A pilot walking program promotes moderate-intensity physical activity during pregnancy.

INTRODUCTION: Walking may be a strategy for increasing moderate-intensity physical activity (MPA) during pregnancy. PURPOSE: This study aimed to promote MPA among overweight and obese pregnant women, via walking, and to evaluate the effect of the intervention on maternal and birth outcomes. METHODS: Thirty-seven overweight or obese pregnant women were randomly assigned to a walking intervention or control group. Anthropometric and objective PA (StepWatch™ Activity Monitor) data were collected for four 1-wk periods: weeks 10-14 (V1), weeks 17-19 (V2), weeks 27-29 (V3), and weeks 34-36 (V4) of gestation. Participants provided information about maternal and birth outcomes. A cadence of ≥ 80 steps per minute was defined as MPA, and "meaningful walking" was defined as moderate walking in ≥ 8-min bouts. ANOVA was used to determine the differences in walking amount and meaningful walks, the Kolmogorov-Smirnov test was used for walking intensity distribution analysis, and Fisher's exact test was used for maternal and infant outcomes analyses. Pearson correlation was used to examine the association between prepregnancy body mass index and gestational weight gain (GWG). RESULTS: There was significantly more MPA among women in the intervention group compared with those in the control group at V2 (overweight, P < 0.0001; obese, P < 0.025), V3 (overweight, P < 0.0001), and V4 (overweight, P < 0.0001; obese, P < 0.025). Women in the intervention group significantly increased their meaningful walks at V2 (P = 0.054), V3 (P = 0.01), and V4 (P = 0.014). There were trends for intervention group women to have more favorable maternal and birth outcomes compared with the control group. Rates of GWG at measurement points during pregnancy were significantly associated with preceding rates of GWG. CONCLUSION: The pilot, unsupervised walking intervention increased the MPA of overweight and obese women during pregnancy.

The energy expenditure of an activity-promoting video game compared to sedentary video games and TV watching.

BACKGROUND: In the present study we investigated the effect of television watching and the use of activity-promoting video games on energy expenditure in obese and lean children. METHODS: Energy expenditure and physical activity were measured while participants were watching television, playing a video game on a traditional sedentary video game console, and while playing the same video game on an activity-promoting video game console. RESULTS: Energy expenditure was significantly greater than television watching and playing video games on a sedentary video game console when children played the video game on the activity-promoting console. When examining movement with accelerometry, children moved significantly more when playing the video game on the Nintendo Wii console. CONCLUSION: Activity-promoting video games have shown to increase movement, and be an important tool to raise energy expenditure by 50% when compared to sedentary activities of daily living.

Accuracy of physical activity assessment during pregnancy: an observational study.

BACKGROUND: Prenatal physical activity may improve maternal and infant health and lower future disease risk for both mother and baby; however, very few physical activity assessment methods have been validated for use during pregnancy. The purpose of this study was to evaluate the accuracy of a subjective physical activity record (PAR) and an objective activity monitor, against a reference standard to quantify moderate and vigorous physical activity (MVPA) in pregnant women. The reference standard was based on participant interviews to determine if a woman was an exerciser and confirmed with information obtained from the PAR and a heart rate monitor. METHODS: Fifty-two pregnant women completed a physical activity record (PAR) and wore a SenseWear® Mini Armband (SWA) activity monitor over a 7-day period at 18 weeks gestation. Total minutes spent in MVPA were totaled from both modalities and evaluated against the reference standard using contingency analysis and Pearson's chi-square test to evaluate the number of women meeting minimum prenatal physical activity recommendations (at least 3, 30 minute sessions of exercise per week). Both modalities were also tested individually and collectively to assess their ability as indicators of activity using empirically determined cut-offs as indicated by receiver-operator characteristic curves. These experimentally-derived criteria were also tested with Pearson's chi-square test. RESULTS: According to the reference standard, 13 of 52 participants (25%) met the criterion of 3, 30 minute sessions of volitional, moderate-intensity activity. When compared to the reference standard, both the PAR and SWA overestimated exercise status; 42 (81%) and 52 (100%) participants, respectively, achieved 90 minutes of MVPA (P < 0.0001 for both comparisons). Single-modality predictors of MVPA did not show a significant correlation. A composite predictor of MVPA offered the most favorable option for sensitivity and specificity (true positives, n = 8 and true negatives, n = 36) using cut-offs of 280 and 385 minutes/week for the PAR and SWA, respectively. CONCLUSION: Compared to the reference standard, time spent in MVPA obtained from the PAR or SWA overestimated the prevalence of women meeting prenatal exercise recommendations. The most accurate predictor of women meeting current prenatal exercise guidelines was identified by using the PAR and SWA collectively.

Activity-promoting video games and increased energy expenditure.

OBJECTIVES: To test the hypothesis that both children and adults would expend more calories and move more while playing activity-promoting video games compared with sedentary video games. STUDY DESIGN: In this single-group study, 22 healthy children (12 +/- 2 years; 11 male, 11 female) and 20 adults (34 +/- 11 years; 10 male, 10 female) were recruited. Energy expenditure and physical activity were measured while participants were resting, standing, watching television seated, sitting and playing a traditional sedentary video game, and while playing an activity-promoting video game (Nintendo Wii Boxing). Physical activity was measured with accelerometers, and energy expenditure was measured with an indirect calorimeter. RESULTS: Energy expenditure was significantly greater than all other activities when children or adults played Nintendo Wii (mean increase over resting, 189 +/- 63 kcal/hr, P < .001, and 148 +/- 71 kcal/hr, P < .001, respectively). When examining movement with accelerometry, children moved significantly more than adults (55 +/- 5 arbitrary acceleration units and 23 +/- 2 arbitrary acceleration units, respectively, P < .001) while playing Nintendo Wii. CONCLUSION: Activity-promoting video games have the potential to increase movement and energy expenditure in children and adults.

Changing the school environment to increase physical activity in children.

We examined the hypothesis that elementary school-age children will be more physically active while attending school in a novel, activity-permissive school environment compared to their traditional school environment. Twenty-four children were monitored with a single-triaxial accelerometer worn on the thigh. The students attended school in three different environments: traditional school with chairs and desks, an activity-permissive environment, and finally their traditional school with desks which encouraged standing. Data from the school children were compared with another group of age-matched children (n = 16) whose physical activity was monitored during summer vacation. When children attended school in their traditional environment, they moved an average (mean +/- s.d.) of 71 +/- 0.4 m/s(2). When the children attended school in the activity-permissive environment, they moved an average of 115 +/- 3 m/s(2). The children moved 71 +/- 0.7 m/s(2) while attending the traditional school with standing desks. Children moved significantly more while attending school in the activity-permissive environment compared to the amount that they moved in either of the traditional school environments (P < 0.0001 for both). Comparing children's activity while they were on summer vacation (113 +/- 8 m/s(2)) to school-bound children in their traditional environment showed significantly more activity for the children on summer vacation (P < 0.0001). The school children in the activity-permissive environment were as active as children on summer vacation. Children will move more in an activity-permissive environment. Strategies to increase the activity of school children may involve re-designing the school itself.

The role of free-living daily walking in human weight gain and obesity.

OBJECTIVE: Diminished daily physical activity explains, in part, why obesity and diabetes have become worldwide epidemics. In particular, chair use has replaced ambulation, so that obese individuals tend to sit for approximately 2.5 h/day more than lean counterparts. Here, we address the hypotheses that free-living daily walking distance is decreased in obesity compared with lean subjects and that experimental weight gain precipitates decreased daily walking. RESEARCH DESIGN AND METHODS: During weight-maintenance feeding, we measured free-living walking using a validated system that captures locomotion and body movement for 10 days in 22 healthy lean and obese sedentary individuals. These measurements were then repeated after the lean and obese subjects were overfed by 1,000 kcal/day for 8 weeks. RESULTS: We found that free-living walking comprises many (approximately 47) short-duration (<15 min), low-velocity ( approximately 1 mph) walking bouts. Lean subjects walked 3.5 miles/day more than obese subjects (n = 10, 10.3 +/- 2.5 vs. n = 12, 6.7 +/- 1.8 miles/day; P = 0.0009). With overfeeding, walking distance decreased by 1.5 miles/day compared with baseline values (-1.5 +/- 1.7 miles/day; P = 0.0005). The decrease in walking that accompanied overfeeding occurred to a similar degree in the lean (-1.4 +/- 1.9 miles/day; P = 0.04) and obese (-1.6 +/- 1.7 miles/day; P = 0.008) subjects. CONCLUSIONS: Walking is decreased in obesity and declines with weight gain. This may represent a continuum whereby progressive increases in weight are associated with progressive decreases in walking distance. By identifying walking as pivotal in weight gain and obesity, we hope to add credence to an argument for an ambulatory future.

Energy expenditure of sedentary screen time compared with active screen time for children.

OBJECTIVE: We examined the effect of activity-enhancing screen devices on children's energy expenditure compared with performing the same activities while seated. Our hypothesis was that energy expenditure would be significantly greater when children played activity-promoting video games, compared with sedentary video games. METHODS: Energy expenditure was measured for 25 children aged 8 to 12 years, 15 of whom were lean, while they were watching television seated, playing a traditional video game seated, watching television while walking on a treadmill at 1.5 miles per hour, and playing activity-promoting video games. RESULTS: Watching television and playing video games while seated increased energy expenditure by 20 +/- 13% and 22 +/- 12% above resting values, respectively. When subjects were walking on the treadmill and watching television, energy expenditure increased by 138 +/- 40% over resting values. For the activity-promoting video games, energy expenditure increased by 108 +/- 40% with the EyeToy (Sony Computer Entertainment) and by 172 +/- 68% with Dance Dance Revolution Ultramix 2 (Konami Digital Entertainment). CONCLUSIONS: Energy expenditure more than doubles when sedentary screen time is converted to active screen time. Such interventions might be considered for obesity prevention and treatment.

Does Non-Exercise Activity Thermogenesis Contribute to Non-Shivering Thermogenesis?

We wanted to examine if spontaneous physical activity contributes to non-shivering thermogenesis. Ten lean, healthy male subjects wore a physical activity, micro-measurement system whilst the room temperature was randomly altered at two hourly intervals between thermoneutral (72°F), cool (62°F) and warm (82°F) temperatures. Physical activity measured during the thermoneutral, cooling and warming periods was not significantly different. Cooling, increased EE above basal and thermoneutral values 2061 ± 344 kcal/day (p <0.01). Thus, the increase in energy expenditure associated with short-term environmental cooling in lean, healthy males does not appear to be due to increased spontaneous physical activity or fidgeting.

Laboratory measurement of posture allocation and physical activity in children.

PURPOSE: The purpose of this study was to validate the combined use of inclinometers and accelerometers to measure body posture and movement in children in a laboratory setting. METHODS: We performed two separate experiments. In the first experiment, we tested the hypothesis that four inclinometers (tilt sensors) could be used to capture body posture in children. We observed and recorded body posture in eight healthy children (mean +/- SD; body mass index (BMI), 18 +/- 3 kg x m(-2)) on 2880 occasions and compared these records with the inclinometer data. In the second experiment, the hypothesis was that two inclinometers could be used to determine whether 18 children (BMI, 21 +/- 5 kg x m(-2)) were sedentary. We observed and recorded sedentariness (sitting/lying compared to standing) on 5575 occasions and compared these records with the inclinometer data. In both of these experiments, we also addressed the hypothesis that accelerometer output, when measured at varying velocities, correlated with walking energy expenditure. RESULTS: In experiment 1, body posture was correctly identified in 2880 out of 2880 inclinometer measurements. In experiment 2, sedentary behavior was correctly identified in 5575 out of 5575 occasions. For the entire group, acceleration and body weight correlated well with energy expenditure (r2 = 0.84). CONCLUSION: The inclinometer-accelerometer system that we tested can be used to measure body posture and movement. We can measure sedentary behavior using two inclinometers instead of four inclinometers. This monitoring system may be useful for measuring energy expenditure, body posture, and physical activity in children.

Precision and accuracy of an ankle-worn accelerometer-based pedometer in step counting and energy expenditure.

BACKGROUND: Walking is a widely used approach to increase physical activity levels in obese patients. In this paper, we investigate the precision and accuracy of an ankle-worn dual-axis accelerometer (Stepwatch) and investigate its potential application as a predictor of energy expenditure. METHODS: Twenty healthy subjects (10 lean, 10 obese) wore spring-levered (Accusplit), piezoelectric (Omron HF-100), and Stepwatch pedometers. Subjects walked on a treadmill at 1, 2, and 3 mph and in a hallway at 1 and 1.85 mph, during which energy expenditure was measured. RESULTS: The Stepwatch counted 99.7 +/- 0.67% (mean +/- SEM) of the manual counts. In comparison, the Omron pedometer counted 61 +/- 3.3% and the Accusplit counted 26 +/- 2.8% of the manual counts at 1 mph although all pedometers were accurate (> 98% of counts) at 3 mph. In repeated measures, the Stepwatch produced negligible variance (SD = 0.36) over all speed whereas the other pedometers showed a large amount of variance at all speed (SD = 4-13). Stepwatch counts were predictive of walking energy expenditure corrected by weight (r2 > 0.8). CONCLUSION: The counts from the Stepwatch were virtually identical to the manual counts from a trained investigator and provided a reliable predictor of walking energy expenditure.