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PURPOSE This study aimed to determine whether interrupting prolonged sitting with three different walking-bout schedules improves glycemic metabolism relative to continuous prolonged sitting in sedentary adults. METHODS In a randomized, crossover trial, 16 inactive healthy adults (7 men, 24 ± 3 yr old) completed four 26-h laboratory sessions, including 22.5 h in an energy expenditure (EE)-testing calorimeter chamber. The four 9-h intervention periods were as follows: 9-h uninterrupted sitting (SIT), 30-min sitting/3-min brisk (60% V˙O2max) treadmill walk (WALK3), 45-min sitting/5-min (WALK5), or 60-min sitting/8-min (WALK8). Coprimary outcomes included the difference in the mean interstitial glucose concentration, total area under the curve (tAUC), and incremental area under the curve (iAUC) for the entire 26 and 9 h (intervention period) during three activity-bout conditions compared with SIT. RESULTS Compared with SIT, the 26-h mean glucose concentration was attenuated in WALK8 (Δmean -0.22 mmol·L [95% confidence interval = -0.43 to -0.001], P = 0.048) without adjustment for EE and attenuated in WALK3 (Δ-0.47 mmol·L [-0.75 to -0.10]), WALK5 (Δ-0.47 mmol·L [-0.83 to -0.10]), and WALK8 (Δ-0.53 mmol·L [-0.92 to -0.13]) after adjustment for EE (all P < 0.01). The 26-h tAUC was reduced in WALK3 (Δ-11.18 mmol·L per 26 h [-20.07 to -2.29]), WALK5 (2.12.67 mmol·L per 26 h [-22.54 to -2.79]), and WALK8 (Δ-13.85 mmol·L per 26 h [-24.60 to -3.10]) (all P < 0.01), as well as the iAUC (all P < 0.05), only after adjustment for EE. The 9-h mean glucose concentration, tAUC, and iAUC decreased in the three activity-break conditions regardless of EE adjustment (all P < 0.05). CONCLUSIONS All three walking-bout conditions improved glycemic metabolism compared with SIT, independent of EE, in inactive, healthy adults.

CAO, Z., N. MIYATAKE, M. HIGUCHI, M. MIYACHI, K. ISHIKAWA-TAKATA, and I. TABATA. Predicting VO 2max with an Objectively Measured Physical Activity in Japanese Women. Med. Sci. Sports Exerc., Vol. 42, No. 1, pp. 179―186, 2010. Purpose: To investigate the use of the accelerometer-determined physical activity (PA) intensity variables as the objective PA variables for estimating VO 2max in Japanese adult women. Methods: The subjects of this study were 148 Japanese women aged 20 to 69 yr. Maximal oxygen uptake (VO 2max ) was measured with a maximal incremental test on a bicycle ergometer. Daily step counts (SC) and the amount spent in moderate to vigorous PA (MVPA) and vigorous PA (VPA) were measured using accelerometer-based activity monitors for 7 consecutive days. Using data of age, SC, MVPA, or VPA, and either body mass index (BMI) or waist circumference (WC), the nonexercise VO 2max prediction models were derived as BMI models MVPA , WC models MVPA , BMI models VPA , and WC models VPA , and cross-validated by using two separate cross-validation procedures. Results: SC, MVPA, and VPA were significantly related to VO 2max (r = 0.43, r = 0.52, and r = 0.58, respectively). The multiple correlation coefficients for the BMI and WC models MVPA were 0.83 and 0.85, respectively, and for the BMI and WC models VPA , they were 0.85 and 0.86, respectively. The SEE was 3.3 and 3.1 mL·kg ― 1 ·min ―1 for the BMI and WC models MVPA , respectively, and it was 3.1 and 3.0 mL·kg ―1 ·min ―1 for the BMI and WC models VPA , respectively. All regression models demonstrated a high level of cross-validity supported by the minor shrinkage of the coefficient of determination and the increment of SEE in the predicted residual sum of squares procedure, and by small constant errors for the subgroups of age, SC, and VO 2max between 25 and 35 mL·kg ―1 ·min ―1 . Conclusions: This study demonstrated that multiple regression models using data of MVPA or VPA were useful in predicting VO 2max for Japanese adult women.