ABSTRACT
The purpose of this study was to examine the effect of active recovery between two strenuous anaerobic exercises separated by a short time interval. Eight healthy adult male volunteers (age: 24.8±1.8 yrs, height: 170.6±2.5 cm, weight : 70.1 ±2.5 kg) underwent five exercise sessions. Each session consisted of a warm-up, the first anaerobic exercise test (40 sec of exhaustive cycle ergometer exercise), a 30 min inactive (seated) or active recovery period, and a second anaerobic exercise test. During the active recovery period, subjects executed one of four different intensity pedaling tests (60, 80, 100, 120% of predetermined lactate threshold intensity) for 10 min. There were no significant differences in mean power and peak blood lactate concentration among sessions during the first anaerobic exercise test. Significant differences were found in the blood lactate concentration among sessions during the second anaerobic exercise test, and significant differences were found in mean power for the second anaerobic exercise. Optimal intensity related to the blood lactate removal rate was 83.3±7.1%LT, and that related to the working capacity recovery rate was 68.3±11.8%LT.<BR>From these results, concerning blood lactate removal rate, it was suggested that between 80%LT and 100%LT was an effective intensity. As for performance, the effective intensity was less than 100%LT.
ABSTRACT
The purpose of this study was to determine the change in elbow flexor isometric torque at different phases of the menstrual cycle in humans. The subjects were six eumenorrheic females (age 22.0±3.5yr ; height 156.5±3.3cm ; body mass 50.2±4.9 kg) . The serum luteinizing hormone (LH), estradiol and progesterone levels, maximal voluntary contraction (MVC), integrated electromyographic activity (iEMG), interpolated twitch torque, evoked contractile properties, anthropometric parameters and Profile of Mood States (POMS) were measured at three different phases of the menstrual cycle, i. e., the menstrual, ovulatory and luteal phases. The MVC was significantly higher in the ovulatory phase than in the menstrual and luteal phases (P<0.05) . The iEMG, calculated voluntary activation and anthropometric parameters did not change significantly over the menstrual cycle. The MVC/iEMG ratio (electromechanical efficiency) and the evoked peak torque were also significantly higher in the ovulatory phase than in the menstrual and luteal phases (P<0.05, P<0.01) . In the menstrual phase, the fatigue and anger subscale score of POMS were significantly higher (P<0.05) and the vigor subscale score was significantly lower than in the other phases (P<0.05) . These results indicate that the variation in MVC observed over the menstrual cycle may be related to the intrinsic contractile properties rather than neural or psychological factors.
ABSTRACT
The present study was primarily designated as “Chino-Japanese cooperative study on physical fitness of junior track and field athletes” (1989) . The participants were male and female track runners of both countries ranging in age from 13 to 17 years.<BR>Skeletal age and stature for each sex and athletic event for the present series were compared between the two countries. The data of the present series were then compared with the earlier series, that is, the reference data derived from “Chino-Japanese cooperative study on physical fitness of children and youth” (1986) .<BR>Regarding the mean skeletal age of reference data (13 to 17 yrs.), the Japanese are more advanced (0.6 years in boys; 0.5 years in girls) than the Chinese, respectively. On the other hand, for the mean stature, the Chinese are taller (1.92cm in boys; 2.16cm in girls) .<BR>In the present series, the mean differences for skeletal age between the two countries show a tendency to be smaller than those in the reference data (0.38 years for boys and 0.39 years for girls in 100m runners; 0.15 years for boys in 1500m runners and girls in 800m runners), respectively.<BR>Although the mean differences of skeletal age between the two countries are becoming smaller, the stature of the Chinese boys and girls are getting taller than the Japanese (6.9cm in boys and 5.60cm in girls in 100m runners) . The mean differences are not so great as in 100m runners, however, it is 2.50cm in boys of 1500m runners and 4.05cm in girls of 800m runners.<BR>Comparison of the athletic records between the two countries was made and in general little difference was found. The Chinese records are more complete than the Japanese and show statistically significant difference particularly in 17 years old.<BR>In conclusion, the Chinese junior track runners seem to mature later skeletally or biologically than the Japanese, even though they are already taller than the Japanese. As a natural result, more gain in stature and more improvement in the athletic records will be expected for them. Otherwise some differences between the two countries in the process of sampling of the present study could be questioned.
ABSTRACT
The effects of voluntary exercise on resting systolic blood pressure and vascular lesions of stroke-prone spontaneously hypertensive rats (stroke-prone SHR) were investigated with and without 1 % saline loading. Forty male stroke-prone SHR aged 7 weeks were assigned to one of 4 experimental groups. Each consisted 10 animals ; sedentary control (S), sedentary with 1 % saline loading (SS), exercised control (E), and exercised with 1 % saline loading (ES) . Animals were sacrificed at the 5 th week. In the prehypertensive phase, resting caudal arterial systolic blood pressure was significantly lower in the E group than in the S group. However, after being loaded with 1 % saline, the ES group showed higher resting systolic blood pressure than those of the SS group. In addition, the ES group revealed severer renal, myocardial, and cerebrovascular lesions than those of the rest of the groups.
ABSTRACT
The purpose of the present study was to determine the effect of isometric strength training in prepubescent boys and girls on muscle strength and cross-sectional area of upper arm muscle. Subjects were ninety-nine healthy elementary school children from the 1 st, 3 rd and 5th grades and who were assigned to either training (TG, n=52) or control (CG, n=47) groups. The TG participated in a strength training program for 12 weeks which consisted of three maximaly sustained isometric contractions of elbow flexion for ten sec, twice a day, three days per week, whereas the CG did not participate in a special training program during this period. The cross-sectional areas of whole tissue, muscle, fat, and bone of the upper arm were measured by ultrasonic methods. Maximum isometric and isokinetic muscle strength of elbow flexion and extension were measured by means of a Cybex II. The hand-wrist X-ray photograph was used to estimate the skeletal age (TW 2 method) . Means (SDs) of skeletal age (yrs) were 6.27 (0.98), 8.48 (0.89), and 10.77 (1.22) for 1 st, 3 rd, and 5 th graders, respectively. After the 12-week training period, the cross-sectional area of the whole tissue increased significantly in both TG (8.9%, 2.52 cm<SUP>2</SUP>) and CG (7.3%, 2.11 cm<SUP>2</SUP>) . This interment in the TG was due to the significant increases in both muscle and bone areas, while that in CG was due to the significant increase only in fat area. Mean increase in muscle area in the TG was 10.3% (1.29 cm<SUP>2</SUP>) with this increase notable in 5th graders (12.5% for males and 12.7% for females) . The increment in cross-sectional area of muscle with training significantly correlated with the skeletal age (r=0.36, p<0.01) . Maximum isometric strength in the TG increased by 5.7% (0.3kg) in flexion and 17.5% (1.2 kg) in extension and in the CG, -0.3 kg (-1.0%) in flexion and 5.7% (0.3 kg) in extension. The increases in the strength of elbow extension were statistically significant in 1st (p<0.01), 3rd (p<0.05), and 5th (p<0.05) grade males. On the other hand, maximum isokinetic strength did not change with training. Muscle strength per cross-sectional area did not show a significant increase except in the training group of 5th grade boys. It was suggested that the effects of strength training on muscle area and strength for prepubescents were similar in its direction to but different in its magnitude from those found in adults.
ABSTRACT
In this study, we investigated the effect of exercise training on serum and liver chblesterol levels and on biosynthesis of liver cholesterol in rats. The training was carried out at low [Low-Ex, 60% max O<SUB>2</SUB> consumption (VO<SUB>2</SUB>) ] and high (High-Ex, 75% max VO<SUB>2</SUB>) intensities for 16 weeks. The energy expenditure was adjusted to be equivalent. The succinate dehydrogenase activities of gastrocnemius muscle in the Low-Ex group and High-Ex group were higher than that of control, 36% and 109% (p<0.05) respectively. The levels of total and high density lipoprotein cholesterol in serum were 14-26% lower than those of control, but no difference was detected between the trained groups. The activity of HMG-CoA reductase in liver microsome was significantly higher than that of control for both trained groups. However, the stimulation of this enzyme activity was not changed by training intensity.
ABSTRACT
Oxidation of lactate at rest (RE, n=4), or after short strenuous exercise (EX, n=6) was investigated in rats. Food and water were given ad libitum before experiment. In EX, rats ran to exhaustion at the speed of 80-100 m·min<SUP>-1</SUP>. Immediately after exercise, 4 μCi of (U-<SUP>14</SUP>C) lactate was injected into aorta through an indwelling catheter. In RE, (U-<SUP>14</SUP>C) lactate was injected into the rats at rest. Expired gas was collected by a Brooks type bottomless chamber on treadmill belt for 120 min. In EX, exercise duration was 109±18 sec (mean±SE), and maximum blood lactate concentration after the exercise was 23.7±2.1 mM (mean±SE) . Cumulative percent recovery of <SUP>14</SUP>C as <SUP>14</SUP>CO<SUB>2</SUB> for 120 min was 48.5±2.8% for EX and 61.7±0.9% for RE (mean±SE) . Significant difference was found between these two rates (p<0.01) . After 50 min of recovery, mean volume of <SUP>14</SUP>CO<SUB>2</SUB> expired per min in RE was significantly greater than that in EX (p<0.01) . Mean volume of <SUP>14</SUP>CO<SUB>2</SUB> expired per min per VCO<SUB>2</SUB> in RE was always greater than that in EX, and significant difference was found at 7.5 min of recovery (p<0.01) . It is concluded that although the rate of recovery of <SUP>14</SUP>C as <SUP>14</SUP>CO<SUB>2 </SUB>after exercise is lower than that at rest, the major pathway of lactate metabolism after short strenuous exercise is oxidation.
ABSTRACT
In order to investigate an effect of exercise on physical growth and maturation, physical characteristics (height, weight, chest girth, bi-acromial diameter, bi-iliac diameter and span) and skeletal age were measured for 34 boys of control group and 37 boys of soccer group. Skeletal age was evaluated from hand wrist radiographs by TW II method.<BR>Result showed that the values of physical characteristics in the control group were larger than those in the soccer group, but the differences were not statistically significant. Mean skeletal age in each age group of the soccer group closely approximated the chronological age, but that in the control group was inclined to proceed earlier than the chronological age. The correlations of all the physical characteristics with skeletal age were higher than with chronological age in both groups. Those correlations with chrono-logical age in the soccer group were lower than those in the control group.<BR>Based on the values of the subjects in this study, this fact leads to the conclusion that skeletal age is in fact a better predictor of physical characteristics than chronological age is. Physical characteristics of the boys in the soccer group correlate higher with skeletal age than with chronological age. In relation to the skeletal maturation, each physical characteristics in the control group shows a similar growth. In the soccer group, weight and chest girth show differences of growth from other physical characteristics.
ABSTRACT
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.
ABSTRACT
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) . LT<SUB>1</SUB> was determined as the point where blood lactate concentration (La) increased from rest level, and LT<SUB>2</SUB> was determined by the gradient, La/VO<SUB>2</SUB>. body weight<SUP>-1</SUP> (2 mM/10 ml. kg<SUP>-1</SUP>, min<SUP>-1</SUP>) .<BR>LT<SUB>1</SUB> and LT<SUB>2</SUB> in S group were significantly higher than those in C group expressed with absolute and relative values of VO<SUB>2</SUB> (1. min<SUP>-1</SUP>, ml. kg<SUP>-1</SUP>. min<SUP>-1</SUP>, % VO<SUB>2</SUB>max) . No significant differences in La, ventilation responses, and heart rate at the point of LT<SUB>1</SUB> and LT<SUB>2</SUB> were observed between S and C group, La showed slight decrease and was kept at lower level in S group with increase of VO<SUB>2</SUB>, compared with C group. On the contrary, La in C group began to increase at lower level of VO<SUB>2</SUB>. 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 VO<SUB>2</SUB> and La between athletic children and non-athletic children were similar to those observed in adults athletes and non-athletes.<BR>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.
ABSTRACT
The relationships between running performances (200 m running time and 5-min run) and VO<SUB>2</SUB>max, 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 VO<SUB>2</SUB>max. In group S, faster runners showed higher peak post 200 m run lactate concentration. 5-min run correlated significantly with VO<SUB>2</SUB>max 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 VO<SUB>2</SUB>max and LT determine, in part, boy's running performances, but percent fat do not.
ABSTRACT
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 (Vo<SUB>2</SUB>max), 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.<BR>Significant differences were found in Vo<SUB>2</SUB>max (p<0.05), values of which were 2.13±0.07 1⋅min<SUP>-1</SUP> for S. and 1.86±0.08 1⋅min<SUP>-1</SUP> for C., respectively, and in Qmax (p<0.001), values of which were 17.9±1.41⋅min<SUP>-1</SUP> for S. and 12.4+0.71⋅min<SUP>-1</SUP> for C. G., respectively. There were no significant differences in HRmax and V<SUB>E</SUB> between both groups. Values of stroke volume and V<SUB>E</SUB>/Vo<SUB>2</SUB>max 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 Vo<SUB>2</SUB>max and Qmax. It was also found that the higher Vo<SUB>2</SUB>max was, the higher Qmax was attaind.