Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Physics”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 559 records · Page 31Linked to original sources
PubMed2002

Socioeconomic status differences in recreational physical activity levels and real and perceived access to a supportive physical environment.

BACKGROUND: Spatial access to recreational facilities and perceptions of the neighborhood environment and physical activity levels were examined by the socioeconomic status of area of residence (SES). METHODS: A cross-sectional survey of adults (18-59 years) (n = 1,803) stratified by SES using a geographic-based index was conducted. RESULTS: Respondents in low SES areas had superior spatial access to many recreational facilities, but were less likely to use them compared with those living in high SES areas. They were more likely to perceive that they had access to sidewalks and shops, but also perceived that their neighborhood was busier with traffic, less attractive, and less supportive of walking. After adjustment, respondents living in low SES areas were 36% less likely to undertake vigorous activity. While they were more likely to walk for transport, this was not statistically significant (OR, 1.27; 95% CI, 0.98-1.64), nor were other SES differences in walking for recreation and walking as recommended. Modifiable environmental factors were associated with walking and vigorous activity, especially perceived access to sidewalks and neighborhood attractiveness. Spatial access to attractive, public open space was associated with walking. CONCLUSIONS: Creating supportive environments--particularly sidewalks in attractive neighborhoods--has the potential to increase walking and vigorous activity.

Adolescent↗
PubMed1981

The relationship between plasma membrane lipid composition and physical-chemical properties. II. Effect of phospholipid fatty acid modulation on plasma membrane physical properties and enzymatic activities.

The fatty acid composition of plasma membrane phospholipids of the murine T lymphocyte tumor EL4 were systematically modified in an attempt to understand the relationship between lipid bilayer composition and plasma membrane physical and biological properties. Two plasma membrane enzyme activities, adenylate cyclase and ouabain-sensitive (Na+ + K+)-ATPase, were measured in normal and fatty acid-substituted EL4 plasma membrane fractions. The fatty acid effect on enzyme activities was similar to previously reported effects of fatty acids on cytotoxic T cell function. The activity of both enzymes was inhibited by saturated fatty acids, while unsaturated fatty acids had a moderate enhancing effect on both enzyme activities. Using two different nitroxide derivatives of stearic acid, the order parameter and approximate rotational correlation times were calculated from ESR spectra of normal and fatty acid-modified plasma membranes. No significant differences was found in either parameter in these membranes. These results, in conjunction with earlier data from our laboratory and others, suggest that caution should be exercised in inferring changes in membrane 'fluidity' based on lipid modulation of biological membranes.

Adenylyl Cyclases↗
PubMed2003

Influence of physical activity-related joint stress on the risk of self-reported hip/knee osteoarthritis: a new method to quantify physical activity.

BACKGROUND: The relationship between physical activity (PA) and the development of hip/knee osteoarthritis (OA) has not been clearly defined. The purpose of this study was to develop a method to quantify PA-related joint stress and to assess its influence on the risk of hip/knee OA. METHODS: Participants in a large longitudinal study, without knee/hip OA (n = 5284), were asked about their PA participation in 1986. PA-related joint stress was calculated using information on the frequency, intensity, and duration of individual types of PA, and incorporated a quantification of joint stress. Self-reported, physician-diagnosed hip/knee OA was ascertained by survey in 1990, 1995, and 1999 (average length of follow-up: 12.8 years). METHODS: The joint stress PA score was not associated with an increased risk of hip/knee OA. Also, among walkers and runners there was no association between the frequency, pace, or weekly training mileage and hip/knee OA. Older age, previous joint injury and surgery, and higher body mass index were confirmed as independent risk factors for hip/knee OA. CONCLUSIONS: Participation in PA as an adult does not increase the risk of hip/knee OA and there does not seem to be a threshold of increasing risk with increased training among walkers and runners.

Female↗
PubMed2001

Physical inactivity as a determinant of the physical activity level in the elderly.

OBJECTIVE: To assess the relationship between the mean physical activity level (PAL) and the time spent on activities of three different intensity levels in an elderly population. Data was compared with previously obtained data from a group of younger adults. SUBJECTS: Fourteen elderly women and 14 elderly men (61+/-4 y; 27+/-5 kg/m(2); 33+/-7% body fat), and 14 young women and 16 young men (27+/-5 y, 24+/-2 kg/m(2)). MEASUREMENTS: PAL was determined as average daily metabolic rate (ADMR) combined with a measurement of basal metabolic rate (BMR): PAL=ADMR/BMR. ADMR was measured with the doubly labeled water method. BMR was measured with a ventilated hood system. Time spent on activity and activity intensity was measured by using a tri-axial accelerometer (7x2x0.8 cm, 30 g) over a 2 week interval. RESULTS: Mean PAL was 1.65+/-0.14. PAL was inversely related to the percentage of time spent on low-intensity activity (lying, sitting and standing), r= -0.43; P<0.05. Older subjects spent significantly more time at these activities than 20 to 35-y-old subjects (82+/-7% vs 65+/-7%; P<0.0001). A significant relation was not observed between PAL and the percentage of time spent on moderate (walking) or high (household activities, exercise and sports) intensity activity, or activity monitoring time (14.4+/-1.2 h/day). CONCLUSION: In the elderly, spending relatively more time on low-intensity activities affects the mean PAL negatively. To obtain a higher PAL does not necessarily imply high-intensity activities like sports.

Acceleration↗