EFFECTS OF ENDURANCE TRAINING ON THE THICKNESS OF THE MUSCLE FIBER-CAPILLARY BARRIER IN SOLEUS MUSCLE OF GROWING RATS / 体力科学

The muscle fiber-capillary barrier consists of the capillary endothelium and the interstitium. Thinning of the barrier is physiologically significant for gas exchange in skeletal muscle because it shortens the diffusion distance of gases. The purpose of the present study was to examine the effect of endurance training on the ultrastructure of the muscle fiber-capillary barrier in soleus muscle of growing rats. Seventeen male Fischer 344 rats, aged 5 weeks, were assigned to either an exercisetrained group (ET, n=5), a paired-weight sedentary group (PWS, n=6), or a sedentary group (S, n=6), and matched as closely as possible with regard to body mass and Vo<SUB>2max</SUB>. The ET group performed a treadmill running program for 5 days/week for 10 weeks. The ET and S rats were freely fed rat chow and water. The PWS rats had their food intake restricted so that their mean body mass would be the same as that of the ET rats. After the training period, the diffusion distance in the ET group was significantly shorter than that in the PWS and S groups. There were no differ-ences in the thicknesses of the capillary endothelium among the three groups, but the interstitium was significantly thinner in the ET group than in the PWS and S groups. The degree of decrease in the interstitium thicknesses in the ET group was almost equal to that of the diffusion distance. Therefore it was identified that endurance training shortens the diffusion distance, which depends on thinning of the interstitium. These results suggest that morphological adaptation to endurance training partly contributes to the improvement of gas exchange in the muscle and aerobic work capacity.

Changes in the effects of 18 month endurance run training on aerobic work capacity in young children / 体力科学

Eight young girls as an experimental group (E group) and another eight as a control group (C group), (all aged 4-5 years), participated in the present study to observe the effects of training from May 1992 through November 1993. E group performed a 915m endurance run on an agricultural road every day except Sundays for an 18 month training period. No special training was given to C group. In May 1992 (T 1), November 1992 (T 2), May 1993 (T 3), and November 1993 (T 4), both groups underwent treadmill tests in order to check aerobic variables such as heart rate (HR) and oxygen uptake (VO<SUB>2</SUB>) during the course of the training period.<BR>Times required for the run became shorter from summer to fall and from winter to spring (shortening phase), whereas they became prolonged from spring to summer and from fall to winter (prolongation phase) . Therefore, there was a definite seasonality of performance endurance. The rates of shortening in the required times observed from summer to fall were considerably higher than from winter to spring, and this was reflected in the significant improvement of maximal running speed on the treadmill (Vmax) and maximal oxygen uptake in terms of body weight (VO<SUB>2</SUB>max⋅ TBW<SUP>-1</SUP>) from T 1 to T 2 as well as from T 3 to T 4. Thus, significant differences were found between the groups at T 2 and T 4. HR levels during the endurance run were close to 95% HRmax regardless of the phase. Accordingly, the prolongation phases, during which circulatory parameters and ventilatory capacity were least improved, could be regarded as a preparatory period for the following shortening period, during which work load intensities furthermore increased the arteriovenous oxygen differences. Thus, when planning research on the effects of training on aerobic work capacity in the field, special attention should be paid to the season and the training period, and the timing of the examination for training effects, or otherwise, misleading conclusions could be drawn.

The effect of iron supplemented food intake on iron status, hematological profiles and aerobic work capacity of female athletes / 体力科学

In order to prevent sports anemia, caused especially by iron deficiency or shortage, a special type of food supplementation was designed. This was called“iron-food”and contained 510% of the therapeutic iron dose. According to hemoglobin (Hb) values, female subjects who had been performing hard daily training were divided into two groups ; an anemia group (A group, Hb≤11.9 g/dl, n=4) and a potential anemia group (PA group, 12.0≤Hb≤12.9g/dl, n=4) . Then the iron-food was administered for six weeks following placebo treatment. Iron status, hematological profiles and aerobic work capacity of the two groups were examined before and after the two periods to investigate the effect of the iron-food. Serum iron, iron saturation and ferritin were significantly increased in the PA group. Serum iron tended to be increased in the A group, but not significantly. Red blood cell count, Hb and hematocrit were significantly increased in the PA group, and the reticulocyte count was also increased in the A group. These results suggest that iron-food helped to increase daily iron intake in the anemic subjects, but not to a sufficient extent to aid recovery from anemia. However the ironfood was effective for improving iron status in subjects with potential anemia (latent iron deficiency) .

Effects of physical training on red blood cell properties, in particular red cell 2,3-DPG and aerobic work capacity / 体力科学

The purpose of this study was to examine the effects of physical training on red blood cell properties, in particular red cell 2, 3-diphosphoglycerate (2, 3-DPG) and aerobic work capacity. The subjects were 28 healthy men and they were divided into three groups: Group 1 (12 athletes-long distance runners, cross country skiers performing daily aerobic training), Group 2 (8 athletes-sprinters (400 m), alpine skiers playing aerobic and anaerobic training every day) and Control (8 untrained persons) .<BR>The results obtained were as follows:<BR>1) In aerobic work capacity (VO<SUB>2</SUB>max/w, O<SUB>2</SUB> pulse max) there was significant difference (p<0.01) among 3 groups (Group 1>Group 2>Control) .<BR>2) Red blood cell properties (RBC, Hb, Hct) of each group showed no significant difference. However MCH, MCHC of Group 1 was significantly lower than Group 2 and Control, MCV was also a tendency to be lower. Red cell 2, 3-DPG concentration was significantly higher in Group 1, 2 as compared with Control. But there was no significant difference between Group 1 and Group 2.<BR>3) Red cell distribution curve of Group 1 tended to shift to the left in comparison with other two groups.<BR>4) The relationship between VO<SUB>2</SUB>max/w and red cell 2, 3-DPG significantly correlated for all subjects composing the three groups. In addition a significant correlation was found for Group 1.