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BACKGROUND@#It has been pointed out that prolonged television (TV) viewing is one of the sedentary behaviors that is harmful to health; however, the association between socioeconomic status (SES) and prolonged TV viewing time has not been sufficiently investigated in Japan.@*METHODS@#The study population are the participants of NIPPON DATA2010, which is a prospective cohort study of the National Health and Nutrition Survey 2010 in Japan. They were residents in 300 randomly selected areas across Japan. This study included 2752 adults. SES was classified according to the employment status, educational attainment, living status, and equivalent household expenditure (EHE). Prolonged TV viewing time was defined as more than or equal to 4 h of TV viewing per day. Multivariable logistic regression analyses were conducted to examine the association of SES with prolonged TV viewing time.@*RESULTS@#The mean TV viewing time was 2.92 h in all participants. Of 2752 participants, 809 (29.4%) prolonged TV viewing, and the mean TV viewing time of them was 5.61 h. The mean TV viewing time in participants without prolonged TV viewing time was 1.81 h. The mean TV viewing time was prolonged as age classes increased and significantly longer in aged ≥60 years. Prolonged TV viewing time was associated with not working for all age classes and sexes. Only among women, education attainment and living status were also associated with prolonged TV viewing time. For education attainment, the lower the received years of education, the higher odds ratios (OR) of prolonged TV viewing time. For living status, in women aged <60 years, living with others had a significantly higher OR compared to living with spouse. On the other hand, in women aged ≥60 years, living alone had a significantly higher OR. EHE did not have any significant associations with prolonged TV viewing time.@*CONCLUSIONS@#In a general Japanese population, it should be noted that the association between SES and prolonged TV viewing time differed by age and sex. Particularly, it must draw attention to the prolonged TV viewing in elderly. The intervention in order to shorten TV viewing time needs to consider these attributes.
Subject(s)
Adolescent , Adult , Aged , Aged, 80 and over , Child , Child, Preschool , Female , Humans , Infant , Male , Middle Aged , Young Adult , Educational Status , Japan , Prospective Studies , Sedentary Behavior , Sex Factors , Social Class , Socioeconomic Factors , Television/statistics & numerical dataABSTRACT
Walking football was born in United Kingdom around 2011, that is forbidden to running. In recent years, walking football has become increasingly popular as a sport that diverse people can enjoy together. However, it is not clarified exercise intensity and how they feel after playing walking football. We aimed to determine the intensity when playing walking football and investigated how mood change. Twenty-six men and women (18 males, 8 females) out of those who participated in walking football event agreed to the present study. Heart rate (HR) was measured using wearable device with photoplethysmography when playing walking football. Metabolic equivalents (METs) was assessed using a triaxial accelerometer worn on the waist. McGill pain questionnaire was used to assess pain sites and number. To assess change in mood, short version of physical activity enjoyment scale (sPACES) was used before and after playing walking football. Borg scale was measured before and after walking football. The HR and METs were respectively as follows; male, 111.9 ± 11.4 bpm and 4.3 ± 0.6METs; female, 118.6 ± 16.2 bpm and 4.8 ± 0.7METs. There was no significant difference between men and women in both HR and METs during walking football. The sPACES was indicated significantly positive changes in mood, and Borg scale was significantly increased after playing walking football, without increasing acute or chronic pain. The walking football is safe and moderate-intensity sports and induce positive changes in mood.
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This study aimed to develop affective experience, attitude, and behavioral intention scales for exercise, and examine their associations with exercise behavior. A web-based questionnaire survey was conducted among 500 individuals aged 60 to 69 years at baseline. The survey measured respondents’ affective experiences, attitude, behavioral intention, exercise behavior, and demographic factors. The same survey was conducted 2 weeks (n = 345) and 1 year later (n = 338). Exploratory and confirmatory factor analyses showed that the factor structures of the affective experience (2 factors: 3 items each for positive experience and negative experience), attitude (2 factors: 3 items each for affective attitudes and instrumental attitudes), and behavioral intention scales (2 factors: 4 items each for intention to maintain behavior and intention to overcome barriers) were acceptable. For these scales, the Cronbach’s alpha coefficients ranged from 0.69 to 0.92, Pearson’s correlation coefficients for baseline and 2-week follow-up ranged from 0.51 to 0.81, and Cohen’s d values for the associations with exercise behavior ranged from 0.46 to 0.98. After adjusting for demographic factors and exercise behavior at baseline, structural equation modeling showed that an affective attitude toward exercise at baseline significantly predicted exercise behavior at 1-year follow-up (standardized coefficient = 0.27), and that the affective attitude was predominantly explained by the positive affective experience of exercise (standardized coefficient = 0.80). The results confirmed the validities and reliabilities of the scales. Positive affective experiences and affective attitudes may be important determinants of exercise behavior.
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We aimed to evaluate the associations of individual-level social capital (SC) and physical activity (PA) among Japanese elderly men and women. Individuals aged 65 or above were selected via population-based random sampling of 3000 adults, aged 20 years or above and living in Fujisawa city, who were asked to complete self-administered questionnaires. The sample consisted of 260 men [median (25-75% tile) age 73 (68-78) yrs] and 274 women [73 (68-78) yrs]. The daily duration of PA, SC [e.g., norms of reciprocity (mutual support in the community), social networks (relationship with community people, exchange with other generations), social participation (participation in community organization activities)], socio-economic status [educational attainment, work with income, perceived household economic status], and demographic characteristics [sex, age, living arrangements, BMI, physical limitations] were assessed. Multivariate logistic regression analyses were used to calculate odds ratios (OR) for associations of SC with PA, stratified by sex. High level of mutual support in the community, relationship with community people, and exchange with other generations were associated with longer PA time in men after adjusting for potential confounders in the final model (OR = 2.40 (95% CI: 1.24-4.67), 5.28 (1.42-19.66), and 4.24 (1.15-15.67), respectively). In women, relationship with community people and participation in community organization activities were associated with longer PA time (3.10 (1.32-7.26) and 2.50 (1.27-4.91), respectively). The association of individual-level SC and PA differed between men and women. Future studies can investigate whether similar results can be obtained in other areas or attempt to conduct a large-scale survey.
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Several studies have shown that low cardiorespiratory fitness (CRF) or heavy alcohol consumption is risks of total or certain types of cancer death. However, the combined influence of CRF and drinking habits on total cancer mortality is not clear. The purpose of this study was to investigate the joint effect of CRF and drinking habits on total cancer mortality among Japanese men. We evaluated the CRF and drinking habits on risk of total cancer mortality in 8,760 Japanese men (age: 19-59 yr) who were given a submaximal exercise test, a medical examination test, and questionnaires on their health habits. CRF was measured using a cycle ergometer test, and the men were classified into two categories by CRF levels based on the reference value of CRF (R-CRF) in “Physical Activity Reference for Health Promotion 2013” (Under R-CRF and Over R-CRF). Also, the men were assigned to Non Drinking, Moderate Drinking, and Heavy Drinking categories. There were 178 cancer deaths during the 20-yr follow-up period. Relative risk and 95% confidence intervals for total cancer mortality were obtained using the Cox proportional hazards model while adjusting for age, body mass index, systolic blood pressure, and smoking habits. Using the Under R-CRF & Heavy Drinking group as reference, the relative risk and 95% confidence intervals were 0.37 (0.16–0.85) for the Over R-CRF & Non Drinking group. This result suggests that Japanese male with a high CRF and a low drinking habit have a lower risk of total cancer mortality.
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A physical activity reference value for health promotion, 23 METs-h/week was established by the Ministry of Health, Welfare, and Labour in Japan in 2006. The purpose of this study was to determine the daily step counts (steps/day) that classify adults as meeting the 23 METs-h/week reference value by using objective measurements. Objectively measured physical activity levels of 1837 Japanese adults aged from 23 - 69 yrs from both urban and rural Japanese cohorts were provided. Amount of physical activity and daily step counts were assessed using a triaxial accelerometer (Actimarker EW4800; Panasonic Electric Works). Receiver operating characteristics (ROC) curve analysis determined the optimal daily step counts (steps/day) that discriminated adults who met the reference value from those who did not. Approximately 48 % of Japanese adults met the 23 METs-h/week of physical activity reference value. ROC curve analysis found that 9341 steps/day produced 77.1 % of sensitivity and 79.5 % of specificity in all subject. When the analysis was performed in each cohort, 9980 steps/day and 8640 steps/day were indicated as the optimal daily step counts for them to meet 23 METs-h/week in urban and rural cohort, respectively. These data suggest that Japanese adults are likely to meet 23 METs-h/week of physical activity reference value if they accumulate between 8500 and 10,000 steps/day of daily step counts.
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The purpose of this study was to develop prediction models of sarcopenia in 1,894 Japanese men and women aged 18-85 years. Reference values for sarcopenia (skeletal muscle index, SMI; appendicular muscle mass/height<sup>2</sup>, kg/m<sup>2</sup>) in each sex were defined as values two standard deviations (2SD) below the gender-specific means of this study reference data for young adults aged 18-40 years. Reference values for predisposition to sarcopenia (PSa) in each gender were also defined as values one standard deviations (1SD) below. The subjects aged 41 years or older were randomly separated into 2 groups, a model development group and a validation group. Appendicular muscle mass was measured by DXA. The reference values of sarcopenia were 6.87 kg/m<sup>2</sup> and 5.46 kg/m<sup>2</sup>, and those of PSa were 7.77 kg/m<sup>2</sup> and 6.12 kg/m<sup>2</sup>. The subjects with sarcopenia and PSa aged 41 years or older were 1.7% and 28.8% in men and 2.7% and 20.7% in women. The whole body bone mineral density of PSa was significantly lower than in normal subjects. The handgrip strength of PSa was significantly lower than in normal subjects. Stepwise regression analysis indicated that the body mass index (BMI), waist circumference and age were independently associated with SMI in men; and BMI, handgrip strength and waist circumference were independently associated with SMI in women. The SMI prediction equations were applied to the validation group, and strong correlations were also observed between the DXA-measured and predicted SMI in men and women. This study proposed the reference values of sarcopenia in Japanese men and women. The prediction models of SMI using anthropometric measurement are valid for alternative DXA-measured SMI in Japanese adults.
ABSTRACT
The purpose of this study was to develop prediction models of sarcopenia in 1,894 Japanese men and women aged 18-85 years. Reference values for sarcopenia (skeletal muscle index, SMI; appendicular muscle mass/height2, kg/m2) in each sex were defined as values two standard deviations (2SD) below the gender-specific means of this study reference data for young adults aged 18-40 years. Reference values for predisposition to sarcopenia (PSa) in each gender were also defined as values one standard deviations (1SD) below. The subjects aged 41 years or older were randomly separated into 2 groups, a model development group and a validation group. Appendicular muscle mass was measured by DXA. The reference values of sarcopenia were 6.87 kg/m2 and 5.46 kg/m2, and those of PSa were 7.77 kg/m2 and 6.12 kg/m2. The subjects with sarcopenia and PSa aged 41 years or older were 1.7% and 28.8% in men and 2.7% and 20.7% in women. The whole body bone mineral density of PSa was significantly lower than in normal subjects. The handgrip strength of PSa was significantly lower than in normal subjects. Stepwise regression analysis indicated that the body mass index (BMI), waist circumference and age were independently associated with SMI in men; and BMI, handgrip strength and waist circumference were independently associated with SMI in women. The SMI prediction equations were applied to the validation group, and strong correlations were also observed between the DXA-measured and predicted SMI in men and women. This study proposed the reference values of sarcopenia in Japanese men and women. The prediction models of SMI using anthropometric measurement are valid for alternative DXA-measured SMI in Japanese adults.
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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.<br>
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<p><b>OBJECTIVES</b>We investigated the correlation between changes in body weight and body composition parameters.</p><p><b>METHODS</b>We used the data of 2635 Japanese (40.2±12.2 years) at baseline and at 1-year follow-up from a database of 13522 subjects, which is available at the Okayama Southern Institute of Health in Okayama prefecture, Japan. Body weight, waist circumference at the umbilical level, hip circumference, and body fat percentage were used in the analyses.</p><p><b>RESULTS</b>Body composition parameters were significantly reduced after 1 year. Changes in body weight significantly correlated with changes in waist circumference, changes in hip circumference, and changes in body fat percentage. A decrease in body weight of 3 kg corresponded to a 3.45 cm decrease in waist circumference in men and a 2.83 cm decrease in that in women.</p><p><b>CONCLUSION</b>A decrease in body weight of 3 kg corresponded to an almost 3 cm decrease in waist circumference at the umbilical level in Japanese men and women.</p>
ABSTRACT
Objectives: We investigated the correlation between changes in body weight and body composition parameters. Methods: We used the data of 2635 Japanese (40.2±12.2 years) at baseline and at 1-year follow-up from a database of 13522 subjects, which is available at the Okayama Southern Institute of Health in Okayama prefecture, Japan. Body weight, waist circumference at the umbilical level, hip circumference, and body fat percentage were used in the analyses. Results: Body composition parameters were significantly reduced after 1 year. Changes in body weight significantly correlated with changes in waist circumference, changes in hip circumference, and changes in body fat percentage. A decrease in body weight of 3 kg corresponded to a 3.45 cm decrease in waist circumference in men and a 2.83 cm decrease in that in women. Conclusion: A decrease in body weight of 3 kg corresponded to an almost 3 cm decrease in waist circumference at the umbilical level in Japanese men and women.
Subject(s)
Body Weight , Adipose TissueABSTRACT
The purpose of the present study was to clarify effect of increase in calf pressure on calf venous compliance. The calf pressures were increased by wearing elastic compression stockings with different pressures (Calf pressure 0, 12, 17, 21 mmHg). Healthy twelve people (six men and six women, 43.3±15.3 years) volunteered to participate in this study. Changes in calf venous volume during spine rest were measured by mercury plethysmography. We analyzed the calf venous compliance by inflating the venous collecting cuff to 60 mmHg for 7 min, then decreasing cuff pressure at 1 mmHg/sec (over 1 min) to 0 mmHg, using cuff pressure as an estimate of venous pressure. This method produced pressure-volume curves fitting the quadratic regression (Δlimb volume)=β<sub>0</sub>+β<sub>1</sub>·(cuff pressure)+β<sub>2</sub>·(cuff pressure)<sup>2</sup>, where Δ is change. The higher calf venous compliance and volume were observed in with the higher pressure stocking. These results suggest that higher calf pressure induced by wearing elastic compression stocking increases calf venous compliance and maximum venous outflow.
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The aim of this studv was to clarify the effects of water immersion on the cardiovascular recovery process following submaximal steady state exercise on land. Seven male subjects (23 yrs old) underwent experiments under four separate conditions on separate days (15 minutes of cycling exercise at 50% and 80% maximal oxygen consumption followed by 16 minutes of recovery in a sitting position in water and out of water) . Concerning conditions in water, mean water temperature was 29.4 degrees, and the immersion level was set at xiphoid. Mean room temperature in out of water conditions, and during all conditions of exercise, was 24.4 degrees. Oxygen consumption (VO<SUB>2</SUB>), heart rate (HR) and blood pressure (systolic: SBP, diastolic: DBP) were measured under each condi tion. Mean blood pressure was calculated from SBP and DBP (MBP=1/3× ( SBP-DBP) +DBP) . Stroke volume (SV) was measured by Doppler echocardiography, and then cardiac output (CO=SV×HR), total peripheral resistance (TPR=NIBP/CO) and arteriaVmixed venous oxygen difference (a-v O<SUB>2</SUB>diff=VO<SUB>2</SUB>/CO) were calculated. In comparison with the same exercise intensity condition, there were no significant differences between recovery processes of VO<SUB>2</SUB>, HR, SBP, DBP and MBP in and out of water. SV and CO were significantly higher (p<0.05) during the recovery process in water than out of water (SV: at 50 and 80% maximal oxygen consumption conditions, CO: at 80% condition) . The TPR and a-v O<SUB>2</SUB>diff were significantly lower (p<0.05) during the recovery process in water than out of water at 80% oxygen consumption condition. These results indicate that water immersion facilitates circulating blood volume during the recovery process without increasing blood pressure, especially during recovery after high intensity exercise. Therefore, we suggest that increased left ventricular preload with immersion would be an important factor in cardiovascular regulation not only at rest but also during recovery after exercise.
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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 (Vo<SUB>2</SUB>max) 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 Vo<SUB>2</SUB>max or peak oxygen uptake (peak Vo<SUB>2</SUB>) . The significant negative correlations were found between HR and In HF power (meta-analysis and the cross-sectional study ; r<SUP>2</SUP> = 0.42 and 0.44, respectively) . Endurance training in the intervention study increased peak Vo<SUB>2</SUB> 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.
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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%Vo<SUB>2</SUB>max. 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.
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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.
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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%Vo<SUB>2</SUB>max, 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.
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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 0<SUB>2</SUB> uptake (VO<SUB>2</SUB>max) . 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%VO<SUB>2</SUB>max. 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.
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The purpose of the present study was to investigate the effect of maximal interval training for 10 weeks on arterial oxygen saturation (SaO<SUB>2</SUB>) 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 (VO<SUB>2</SUB>max), interspersed with 2-min recovery cycle at 50%VO<SUB>2</SUB>max. VO<SUB>2</SUB>max and ventilatory data measured every week. SaO<SUB>2</SUB>, end-tidal oxygen partial pressure (PETO<SUB>2</SUB>), end-tidal carbon dioxide partial pressure (PETCO<SUB>2</SUB>) and the ventilatory equivalent for oxygen (VE/VO<SUB>2</SUB>) measured during 5-min heavy exercise at 90%VO<SUB>2</SUB>max every other week. VO<SUB>2</SUB>max significantly increased from 52.5±4.9 to 60.6±5.8 ml⋅ml<SUP>-1</SUP>⋅kg<SUP>-1</SUP> during the training. SaO<SUB>2</SUB> reduced significantly from 95.4±1.1 to 93.3±1.8%, similarly PETO<SUB>2</SUB> and VE/VO<SUB>2</SUB> reduced during the training. A significant positive correlation was found among SaO<SUB>2</SUB>, PETO<SUB>2</SUB> and VE/VO<SUB>2</SUB> during heavy exercise (SaO<SUB>2</SUB>-PETO<SUB>2</SUB>, r<SUP>2</SUP>=0.48, P<0.05 ; SaO<SUB>2</SUB>-VE/VO<SUB>2</SUB>, r<SUP>2</SUP>= 0.49, P<0.05; PETO<SUB>2</SUB> - VE/VO<SUB>2</SUB>, r<SUP>2</SUP>=0.81, P<0.05) . These results suggest that-50% of the arterial O<SUB>2</SUB> desaturation during heavy exercise can be accounted for by low ventilatory response. Therefore the maximal intervsal training induced arterial O<SUB>2</SUB> desaturation during heavy exercise, which can be half explained by low ventilatory response.
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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<SUP>-1</SUP>) One session consisted of five periods of exercise of 3-min duration on a cycle ergometer at a power output of 100% maximal O<SUB>2</SUB> uptake (Vo<SUB>2</SUB>max), interspersed with 2-min recovery cycling at 50%Vo<SUB>2</SUB>max. The echocardiograms at rest and during mild exercise (100W) were recorded before and after the training. The interval training significantly increased Vo<SUB>2</SUB>max. 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.