Prediction and validation of total and regional skeletal muscle volume by using anthropometric measurements in prepubertal Japanese children.

It is difficult to easily estimate skeletal muscle (SM) volume in children. We aimed to develop regression-based prediction equations to estimate the total body and regional SM volume using calliper measurements of skinfold thickness and limb circumference and to investigate the validity of these equations. In total, 142 healthy, prepubertal, Japanese children, aged 6-12 years, were divided into two groups: the model development group (sixty boys, thirty-eight girls) and the validation group (twenty-six boys, eighteen girls). Contiguous magnetic resonance images were obtained from the first cervical vertebra to the ankle joints as reference data. SM volume was calculated from the summation of the digitised cross-sectional areas. Limb and waist circumferences were measured at mid-upper arm, mid-thigh, maximal calf and at the level of umbilicus. Each girth was corrected for subcutaneous adipose tissue thickness, as estimated by skinfold thickness measurements. Skinfold thickness was measured at the posterior upper arm, anterior thigh, medial calf and lateral to the umbilicus, using callipers. Significant correlations were observed between the site-matched SM volume, measured by MRI, and each corrected girth × standing height value in the model development group. When these SM volume prediction equations were applied to the validation group, the measured total body and regional SM volume were similar to the predicted values. These results suggest that the anthropometric prediction equations developed in this study provide reliable information about the total and regional SM volume in prepubertal Japanese children, with varying degrees of estimation accuracy for each region.

Fat-Free Mass Index as a Surrogate Marker of Appendicular Skeletal Muscle Mass Index for Low Muscle Mass Screening in Sarcopenia.

OBJECTIVES: We aimed to examine the relationship between the fat-free mass index (FFMI; FFM/height2) and appendicular skeletal muscle mass index (ASMI; ASM/height2), measured using both bioelectrical impedance analysis (BIA) and dual-energy X-ray absorptiometry (DXA), and investigate the effects of age and obesity. We also evaluated the suitability of BIA-measured FFMI as a simple surrogate marker of the ASMI and calculated the optimal FFMI cutoff value for low muscle mass screening to diagnose sarcopenia. DESIGN: Cross-sectional study. SETTING AND PARTICIPANTS: This study included 1313 adults (women, 33.6%) aged 40-87 years (mean age, 55 ± 10 years) from the WASEDA'S Health Study. METHODS: Body composition was measured using multifrequency BIA and DXA. Low muscle mass was defined according to the criteria of the Asian Working Group for Sarcopenia 2019. RESULTS: BIA-measured FFMI showed strong positive correlations with both BIA- (r = 0.96) and DXA-measured (r = 0.95) ASMIs. Similarly, in the subgroup analysis according to age and obesity, the FFMI was correlated with the ASMI. The areas under the receiver operating characteristic curve for screening low muscle mass defined by DXA-measured ASMI using BIA-measured FFMI values were 0.95 (95% CI 0.93-0.97) for men and 0.91 (95% CI 0.87-0.94) for women. The optimal BIA-measured FFMI cutoff values for screening low muscle mass defined by DXA-measured ASMI were 17.5 kg/m2 (sensitivity 89%, specificity 88%) for men and 14.6 kg/m2 (sensitivity 80%, specificity 86%) for women. CONCLUSIONS AND IMPLICATIONS: The FFMI showed a strong positive correlation with BIA- and DXA-measured ASMIs, regardless of age and obesity. The FFMI could be a useful simple surrogate marker of the ASMI for low muscle mass screening in sarcopenia in community settings. The suggested FFMI cutoff values for predicting low muscle mass are <18 kg/m2 in men and <15 kg/m2 in women.

Characteristics of total body and appendicular bone mineral content and density in Japanese collegiate Sumo wrestlers.

The purpose of this study was to explore the characteristics of total body and appendicular bone mineral content (BMC, kg) and bone mineral density (BMD, g/cm2) in Japanese collegiate Sumo wrestlers. A total of 54 male college Sumo wrestlers were recruited for the study and assigned to two groups according to their body weight (middleweight, 85-115 kg, n = 23 and heavyweight, > 115 kg, n = 31). The BMC, BMD, fat mass, and lean soft tissue mass (LSTM) values were measured using dual-energy X-ray absorptiometry for the total body and appendicular regions. Heavyweight Sumo wrestlers had significantly higher body weight, fat mass, and LSTM compared to middleweight Sumo wrestlers. The mean total body and regional BMC values were significantly higher in heavyweight than in middleweight Sumo wrestlers. The total body and leg BMD was significantly higher in heavyweight than in middleweight Sumo wrestlers, and was significantly correlated with body weight, but not arm BMD. The present study indicates that BMC and BMD might not sharply elevate among even heavyweight athletes, although heavier Sumo wrestlers had a greater BMC and BMD.

Comparison between DXA and MRI for the Visceral Fat Assessment in Athletes.

The use of dual-energy X-ray absorptiometry (DXA) may be invalid for assessing athletes with larger bodies, larger lean body mass, and thicker trunks. This study compared the athletes' visceral adipose tissue (VAT) assessed using DXA and magnetic resonance imaging (MRI). Eighty-two Japanese male collegiate athletes from 18 sports participated in this study. VAT was assessed using the dual-energy scan that coincided with the 4th lumbar vertebra. The sum of eight magnetic resonance slices corresponding to the region of the dual-energy scan was used for comparison. The VAT volume was higher with the dual-energy scan than with MRI (difference: 35 cm3, p<0.01). A significant correlation was noted between the volumes measured using both modalities (r=0.88, p<0.01). Magnetic resonance-derived volumes less than 600 cm3 showed a stronger significant correlation with dual-energy-derived volumes. However, magnetic resonance-derived VAT volumes exceeding 600 cm3 were not significantly correlated with dual-energy-derived volumes. In conclusion, VAT volumes derived from DXA were larger and significantly correlated with those derived from MRI across a wide range of values. Methods using DXA for assessing the visceral fat volume may require adjustment to estimate abdominal visceral fat volume in athletes, with care taken when using such methods for heavyweight athletes.

Development and validation of a simple anthropometric equation to predict appendicular skeletal muscle mass.

BACKGROUND & AIMS: A limited number of studies have developed simple anthropometric equations that can be implemented for predicting muscle mass in the local community. Several studies have suggested calf circumference as a simple and accurate surrogate maker for muscle mass. We aimed to develop and cross-validate a simple anthropometric equation, which incorporates calf circumference, to predict appendicular skeletal muscle mass (ASM) using dual-energy X-ray absorptiometry (DXA). Furthermore, we conducted a comparative validity assessment of our equation with bioelectrical impedance analysis (BIA) and two previously reported equations using similar variables. METHODS: ASM measurements were recorded for 1262 participants (837 men, 425 women) aged 40 years or older. Participants were randomly divided into the development or validation group. Stepwise multiple linear regression was applied to develop the DXA-measured ASM prediction equation. Parameters including age, sex, height, weight, waist circumference, and calf circumference were incorporated as predictor variables. Total error was calculated as the square root of the sum of the square of the difference between DXA-measured and predicted ASMs divided by the total number of individuals. RESULTS: The most optimal ASM prediction equation developed was: ASM (kg) = 2.955 × sex (men = 1, women = 0) + 0.255 × weight (kg) - 0.130 × waist circumference (cm) + 0.308 × calf circumference (cm) + 0.081 × height (cm) - 11.897 (adjusted R2 = 0.94, standard error of the estimate = 1.2 kg). Our equation had smaller total error and higher intraclass correlation coefficient (ICC) values than those for BIA and two previously reported equations, for both men and women (men, total error = 1.2 kg, ICC = 0.91; women, total error = 1.1 kg, ICC = 0.80). The correlation between DXA-measured ASM and predicted ASM by the present equation was not significantly different from the correlation between DXA-measured ASM and BIA-measured ASM. CONCLUSIONS: The equation developed in this study can predict ASM more accurately as compared to equations where calf circumference is used as the sole variable and previously reported equations; it holds potential as a reliable and an effective substitute for estimating ASM.

Female Athletes Genetically Susceptible to Fatigue Fracture Are Resistant to Muscle Injury: Potential Role of COL1A1 Variant.

PURPOSE: We aimed to investigate the hypothesis that type I collagen plays a role in increasing bone mineral density (BMD) and muscle stiffness, leading to low and high risks of fatigue fracture and muscle injury, respectively, in athletes. As a potential mechanism, we focused on the effect of the type I collagen alpha 1 chain gene (COL1A1) variant associated with transcriptional activity on bone and skeletal muscle properties. METHODS: The association between COL1A1 rs1107946 and fatigue fracture/muscle injury was evaluated in Japanese athletes. Effects of the polymorphism on tissue properties (BMD and muscle stiffness) and type I collagen α1/α2 chain ratios in muscles were examined in Japanese nonathletes. RESULTS: The C-allele carrier frequency was greater in female athletes with fatigue fracture than in those without (odds ratio = 2.44, 95% confidence interval [CI] = 1.17-5.77) and lower in female athletes with muscle injury than in those without (odds ratio = 0.46, 95% CI = 0.24-0.91). Prospective validation analysis confirmed that in female athletes, muscle injury was less frequent in C-allele carriers than in AA genotype carriers (multivariable-adjusted hazard ratio = 0.27, 95% CI = 0.08-0.96). Among female nonathletes, the C-allele of rs1107946 was associated with lower BMD and lower muscle stiffness. Muscle biopsy revealed that C-allele carriers tended to have a larger type I collagen α1/α2 chain ratio than AA genotype carriers (2.24 vs 2.05, P = 0.056), suggesting a higher proportion of type I collagen α1 homotrimers. CONCLUSION: The COL1A1 rs1107946 polymorphism exerts antagonistic effects on fatigue fracture and muscle injury among female athletes by altering the properties of these tissues, potentially owing to increased levels of type I collagen α1 chain homotrimers.

Visceral fat and cardiorespiratory fitness with prevalence of pre-diabetes/diabetes mellitus among middle-aged and elderly Japanese people: WASEDA'S Health Study.

The relationships between cardiorespiratory fitness (CRF) measurements not confounded by adiposity and the prevalence of pre-diabetes mellitus (pre-DM) and diabetes mellitus (DM) are not well known. Thus, we aimed to investigate the associations of visceral fat (VF) and CRF with the prevalence of pre-DM/DM among Japanese adults. The study included 970 individuals (327 women and 643 men) who were 40-87 years old and had complete health examinations, abdominal fat area, and fitness data from WASEDA'S Health Study during 2015-2018. The VF area was measured using magnetic resonance imaging. CRF was measured using a cycle ergometer and was defined as VO2peak divided by fat free mass. The pre-DM/DM was identified based on the questionnaire and fasting blood tests. The odds ratios (ORs) and 95% confidence intervals (CIs) for prevalence of pre-DM/DM were calculated. Seventy-three participants had pre-DM and 48 participants had DM. Compared to the low VF group, the high VF group had a higher prevalence of pre-DM/DM (OR: 1.87, 95% CI: 1.18-2.96), although no significant relationship was observed between CRF and pre-DM/DM prevalence (P for trend = 0.239). The sub-group analyses also revealed no significant relationship between CRF and pre-DM/DM prevalence in the low VF group (P for trend = 0.979), although CRF values were inversely related to the prevalence of pre-DM/DM in the high VF group (P for trend = 0.024). Although CRF was not independently related to the prevalence of pre-DM/DM after adjusting for adiposity, higher VF values were related to a higher prevalence of pre-DM/DM. In addition, CRF levels were inversely associated with the prevalence of pre-DM/DM only among high VF individuals.

The Relationship between Changes in Organ-Tissue Mass and Sleeping Energy Expenditure Following Weight Change in College Sumo Wrestlers.

Background and objectives: It has been well established that the resting energy expenditure (REE) for the whole body is the sum of the REE for each organ-tissue in young and middle-aged healthy adults. Based on these previous studies, although it is speculated that sleeping energy expenditure (SEE, which has small inter-individual variability) changes with a commensurate gain or reduction in the resting metabolic rate of each organ-tissue, it is unclear whether a change in organ-tissue masses is directly attributed to the fluctuation of SEE at present. This study aimed to assess the relationship between changes in organ-tissue mass and sleeping energy expenditure (SEE) following weight change in college Sumo wrestlers. This included blood analysis, which is related to energy expenditure. Materials and Methods: A total of 16 healthy male college Sumo wrestlers were recruited in this study. All measurements were obtained before and after weight change. Magnetic resonance imaging measurements were used to determine the volume of the skeletal muscle (SM), liver, and kidneys, and an indirect human calorimeter was used to determine SEE before and after weight change. Results: The change in body mass and SEE ranged between -8.7~9.5 kg, and -602~388 kcal/day. Moreover, changes in SM, liver, and kidneys ranged between -3.3~3.6 kg, -0.90~0.77 kg, and -0.12~0.07 kg. The change in SEE was not significantly correlated with the change in SM or liver mass, nor with blood analyses; however, a significant relationship between the change in kidney mass and SEE was observed. Conclusions: Based on our results, there is a possibility that the mass of the kidneys has an effect on the change in SEE following weight change in college Sumo wrestlers.

Cut-offs for calf circumference as a screening tool for low muscle mass: WASEDA'S Health Study.

AIM: To re-evaluate the suitability of calf circumference as a surrogate marker of low muscle mass measured by both bioelectrical impedance analysis (BIA) and dual-energy X-ray absorptiometry (DXA). We also examined the effects of obesity and age on low muscle mass screening using calf circumference. METHODS: In total, 1239 adults participated in this cross-sectional study. We measured the maximum calf circumference in a standing position and appendicular skeletal muscle mass (ASM) using BIA and DXA. We defined low muscle mass based on the Asian Working Group for Sarcopenia 2019 consensus. RESULTS: Calf circumference was positively correlated with BIA-measured ASM/height2 (men: r = 0.81, women: r = 0.73) and DXA-measured ASM/height2 (men: r = 0.78, women: r = 0.76). In the subgroup analyses by obesity and age, calf circumference was also positively correlated with ASM/height2 . The optimal calf circumference cut-offs for low muscle mass screening measured by BIA and DXA were 35 cm (sensitivity 91%, specificity 84%) and 36 cm (sensitivity 82%, specificity 80%) for men, and 33 cm (sensitivity 82%, specificity 84%) and 34 cm (sensitivity 85%, specificity 72%) for women, respectively. CONCLUSIONS: Calf circumference is positively correlated with BIA- and DXA-measured muscle mass regardless of obesity and age and is a simple and accurate surrogate marker of muscle mass for diagnosing sarcopenia. Geriatr Gerontol Int 2020; 20: 943-950.

Differences in Muscle O2 Dynamics During Treadmill Exercise Between Aerobic Capacity-Matched Overweight and Normal-Weight Adults.

The aim of this study was to compare muscle O2 dynamics during exercise between aerobic capacity-matched overweight and normal-weight adults. Overweight women (OW, n = 9) and normal-weight women (NW, n = 14) performed graded treadmill exercise until exhaustion. Muscle O2 saturation (SmO2) and relative changes from rest in deoxygenated hemoglobin concentration (∆deoxy-Hb) and total hemoglobin concentration (∆total-Hb) were monitored continuously at gastrocnemius medialis muscle by near infrared spatial resolved spectroscopy. Significantly higher SmO2 and lower ∆deoxy-Hb and ∆total-Hb were observed in OW compared with NW. Pulmonary O2 uptake (VO2) normalized by fat-free mass was matched between groups. In both groups, peak VO2 was significantly correlated with change in SmO2 and ∆deoxy-Hb. Our findings suggest that both muscle blood volume and deoxygenation were lower in overweight adults, compared to aerobic capacity-matched normal-weight adults. Moreover, lowered muscle O2 extraction was related to peak VO2 in overweight adults, as well as in normal-weight adults.

The relationship between organ-tissue body composition and resting energy expenditure in prepubertal children.

BACKGROUND/OBJECTIVES: In this study, we ascertained the relationship between resting energy expenditure (REE) obtained using two procedures: indirect calorimetry and from organ-tissue mass, calculated employing magnetic resonance imaging (MRI), and adult metabolic rate constants, in prepubertal children. Differences between the measured and the calculated REEs were assessed according to age at puberty approaching stage. SUBJECTS/METHODS: We recruited 6-12 years old 110 healthy Japanese prepubertal children (40 girls and 70 boys). Organ-tissue masses for different organs (skeletal muscle, liver, kidneys, brain and adipose tissue) were determined using MRI and dual-energy X-ray absorptiometry. Heart and residual masses were calculated on the basis of each equation. REE was measured using the Douglas bag technique (measured REE). On the other hand, calculated REE was obtained by multiplying the sum of body compartments with the corresponding adult tissue respiration rate. RESULTS: The measured REE was significantly greater than the calculated REE in both, boys and girls, although a significant association was noticed between the two REEs in both the sexes. Besides, correlation between age and difference in the two REEs was found to be significant only in girls. CONCLUSIONS: The present study revealed that: (1) measured and calculated REEs differ by approximately 300 kcal/day in a relatively large sample of prepubertal children, and (2) the difference in organ-tissue mass between the measured and calculated REEs increased from approximately 200 to 400 kcal/day during the developmental process in girls but not in boys.

Lean Soft Tissue Mass Measured Using Dual-Energy X-Ray Absorptiometry Is an Effective Index for Assessing Change in Leg Skeletal Muscle Mass Following Exercise Training.

It is difficult to precisely and easily estimate the changes in skeletal muscle mass (SMM) following exercise training. We aimed to assess whether the change in lean soft tissue mass measured using dual-energy X-ray absorptiometry (DXA) reflects the change in SMM measured using magnetic resonance imaging (MRI) following exercise training in both the leg and trunk regions. Anthropometry, DXA, and MRI measurements of the trunk and leg regions were obtained in 10 male college sumo wrestlers before and after exercise training (mean duration between measurements: ~2 yr). Contiguous magnetic resonance images with 1-cm slice thickness and without gap were obtained from the first cervical vertebra to the ankle joints as reference data. Skeletal muscle volume was calculated from the summation of the digitized cross-sectional areas. The volume measurements were converted into mass by using an assumed skeletal muscle density (1.041 g/cm3). Trunk and leg areas, using DXA regional computer-generated lines, were adjusted to coincide with each discrete region by using MRI. Although the change in the DXA-measured lean soft tissue mass in the trunk region was significantly different from that of the MRI-measured SMM (Cohen's d = -1.3145, concordance correlation coefficient = 0.26, p < 0.01), the changes were similar in the leg region (Cohen's d = 0.07, concordance correlation coefficient = 0.87, p = 0.88). The exercise training-induced change in lean soft tissue mass significantly correlated with that in SMM, both in the leg (r = 0.88, p < 0.01) and trunk (r = 0.64, p < 0.05) regions. Bland-Altman analysis did not indicate a bias for the changes in leg lean soft tissue mass and SMM following exercise training. These results suggest that lean soft tissue mass measured using DXA is an effective index for assessing change in leg SMM following exercise training.

Body mass-to-waist ratio strongly correlates with skeletal muscle volume in children.

PURPOSE: We hypothesized that body mass-to-waist ratio is strongly associated with the total-body skeletal muscle volume (SMV) in children. The purpose of the present study was to examine this hypothesis. METHODS: By using magnetic resonance imaging, total-body SMV (SMVMRI) was determined in 70 boys and 53 girls aged 6 to 12 years. Waist was measured at each of the level of umbilicus (Wumb) and the minimum circumference (Wmin), and the ratio of body mass to each of the two measured values was calculated (BM/Wumb and BM/Wmin, respectively). A single regression analysis was used to examine the relationships between SMVMRI and either BM/Wumb or BM/Wmin. On the basis of the obtained regression equations, SMVMRI was estimated and referred to as SMVBM/Wumb or SMVBM/Wmin. RESULTS: In both boys and girls, SMVMRI was highly correlated to BM/Wumb (r = 0.937 for boys and r = 0.939 for girls, P < 0.0001) and BM/Wmin (r = 0.915 and 0.942, P < 0.0001). R2 and the standard error of estimate for SMVBM/Wumb were 0.878 and 706.2 cm3, respectively, in boys and 0.882 and 825.3 cm3, respectively, in girls, and those for SMVBM/Wmin were 0.837 and 814.0 cm3, respectively, in boys and 0.888 and 804.1 cm3, respectively, in girls. In both boys and girls, there were no significant differences between SMVMRI and either SMVBM/Wumb or SMVBM/Wmin, without systematic errors in Band-Altman plots. There was no significant effect of model on the absolute values of the residuals in both boys and girls. CONCLUSION: The current results indicate that body mass-to-waist ratio can be a convenient outcome measure for assessing the total-body skeletal muscle volume in children.

Validity of segmental bioelectrical impedance analysis for estimating fat-free mass in children including overweight individuals.

This study examined the validity of segmental bioelectrical impedance (BI) analysis for predicting the fat-free masses (FFMs) of whole-body and body segments in children including overweight individuals. The FFM and impedance (Z) values of arms, trunk, legs, and whole body were determined using a dual-energy X-ray absorptiometry and segmental BI analyses, respectively, in 149 boys and girls aged 6 to 12 years, who were divided into model-development (n = 74), cross-validation (n = 35), and overweight (n = 40) groups. Simple regression analysis was applied to (length)2/Z (BI index) for each of the whole-body and 3 segments to develop the prediction equations of the measured FFM of the related body part. In the model-development group, the BI index of each of the 3 segments and whole body was significantly correlated to the measured FFM (R2 = 0.867-0.932, standard error of estimation = 0.18-1.44 kg (5.9%-8.7%)). There was no significant difference between the measured and predicted FFM values without systematic error. The application of each equation derived in the model-development group to the cross-validation and overweight groups did not produce significant differences between the measured and predicted FFM values and systematic errors, with an exception that the arm FFM in the overweight group was overestimated. Segmental bioelectrical impedance analysis is useful for predicting the FFM of each of whole-body and body segments in children including overweight individuals, although the application for estimating arm FFM in overweight individuals requires a certain modification.

Prediction and validation of total and regional skeletal muscle volume using B-mode ultrasonography in Japanese prepubertal children.

Very few effective field methods are available for accurate, non-invasive estimation of skeletal muscle volume (SMV) and mass in children. We aimed to develop regression-based prediction equations for SMV, using ultrasonography, in Japanese prepubertal children, and to assess the validity of these equations. In total, 145 healthy Japanese prepubertal children aged 6-12 years were randomly divided into two groups: the model development group (sixty boys, thirty-seven girls) and the validation group (twenty-nine boys, nineteen girls). Reference data in the form of contiguous MRI with 1-cm slice thickness were obtained from the first cervical vertebra to the ankle joints. The SMV was calculated by the summation of digitised cross-sectional areas. Muscle thickness was measured using B-mode ultrasonography at nine sites in different regions. In the model development group, strong, statistically significant correlations were observed between the site-matched SMV (total, arms, trunk, thigh and lower legs) measured by MRI and the muscle thickness×height measures obtained by ultrasonography, for both boys and girls. When these SMV prediction equations were applied to the validation groups, the measured total and regional SMV were also very similar to the values predicted for boys and girls, respectively. With the exception of the trunk region in girls, the Bland-Altman analysis for the validation group did not indicate any bias for either boys or girls. These results suggest that ultrasonography-derived prediction equations for boys and girls are useful for the estimation of total and regional SMV.

Skeletal muscle deoxygenation responses during treadmill exercise in children.

Muscle O2 saturation (SmO2) and blood volume response in activating muscles during treadmill exercise were compared between prepubertal boys (n = 9, age: 9 ± 1 years) and young men (n = 9, age: 22 ± 2 years). SmO2 and blood volume responses were monitored continuously during the exercise at the gastrocnemius medialis muscle by near infrared spatial resolved spectroscopy. SmO2 was significantly decreased only at peak exercise in the boys, even though a significant decrease in SmO2 was observed at 60, 80, and 100 % of peak O2 uptake in the men (p < 0.05). No significant increase in blood volume was observed in the boys, while blood volume was significantly increased in the men with increased exercise intensity (p < 0.05). These results suggest that both blood volume and deoxygenation response in activating muscle may be minor in prepubertal boys, compared to young men. The blunted deoxygenation response in prepubertal boys may be caused by undeveloped diffusive O2 transport (i.e. mitochondrial respiration).

Determination of the exercise intensity that elicits maximal fat oxidation in short-time testing.

Maximal fat oxidation (MFO) rate and the exercise intensity that elicits MFO (FATmax-intensity) were designed to evaluate fat metabolism capacity and to provide individuals with a target exercise intensity during prolonged exercise. However, the previous methods of determining FATmax-intensity were time-consuming. The purpose of this study was to examine the validity of FATmax-intensity determined by short-time testing. Nine healthy young men performed ramp exercise, in a short-time test, until exhaustion and 5 constant-load exercises of 60 min each at individual FATmax-intensity determined by ramp protocol (FATmax-intensity(R)), FATmax-intensity(R) ± 5% of peak oxygen uptake (VO2peak) and FATmax-intensity(R) ± 10%VO2peak. FATmax-intensity was determined among 5 trials at points of early exercise (10 min) and prolonged exercise (60 min) to evaluate the validity of FATmax-intensity(R). Ten minutes after starting constant-load exercise, FATmax-intensity(R) showed the highest fat oxidation among 5 trials, even though MFO by ramp protocol was overestimated. Therefore, it may be useful for evaluation of fat metabolism to include the measurement of the FATmax-intensity in a routine ramp test. However, because FATmax-intensity(R) did not elicit the highest fat oxidation among 5 trials of 60 min each after starting constant-load exercise, FATmax-intensity(R) may not be effective for prolonged exercise training.

Effects of sleep deprivation on autonomic and endocrine functions throughout the day and on exercise tolerance in the evening.

The aim of this study was to investigate the effects of sleep deprivation on autonomic and endocrine functions during the day and on exercise tolerance in the evening. Ten healthy young males completed two, 2-day control and sleep deprivation trials. For the control trial, participants were allowed normal sleep from 23:00 to 07:00 h. For the sleep deprivation trial, participants did not sleep for 34 h. Autonomic activity was measured from 19:00 h on day 1 to 16:00 h on day 2 by frequency-domain measures of heart rate variability. Endocrine function was examined by measuring adrenocorticotropic hormone and cortisol from venous blood samples collected on day 2 at 09:00, 13:00, and 17:00 h and immediately after an exercise tolerance testing. Autonomic regulation, particularly parasympathetic regulation estimated from the high-frequency component of heart rate variability analysis, was significantly higher in the sleep deprivation trial than in the control trial in the morning and afternoon of day 2. Plasma adrenocorticotropic hormone concentrations were significantly higher at 09:00 and 13:00 h of day 2 under sleep deprivation. Heart rate during exercise was significantly lower following sleep deprivation. Therefore, the effects of sleep deprivation on autonomic regulation depend on the time of the day.

Predicting total fat mass from skinfold thicknesses in Japanese prepubertal children: a cross-sectional and longitudinal validation.

The present study was performed to develop regression based prediction equations for fat mass from skinfold thickness in Japanese children, and to investigate the cross-sectional and longitudinal validity of these equations. A total of 127 healthy Japanese prepubertal children aged 6-12 years were randomly separated into two groups: the model development group (54 boys and 44 girls) and the cross-sectional validation group (18 boys and 11 girls). Fat mass was initially determined by using DXA (Hologic Delphi A-QDR whole-body scanner) to provide reference data. Then, fat thickness was measured at triceps and subscapular using an Eiken-type skinfold calipers. Multiple anthropometric and DXA measures were obtained one year later for 28 of the original 127 subjects (longitudinal validation group: 14 boys and 14 girls). Strong significant correlations were observed between total fat mass by DXA measurement and the skinfold thickness × height measures by caliper in the model development group of boys and girls (R2=0.91-0.92, p<0.01). When these fat mass prediction equations were applied to the cross-sectional and longitudinal validation groups, the measured total fat mass was also very similar to the predicted fat mass. In addition, there were significant correlations between the measured and predicted total fat mass for boys and girls, respectively, although Bland-Altman analysis indicated a bias in cross-sectional validation group. Skinfold-derived prediction equations underestimate for obese children but are generally useful for estimating total fat mass in field research.

Prediction and validation of total and regional fat mass by B-mode ultrasound in Japanese pre-pubertal children.

The present study was performed to develop regression-based prediction equations for fat mass by ultrasound in Japanese children and to investigate the validity of these equations. A total of 127 healthy Japanese pre-pubertal children aged 6-12 years were randomly separated into two groups: the model development group (fifty-four boys and forty-four girls) and the validation group (eighteen boys and eleven girls). Total body, trunk, arm and leg fat masses were initially determined by dual-energy X-ray absorptiometry (DXA, Delphi A-QDR whole-body scanner; Hologic, Inc., Bedford, MA, USA). Then, fat thickness was measured by B-mode ultrasound (5 MHz scanning head) at nine sites (arm: lateral forearm, anterior and posterior upper arm; trunk: abdomen and subscapular; leg: anterior and posterior thigh, anterior and posterior lower leg). Regression analyses were used to describe the relationships between the site-matched fat masses (total body, arm, trunk and leg) obtained by DXA and ultrasound in the development group. When these fat mass prediction equations were applied to the validation group, the measured total and regional fat mass was very similar to the predicted fat mass (mean difference calculated as predicted - measured fat mass ± 2 SD; total body 0·1 (SD 0·5) kg, arm 0·1 (SD 0·3) kg, trunk - 0·1 (SD 0·3) kg, leg 0·1 (SD 0·5) kg for boys; total body 0·5 (SD 1·3) kg, arm 0·0 (SD 0·3) kg, trunk 0·1 (SD 0·8) kg, leg 0·3 (SD 0·6) kg for girls), and the Bland-Altman analysis did not indicate a bias. These results suggest that ultrasound-derived prediction equations for boys and girls are useful for estimating total and regional fat mass.