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Christopher L. Melby, Kristen L. Osterberg, Alyssa Resch, Brenda Davy, Susan Johnson and Kevin Davy

Thirteen physically active, eumenorrheic, normal-weight (BMI ≤ 25 kg/m2) females, aged 18–30 years, completed 4 experimental conditions, with the order based on a Latin Square Design: (a) CHO/Ex: moderate-intensity exer-· cise (65% V̇O2peak) with a net energy cost of ~500 kcals, during which time the subject consumed a carbohydrate beverage (45 g CHO) at specific time intervals; (b) CHO/NoEx: a period of time identical to (a) but with subjects consuming the carbohydrate while sitting quietly rather than exercising; (c) NoCHO/ Ex: same exercise protocol as condition (a) during which time subjects consumed a non-caloric placebo beverage; and (d) NoCHO/NoEx: same as the no-exercise condition (b) but with subjects consuming a non-caloric placebo beverage. Energy expenditure, and fat and carbohydrate oxidation rates for the entire exercise/sitting period plus a 90-min recovery period were determined by continuous indirect calorimetry. Following recovery, subjects ate ad libitum amounts of food from a buffet and were asked to record dietary intake during the remainder of the day. Total fat oxidation (exercise plus recovery) was attenuated by carbohydrate compared to placebo ingestion by only ~4.5 g. There was a trend (p = .08) for a carbohydrate effect on buffet energy intake such that the CHO/Ex and CHO/NoEx energy intakes were lower than the NoCHO/Ex and NoCHO/NoEx energy intakes, respectively (mean for CHO conditions: 683 kcal; NoCHO conditions: 777 kcal). Average total energy intake (buffet plus remainder of the day) was significantly lower (p < .05) following the conditions when carbohydrate was consumed (CHO/Ex = 1470 kcal; CHO/NoEx = 1285 kcal) compared to the noncaloric placebo (NoCHO/Ex =1767 kcal; NoCHO/ NoEx = 1660 kcal). In conclusion, in young women engaging in regular exercise, ingestion of 45 g of carbohydrate during exercise only modestly suppresses total fat oxidation during exercise. Furthermore, the ingestion of carbohydrate with or without exercise resulted in a lower energy intake for the remainder of the day

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Susan A. Johnson and Malissa Martin

Column-editor : Malissa Martin

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Tyler G. Johnson, Timothy A. Brusseau, Susan Vincent Graser, Paul W. Darst and Pamela H. Kulinna

Background:

The purpose of this study was to conduct a secondary analysis by combining 2 pedometer data sets to describe and analyze pedometer-determined steps/day of children by ethnicity and metropolitan status.

Methods:

Participants were 582 children (309 girls, 273 boys; 53% Hispanic, 26% Caucasian, 21% African American) age 10 to 11 years (M = 10.37 ± 0.48) attending 1 of 10 schools located in urban, suburban, and rural settings. Participants wore a research grade pedometer for at least 3 week/school days. Mean steps/ day were analyzed by gender, ethnicity, and metropolitan status.

Results:

Statistical analyses indicated 1) boys (12,853 ± 3831; P < .001) obtained significantly more steps/day than girls (10,409 ± 3136); 2) African American (10,709 ± 3386; P < .05) children accumulated significantly less steps/day than Hispanic (11,845 ± 3901) and Caucasian (11,668 ± 3369) children; and 3) urban (10,856 ± 3706; P < .05) children obtained significantly less steps/day than suburban (12,297 ± 3616) and rural (11,934 ± 3374) children.

Conclusions:

Findings support self-report data demonstrating reduced physical activity among African American children and youth, especially girls, and among children and youth living in urban areas. Possible reasons for these discrepancies are explored.

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Sarah M. Camhi, Susan B. Sisson, William D. Johnson, Peter T. Katzmarzyk and Catrine Tudor-Locke

Background:

Objective physical activity data analyses focus on moderate-to-vigorous physical activity (MVPA) without considering lower intensity lifestyle-type activities (LA). We describe 1) quantity of LA (minutes and steps per day) across demographic groups, 2) proportion of LA to total physical activity, and 3) relationships between LA and MVPA using NHANES 2005−2006 accelerometer adult data (n = 3744).

Methods:

LA was defined as 760 to 2019 counts per minute (cpm) and MVPA as ≥2020 cpm. LA was compared within gender, ethnicity, age, and BMI groups. Regression analyses examined independent effects. Correlations were evaluated between LA and MVPA. All analyses incorporated sampling weights to represent national estimates.

Results:

Adults spent 110.4 ± 1.6 minutes and took 3476 ± 54 steps per day in LA. Similar to MVPA, LA was highest in men, Mexican Americans, and lowest in adults ≥60 years or obese. When LA was held constant, ethnic differences no longer predicted MVPA minutes, and age no longer predicted MVPA steps. LA and MVPA minutes (r = .84) and steps per day (r = .72) were significantly correlated, but attenuated with MVPA modified bouts (≥10 minutes sustained activity).

Conclusions:

LA accumulation differs between demographic subgroups and is related to MVPA: adults who spend more minutes and steps in MVPA also spend them in LA.