Specific medical checkups and health guidance procedures to prevent and alleviate metabolic syndrome in middle-aged or older subjects (aged 40–75 years old) were initiated in workplaces and autonomous communities throughout Japan in April 2008, according to the guidance of the Ministry of Health, Labor and Welfare of Japan. As it is important to provide instruction regarding exercise, physical activities and diet, a safe and efficient evidence-based instruction program is required. The requirements for such a program are as follows: (1) knowledge of necessary exercise and physical activity levels for prevention and alleviation of metabolic syndrome; (2) ability to appropriately evaluate the physical activity level of subjects; (3) motivation of subjects to positively modify their behavior; (4) sufficient consideration of exercise and diet combination; (5) conducting sufficient risk management to prevent accident and injury; and (6) acquiring necessary licenses for instruction. The subject should then actively engage in exercise and physical activity based on the instruction given.

The purpose of the present study was to investigate the effect of maximal interval training for 10 weeks on arterial oxygen saturation (SaO₂) and ventilatory response during heavy exercise. Seven subjects volunteered for participation in the study. All subjects performed an interval training 4 days per week. Training protocol per day consisted of five periods of exercise of 3-min duration on a cycle ergometer at a power output on 100% maximal oxygen uptake (VO₂max), interspersed with 2-min recovery cycle at 50%VO₂max. VO₂max and ventilatory data measured every week. SaO₂, end-tidal oxygen partial pressure (PETO₂), end-tidal carbon dioxide partial pressure (PETCO₂) and the ventilatory equivalent for oxygen (VE/VO₂) measured during 5-min heavy exercise at 90%VO₂max every other week. VO₂max significantly increased from 52.5±4.9 to 60.6±5.8 ml⋅ml^-1⋅kg^-1 during the training. SaO₂ reduced significantly from 95.4±1.1 to 93.3±1.8%, similarly PETO₂ and VE/VO₂ reduced during the training. A significant positive correlation was found among SaO₂, PETO₂ and VE/VO₂ during heavy exercise (SaO₂-PETO₂, r²=0.48, P<0.05 ; SaO₂-VE/VO₂, r²= 0.49, P<0.05; PETO₂ - VE/VO₂, r²=0.81, P<0.05) . These results suggest that-50% of the arterial O₂ desaturation during heavy exercise can be accounted for by low ventilatory response. Therefore the maximal intervsal training induced arterial O₂ desaturation during heavy exercise, which can be half explained by low ventilatory response.

The purpose of the present study was to compare between healthy male endurance trained athletes (T, n=6) and sedentary control subjects (S, n=6) for the blood velocity profile in left ventricle at rest and during exercise. Peak velocity of blood injection into the left ventricle at diastole (dV), peak velocity of blood ejection out of the left ventricle at systole (sV), duration of blood injection (dD) and duration of blood ejection (sD) were measured by pulsed Doppler sonography at rest and during cyclic ergometer exercise at intensity of 40, 60 and 80% maximal 0₂ uptake (VO₂max) . The dV tended to be higher T than S at rest and during exercise at all intensities, and statistical significance existed at rest and during exercise at 80%VO₂max. However, there was no significant differences in the sV between T and S. In addition, the dV/sV in T was significantly highter than that in S at rest and during exercise at all intensities. These results indicate that Pulling velocity on the left ventricle in T was faster than that in S. In other words, these indicate that preload on the left ventricle in T was larger than that in S. Moreover, the relationship between stroke volume and dV (r=0.50, p<0.001) was closer than that between stroke volume and sV (r=0.30) in all subjects at rest and during exercise. These data suggest that the contribution of enhanced dV was stronger than that of sV to the larger stroke volume observed in dV.

In a recent study, endurance athletes, i.e. cyclists and long-distance runners, were found to have larger arterial conductance vessels than untrained controls. The aim of the present study was to determine the blood flow profiles of dilated vessels in these endurance-trained athletes. Twelve endurance-trained athletes (ET group) and twelve untrained control subjects (UC group) volunteered for the study. The cross-sectional area (CSA), peak and mean blood velocity in the ascending aorta (pV and mV), blood pressure (BP), and heart rate (HR) were measured in the semi-supine position on a cycle ergometer fitted with a backrest, at rest and during exercise at 40%, 60%, and 80%Vo₂max. Furthermore, stroke volume (SV), cardiac output (CO), total peripheral resistance, and double product were calculated. The SV and CO of the ET group were significantly larger than those of the UC group during exercise. The CSA of the ascending aorta in the ET group was significantly larger than that in the UC group at rest and during exercise. There were no differences in the mV and mean BP between the two groups. Upon comparison at the same SV, pV, mV, the total peripheral resistance, and double product of the ET group were lower than those of the UC group. These results suggest that the dilation of the arterial conductance vessels with endurance training contri-butes to an increase in blood flow to the exercising muscles without a rise in mechanical stress (shear stress and pressure) to the aortic wall. In other words, the arterial conductance vessels adapt morphologically to maintain an adequate degree of the mechanical stress on the aortic wall.

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_2max. 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.

To clarify the mechanism responsible for the increase in stroke volume (SV) due to training, we investigated the effects of interval training on the left ventricle using M-mode echocardiography. Six healthy male subjects volunteered to undergo 48 training sessions for 12 weeks (4 sessions· week^-1) One session consisted of five periods of exercise of 3-min duration on a cycle ergometer at a power output of 100% maximal O₂ uptake (Vo₂max), interspersed with 2-min recovery cycling at 50%Vo₂max. The echocardiograms at rest and during mild exercise (100W) were recorded before and after the training. The interval training significantly increased Vo₂max. Although there was no significant difference in SV at rest before and after the training, the training increased SV significantly during exercise. Before the training, there was a significant difference in left ventricular enddiastolic dimension (LVEDD) and left ventricular end-diastolic volume (LVEDV) at rest and during exercise. However, after the training, LVEDD and LVEDV during exercise were significantly larger than those at rest. These results suggest that interval training for 12 weeks increases diastolic filling (elasticity) of the left ventricle during exercise in healthy young men, partly contributing to the increase in SV due to the training.

A study was conducted to determine non-invasively the effects of endurance training on the size of the inferior vena cava in humans. Twelve healthy male subjects were assigned to either an exercise-trained group (ET, n=7) or a sedentary control group (S, n=5) . The ET group underwent cycle-endurance training for 8 weeks (80%Vo₂max, 40 min/day, 4 days/week) . The S group led normal lives during the 8-week period. Before and after the training period, cross-sectional areas (CSA) of the inferior vena cava and the ascending and abdominal aorta were measured by echography. The CSA of the inferior vena cava after training was significantly larger than that before training in the ET group. There was no significant difference in the S group. These results indicate that the inferior versa cava can be morphologically altered as an adaptive response to endurance training. We consider that this adaptation partly contributes to the improvement in the efficiency of venous return from exercising muscles to the heart. Although the present training also increased the CSA of the aorta, the degree of change was smaller than that seen in the inferior vena cava, implying that the factors of adaptation and adaptability to endurance training in the inferior vena cava differ from those in the aorta.

We investigated whether the autonomic nervous system (ANS) modulation contribute to the bradycardia induced by endurance training. First, the meta-analysis approach was used to collect group mean values of maximal oxygen consumption (Vo₂max) and heart rate variability (HRV) from 14 studies involving 30 groups and 485 subjects. Subsequently, we performed a cross-sectional (n=116) and intervention (n=training group : 10 and control group : 6) studies. In both studies, ANS modulation was estimated by spectral analysis of HRV. In the meta-analysis and cross-sectional study, HR and natural logarithmic high frequency power (In HF power) were correlated with Vo₂max or peak oxygen uptake (peak Vo₂) . The significant negative correlations were found between HR and In HF power (meta-analysis and the cross-sectional study ; r² = 0.42 and 0.44, respectively) . Endurance training in the intervention study increased peak Vo₂ and resting In HF power, and decreased resting HR. These results strongly suggest that endurance training induces an increase in resting ANS modulation especially parasympathetic modulation. Furthermore, about half of the variability of resting HR can be accounted for by difference in parasympathetic modulation.