ABSTRACT
The purpose of this study was to investigate the effects of creatine loading on rowing performance in well-trained male competitive rowers (age 19.4±0.2 yr, height 182.2 ± 1.2 cm, weight 76.6±1.1 kg, mean±SE) . Twenty subjects were randomly separated into creatine (n=10) or placebo group (n=10) . Subjects performed simulated 2000 m rowing race and 20 sec maximal rowing on a rowing ergometer, before and after 6 days of creatine (20g of creatine monohydrate plus 4g of lactose per day) or placebo (24g of lactose per day) ingestion, The creatine and placebo were administered in a double-blind research design. Performance time for 2000 m rowing was improved significantly from 407.9±5.3sec to 404.7±5.4sec (p<0.01) in the creatine group, but no significant changes were observed in the placebo group. No significant changes were observed in power output during 20 sec maximal rowing in either groups. These results suggest that creatine loading can enhance performance in simulated 2000 m rowing race in well-trained competitive male rowers but has no beneficial effect on 20 sec maximal rowing.
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.
ABSTRACT
This paper was aimed to evaluate cardiovascular function and physical fitness of athletes during active athletic life and after the cessation of physical training, and to discuss on cardiovascular future of ex-athletes. Subjects included 301 men and 64 women athletes who participated in Tokyo Olympic games. Four to 12 years' follow-up study was performed in 88 men athletes. (1) . The characteristic findings of ECG during active athletic period were sinus bradycardia, increased voltage of QRS, irbbb and first or second degree AV block. Ninety-five percents of cases with sinus bradycardia and all cases with AV block showed normal heart rate and normal AV conduction within 4 years the cessation of training. Irbbb persisted longer than other items and 60 percents of cases with irbbb had the similar findings 12 years after the cessation of training. (2) . Increased heart size observed during active athletic life returned to normal in 4 to 8 years after the cessation of training. (3) . Blood pressure was not changed before and after the cessation of training. (4) . Little changes were observed in grip strength, 12 years after the cessation of training. Although there was a slight decrease on back lift strength and ability of vertical jump 12 years after the cessation of training, they were still higher than normal. (5) . Havard step test score was obviuously decreased 12 years after the cessation of training, although it was still maintained highly than normal. From this study, it may be inferred that the effect of physical training to cardiovascular function does not persisit for a long time. On the contrary, increased muscle strength such as grip strength, back lift strength and vertical jump persist for a rather long time, once it was increased by vigorous physical training.