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  • Author: Mitsuru Higuchi x
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Zhen-Bo Cao, Taewoong Oh, Nobuyuki Miyatake, Kazuyo Tsushita, Mitsuru Higuchi and Izumi Tabata

Background:

This study aimed to determine the optimal number of steps per day needed to meet the current physical activity guidelines in a large population sample of Japanese adults.

Methods:

An accelerometer-based activity monitor (Kenz Lifecorder) was used to simultaneously measure moderate-to-vigorous intensity physical activity (MVPA) and step counts in 940 Japanese adults (480 women) aged 20 to 69 years. The step count per day equivalents to 2 different physical activity recommendations (23 MET-h/wk and 150 min/wk of MVPA) were derived using linear regression analysis and receiver operating characteristic (ROC) methodology.

Results:

Linear regression analysis showed that daily step counts correlated with weekly PAEE (r = .83) and daily minutes of MVPA (r = .83). Linear regression analysis also showed that 23 MET-h/wk of MVPA is equivalent to 11,160 steps/d, and 150 min/wk of MVPA is equivalent to 7716 steps/d. ROC analysis yielded similar findings: 10,225 steps/d are required to accumulate ≥ 23 MET-h/wk of MVPA and 7857 steps/d are needed to meet the recommendation of ≥ 150 min/wk of MVPA.

Conclusions:

The findings suggest that 10,000 to 11,000 and 7700 to 8000 steps/d represent the optimal thresholds for accumulating ≥ 23 MET-h/wk of MVPA and ≥ 150 min/wk of MVPA, respectively, for Japanese adults.

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Yuko Gando, Haruka Murakami, Ryoko Kawakami, Noriko Tanaka, Kiyoshi Sanada, Izumi Tabata, Mitsuru Higuchi and Motohiko Miyachi

Background:

It is unclear whether light physical activity is beneficially associated with insulin resistance, similar to moderate and/or vigorous physical activity. This cross-sectional study was performed to determine the relationship between the amount of light physical activity, as determined with a triaxial accelerometer, and insulin resistance.

Methods:

A total of 807 healthy men and women participated in this study. Physical activity was measured using a triaxial accelerometer worn for 28 days and summarized as light intensity (1.1–2.9 METs) or moderate to vigorous intensity (≥ 3.0 METs). Insulin resistance was evaluated by HOMA_R (FPG [mg/dL] × IRI [μU/mL]/405).

Results:

The daily time spent in light physical activity was inversely associated with HOMA_R (r = –0.173, P < 0.05). After adjustment for confounders, the association between light physical activity and HOMA_R remained statistically significant (β = –0.119, P < .05). Light physical activity remained significantly associated with HOMA_R following further adjustment for moderate to vigorous intensity activity (β = –0.125, P < .05). Similar results were observed when light physical activity was modeled as quartiles, especially in elderly women.

Conclusions:

These cross-sectional data suggest that light-intensity physical activity is beneficially associated with insulin resistance in elderly Japanese women.

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Sakiho Miyauchi, Satomi Oshima, Meiko Asaka, Hiroshi Kawano, Suguru Torii and Mitsuru Higuchi

The purpose of this study was to determine whether overfeeding and high-intensity physical training increase organ mass. We examined this question using cross-sectional and longitudinal studies in which we measured collegiate male American football players. Freshman (n = 10) and senior players in their second and third years of college (n = 17) participated in the cross-sectional study. The same measurements of the same freshman players (n = 10) were assessed after the one-year weight gain period in the longitudinal study. Fat-free mass (FFM), skeletal muscle, and adipose tissue mass were obtained using dual-energy X-ray absorptiometry. Liver, kidney, brain, and heart volumes were calculated using magnetic resonance imaging or echocardiography. Compared with the freshman players, the senior players had 10.8 kg more FFM, and 0.29 kg, 0.08 kg, and 0.09 kg greater liver, heart, and kidney mass, respectively. In the longitudinal study, FFM, liver, heart, and kidney mass of the freshman players increased by 5.2 kg, 0.2 kg, 0.04 kg, and 0.04 kg, respectively, after one year of overfeeding and physical training. On the other hand, the organ-tissue mass to FFM ratio did not change, except for the brain, in either the cross-sectional or longitudinal studies. Our results indicated that the organtissue masses increased with overfeeding and physical training in male collegiate American football players.

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Xiaomin Sun, Zhen-Bo Cao, Kumpei Tanisawa, Satomi Oshima and Mitsuru Higuchi

Low serum 25-hydroxyvitamin D [25(OH)D] concentrations are associated with a high risk of insulin resistance and Type 2 diabetes mellitus in adults. However, it is unknown whether this is the case for American collegiate football and rugby football athletes. This study investigated the associations between serum 25(OH)D concentrations and glucose profiles in male collegiate football athletes. Thirty-four collegiate athletes (13 American football players and 21 rugby football players) aged 21 years were recruited. Their body fat percent and visceral fat area were measured by dual-energy X-ray absorptiometry and magnetic resonance imaging, respectively. The participants completed an oral glucose tolerance test (75 g glucose) with venous blood samples obtained at time points 0, 30, 60, 90, and 120 min for the determination of plasma glucose and serum insulin concentrations. Fasting serum 25(OH)D concentrations were also measured. The prevalence of vitamin D deficiency and insufficiency was 17.6% and 58.8%, respectively. The serum 25(OH)D concentrations were negatively associated with the increments in the areas under the curve (iAUC) for glucose (r = −.429, p = .011) and were borderline significantly correlated with the Matsuda index (r = −.303, p = .082). No relationships were observed between the serum 25(OH)D concentrations and other glucose profiles. Multiple stepwise regression analysis of glucose iAUC concentrations as the dependent variable indicated that the serum 25(OH)D concentrations, but not body fat indicators, were independently associated with glucose iAUC (β = −0.390, p = .025). The serum 25(OH)D concentrations were only an independent predictor for glucose iAUC in male collegiate football athletes, suggesting that increased 25(OH)D concentrations would be helpful for maintaining glucose homeostasis.

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Zhen-Bo Cao, Nobuyuki Miyatake, Tomoko Aoyama, Mitsuru Higuchi and Izumi Tabata

Background:

The purpose was to develop new maximal oxygen uptake (VO2max) prediction models using a perceptually regulated 3-minute walk test.

Methods:

VO2max was measured with a maximal incremental cycle test in 283 Japanese adults. A 3-minute walk test was conducted at a self-regulated intensity corresponding to ratings of perceived exertion (RPE) 13.

Results:

A 3-minute walk distance (3MWD) was significantly related to VO2max (r = .60, P < .001). Three prediction models were developed by multiple regression to estimate VO2max using data on gender, age, 3MWD, and either BMI [BMI model, multiple correlation coefficients (R) = .78, standard error of estimate (SEE) = 5.26 ml⋅kg-1⋅min-1], waist circumference (WC model, R = .80, SEE = 5.04 ml⋅kg-1⋅min-1), or body fat percentage (%Fat model, R = .84, SEE = 4.57 ml⋅kg-1⋅min-1), suggesting that the %Fat model is the best model [VO2max = 37.501 + 0.463 × Gender (0 = women, 1 = men) – 0.195 × Age – 0.589 × %Fat + 0.053 × 3MWD]. Cross-validation by using the predicted residual sum of squares (PRESS) procedures demonstrated a high level of cross-validity of all prediction models.

Conclusions:

The new VO2max prediction models are reasonably applicable to estimating VO2max in Japanese adults and represent a quick, low-risk, and convenient means for estimating VO2max in the field.