Allometry theory to create a standard value for bone mineral content for menstruating adult females and examination of usefulness / 体力科学

Evidence suggests that sports activity can induce site-specific changes in bone mineral content (BMC) in athletes. Therefore, the first purpose of this study was to create a standard value for BMC (SV_BMC) that is independent of body size and physical exercise effect. The second purpose was to examine usefulness for the SV_BMC. In creating the SV_BMC, we recruited non-customer subjects who engaged in regular exercise but did not have site-specific changes to their bony structure. We studied 285 females (34.0±6.5 years) that were currently active, free from hormone treatment, and were not taking medication for any condition. Furthermore, all female subjects reported having a normal menstrual cycle. Bone area (BA), BMC and areal bone mineral density (aBMD) were measured by dual-energy X-ray absorption. Measurements of almost the complete skeleton, with the exception of the head, were taken (herein referred to as sub-total). This included scans of the entire spinal column, all 12 ribs, pelvis, full legs and arms. An allometry formula that relates BMC and BA was applied to determine the SV_BMC. To exclude the effect of body size, calculations were determined using the perpendicular distance from the data of each individual to that determined by allometry regression. Finally, the mean and standard deviation of the distance were converted into T-scores. In examination of reliability for the SV_BMC, we calculated the SV_BMC for three customer females who engaged in regular exercise. We found a significantly positive relationship between SV_BMC and weight/BMI. This correlation was weaker than the relationship between SV_BMC and BMC, as expected, or the relationship between SV_BMC and aBMD, with the exception of SV_BMC in the pelvis. In conclusion, this study suggests that SV_BMC is less affected by body size than by BMC or aBMD and the SV_BMC was provided highly useful in case study.

The effect of bench-stepping exercise training on BMD, BMC and bone metabolism in menopausal women / 体力科学

Since the effect of the submaximal aerobic exercise on bone had been controversial, the aim of this study was to elucidate the effect of the bench step (BS), that seemed to deliver higher mechanical load on bone than any other aerobic exercises, on the total bone mineral content (BMC) and the bone metabolism of menopausal women. Sixteen menopausal women (65 ± 9 years old) as the exercise group (ExG) and 28 pre-menopausal women (43 ± 3 years old) as the control group (CG) were studied. ExG carried out BS training with the exercise intensity at lactate threshold (LT) for 21 weeks. In ExG, BMC was measured by dual energy X-ray absorptiometry (DXA) at one year before the intervention (A year before), pre-intervention (Pre) and post-intervention (Post). Serum osteocalcin (OC) as the marker of bone formation and serum type I collagen cross-linked N-telopeptide (NTx) as the marker of bone absorption at Pre, 11th week of the intervention and Post. In CG, BMC was measured annually without the intervention. In ExG, OC was not changed, but NTx was significantly decreased by intervention (<i>p</i><0.05). The decreased amount of annual change in BMC between a year before and Pre (T1) was significantly higher compared to that between Pre and Post (T2) (<i>p</i><0.01) and CG (<i>p</i><0.001). There was no significant difference between T2 and CG. In conclusion, BS with LT could prevent decreasing BMC in menopausal women, and maintain the same level of BMC in pre-menopausal women by suppressing the bone absorption.

Change in heart rate at double product break point and validity of utilizing age-predicted heart rate at 50%VO₂max due to improvement of cardiovascular fitness / 体力科学

Previously, we have reported that age-predicted heart rate at 50%VO₂max (HR@50%VO₂max) is an effective index of adjusting appropriate exercise intensity for health promotion exercise. Thus, the aim of this study is to elucidate the change in HR at double product break point (HR@DPBP) and the validity of HR@50%VO₂max due to improvement of cardiovascular fitness. Ninety two healthy adults (57 +/- 9 years old), who participated in the health exercise training course, were studied. Participants were instructed how to control the intensity of physical activity for DPBP during their daily life. DPBP was determined with the use of incremental exercise test, and METs at DPBP (METs@DPBP), HR@DPBP, ratings of perceived exertion at DPBP (RPE@DPBP) were measured before and after the course. HR@50%VO₂max was calculated with the following formula; 138 - age/2 (bpm). METs@DPBP significantly increased (p<0.001) after 10 weeks of the course, whereas HR@DPBP did not change. Interestingly, however, there was a significantly positive correlation (p<0.001) between amount of change in METs@DPBP and that in HR@DPBP (ΔHR@DPBP). Multiple linear regression analysis indicated this correlation was independent from sex, age and amount of change in HR at rest (p<0.001). Before and after the course, proportion of study subjects’ %ΔHRs ((HR@50%VO₂max - HR@DPBP) / HR@DPBP x 100) within -10% ~ +10% were both 48.9%, and proportion of study subjects’ RPEs@DPBP within 11~13 were 92% and 85%, respectively. In this study, it was identified that significantly positive relation between amount of change in cardiovascular fitness and that of ΔHR@DPBP. This finding was independent from potentially affecting factors. In conclusion, this longitudinal study could suggest that HR@50%VO₂max and RPE were valuable indexes of determining exercise intensity for health promotion exercise.

THE RELATION BETWEEN DOUBLE PRODUCT BREAK POINT DURING SUB-MAXIMAL EXERCISE AND ARTERIAL STIFFNESS IN HEALTHY ADULT FEMALES / 体力科学

The purpose of this study was to elucidate the relation between double product break point (DPBP) and pulse wave velocity (PWV).Two hundred three healthy Japanese females were studied (mean age; 53.5 +/- 11.7 years old). The DPBP was measured by continuous incremental exercise test with a bicycle ergometer (ML-3600, Fukuda Electronic Co. Ltd). The work rate at DPBP was converted into metabolic equivalents (METs@DPBP). The brachial-ankle PWV (baPWV) was also measured. In addition, height, weight and mean blood pressure (mBP) were measured and physical activity condition in daily life (PA) was evaluated by questionnaire.The mean METs@DPBP was 5.0 +/- 0.7 METs. The mean baPWV was 1,373 +/- 254 cm/ sec. The relation between METs@DPBP and baPWV was investigated with the use of multiple linear regression models with adjustment for affecting factors of baPWV.In this study, it was identified that there was a significantly inverse relation between METs@DPBP and baPWV (<i>p</i> <0.01). This finding was independent from age, height, weight, mBP and PA. Thus, there was an inverse relation between sub-maximal aerobic capacity and arterial stiffness.

AN INVERSE ASSOCIATION BETWEEN PREDICTED 50%VO₂MAX PER BODY WEIGHT AND CORONARY RISK FACTORS / 体力科学

The aim of this study is to elucidate the relationship between the predicted 50%VO₂max/wt (ml/kg/min) and coronary risk factors (CRFs).Seven hundred eighty six men (37.3 +/- 13.5 years old) and 1,268 women (41.5 +/- 13.6 years old) were studied. The predicted 50%VO₂max/wt was calculated by utilizing data from the continuous incremental exercise test with a stationary bicycle ergometer and the age-predicted heart rate at 50%VO₂max (=138-age/2). As CRFs, percent body fat, systolic blood pressure, diastolic blood pressure, total cholesterol, triglyceride, high density lipoprotein cholesterol, fasting blood sugar and HbA1c were measured.The age-adjusted odds ratio of having abnormal values in CRFs across quartiles of the predicted 50%VO₂max/wt (highest to lowest) were 1.00 (reference), 1.39, 2.64, and 6.78 in men, and 1.00, 1.73, 2.33 and 3.44 in women (for trend, <i>p</i><0.001), respectively.This study indicated that the lower 50%VO₂max/wt resulted in the higher odds ratio of having abnormal values in CRFs among Japanese. It was also confirmed that the sub-maximal aerobic capacity was associated with CRFs.

COMPARISON OF HEART RATE AT DOUBLE PRODUCT BREAK POINT TO AGE-PREDICTED HEART RATE AT 50%VO₂max / 体力科学

In this study, we examined a reliability of age-predicted heart rate (HR) for the 50%VO₂max which is widely used during a training program for health promotion as compared to HR at the double product break point (DPBP). Two hundred fifty six non-hypertensive subjects (NHT), and 49 hypertensive ones under medication (HT) were studied. HT subjects were divided into two subgroups based on antihypertensive medications, ones with HR non-suppression agents (HT+HRNS) and the other with HR suppression agents (HT+HRS). DPBP was measured with the use of an incremental exercise test, and HR at DPBP (HR@DPBP) was determined. Age-predicted HR for the 50%VO₂max intensity of exercise was calculated with the following formula; HR=138–age/2. Measurable rate of DPBP and HR@DPBP in NHT, HT+HRNS and HT+HRS were 93.8% and 120±14bpm, 92.7% and 104±12bpm, 78.5% and 94±16bpm, respectively. There were significant differences in HR@DPBP and age-predicted HR in NHT and HT+HRS (<i>p</i><0.01 in both groups). But %ΔHR ((age-predicted HR–HR@DPBP)/HR@DPBP x 100) within -10%∼+10% in NHT, HT+HRNS and HT+HRS were 68%, 58% and 14%, respectively. This might be due to HR at rest with sitting position that was significantly correlated to %ΔHR in all groups (r=-0.604, <i>p</i><0.001 in NHT, r=-0.689, <i>p</i><0.001 in HT+HRNS and r=-0.761, <i>p</i><0.05 in HT+HRS, respectively). And the range of HR at rest with sitting position corresponding to -10%∼+10% of %ΔHR were 70∼95bpm in NHT, 71∼93bpm in HT+HRNS and 83∼102bpm in HT+HRS. In addition, this study indicated that DPBP could be measured even under antihypertensive medication that might affect DPBP measurement.In conclusion, we demonstrated that HR at DPBP and age-predicted HR were similar among 58-68% of NHT and HT+HRNS. And the range of HR at rest with sitting position to ensure reliability of age-predicted HR was elucidated.