A study on risk factors inducing stress fractures in young Japanese long-distance runners -effects of training distance and intensity- / 体力科学

The purpose of this study was to examine the risk factors of stress fractures in terms of training distance and intensity in young male Japanese high school long-distance runners. Nine hundred and twenty-five runners from high schools, colleges, and work teams responded to our questionnaire. Our analysis of the questionnaire found that the onset rates of stress fractures in males were 25.0%, 40.2%, and 55.3% in high school runners, collegiate runners, and work team runners, respectively, suggesting that young Japanese long-distance runners are more likely to suffer from stress fractures than European and American runners. Stress fractures occurred in male high school and collegiate runners after training that had increased running distance (24.7% and 33.1%, respectively) or running intensity (17.0% and 9.6%), or both increased running distance and increased running intensity (29.8% and 34.6%), suggesting that an increase in running distance at moderate intensity might be a major risk factor in stress fractures in young male long-distance runners. Data from college and work team runners that ran all three years of high school show that stress fractures are most likely to occur in May of the high school freshman year. These results suggested a need to reconsider training programs for freshmen to prevent stress fractures in young runners.

Daily steps corresponding to the reference quantity of physical activity of Exercise and Physical Activity Reference for Health Promotion 2006 (EPAR2006) assessed by accelerometer / 体力科学

The purpose of this study was to determine daily steps corresponding to the reference value for the quantity of Physical Activity and Exercise for Health Promotion 2006 (23 METs·h/wk) considering non-locomotive activities. Two hundred and thirty one men and 224 women wore a tri-axial accelerometer for two weeks. We analyzed the data in each age group (young (less than 40 years), middle-aged (40 to 59 years), and elderly (60 years or more) groups), also. There were significant relationships between daily steps and locomotive activity (r = 0.762 to 0.820, p < 0.001) and total (locomotive and non-locomotive) physical activity (r = 0.706 to 0.824, p < 0.001) with intensity of 3 METs or more in all groups. The daily steps corresponding to 23 METs·h/wk, calculated using regression lines between the daily steps and total physical activities with intensity of 3 METs or more in men and women were 6,534 steps/d and 6,119 steps/d. On the other hand, the daily steps corresponding to 23 METs·h/wk, calculated using regression lines between the daily steps and locomotive activities with intensity of 3 METs or more in men and women were 7,888 steps/d and 8,584 steps/d. These results suggest that non-locomotive activity should also be taken into consideration in the case of assessment of a daily physical activity.

A DIGE PROTEOMIC ANALYSIS FOR LOW-INTENSITY EXERCISE-TRAINED RAT SKELETAL MUSCLE / 体力科学

<b>Background:</b> Exercise training induces various adaptations in skeletal muscles. However, the mechanisms remain unclear. <b>Purpose:</b> Therefore, we conducted 2D-DIGE proteomic analysis, which has not yet been used for elucidating adaptations of skeletal muscle after low-intensity exercise training (LIT). <b>Methods:</b> For five days, rats performed LIT, which consisted of two 3-h swimming exercise with45-m rest between the exercise bouts. 2D-DIGE analysis was conducted on epitrochlearis muscles excised eighteen hours after the final training exercise. <b>Results:</b> Proteomic profiling revealed that, out of 681 detected and matched spots, 22 proteins exhibited changed expression by LIT compared with sedentary rats. All proteins were identified by MALDI-TOF/MS. <b>Conclusion:</b> The proteomic 2D-DIGE analysis following LIT identified expressions of skeletal muscle proteins, includingATPsynα, UQCRC1, dihydrolipoamide dehydrogenase, dihydrolipoamide acetyltransferase, that were not previously reported to change their expressions after exercise-training.

PREDICTION MODELS OF SARCOPENIA IN JAPANESE ADULT MEN AND WOMEN / 体力科学

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.

AMOUNT AND INTENSITY OF PHYSICAL ACTIVITY IN RELATION TO CARDIORESPIRATORY FITNESS IN JAPANESE MIDDLE-AGED AND ELDERLY MEN / 体力科学

PORPOSE: This study aimed to investigate the relation between cardiorespiratory fitness(CRF) and physical activity, especially vigorous physical activity, in Japanese middle-aged and elderly men.METHODS: Eighty-five men aged 30-69 years participated in this study. CRF was assessed by measuring the maximal oxygen uptake based on weight (VO₂max/wt) in an incremental test on a bicycle ergometer. METs·h/week was measured as the parameter of physical activity by using accelerometers. We defined the amount of physical activity higher than 3 METs as “Physical activity ; PA”in this study. Then, PA was divided into “Moderate physical activity ; MPA”(higher than 3 METs and below 6 METs)and “Vigorous physical activity ; VPA”(higher than 6 METs).RESULTS : CRF was positively correlated with PA(r=0.318, P<0.01), MPA(r=0.230, P<0.05), and VPA(r=0.301, P<0.01) and negatively correlated with age(r=-0.607, P<0.001), BMI(r=-0.369, P<0.01), and waist circumference(WC)(r=-0.486, P<0.001). After adjusting for age and WC, the multiple regression analysis revealed that PA was positively correlated with CRF(P<0.01). VPA was positively correlated with CRF(P<0.05) after adjusting for age, WC, and MPA. MPA was not correlated with CRF in the case of adjusting for age and WC.CONCLUSION : This study suggested that physical activity higher than 3 METs was positively associated with cardiorespiratory fitness independently of age and waist circumference, and particularly vigorous physical activity may contribute to increased cardiorespiratory fitness in middle-aged and elderly men. Thus physically active life with maintenance of adequate waist circumference may help to prevent age-related decline in cardiorespiratory fitness.

Retraction: PREDICTION MODELS OF SARCOPENIA IN JAPANESE ADULT MEN AND WOMEN / 体力科学

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.

DEVELOPMENT OF VO_2max PREDICTION MODELS FROM 3-MINUTE WALK TEST / 体力科学

The purpose of the study was to develop new VO_2max prediction models for Japanese men using a 3-minute walk test. One hundred and twenty-seven Japanese men aged from 20 to 69 years were recruited as subjects of the present study. Maximal oxygen uptake (VO_2max) was measured with a maximal incremental test on a bicycle ergometer. The prediction models were derived using data of age, 3-minute walking distance (3MWD), and either BMI, waist circumference (WC), or %Fat. This data was cross-validated by using PRESS cross-validation procedures. 3MWD was significantly related to VO_2max (<i>r</i> = 0.54, P<0.001). The multiple correlation coefficients for the BMI, WC, and %Fat models, respectively, were 0.81, 0.82, and 0.85. The standard error of estimate (SEE) was 4.5, 4.4, and 4.1 ml·kg^-1·min^-1, respectively, for the BMI, WC, and %Fat models. All regression models demonstrated a high level of cross-validity supported by the minor shrinkage of the coefficient of determination and increment of SEE in the PRESS procedure. This study demonstrated that 3MWD was useful for predicting VO_2max accurately using VO_2max prediction models for Japanese men. The new non-exercise prediction equations derived in this study are applicable to estimating VO_2max in Japanese adult men.

METABOLIC SYNDROME RISK FACTORS IN RELATION TO AEROBIC FITNESS IN JAPANESE MIDDLE-AGED AND ELDERLY PEOPLE －ANALYSIS BASED ON “EXERCISE AND PHYSICAL ACTIVITY REFERENCE FOR HEALTH PROMOTION 2006 (EPAR2006)”－ / 体力科学

PORPOSE: This study aimed to compare the prevalence of metabolic syndrome (MS) risk factors and its components in different levels of aerobic fitness established by “Exercise and Physical Activity Reference for Health Promotion 2006 (EPAR2006)” in Japanese middle-aged and elderly people.METHOD: Men (n=102) and women (n=133), aged 30-69yrs, participated in this study. The prevalence of MS risk factors was evaluated as the number of MS risk factors, according to the diagnostic criterion for Japanese-specific MS. Aerobic fitness was quantified as maximal oxygen uptake (VO₂max). Subjects were classified into the three groups by aerobic fitness level based on “Reference values” and “Reference range” established in EPAR2006; 1) High fitness group (H); VO₂max (mL/kg/min) is higher than “Reference values”, 2) Medium fitness group (M); VO₂max is below “Reference values” but within “Reference range”, 3) Low fitness group (L); VO₂max is lower than “Reference range”.RESULTS: In men, M and L groups showed significantly higher frequency of risk factors for MS than H group (H: 1.09±0.98, M: 1.81±1.07, L: 2.27±0.70, P＜0.01). In women, L group showed significantly higher frequency of risk factors for MS than H and M groups (H: 0.57±0.80, M: 0.81±1.01, L: 1.53±1.07, P＜0.01).CONCLUSION: These results suggest that higher MS risk appears when the VO₂max is lower than “Reference values” in men, and below “Reference range” in women, and that particularly, men with low aerobic fitness have higher MS risk.

Effects of Swimming Exercise on Maximal Aerobic Capacity and Plasma Lipid-Lipoprotein Profile of Postmenopausal Women / 体力科学

This study was designed to evaluate effects of long-term swimming training on maximal aerobic capacity and sernm lipid and lipoprotein profile of postmenopausal women. In the first study, 12 swimming-trained postmenopausal women (age: 58±3 yrs, BMI : 22± 2 kg/m<SUP>2</SUP>, training distance : 3.6±1.6 km/wk, mean±SD) were compared cross-sectionally with 50 age-matched untrained women (58±5 yrs, 23±2 kg m<SUP>2</SUP>) . Swimming-trained women had higher maximal oxygen uptake (Vo2max) than untrained (34± 5 vs. 30± 5 ml/kg/min, P<0.05) . Serum total- and HDL-cholesterol (T-C and HDL-C) and triglyceride (TG) concentrations in swimmers were similar to those in untrained (T-C: 232±23 vs. 220±44 mg/dl, HDL-C : 69±15 vs. 72±17 mg/dl, TG : 83±21 vs. 99±67 mg/dl) . On the other hand, swimmers had higher serum LDL-cholesterol concentrations (LDL-C) than untrained women (161±28 vs. 138±25 mg/dl, P<0.05) . The second study was conducted to test the effects of a 2-year swimming program on Vo2max and serum lipid and lipoprotein concentrations of postmenopausal untrained women. After the swimming program 10 trained women (age : 59±7 yrs, BMI : 23±3 kg/m<SUP>2</SUP>, Vo2max : 30± 3 mlikg/min at baseline, training condition : one hour session, frequency: 1.5±0.4 times/week during the program) and 12 untrained women (60± 5 yrs, 23± 3 kg/m<SUP>2</SUP>, 29± 5 ml/kg/min at baseline) were retested. No change in BMI was observed in the two groups. At the 2-year follow-up, the trained women increased Vo2max (34± 5 ml/kg/min, P<0.05), whereas no change in Vo2max was observed in the untrained women (30± 5 ml/kg/min) . No changes occurred in concentrations of T-C (Trained : 238±25 233±21 mg/dl, Untrained : 236±20 236±32mg/dl), HDL-C (Trained : 70 ± 15→74 ± 16 mg/dl, Untrained: 69 ± 15→69 ± 14 mg/dl), LDL-C (Trained : 150 ±29 144±27mg/dl, Untrained : 144±15→145±23mg/dl), and TG (Trained : 90±32 74±25 mg/dl, Untrained : 115±81 106±52mg/dl) . These results suggest that although a long-term swimming program can increase maximal aerobic capacity, favorable changes in sernm lipids or lipoproteins can not be expected for postmenopausal women.

The Effects of Swimming Exercise on Bone Mineral Density in Postmenopausal Women / 体力科学

In this study, we investigated the effects of a 2-year swimming program on suppressing bone loss in postmenopausal women. There were 22 subjects who participated in the swimming program (mean age 59.5 yr) and 19 controls (mean age 59.3 yr) . The program consisted of one-hour exercise sessions ; and the swimmers had on average 1.5 sessions per week. BMD at the lumbar spine (L2-L4) and proximal femur (neck, trochanter, and Ward's triangle) were measured by dual X-ray absorptiometry (DXA) ; and leg extensor power was measured using a dynamic leg extensor power rig. All the measurements were taken at baseline, 1 and 2 years. Height, weight, calcium intake and daily activity profiles were similar between the two groups, and these changed little throughout the experiment. In regard to leg extensor power, the swimming group had a significant increase at 1 and 2 years. At 2 year, the swimming group demonstrated 4.4%, 5.7% and 3.4% increases in BMD at the femoral neck, trochanter and Ward's triangle, respectively, while the control group showed slight decreases of BMD at the femoral neck (-0.2%) and Ward's triangle (-1.4%) . Significant differences in the rate of change in BMD at each site were observed between the two groups. The swimming group showed a decrease in lumbar spine BMD, as did the control group and the rate of the decline did not differ between the two groups. This study suggests that a 2-year swimming program for postmenopausal women can induce the beneficial effects of retarding bone loss at the proximal femur site and increasing leg extensor power.

Effect of high intensity intermittent training and resistance training on the maximal oxygen defieit and VO2max / 体力科学

This study examined the effects of (1) an intermittent training using a mechanically braked cycle ergometer and (2) resistance training using free weight on the maximal oxygen deficit and VO<SUB>2</SUB>max. For the first 6 weeks, six subjects trained using an intermittent training protocol five days per week. The exhaustive intermittent training consisted of seven to eight sets of 20 s exercise at anintensity of about 170% of VO<SUB>2</SUB>max with a 10 s rest between each bout. After the training, the maximal oxygen deficit increased significantly from 64.3±5.0 ml⋅kg<SUP>-1</SUP> to 75.1±5.7 ml⋅kg<SUP>-1</SUP> (p<0.01), while VO<SUB>2</SUB>max increased from 52.0±2.7 ml⋅kg<SUP>-1</SUP>⋅min<SUP>-1</SUP> to 57.6±2.9 ml⋅kg<SUP>-1</SUP>⋅min<SUP>-1</SUP> (p<0.05) . For the following 6 weeks, the subjects used the same intermittent training for 3 days per week and a resistance training for the other 3 days per week. The resistance training consisted of (1) 4 sets of 12 bouts of squat and leg curl exercise at 12 repetition maximum (RM) . (2) 2 sets of maximal bouts of the same exercise with a load of 90%, 80%, and 70% of 1 RM. After the training period, the maximal oxygen deficit increased further to the value of 86.8±5.9 ml⋅kg<SUP>-1</SUP>which was significantly higher than the value attained at the end of the intermittent training. On the other hand, VO<SUB>2</SUB>max did not increase significantly from the value observed at the end of the 6 weeks of intermittent training. Body weight was not significantly changed throughout the 12-week training period. Maximal circumference of the thigh did not changed during the first 6-week of the intermittent training period (pre-training: 57.1±1.2 cm, after 6-week training: 57.3±1.1 cm), while it increased significantly after the last 6-week combined training (59.0±0.8 cm, p<0.05) . In conclusion, this study showed that (1) high intensity intermittent training improves both the anaerobic and aerobic energy supplying systems, (2) additional resistance training with the intermittent training further increases the anaerobic energy supplying system, probably through increased muscle mass.