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Youn Soo Jung, Steven A. Hawkins and Robert A. Wiswell

The purpose of this study was to determine the contribution of body composition and muscle strength to racial differences in bone mineral density (BMD) in chronically active older adults. Participants were 49 men and 56 women grouped according to self-selected race (Black, Asian, or White). BMD, body composition, and knee strength were measured. Asian men had significantly lower body mass, strength, and BMD than White and Black men did (p < .05). Asian and White women had significantly lower body mass and BMD than Black women did (p < .05), with few strength differences between groups. When lean mass was controlled by ANCOVA. racial differences in BMD disappeared for all bone sites in both sexes. Controlling for body mass eliminated most racial differences in BMD. Controlling for strength did not alter racial differences in BMD for either sex. These results suggest that racial differences in BMD might in part result from differences in lean mass.

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Leon Mabire, Ramakrishnan Mani, Lizhou Liu, Hilda Mulligan and David Baxter

Background:

Brisk walking is the most popular activity for obesity management for adults. We aimed to identify whether participant age, sex and body mass index (BMI) influenced the effectiveness of brisk walking.

Methods:

A search of 9 databases was conducted for randomized controlled trials (RCTs). Two investigators selected RCTs reporting on change in body weight, BMI, waist circumference, fat mass, fat-free mass, and body fat percentage following a brisk walking intervention in obese adults.

Results:

Of the 5072 studies screened, 22 met the eligibility criteria. The pooled mean differences were: weight loss, –2.13 kg; BMI, –0.96 kg/m2; waist circumference, –2.83 cm; fat mass, –2.59 kg; fat-free mass, 0.29 kg; and body fat percentage, –1.38%. Meta-regression of baseline BMI showed no effect on changes.

Conclusions:

Brisk walking can create a clinically significant reduction in body weight, BMI, waist circumference, and fat mass for obese men and women aged under 50 years. Obese women aged over 50 years can achieve modest losses, but gains in fat-free mass reduce overall change in body weight. Further research is required for men aged over 50 years and on the influence of BMI for all ages and sexes.

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Binh Nguyen, Adrian Bauman and Ding Ding

Purpose:

To examine the combined effects of body mass index (BMI), physical activity (PA) and sitting on incident type 2 diabetes mellitus (T2DM) among Australian adults.

Methods:

A sample of 29,572 adults aged ≥45 years from New South Wales, Australia, completed baseline (2006–2008) and follow-up (2010) questionnaires. Incident T2DM was defined as self-reported, physician-diagnosed diabetes at follow-up. BMI was categorized as normal/overweight/obese. PA was tertiled into low/medium/ high. Sitting was dichotomized as higher/lower sitting (≥ 8 hours/day or < 8 hours/day). Odds ratios (OR) were estimated for developing T2DM using logistics regression for individual and combined risk factors, and data stratified by BMI categories.

Results:

During a mean 2.7 (SD: 0.9) years of follow-up, 611 (2.1%) participants developed T2DM. In fully adjusted models, BMI was the only independent risk factor for incident T2DM. In stratified analyses, the association between BMI and T2DM did not differ significantly across sitting or PA categories. Overweight/obese individuals with high PA and lower sitting had higher odds of incident T2DM than normal counterparts with low PA and higher sitting.

Conclusions:

High PA/low sitting did not attenuate the risk of T2DM associated with overweight/obesity. Maintaining a healthy weight, by adopting healthy lifestyle behaviors, is critical for T2DM prevention.

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Michael W. Beets, Guy C. Le Masurier, Aaron Beighle, David A. Rowe, Charles F. Morgan, Jack Rutherford, Michael Wright, Paul Darst and Robert Pangrazi

Background:

The purpose of this study was to cross-validate international BMI-referenced steps/d cut points for US girls (12,000 steps/d) and boys (15,000 steps/d) 6 to 12 years of age.

Methods:

Secondary pedometer-determined physical activity data from US children (N = 1067; 633 girls and 434 boys, 6 to 12 years) were analyzed. Using international BMI classifications, cross-validation of the 12,000 and 15,000 steps/d cut points was examined by the classification precision, sensitivity, and specificity for each age–sex stratum.

Results:

For girls (boys) 6 to 12 years, the 12,000 (15,000) steps/d cut points correctly classified 42% to 60% (38% to 67%) as meeting (achieved steps/d cut point and healthy weight) and failing (did not achieve steps/d cut point and overweight). Sensitivity ranged from 55% to 85% (64% to 100%); specificity ranged from 23% to 62% (19% to 50%).

Conclusion:

The utility of pedometer steps/d cut points was minimal in this sample given their inability to differentiate among children who failed to achieve the recommended steps/d and exhibited an unhealthy weight. Caution, therefore, should be used in applying previous steps/d cut points to US children.

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Richard Lowry, Sarah M. Lee, Deborah A. Galuska, Janet E. Fulton, Lisa C. Barrios and Laura Kann

Background:

Few studies have focused on the relationship between physical activity-related (PA) injury and overweight among youth.

Methods:

We analyzed data from the 2001 and 2003 Youth Risk Behavior Surveys (n = 28,815). Logistic regression was used to examine the independent effects of BMI and frequency of participation in vigorous activity, moderate activity, strengthening exercises, physical education (PE) classes, and team sports on the likelihood of PA injury.

Results:

Approximately 14% of females and 19% of males reported seeing a doctor or nurse during the previous 30 d for an injury that happened while exercising or playing sports. PA injury was associated with participation in team sports, strengthening exercises, and (among females) vigorous physical activity. Controlling for type and frequency of physical activity, injury was not associated with being overweight (BMI ≥ 95th percentile).

Conclusions:

Moderate physical activity and school PE classes may provide relatively low-risk alternatives for overweight youth who need to increase their physical activity.

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Josef Mitáš, Ding Ding, Karel Frömel and Jacqueline Kerr

Background:

Post-communist countries have experienced rapid economic development and social changes, which have been accompanied by changes in health-related lifestyle behaviors, such as physical activity. The purpose of this study was to examine the associations of domain-specific physical activity and total sedentary time with BMI among adults in the Czech Republic.

Methods:

We surveyed a nationally representative sample (n = 4097) of the Czech Republic in fall 2007 using the International Physical Activity Questionnaire (long form). Multiple linear regression analyses were used to examine associations of physical activity, sedentary time and sociodemograhic characteristics with BMI.

Results:

Older age, lower educational attainment, and lower levels of leisure-time physical activity were associated with higher BMI. Compared with those living in large cities, men living in small towns and women living in small villages had higher BMI.

Conclusions:

This study has identified correlates of BMI in the Czech Republic. Although more evidence from longitudinal studies is needed, findings from the current study can inform interventions to prevent the rising obesity epidemic.

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Gregory J. Norman, Sandra K. Nutter, Sherry Ryan, James F. Sallis, Karen J. Calfas and Kevin Patrick

Background:

Neighborhood-level environmental features have been associated with adult physical activity and weight status, but this link has not been established for adolescents.

Methods:

Community design and access to recreational facilities variables were derived using geographic information systems (GIS) for 799 adolescents (age 11 to 15 y, mean = 12.8 y, 53% girls, 43% ethnic minority). Environment variables were calculated for a 1-mile buffer around each participant’s residence. Accelerometers measured min/d of physical activity.

Results:

Number of nearby recreation facilities and number of nearby parks correlated positively with girls’ physical activity, and intersection density inversely related to girls’ physical activity. Retail floor area ratio correlated positively with boys’ physical activity. No community design or access to recreation variables were related to BMI-percentile.

Conclusions:

There was limited evidence that both community design and access to recreation facilities variables were associated with adolescent physical activity, but additional built environment variables need to be studied that have particular relevance for youth.

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Lyutha K. Al Subhi, Shekar Bose and Maraim F. Al Ani

Background:

A cross-country profile of physical activity and sedentary behavior is lacking within Eastern Mediterranean region (EMR) counties. The objectives were to examine prevalence of physical activity and sedentary behavior among adolescents of 10 EMR countries, and to describe potential differences in the 2 factors by sex, age, and BMI.

Methods:

A total of 23,562 adolescents were included from 10 EMR counties based on completeness of data (physical activity, sedentary behavior, age, sex, weight and height) from the Global school-based student health survey (GSHS).

Results:

Overall prevalence of physical activity (19%) is low and sedentary behavior is high (29%), with significant differences among counties. Oman had the highest (26%) and Egypt had the lowest (9%) prevalence of active students. Prevalence of sedentary behavior was the highest in United Arab Emirates (40%) and lowest in Pakistan (8%). Physical activity was lower and sedentary behavior was higher among female adolescents. A linear trend was observed between BMI and both physical activity and sedentary behavior; a similar pattern was seen with age.

Conclusions:

There is a need for interventions to increase the prevalence of adolescents meeting physical activity recommendations in the 10 countries. More investigation is required to understand the cultural context of sex and BMI influence on activity patterns.

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Wael Maktouf, Sylvain Durand, Bruno Beaune and Sébastien Boyas

due to the continuous pressure of supporting a large mass. 3 , 7 – 9 Second, a greater mechanical demand related to the large body mass per se and a nonnegligible proportion of body mass further away from the axis of rotation (ie, ankle joint assuming an inverted pendulum model) might cause a greater

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Kayla M. Baker, Sean Healy, David J. Rice and Jeanette M. Garcia

addition, sedentary behavior, specifically television viewing (TV), has been found to negatively impact adolescents’ physical well-being. 7 For instance, researchers found that an increase in TV was related to an increase in body fat and body mass index (BMI), 7 increased rates of depression, 8 and