of leg working muscle during running exercise.

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Little is known about the effects of aerobic exercise on cardiac structure in children. Echocardiographic study was performed at rest in 38 boys aged 11-12 (18 soccer players and 20 untrained) . Soccer players had significantly increased left ventricular end-diastolic dimension (43.6±2.8 vs 40.1±2.8 mm) and left atrial dimension (27.7±3.7 vs 23.0±2.8 mm) . There was no difference in interventricular septum and left ventricular posterior wall thickness between the two groups, these data show that intensive aerobic exercise may influence on cardiac structure in children.

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This study was performed to investigate the exercise-induced stress in growing state in order to prevent the death during or after exercise. Thirty eight male and female subjects in junior high school were administered 5 minutes running test for 3 succesive years. Heart rate, blood pressure, electrocardiogram, and blood biochemical components were measured before and after 5 minutes running test. Prior to 5 minutes running test the investigation of the number of food intake and total steps a day were performed. The results obtained were as follows;
1) After 5 minutes running test, the subjects who had larger increment in CK-MB/ CK ratio walked fewer steps a day and had fewer number of food intake. And they had more drinks, especially juices.
2) In female subjects an excess of body fat was not a risk factor, but not in male subjects.
3) The subjects, who had larger increment in body fat than in body weight, tended to become higher levels in blood pressure and heart rate in resting than others.
4) The subjects, who walked more longer in 2 nd grade than 1 st grade in junior high school, tended to decrease the increment of heart rate before to immediately after 5 minutes running test.
5) Blood biochemical components were normal even if electrocardiogram was abnormal.
6) At 24 hours after 5 minutes running test, CK-MB/CK ratio and serum lipoperoxide levels increased and serum protein and albumin levels defreased in 3 rd grade in junior high school.
Consequently in order to prevent the death during or after exercise the investigation of food intake, total steps a day, and body fat must be administered before exercise sufficiently. And then electrocardiogram and blood biochemical components, especially CK-MB activity must be checked before, during, and after exercise testing.

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To clarify influences of training by repetitious swimmings on fatty acid composition of tissue lipids, these specificities of organs and substrates and these changes by swimming, recovery and training were investigated by using Wister strain male rats and following results were obtained :
1. From viewpoint of fatty acid composition of each tissue lipid, specificities of organs and substrates were characterized and fatty acid composition of each tissue triglyceride (TG) was not related to the composition of cellular component lipids (cardio-lipin; CL, phosphatidylethanolamine; PE, and phosphatidylcholine; PC) .
2. By the training for 5i days, sigificant changes in fatty acid composition of TG, CL, PE and PC of heart muscle appeared. Especially linoleic acid composition of all these substrates significantly increased in the straining group, which did not show decrease of body weight, but in other training group showed significant decrease of body weight, linoleic acid composition of TG and CL of heart muscle significantly lowered and the linoleic acid composition of CL was lower than that of control group. But changes in fatty acid composition of PE and PC did not observed.
3. During the repetitious swimmings, linoleic acid composition of CL of heart muscle gradually increased with number of the swimmings and the peak appeared at 11 times of the swimmings, but those of PE and PC did not change at all. Thus, nutnber of the swimming directly caused changes in the composition of CL of heart muscle and different influences in the composition between CL and other phospholipids (PE and PC) were clearly distinguished.
4. After 30 times of the swimmings, linoleic acid composition of CL of heart and gastrocnemius muscles transiently supercompensated at 5 days, but despite of enough recovery of body weight, linoleic acid composition of CL in all tissues lowered and remarkable differences in the composition between control and the swimming groups appeared at 15 days after the swimming.
From these results, training by the swimming caused changes in linoleic acid composition of cellular component lipids of heart muscle with amount of swimming and the amount will be a key to change in the composition of CL of heart muscle. Then, amount of the swimming per day and recovery period would be a direct factor to cause changes in linoleic acid composition of CL and these changes finally influence on the composition of other cellular component lipids, PE and PC, and become to have a relation to physiological functions.

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The present study was done to elucidate the medical problems and physical fitness of under-weight elementary schoolboys. Eighty nine volunteers, ranging in age from 9 to 12 yrs, were divided into five groups based on the grade of obesity, expressed as % of the standard, taking into account height, age and sex.
The mean grade of obesity for under-weight boys was -12 %, and this group was defined as the experimental group (group I; n=15) . The group III, which contained 23 boys of grade 0 %, and the group V made of 13 boys of grade +33.5 % was defined as the normal control and obese control, respectively.
The measurement of blood pressure, EKG recording, and blood sampling were done in the state of fasting before and after exercise. The exercise was a step test of 5 min duration with a temp of 1 step per 2 seconds, jumping over a bench 25 cm high for 9 years old boys, and 33 cm high for boys of 10 to 12 years. The step test score (PFI) and recovery rate of heart rate (RR (HR) ) were calculated from the EKG. The test battery of physical fitness performance was also done on another experimental day.
The serum levels of total cholesterol (TC), triglyceride (TG), total protein (TP) and hemoglobin (Hgb) were lower in experimental group (EG) than in control groups (CG) . The cholesterol-HDL/TC ratio was conversely higher in EG than in CG. There were no significant differences in the other biochemical measurements between the five groups.
Any abnormal EKG was not recorded before and after exercise throughout the subjects. The frequency of hypertension (above the 135/80 mmHg) was 10.2 % at pre-exercise time. But, none of the boys in EG was found to be hypertensive.
The PFI and physical fitness performance test score showed no differences between EG and group III, however, the score of group V was inferior to that of EG and/or group III. The RR (HR) in EG and over-weight group was lower compared to that for the average-weight boys.
Almost all components in blood measured were elevated after exercise in all the groups. The finding of the highest interest of the exercise-induced elevations of blood constituent levels was an increase in WBC measured as an indicator of stress. The magnitude of increase in WBC (ΔWBC) was higher in EG and the over-weight group than in the average-weight group. In normal subjects, ΔWBC was generally proportional to the work intensity, which, in the present exercise, depended upon the stature and body weight, because the height of bench, tempo and duration of exercise were same for all groups. The work intensity in EG was presumed milder, becasue the mean stature was slightly taller and bodyweight was less heavy compared to those in control groups. But, the greater increase of WBC in EG was observed in spite of a lighter work intensity. According to the Selye's literature, the particular WBC reaction to exercise in the under-weight boys was interpreted as a over-reaction to stress in the state of malnutrition.
From some biochemical parametors, the leaner subjects were assumed to be in a slight malnutrition. And also a later recovery of HR and over-reaction to exercise stress were shown in the under-weight boys group.
It is emphasized that the malnutrition resulting from excessive effort for preventing obesity was unfavourable for children in the growing stage for their healthy growth and development.

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Twenty four hours ambulatory monitoring of electrocardiogram and exercise stress testing were performed in 60 children who were refered to our hospital because of isolated premature ventricular contractions (PVCs) .
Complex ventricular ectopy was found in 28 out of 60 PVC children. Out of 28 subjects with complex ventricular ectopies 21 had PVCs originated from the right ventricle.
Frequency of PVCs per day was high in primary ventricular tachycardia and low in ventricular tachycardia with organic heart disease and there was statistical significance (p<0.01) between these two groups.
There was no characteristics in coupling interval, prematurity index and vulnerability index which could specify ventricular tachycardia, couplets PVCs and isolated PVC.
VT rate in exercise stress testing was higher than that in twenty four hours ambulatory monitoring of electrocardiogram (Holter recording) . Both exercise stress testing and twenty four hours monitering of electrocardiogram should be done to control VT school children.

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