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  • Author: Nobuyuki Miyatake x
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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.

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Julien Tripette, Haruka Murakami, Hidemi Hara, Ryoko Kawakami, Yuko Gando, Harumi Ohno, Nobuyuki Miyatake and Motohiko Miyachi

Caffeine has been described as a sports performance-enhancing substance. However, it is unclear whether it can increase the level of physical activity (PA) in nonathletic individuals. This study investigates the relationship between daily caffeine consumption and (a) daily PA/fitness or (b) intervention-induced changes in PA in women and men. On the basis of responses to a dietary habit questionnaire, which included items on caffeinated beverages, 1,032 Japanese adults, were categorized into lower or higher caffeine consumption groups (relative to the median caffeine consumption). In each group, daily step count; sedentary time; and light, moderate, and vigorous PA outcomes were objectively measured. Physical fitness, including peak oxygen consumption, was also evaluated. The relationship between daily caffeine consumption and the change in the levels of PA was investigated in a subgroup of 202 subjects who participated in a 1-year PA counseling intervention. Women in the higher caffeine consumption group presented higher moderate-to-vigorous PA and step count compared with their counterparts in the lower consumption group (4.0 ± 2.1 vs. 3.3 ± 2.1 MET-hr/day, p < .001; 10,335 ± 3,499 vs. 9,375 ± 3,527 steps/day, p < .001). A significant positive correlation was noted between caffeine consumption and peak oxygen consumption among women (r = .15, p < .001). No caffeine-related effects were noted in men. The lower and higher caffeine consumption groups showed no significant differences in their levels of PA at the end of the 1-year intervention. Therefore, caffeine consumption appears to be associated with higher levels of PA in Japanese women. Further studies are needed to clarify this association.

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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.